Home Diseases and pests Department of Analytical Chemistry. From the history of the Faculty of Chemistry of Moscow State University. Department of Analytical Chemistry MSU Faculty of Chemistry Department of Analytical Chemistry

Diseases and pests

Department of Analytical Chemistry. From the history of the Faculty of Chemistry of Moscow State University. Department of Analytical Chemistry MSU Faculty of Chemistry Department of Analytical Chemistry

"Department of Analytical Chemistry Approved by the methodological committee of the Department of Analytical Chemistry A.V. Ivanov METHODOLOGICAL GUIDE TO QUALITATIVE AND QUANTITATIVE ..."

Moscow State University named after M.V. Lomonosov

Chemical faculty

Department of Analytical Chemistry

Approved by the Methodological Commission

Department of Analytical Chemistry

A.V. Ivanov

METHODOLOGICAL GUIDE

IN QUALITATIVE AND QUANTITATIVE

ANALYSIS

FOR STUDENTS OF THE 2nd YEAR OF GEOGRAPHICAL

FACULTY

Edited by Professor V.M. Ivanov Moscow 2001 Introduction The Methodological Guide is intended as a manual for practical exercises on the course "Qualitative and Quantitative Analysis" for 2nd year students of the Faculty of Geography, specializing in the Department of Soil Geography. The program of the discipline "Qualitative and quantitative analysis for the Faculty of Geography of Moscow State University" aims to study the theoretical foundations of chemical (titrimetric and gravimetric) and instrumental (spectroscopic and electrochemical) methods of analysis and familiarize with the possibilities of their practical application. The methodological guide consists of three parts, the first one includes a calendar plan of lectures and practical classes and questions for colloquia. The scale of rating assessment of knowledge on the positions provided by the curriculum is given. The second part contains methods for conducting qualitative reactions of individual cations and anions, the third "Quantitative analysis" - includes methods for the gravimetric and titrimetric determination of a number of elements in pure solutions and in real objects. The theoretical foundations of the methods are briefly outlined. All proposed methods have been tested by laboratory assistants and engineers of the Department of Analytical Chemistry of Chemical Faculty of Moscow State University.

The first part of the manual was compiled with the participation of Professor, Doctor of Chemical Sciences.

T.N. Shekhovtsova.

Comments and wishes of teachers and students will be received by the author with deep gratitude.

I. COURSE PROGRAM

The calendar plan of classes includes 14 lectures, 16 practical classes, 3 milestone tests (during lecture hours) and 3 colloquiums. There is an exam at the end of the semester.

Plan of lectures and tests Lecture 1 Subject and methods of analytical chemistry. chemical balance.

Factors affecting chemical equilibrium.

Equilibrium constants.

Lecture 2 Acid-base balance.

Lecture 3 Calculation of pH in various systems Lecture 4 Chemical equilibrium in a heterogeneous system.

Lecture 5 Calculation of conditions for dissolution and precipitation. Calculation of the solubility product from the solubility data.

I boundary control work "Acid-base equilibrium and equilibrium in a heterogeneous system".

Lecture 6 Complex formation reactions. complex compounds.

Lecture 7 Organic reagents in analytical chemistry.

Lecture 8 Equilibrium in redox reactions.

Calculation of redox potentials.

Direction of oxidation-reduction reactions.

Lecture 9 Gravimetric method of analysis II milestone test "Redox reactions and reactions of complex formation".

Lecture 10 Titrimetric methods of analysis, their application. Acid-base titration.

Lecture 11 Complexometric and redox titration.

Lecture 12 Metrological foundations of analytical chemistry. Statistical processing of analysis results.

III boundary control work "Titrimetric methods of analysis, metrological foundations of analytical chemistry".

Lecture 13 Introduction to spectroscopic methods of analysis.

Lecture 14. Introduction to electrochemical methods of analysis.

Practice plan

Lesson 1 Introductory talk on qualitative analysis. Qualitative reactions of cations of groups I-III: K+, Na+, NH4+, Mg2+, Ba2+, Ca2+, Pb2+ and anions: SO42-, CO32-, Cl-, NO3-, PO43Qualitative reactions of cations of groups IV-VI: Al3+, Cr3+, Zn2+ , Fe2+, Lesson 2 Fe3+, Mn2+, Co2+, Ni2+, Cd2+, Cu2+.

Homework: calculation of equilibrium constants.

Separation of a mixture of cations by paper chromatography. Conversation Lesson 3 on qualitative analysis schemes.

Homework: calculation of pH in solutions of acids, bases, ampholytes and in buffer mixtures.

Lesson 4 Control task No. 1: analysis of a mixture of cations of groups I-VI and anions (solution).

Homework: calculation of the solubility of poorly soluble compounds, the formation of precipitates.

Control task No. 2: analysis of a solid mixture of cations and anions Lessons 5, or a natural object.

Lesson 7 Colloquium No. 1: Chemical balance. acid-base balance. Equilibrium in a heterogeneous system.

Lessons 8- Introductory talk on gravimetry.

10 Control task No. 3: determination of sulfate ions in a mixture of sodium sulfate and sodium chloride.

Homework: complex formation reactions;

calculation of redox potentials.

Lesson 11 Introduction to acid-base titration.

Preparation of solutions - primary standard solution of sodium carbonate (Na2CO3) and secondary standard solutions - hydrochloric acid (HCl) and sodium hydroxide (NaOH). Standardization of HCl and NaOH.

Lesson 12 Control task No. 4: determination of HCl.

Homework: plotting titration curves.

Lesson 13 Introduction to complexometric titration.

Control task No. 5 - complexometric determination of calcium and magnesium in the joint presence.

Lesson 14 Colloquium №2. Complex formation reactions.

organic reagents. Acid-base and complexometric titration.

Lesson 15 Introductory talk on redox balance and titration. Preparation of a primary standard solution of potassium dichromate (K2Cr2O7) or oxalic acid (H2C2O4) and a secondary standard solution of potassium permanganate (KMnO4).

Control task No. 6: determination of iron or water oxidizability Lesson 16 Introductory conversation on the method of flame photometry. Determination of potassium and sodium.

Colloquium No. 3. Redox reactions.

– – –

Chemical equilibrium in a homogeneous system. Its main types:

acid-base, equilibrium of complexation and oxidation-reduction. Factors affecting chemical equilibrium: concentrations of reactants, nature of the solvent, ionic strength of the solution, temperature.

Activity and activity coefficient. Total and equilibrium concentrations.

Competing reactions, coefficient of competing reaction.

Thermodynamic, real and conditional equilibrium constants.

Acid-base balance. Modern concepts of acids and bases. The main provisions of the Bronsted-Lowry theory. Acid-base conjugated pairs. Influence of the nature of the solvent on the strength of acids and bases.

Autoprotolysis constant. Leveling and differentiating effects of the solvent. buffer solutions. Calculation of pH of aqueous solutions of strong and weak acids and bases, ampholytes, buffer solutions.

Chemical equilibrium in a heterogeneous system. The main types of chemical equilibrium in a heterogeneous system: liquid-solid phase (solution precipitate), liquid-liquid. Equilibrium constant of the precipitation/dissolution reaction (solubility product). Thermodynamic, real and conditional equilibrium constants. Precipitation and dissolution conditions. Calculation of the solubility of precipitation under various conditions.

Colloquium #2.

Complex formation reactions. organic reagents.

Acid-base and complexometric titration.

Complex compounds and organic reagents. Types and properties of complex compounds used in analytical chemistry. Stepwise complexation. Thermodynamic and kinetic stability of complex compounds. Influence of complexation on the solubility of compounds and the redox potential of the system.

Theoretical foundations of the interaction of organic reagents with inorganic ions. Functional-analytic groups. Theory of analogies of the interaction of metal ions with inorganic reagents such as H2O, NH3, H2S and oxygen-, nitrogen-, sulfur-containing organic reagents. Chelates, intercomplex compounds. Using complex compounds in analysis to detect, separate, mask, and identify ions.

Titrimetric methods of analysis. Titration methods: direct, reverse, displacement, indirect. Acid-base titration. Requirements for reactions in acid-base titration. Titration curves, equivalence point, end point of titration. Indicators. Primary and secondary standards, working solutions. Construction of titration curves, indicator selection, titration error. Examples of practical application of acid-base titration - determination of HCl, NaOH, Na2CO3.

complexometric titration. Requirements for complex formation reactions used in titrimetry. The use of aminopolycarboxylic acids. Metal-chromic indicators and requirements for them.

Construction of titration curves.

Colloquium No. 3.

Redox reactions.

Practical application in titrimetry. Instrumental methods of analysis.

Redox reactions. Reversible redox systems and their potentials. Equilibrium electrode potential. Nernst equation. Standard and formal redox potentials. Influence of various factors on the formal potential: pH of the solution, ionic strength of the solution, processes of complex formation and precipitation, concentration of complexing substances and precipitants. The equilibrium constant of redox reactions and the direction of redox reactions.

Redox titration. Construction of titration curves. Methods for fixing the end point of the titration in redox titration. Methods: permanganometric, iodometric, dichromatometric.

Spectroscopic methods of analysis. The main characteristics of electromagnetic radiation (wavelength, frequency, wave number, intensity). Spectra of atoms. Methods of atomic emission and atomic absorption spectroscopy. Spectra of molecules. The Bouguer-Lambert-Beer law.

Methods for determining the concentration of substances. Spectrophotometric and luminescent methods.

Electrochemical methods. Electrochemical cell, indicator electrode and reference electrode. Ionometry, potentiometric titration.

Coulometry: direct and coulometric titration; Faraday's law.

Classical voltammetry. Conductometry: direct and conductometric titration, on-line control options.

Literature

1. Fundamentals of analytical chemistry. In 2 vols. P / ed. Yu.A.Zolotova. M.: Higher. school, 2000.

2. Fundamentals of analytical chemistry. Practical guide. P / ed. Yu.A.Zolotova.

M.: Higher. school, 2001.

3. Methods for detecting and separating elements. Practical guide.

P / ed. I.P. Alimarina. M.: MGU, 1984.

4. Belyavskaya T.A. A practical guide to gravimetry and titrimetry. M.:

5. Dorokhova E.N., Nikolaeva E.R., Shekhovtsova T.N. Analytical chemistry (guidelines). M.: MGU, 1988.

6. Handbook on analytical chemistry. P / ed. I.P. Alimarin and N.N. Ushakova. M.: MGU, 1975.

7. Ushakova N.N. Course of analytical chemistry for soil scientists. M.: MSU, 1984.

8. Dorohova E.N., Prokhorova G.V. Tasks and questions in analytical chemistry. M.:

Mir, 1984 or M.: Academservice, 1997.

– – –

1. Analytical reactions of group I cations.

Reactions of potassium ions.

1. Sodium hydrogen tartrate NaHC4H4O6. Add 3-4 drops of NaHC4H4O6 solution to 3-4 drops of K+ salt solution in a test tube. Stir the contents of the test tube with a glass rod; White crystalline precipitate of potassium hydrotartrate is soluble in hot water, in strong acids, alkalis, insoluble in acetic acid.

2. Sodium hexanitrocobaltate Na3. To a drop of K+ salt solution at pH 4-5 add 1-2 drops of the reagent and, if the precipitate does not immediately precipitate, let the solution stand or slightly heat it in a water bath. A bright yellow crystalline precipitate precipitates, soluble in strong acids but insoluble in acetic acid. Under the action of alkalis, the precipitate decomposes with the formation of a dark brown precipitate.

3. Microcrystalloscopic reaction with lead hexanitrocuprate Na2PbCu(NO2)6. A drop of K+ salt solution is placed on a glass slide, a drop of Na2PbCu(NO2)6 solution ("K+ reagent") is placed next to it, and the drops are connected with a glass rod. Let stand, after which the formed cubic crystals are examined under a microscope.

4. Flame coloring. Volatile salts of K + (eg KCl) color the flame of the burner in a pale violet color. In a direct vision spectroscope, a dark red line is observed at 769 nm. It is better to view the flame through a blue glass or indigo solution - under these conditions, potassium can be detected in the presence of sodium, because. blue glass or indigo solution absorbs the yellow color of sodium.

Reactions of sodium ions.

1. Potassium antimonate K. To 2-3 drops of Na+ salt solution add 2-3 drops of K solution and rub the walls of the tube with a glass rod while cooling the tube under running water. Leave the solution for some time and make sure that the precipitate is crystalline: after closing the test tube with a rubber stopper, it is turned over. Large cubic crystals will be visible on the walls. The precipitate decomposes under the action of acids, dissolves in alkalis.

The reaction is insensitive.

2. Microcrystalloscopic reaction with zincuranyl acetate Zn(UO2)3(CH3COO)8. A drop of Na+ salt solution is placed on a glass slide, a drop of Zn(UO2)3(CH3COO)8 solution is placed next to it, and the drops are connected with a glass rod. Let stand and examine the formed crystals under a microscope.

3. Flame coloring. Volatile Na+ salts (eg NaCl) turn the burner flame yellow. In a direct vision spectroscope, a yellow line is observed at 590 nm.

Reactions of ammonium ions.

1. Strong alkalis. The reaction is carried out in a gas chamber. A glass cylinder is placed on a glass slide, inside which 1-2 drops of NH4 + salt solution and 1-2 drops of 2 M NaOH or KOH solution are added, making sure that the alkali solution does not get on the upper edge of the cylinder. Cover the cylinder with another glass slide, attaching wet indicator paper (universal indicator or litmus) or filter paper moistened with Hg2(NO3)2 solution to its inner side. Observe the color change of the indicator paper.

2. Nessler reagent K2. To 1-2 drops of NH4+ salt solution in a test tube add 1-2 drops of Nessler's reagent. An orange precipitate forms.

Reactions of magnesium ions.

1. Strong alkalis. To 2 drops of Mg2+ salt solution add 1-2 drops of NaOH solution. A white amorphous precipitate precipitates, soluble in acids and ammonium salts. The reaction can be used to separate Mg2+ from other group 1 cations, since their hydroxides are soluble in water.

2. Sodium hydrogen phosphate Na2HPO4. To 1-2 drops of Mg2+ salt solution in a test tube add 2-3 drops of 2 M HCl solution and 1-2 drops of Na2HPO4 solution. After that, a 2 M NH3 solution is added dropwise, stirring the contents of the test tube after each drop, until a distinct odor or slightly alkaline reaction with phenolphthalein (pH~9). A white crystalline precipitate precipitates, soluble in strong acids and in acetic acid.

3. Quinalizarin. To 1-2 drops of Mg2+ salt solution add a drop of quinalizarin solution and 2 drops of 30% NaOH solution. A blue precipitate is formed.

4. Microcrystalloscopic reaction. 1 drop of Mg2+ salt solution is placed on a glass slide, a drop of a reagent solution is applied next to it - a mixture of Na2HPO4, NH4Cl, NH3. Drops are connected with a glass rod and the resulting crystals are examined under a microscope.

2. Analytical reactions of group II cations.

Reactions of barium ions.

1. Potassium dichromate K2Cr2O7. To 1-2 drops of Ba2+ salt solution in a test tube add 3-4 drops of CH3COONa solution and 1-2 drops of K2Cr2O7 solution.

A yellow crystalline precipitate of BaCrO4 precipitates, insoluble in acetic acid, soluble in strong acids. The reaction is used to separate Ba2+ ions from other group II cations.

2. Sulfuric acid H2SO4. To 1-2 drops of Ba2+ salt solution add 2-3 drops of dilute sulfuric acid. A white crystalline precipitate forms, insoluble in acids. To bring BaSO4 into solution, it is transferred to BaCO3 by repeatedly treating BaSO4 with a saturated solution of Na2CO3, each time draining the liquid from the precipitate, which is then dissolved in acid.

3. Flame coloring. Volatile Ba2+ salts color the burner flame yellow-green. In the direct vision spectroscope, a group of green lines is observed in the wavelength range of 510-580 nm.

Reactions of calcium ions.

1. Ammonium oxalate (NH4)2C2O4. To 2-3 drops of Ca2+ salt solution add 2-3 drops of (NH4)2C2O4 solution. A white crystalline precipitate precipitates, soluble in strong acids but insoluble in acetic acid.

2. Microcrystalloscopic reaction. A drop of Ca2+ salt solution is applied to a glass slide, a drop of H2SO4 solution (1:4) is placed next to it. Drops are connected with a glass rod, allowed to stand, and the resulting needle-like crystals are examined under a microscope (mainly along the edges of the drop).

3. Flame coloring. Volatile Ca2+ salts color the burner flame brick red. In a direct vision spectroscope, a green line at 554 nm and a red line at 622 nm are observed. The lines are arranged symmetrically with respect to the sodium line at 590 nm.

3. Analytical reactions of group III cations.

Reactions of lead ions.

1. Potassium dichromate K2Cr2O7. To 1-2 drops of Pb2+ salt solution in a test tube add 2-3 drops of 2 M CH3COOH solution, 2-3 drops of CH3COONa solution and 2 drops of K2Cr2O7 solution. A yellow precipitate of PbCrO4 precipitates. Centrifuge, separate the precipitate from the solution, and add 2-3 drops of 2 M NaOH solution to the precipitate.

The precipitate dissolves. This reaction makes it possible to distinguish PbCrO4 from BaCrO4, which is insoluble in NaOH.

2. Hydrochloric acid HCl. To 3-4 drops of a Pb2+ salt solution in a test tube add 3 drops of diluted HCl. A white precipitate precipitates, soluble in alkalis, as well as in an excess of HCl or alkali metal chlorides. PbCl2 is highly soluble in water, especially when heated, which is used to separate it from AgCl and Hg2Cl2.

3. Potassium iodide KI. To 1-2 drops of Pb2+ salt solution in a test tube add 1-2 drops of KI solution. A yellow precipitate falls out. A few drops of water and 2 M CH3COOH solution are added to the test tube, heated, and the precipitate dissolves.

Immerse the test tube in cold water and observe the precipitation of golden crystals ("golden rain").

4. Sulfuric acid H2SO4. 3-4 drops of dilute H2SO4 are added to 2-3 drops of a Pb2+ salt solution, a white precipitate forms, soluble in strong alkali solutions or in concentrated solutions of CH3COONH4 or C4H4O6(NH4)2.

4. Analytical reactions of group IV cations.

Reactions of aluminum ions.

1. Alkalis or ammonia. To 3-4 drops of an Al3+ salt solution, a 2 M alkali solution is carefully added dropwise until a white amorphous precipitate of aluminum hydroxide Al2O3.mH2O is formed. When an excess of alkali is added, the precipitate dissolves. If solid NH4Cl is added and heated, aluminum hydroxide precipitates again.

2. Alizarin red. one). 1 drop of Al3+ salt solution is applied to the filter, touching the paper with the tip of the capillary, 1 drop of alizarin red, and the stain is treated with gaseous ammonia, placing the paper over the opening of the bottle with concentrated ammonia solution. A purple dot appears.

The purple color represents the color of alizarin, which it assumes in an alkaline environment. The paper is carefully dried by holding high above the flame of the burner. In this case, ammonia escapes, and the violet color of alizarin turns into yellow, which does not interfere with the observation of the red color of the aluminum varnish.

The reaction is used for fractional detection of Al3+ in the presence of other cations. To do this, a drop of K4 solution is applied to filter paper, and only then a drop of Al3+ salt solution is placed in the center of the wet spot. Cations interfering with the reaction, for example, Fe3+, form sparingly soluble hexacyanoferrates(II) and thus remain in the center of the spot. Al3+ ions not deposited by K4 diffuse to the periphery of the spot, where they can be detected by reaction with alizarin red in the presence of ammonia.

2). In a test tube, to 1-2 drops of Al3+ salt solution add 2-3 drops of alizarin solution to NH3 solution until alkaline reaction. The contents of the tube are heated in a water bath. A red flocculent precipitate falls out.

3. Aluminon. 1-2 drops of aluminon solution are added to 2 drops of Al3+ salt solution and heated in a water bath. Then NH3 solution is added (until an odor appears) and 2-3 drops of (NH4)2CO3. Red flakes of aluminum lacquer form.

Reactions of chromium(III) ions.

1. Caustic alkalis. To 2-3 drops of Cr3+ salt solution add 2-3 drops of 2 M NaOH solution. A grey-green precipitate is formed. The precipitate is soluble in acids and alkalis.

2. Hydrogen peroxide H2O2. To 2-3 drops of Cr3+ salt solution add 4-5 drops of 2 M NaOH solution, 2-3 drops of 3% H2O2 solution and heat for several minutes until the green color of the solution turns yellow.

The solution is kept for further experiments (detection of CrO42-).

3. Ammonium persulfate (NH4)2S2O8. To 5-6 drops of (NH4)2S2O8 solution add 1 drop of 1 M solution of H2SO4 and AgNO3 (catalyst). 2-3 drops of Cr2(SO4)3 or Cr(NO3)3 solution are introduced into the resulting oxidizing mixture and heated. The solution turns yellow-orange. It is kept for further experiments (Cr2O72-).

4. Sodium ethylenediaminetetraacetate (EDTA). To 3-4 drops of a Cr3+ salt solution add 3-5 drops of a 30% CH3COOH solution, 12-15 drops of an EDTA solution (an excess of EDTA is required), check the pH of the solution (pH 4-5) and heat it in a water bath. In the presence of Cr3+, a violet color appears.

Reactions of Cr(VI) ions.

1. Formation of perchromic acid H2CrO6. 5-6 drops of the chromate solution obtained earlier are placed in a test tube. Excess H2O2 is removed by boiling in a water bath, the test tube is cooled under tap water. A few drops of ether, 1 drop of a 3% solution of H2O2 and, with shaking, H2SO4 (1:4) are added dropwise to the solution. The resulting chromium peroxide compound is extracted with ether, the ether layer turns blue.

Reactions of zinc ions.

1. Caustic alkalis. 2-3 drops of 2 M NaOH solution are added to 2-3 drops of Zn2+ salt solution, a white precipitate is formed, soluble in acids, alkalis and ammonium salts (unlike aluminum hydroxide).

2. Ammonium tetrarhodanomercuriate (NH4)2 forms a white crystalline precipitate of Zn with solutions of Zn2+ salts. Typically, the reaction is carried out in the presence of a small amount of the Co2+ salt. The role of Zn2+ is that the Zn precipitate formed by it accelerates, as a seed, the precipitation of a blue Co precipitate, which in the absence of Zn may not precipitate for hours (the formation of a supersaturated solution).

In a test tube, 1-2 drops of water and 3-4 drops of (NH4)2 are added to 1-2 drops of Co2+ salt. The walls of the test tube are rubbed with a glass rod, and no blue precipitate should appear. Then a drop of Zn2+ salt solution is added to the same tube and the walls are again rubbed with a glass rod. In this case, mixed crystals of both compounds are formed, colored in pale blue or dark blue, depending on the amount of Co2+.

3. Hydrogen sulfide and soluble sulfides. To 1-2 drops of Zn2+ salt solution add 1-2 drops of hydrogen sulfide water (or a drop of Na2S). A white precipitate is formed, soluble in strong acids.

4. Microcrystalloscopic reaction. A drop of Zn2+ salt solution is placed on a glass slide, a drop of reagent (NH4)2 is placed nearby, and the drops are connected with a glass rod. Examine the characteristic dendrites under a microscope.

5. Reactions of group V cations.

Reactions of iron(II) ions.

1. Potassium hexacyanoferrate(III) K3. To 1-2 drops of Fe2+ salt solution add 1-2 drops of reagent solution. A dark blue precipitate ("Prussian Blue") is formed.

Reactions of iron(III) ions.

1. Potassium hexacyanoferrate(II) K4. 1-2 drops of reagent are added to 1-2 drops of Fe3+ salt solution. Observe the formation of a dark blue precipitate "prussian blue".

2. Ammonium (potassium) thiocyanate NH4SCN. To 1-2 drops of Fe3+ salt solution add a few drops of NH4SCN (or KSCN) solution. A dark red color appears.

Reactions of manganese ions.

1. The action of strong oxidizing agents.

but). Lead(IV) oxide PbO2. A little PbO2 powder, 4-5 drops of 6 M HNO3 solution, a drop of Mn2+ salt solution are placed in a test tube and heated. After 1-2 minutes centrifuge and, without separating the precipitate, consider the color of the solution. The solution turns raspberry-violet.

b). Ammonium persulfate (NH4)2S2O8. To 5-6 drops of (NH4)2S2O8 solution add a drop of 2 M H2SO4 solution, 1-2 drops of concentrated H3PO4 (to prevent decomposition of permanganate ions), 1-2 drops of AgNO3 solution (catalyst) and heat. A minimum amount of Mn2+ salt solution is added to the heated oxidizing mixture using a glass spatula, stirred, and a crimson-violet color of the solution is observed.

in). Sodium bismuth NaBiO3. 3-4 drops of 6 M HNO3 solution and 5-6 drops of water are added to 1-2 drops of Mn2+ salt solution, after which a little NaBiO3 powder is added to the solution with a glass spatula. After stirring, centrifuge the excess of the reagent and observe the crimson color of the solution.

2. Pyridylazonaphthol (PAN). To 2-3 drops of Mn2+ salt solution add 5-7 drops of water, 4-5 drops of 0.1% ethanol solution of PAN, NH3 to pH 10 and extract with chloroform. The organic phase turns red.

6. Reactions of group VI cations.

Reactions of cobalt ions.

1. Ammonium (potassium) thiocyanate NH4SCN. To 2-3 drops of Co2+ salt solution add solid NH4SCN (KSCN), solid NH4F to bind Fe3+ into a stable colorless complex, 5-7 drops of isoamyl alcohol and shake.

The isoamyl alcohol layer turns blue.

2. Ammonia NH3. 3-4 drops of NH3 solution are added to 1-2 drops of Co2+ salt solution. A blue precipitate of the basic cobalt salt precipitates, which, with a large excess of NH3, dissolves to form a dirty yellow complex compound.

3. Sodium hydroxide NaOH. 2-3 drops of 2 M large NaOH solution are added to 2-3 drops of Co2+ salt solution, a blue precipitate is formed. The precipitate dissolves in mineral acids.

4. Microcrystalloscopic reaction. A drop of a Co2+ salt solution is placed on a glass slide, a drop of a reagent solution (NH4)2 is placed nearby, the drops are connected with a glass rod, and the formed bright blue crystals are examined under a microscope.

Reactions of nickel ions.

1. Dimethylglyoxime. In a test tube, 1-2 drops of dimethylglyoxime solution and 1-2 drops of 2 M NH3 are added to 1-2 drops of Ni2+ salt solution. A characteristic scarlet-red precipitate falls out.

2. Ammonia NH3. NH3 solution is added dropwise to 1-2 drops of Ni2+ salt solution in a test tube until a blue color solution is formed.

3. Sodium hydroxide NaOH. 2-3 drops of 2 M NaOH solution are added to 2-3 drops of Ni2+ salt solution, a green precipitate, soluble in acids, is formed.

Reactions of copper ions.

1. Ammonia NH3. NH3 solution is added dropwise to 1-2 drops of Cu2+ salt solution. A green precipitate of a basic salt of variable composition precipitates, easily soluble in excess NH3 to form a blue complex compound.

2. Potassium hexacyanoferrate(II) K4. To 1-2 drops of Cu2+ salt solution (pH

7) add 1-2 drops of K4 solution. A red-brown precipitate falls out.

3. Potassium iodide KI. To 2-3 drops of Cu2+ salt solution add 1 drop of 1 M H2SO4 solution and 5-6 drops of 5% KI solution, a white precipitate is formed.

Due to the release of iodine, the suspension has a yellow color.

Reactions of cadmium ions.

1. Hydrogen sulfide or sodium sulfide Na2S. 1 drop of Na2S solution is added to 1-2 drops of Cd2+ salt solution, a yellow precipitate is formed.

2. Diphenylcarbazide. Apply 1 drop of a saturated diphenylcarbazide solution, a drop of Cd2+ salt solution to filter paper and keep it for 2-3 minutes over a concentrated NH3 solution. A blue-violet color appears. In the presence of interfering ions, solid KSCN and KI are preliminarily added to the ethanol solution of diphenylcarbazide.

7. Reactions of anions Reactions of sulfate ions.

1. Barium chloride BaCl2. To 1-2 drops of SO42- solution add 2-3 drops of BaCl2 solution. A white crystalline precipitate forms, insoluble in acids. This precipitate of BaSO4 differs from salts of Ba2+ with all other anions, which is used in the detection of SO42-.

Reactions of carbonate ions.

1. Acids. The reactions are carried out in a gas detector. A little carbonate (dry preparation) or 5-6 drops of CaCO3 solution is placed in a test tube, 5-6 drops of 2 M HCl solution are added. Close the stopper with a gas outlet tube, the second end of which is lowered into a test tube with lime water [saturated solution of Ca (OH) 2] and clouding of the lime water is observed.

Reactions of chloride ions.

1. Silver nitrate AgNO3. To 2-3 drops of Cl- solution add 2-3 drops of AgNO3 solution. A white curd precipitate falls out. AgCl is insoluble in HNO3; dissolves easily under the action of substances capable of binding Ag + into a complex, for example, NH3; (NH4)2CO3 (difference from AgBr, AgI); KCN, Na2S2O3.

Reactions of nitrate ions.

1. Iron(II) sulfate FeSO4. A small FeSO4 crystal is added to a drop of the studied NO3- solution placed on a drip plate or on a watch glass, a drop of a concentrated H2SO4 solution is added, a brown ring appears around the crystal.

2. Aluminum or zinc. In a test tube with 3-4 drops of NO3- solution, add 3-4 drops of 2 M NaOH solution and add 1-2 pieces of metallic aluminum or zinc. The tube is closed not very tightly with cotton wool, on top of which moist red litmus paper is placed and heated in a water bath. Litmus paper turns blue.

3. Diphenylamine (C6H5)2NH. 2-3 drops of a solution of diphenylamine in concentrated H2SO4 are placed on a carefully washed and wiped dry watch glass or in a porcelain cup. (If the solution turns blue, the glass or cup was not clean enough.) A very small amount of the studied NO3- solution is added there at the tip of a clean glass rod and mixed. An intense blue color appears.

Reactions of phosphate ions.

1. Molybdenum liquid ((NH4)2MoO4 solution in HNO3). To 1-2 drops of PO43- solution add 8-10 drops of molybdenum liquid and slightly heat up to 40°C. A yellow crystalline precipitate precipitates, insoluble in HNO3, easily soluble in caustic alkalis and NH3.

III. QUANTITATIVE ANALYSIS

Quantification of a substance is based on a physical measurement of some physical or chemical property of that substance as a function of its mass or concentration. There are many methods for quantitative analysis.

They can be divided into two groups:

1) methods based on direct measurement of the mass of the analyte, that is, based on direct weighing on a balance;

2) indirect methods for determining the mass, based on the measurement of certain properties associated with the mass of the component being determined.

Depending on the properties being measured, methods of quantitative analysis are divided into chemical, physico-chemical and physical. Chemical methods include gravimetry and titrimetry with a visual indication of the end point of the titration.

1. Gravimetric Methods Gravimetry is the simplest and most accurate, although rather lengthy method of analysis. The essence of gravimetry lies in the fact that the determined component of the analyte is isolated either in pure form or in the form of a compound of a certain composition, which is then weighed. Gravimetric methods are divided into distillation methods and precipitation methods. Deposition methods are of the greatest importance. In these methods, the component to be determined is precipitated as a poorly soluble compound, which, after appropriate treatment (separation from solution, washing, drying, or calcination), is weighed. When precipitating, you always need to take some excess of the precipitant. To obtain pure, uniform in dispersion, possibly coarse-grained precipitates (if the substance is crystalline), or well-coagulated precipitates (if the substance is amorphous), a number of rules must be observed. The composition of the substance to be weighed (gravimetric form) must strictly correspond to a certain chemical formula.

Gravimetric determination of sulfuric acid in solution The determination of sulfuric acid or sulfate is based on the formation of a crystalline precipitate of BaSO4 according to the reaction:

SO42- + Ba2+ = BaSO4 Precipitated form - BaSO4. The precipitate is isolated from the heated slightly acidic solution.

The precipitate is calcined at a temperature of about 800 DEG C. (gas burner).

Gravimetric form - BaSO4.

Reagents Hydrochloric acid, HCl, 2 M solution.

Barium chloride, BaCl2. 2H2O, 5% solution.

Silver nitrate, AgNO3, 1% solution.

Nitric acid, HNO3, 2 M solution.

Execution of the definition. The H2SO4 solution received from the teacher in a beaker 300 ml, pre-washed to absolute stackability, is diluted with distilled water to 100-150 ml, 2-3 ml of 2 M HCl is added to the solution, the solution is heated almost to a boil and the calculated volume of barium chloride solution is added dropwise to it from a buret. The amount of precipitant is calculated taking into account a 10% excess. During the addition of the precipitant, the solution is stirred with a glass rod. Allow the sediment to collect at the bottom of the beaker and check the completeness of the precipitation by adding a few drops of the precipitant.

If complete precipitation is not achieved, add a few more milliliters of barium chloride solution. The stick is taken out of the glass, the glass is covered with a watch glass (you can use a blank sheet of paper) and left to stand for at least 12 hours.

Sediment maturation can be accelerated by adding 2–3 ml of a 1% solution of picric acid to the test solution before precipitation. In this case, it is enough to leave the solution with the precipitate before filtering for 1-2 hours in a warm place (for example, in a water bath).

The precipitate is filtered on a "blue tape" filter, first pouring a clear liquid onto the filter and collecting the filtrate in a clean beaker. It is useful to check the first portions of the filtrate for completeness of sedimentation. When most of the clear liquid passes through the filter, and almost all of the sediment remains in the beaker where the precipitation was carried out, the filtrate is poured out and an empty beaker is placed under the funnel. Then the precipitate is transferred to the filter with small portions of cold distilled water from the washer. Particles of sediment adhering to the walls of the glass are removed with a stick with a rubber tip. A piece of wet filter is thoroughly rubbed on a glass rod, and then this piece of filter is placed in a funnel. You can wipe the inside of the glass with a piece of damp filter. When the entire precipitate is transferred to the filter, it is washed on the filter 3-4 times with cold water in portions of 10-15 ml. The last washings are checked for completeness of washing with a solution of AgNO3 in a medium of 2 M HNO3 (only slight opalescence is permissible). Then the funnel with the filter is placed in an oven for several minutes, the filter with sediment is dried, and, bending the edges of the filter towards the center, the slightly damp filter with sediment is placed in a porcelain crucible brought to a constant mass (a clean empty crucible is calcined on the full flame of a gas burner). Insert the crucible into the triangle and, holding it high above the small flame of the burner, dry the filter and char it.

When the charring is over, the burner flame is increased, the triangle with the crucible is lowered, the coal is allowed to burn out, after which the precipitate is calcined on the full flame of the burner for 10-15 minutes. After cooling in a desiccator, the crucible with the precipitate is weighed.

Repeat 10-minute incinerations until constant weight (±0.2 mg) is reached.

Calculate the content of H2SO4 in solution:

– – –

In titrimetric analysis, the amount of chemicals is most often determined by accurately measuring the volumes of solutions of two substances that enter into a certain reaction with each other. In contrast to gravimetry, the reagent is taken in an amount equivalent to the substance to be determined. Methods of titrimetric analysis can be classified according to the nature of the chemical reaction underlying the determination of substances. These reactions are of different types - ion combination reactions and oxidation-reduction reactions. In accordance with this, titrimetric determinations are divided into the following main methods: acid-base titration method, complexometric and precipitation titration methods, redox titration methods.

Some general instructions for work

1. After the burettes or pipettes are thoroughly washed, before filling they should be rinsed (2-3 times 5 ml) with the solution with which they will be filled.

2. Titrate each solution at least three times. The scatter of the results of the three titrations should not exceed 0.1 ml.

3. When determining the volume of a drop, the burette is filled to zero with distilled water, 100 drops are released (the drops should drip evenly at a rate of 2–3 per second) and the volume is noted on the burette (the count is carried out no earlier than 30 s after pouring the water). The resulting volume is divided by 100. The determination is repeated at least three times, each time calculating the volume of the drop to 0.001 ml. The discrepancies between the three determinations should not exceed 0.01 ml.

Calculations in titrimetric analysis Substances react with each other in equivalent quantities (n1 = n2).

Equivalent - a conditional or real particle that can add, release, replace one proton in acid-base reactions or be equivalent to one electron in redox reactions.

If analyte A reacts with titrant B according to the equation:

аА + вВ = cC + dD, then it follows from this equation that one particle A is equivalent to v / a particles of substance B. The ratio v / a is called the equivalence factor and is denoted by fequiv.

For example, for the acid-base reaction H3PO4 + NaOH = NaH2PO4 feq(H3PO4) = 1, and for the reaction:

H3PO4 + 2 NaOH = Na2HPO4 + 2 H2O feq(H3PO4) = 1/2.

In the redox half-reaction:

MnO4- + 8 H+ + 5 e = Mn2+ + 5 H2O feq(KMnO4) = 1/5, but in the half-reaction:

MnO4- + 4 H+ + 3 e = MnO(OH)2 + H2O fequiv(KMnO4) = 1/3.

The molecular weight of the equivalent of a substance is the mass of one mole of the equivalent of this substance, which is equal to the product of the equivalence factor by the molecular weight of the substance.

Since the number of equivalents of substances entering into the reaction is n = cVx10-3, where c is the molar concentration, and V is the volume, then for two stoichiometrically reacting substances the equality is true:

If the molar concentration of one substance is known, then by measuring the volumes of reacting substances, it is possible to calculate the unknown concentration of the second substance.

Molar concentration c is the ratio of the number of moles of a solute to the volume. For example, c(1/2 H2SO4) = 0.1 mol/l or c(1/2 H2SO4) = 0.1 M; this means that 1 liter of the solution contains 6.02.10-23x0.1 conditional particles of 1/2 H2SO4 or 4.9 g of H2SO4 are dissolved in 1 liter.

For example, a Ba(OH)2 solution was standardized against a 0.1280 M HCl solution. Titration of 46.25 ml of acid solution required 31.76 ml of base solution.

Therefore, c(1/2 Ba(OH)2) = (46.25 x 0.1280)/31.76 = 0.1864 M and m = c x M xf equiv = 0.1864 x 171.34 x 1 /2 = 15.97 g/l.

In complexation reactions for a substance, it is rather difficult to define the concept of "molecular weight equivalent". In this case, usually proceed from the stoichiometry of the reaction. For example, in complexometry, regardless of the charge of the cation, the reactions proceed according to the equation Mn2+ + H2Y2- = MY(n - 4)+ + 2 H+, that is, with the formation of complexes with a composition of 1:1. Therefore, for the components involved in this reaction, the molecular weights of the equivalents are equal to the molecular weights.

– – –

Preparation of Primary Standard (Na2CO3) and Working Solutions (0.1 M HCl and 0.1 M NaOH) Na2CO3 is weighed to the nearest 0.0001 g to prepare 250 ml of a 0.1000 M solution. On technical scales in a weighing cup, a close to the calculated amount of Na2CO3 is weighed and the mass of the cup with a sample is specified on an analytical balance. Transfer Na2CO3 through a dry funnel into a volumetric flask. 250 ml, and the glass is weighed on an analytical balance and the sample is found by difference. The funnel is washed with distilled water, soda is dissolved in a small amount of distilled water, after which the solution is brought to the mark and mixed thoroughly. Working solutions - 0.1 M HCl and 0.1 M NaOH - are prepared in bottles containing 2 liters of distilled water, adding calculated amounts of conc. HCl (pl. 1.19) and 2 M NaOH solution, respectively, using a graduated cylinder. The solutions are thoroughly mixed, the bottles are closed with siphons and the label is glued. In the case of a NaOH solution, the siphon is closed with a calcium chloride tube.

Standardization of hydrochloric acid by sodium carbonate The CO32- ion is a base that can sequentially add protons:

CO32- + H+ = HCO3HCO3- + H+ = H2CO3 Acid can be titrated either until HCO3- (NaHCO3) is formed in the solution, or to H2CO3. In the first case, half of the sodium carbonate is titrated, in the second

All sodium carbonate. Naturally, if it is titrated to NaHCO3 (the pH of this solution is 8.34, so the titration is carried out in the presence of phenolphthalein as an indicator), then to calculate the amount of Na2CO3 in the test solution, you need to double the number of milliliters of hydrochloric acid used for titration.

If titrated to H2CO3 (solution pH 4.25), then, using methyl orange as an indicator, titrate all sodium carbonate. Reagents Hydrochloric acid, HCl, 0.1 M solution.

Sodium carbonate, Na2CO3, 0.1 M (1/2 Na2CO3) solution.

Indicator methyl orange, 0.1% aqueous solution.

Execution of the definition. Pour hydrochloric acid solution into a burette.

10 ml of sodium carbonate solution are taken with a pipette, transferred to a conical titration flask, ca. 100 ml, add 20 ml of distilled water and 1 drop of methyl orange and titrate with hydrochloric acid until the color of the solution changes from yellow to orange.

When titrating with methyl orange, it is convenient to use a witness, that is, a solution that has a color to which the test solution should be titrated. To prepare a witness, 40 ml of distilled water, one drop of methyl orange and 1-2 drops of a 0.1 M acid solution are added with a graduated cylinder to a 100 ml conical titration flask until an orange color appears.

Standardization of sodium hydroxide solution with hydrochloric acid Due to the large pH jump on the titration curve and the fact that the equivalence point is pH 7, strong acids can be titrated with strong bases with indicators whose pT values lie at both pH 7 and pH 7.

Reagents Hydrochloric acid, HCl, 0.1 M solution.

Sodium hydroxide, NaOH, 0.1 M solution.

Execution of the definition. 1. Titration with methyl orange. In a burette thoroughly washed and then rinsed with sodium hydroxide solution, sodium hydroxide solution is poured and the burette is closed with a calcium chloride tube. After rinsing the pipette with a solution of hydrochloric acid, 10 ml of this solution is taken with a pipette and transferred to a 100 ml conical titration flask, 20 ml of distilled water, 1 drop of methyl orange are added here with a graduated cylinder and titrated with a sodium hydroxide solution until the color of the solution changes from red through orange to pure yellow. Titrate at least three times. The results of the three titrations should differ from each other by no more than 0.1 ml.

2. Titration with phenolphthalein. 10 ml of hydrochloric acid solution, 2-3 drops of phenolphthalein are placed into a titration flask with a pipette and titrated with sodium hydroxide solution until a pale pink color is stable for 30 s. Titration should be as fast as possible and the solution should not be stirred too vigorously to avoid absorbing CO2 from the air.

Determination of hydrochloric acid Reagents Sodium hydroxide, NaOH, 0.1 M solution.

Indicators: methyl orange, 0.1% aqueous solution; or phenolphthalein, 0.1% solution in 60% ethanol.

Execution of the definition. The solution received from the teacher in a volumetric flask is brought to the mark with distilled water, thoroughly mixed, an aliquot (10 ml) is taken with a pipette and transferred to a conical flask for titration. Add 1-2 drops of an indicator, and titrate with NaOH solution from a burette closed with a calcium chloride tube. until the color of the indicator changes (see "Standardization of sodium hydroxide with hydrochloric acid").

Calculate the HCl content in the solution using the formula:

– – –

Complexometric titration is based on the formation of complexes of metal ions with amino polycarboxylic acids (complexons). Of the numerous aminopolycarboxylic acids, ethylenediaminetetraacetic acid (H4Y) is most commonly used. For this, the dihydrate of its disodium salt Na2H2Y.2H2O (EDTA) is usually used. This salt can be obtained by adding sodium hydroxide to the acid suspension to pH ~ 5. In most cases, a commercial preparation is used to prepare an EDTA solution, and then the solution is standardized. You can also use fixanal EDTA.

The interaction reactions of cations with different charges with EDTA in solution can be represented by the equations:

Ca2+ + H2Y2- = CaY2- + 2 H+ Bi3+ + H2Y2- = BiY- + 2 H+ Th4+ + H2Y2- = ThY + 2 H+ It can be seen that, regardless of the charge of the cation, complexes with a component ratio of 1:1 are formed. Therefore, the molecular weights of the EDTA equivalent and the metal ion to be determined are equal to their molecular weights. The extent of the reaction depends on the pH and the stability constant of the complexonate.

Cations that form stable complexonates, such as Fe(III), can be titrated in acidic solutions. Ions Ca2+, Mg2+ and others, which form relatively less stable complexonates, are titrated at pH 9 and above.

The end point of the titration is determined using metal indicators of chromophore organic substances that form intensely colored complexes with metal ions.

Determination of calcium and magnesium in the joint presence The stability constants of calcium and magnesium complexonates differ by 2 orders of magnitude (the logarithms of the stability constants are 10.7 and 8.7 for calcium and magnesium, respectively, at 20 ° C and an ionic strength of 0.1). Therefore, these ions cannot be titrated separately using only the difference in the stability constants of the complexonates. At pHopt ~ 9 - 10, eriochrome black T is used as a metal indicator. Under these conditions, the amount of calcium and magnesium is determined.

In another aliquot, a pH of 12 is created by introducing NaOH, while magnesium precipitates in the form of hydroxide, it is not filtered, and calcium is determined complexometrically in the solution in the presence of murexide, fluorexone, or calcium, which are metal indicators for calcium. Magnesium is determined by difference.

The method is suitable for determining the hardness of water. Traces of heavy metals are titrated together with calcium and magnesium; therefore, they are masked before titration with potassium cyanide or precipitated with sodium sulfide or sodium diethyldithiocarbamate. Virtually all ions present in water can be masked with potassium cyanide and triethanolamine; alkali metals, calcium and magnesium are not masked.

1.0 ml of 0.0100 M EDTA solution is equivalent to 0.408 mg of Ca;

0.561 mg CaO; 0.243 mg Mg; 0.403 mg MgO.

EDTA reagents, 0.05 M solution.

Ammonia buffer solution pH 10 (67 g NH4Cl and 570 ml 25% NH3 in 1 L solution).

NaOH or KOH, 2 M solutions.

Metal indicators: eriochrome black T; murexide (instead of murexide, fluorexone or calcium can be used), (mixtures with sodium chloride in a ratio of 1:100).

Fulfillment of definition.1. Determination of the amount of calcium and magnesium.

Pipette 10 ml of the analyzed solution from a volumetric flask with a capacity of 100 ml into a conical flask for titration with a capacity of 100 ml, add 2 - 3 ml of a buffer solution with a pH of 10, 15 ml of water, mix and add at the tip of a spatula 20

30 mg of a mixture of Eriochrome Black T and sodium chloride. Stir until complete dissolution of the indicator mixture and titrate with EDTA solution until the color of the solution changes from wine-red to blue.

2. Determination of calcium. Pipette 10 ml of the analyzed solution into a 100 ml conical flask, add 2–3 ml of NaOH or KOH solutions, dilute with water to approximately 25 ml, inject 20–30 mg of indicator mixtures of murexide, fluorexone or calcium with sodium chloride and titrate with EDTA solution until the color of the solution changes from one drop of EDTA solution.

The color change at the end point of the titration depends on the selected metal indicator. When using murexide, the color changes from pink to lilac-violet; when using fluorexone - from yellow with green fluorescence to colorless or pinkish with a sharp decrease in fluorescence intensity; when using calcium - from pale yellow to orange. In the latter case, only a 2 M KOH solution creates an alkaline environment.

3. Determination of magnesium. The volume of titrant used for titration of magnesium is calculated from the difference between the volumes of EDTA used for titration at pH 10 and at pH 12.

a cV MV m= CaO EDTA EDTA k

– – –

2.3. Redox Titrations The methods used are based on redox reactions. They are usually named according to the titrant used, for example, dichromatometry, iodometry, permanganatometry, bromatometry. In these methods, K2Cr2O7, I2, KMnO4, KBrO3, etc. are used as titrated solutions, respectively.

2.3.1. dichromatometry

In dichromatometry, potassium dichromate is the primary standard. It can be prepared by accurately weighing it, as it is easily purified by recrystallization from an aqueous solution and retains a constant concentration for a long time.

In an acidic environment, dichromate is a strong oxidizing agent and is used to determine reducing agents; it itself is reduced to chromium (III):

Cr2O72- + 14 H+ + 6e = 2 Cr3+ + 7 H2O Еo (Cr2O72-/2 Cr3+) = 1.33 V When titrated with potassium dichromate, redox indicators are used - diphenylamine, diphenylbenzidine, etc.

Determination of iron(II)

Titration of iron(II) is based on the reaction:

6 Fe2+ + Cr2O72- + 14 H+ = 6 Fe3+ + 2 Cr3+ + 7 H2O During titration, the concentration of iron(III) ions increases and the potential of the Fe3+/Fe2+ system increases, which leads to premature oxidation of the diphenylamine indicator. If phosphoric acid is added to the titrated solution, the color of the indicator changes dramatically at the end point of the titration.

Phosphoric acid lowers the redox potential of the Fe3+/Fe2+ system, forming a stable complex with iron(III) ions.

Solutions of iron(II) salts often contain iron(III) ions, so iron(III) ions must be reduced before titration. Metals (zinc, cadmium, etc.), SnCl2, H2S, SO2 and other reducing agents are used for reduction.

Reagents Potassium dichromate, K2Cr2O7, 0.05 M (1/6 K2Cr2O7) solution.

Hydrochloric acid, HCl, concentrated c pl. 1.17.

Sulfuric acid, H2SO4, concentrated with a melting point of 1.84.

Phosphoric acid, H3PO4, concentrated with a melting point of 1.7.

Zinc metal, granular.

Diphenylamine indicator, 1% solution in conc. H2SO4.

Execution of the definition. An aliquot of the 10 ml solution is pipetted into a conical titration flask, ca. 100 ml, add 5 ml conc.

Hcl. The flask is closed with a small funnel, 3-4 granules of metallic zinc are added and heated in a sand bath (the reaction should not go very violently) until the solution becomes colorless and the zinc is completely dissolved. Cool under running cold water, add 3-4 ml H2SO4, cool, add 5 ml H3PO4, 15

20 ml of distilled water, 2 drops of diphenylamine solution and titrate with potassium dichromate solution until a blue color appears.

Find content using the formula:

– – –

In a strongly acidic medium, permanganate ions have a high redox potential, reducing to Mn2+, and they are used to determine many reducing agents:

MnO4- + 5 e + 8 H+ = Mn2+ + 4 H2O Eo(MnO4-/Mn2+) = 1.51 V.

When titrating with permanganate, as a rule, indicators are not used, since the reagent itself is colored and is a sensitive indicator: 0.1 ml of a 0.01 M KMnO4 solution colors 100 ml of water in a pale pink color.

A standard solution of Na2C2O4 is prepared either by weighing (accurate to 0.0001 g) or from fixanal. The working solution of KMnO4 is prepared in a bottle containing 2 liters of distilled water by diluting the calculated amount with 1 M solution;

the resulting solution is thoroughly mixed and closed with a siphon with a calcium chloride tube.

Standardization of a solution of potassium permanganate with sodium oxalate The reaction between oxalate ions and permanganate ions is complex and is not described by the often given equation:

5 C2O42- + 2 MnO4- + 16 H+ = 2 Mn2+ + 8 H2O + 10 CO2, although the initial and final products correspond to those given in the written equation. In reality, the reaction proceeds in several stages, and for it to start, at least traces of Mn2+ must be present in the solution:

MnO4- + MnC2O4 = MnO42- + MnC2O4+

The manganate ion in an acidic solution quickly disproportionates:

Mn(VI) + Mn(II) = 2 Mn(IV) Mn(IV) + Mn(II) = 2 Mn(III) where n = 1, 2, 3; they slowly decompose with the formation of Mn(II) and CO2. Thus, until sufficient concentrations of manganese(II) accumulate in the solution, the reaction between MnO4- and C2O42- proceeds very slowly. When the concentration of manganese(II) reaches a certain value, the reaction begins to proceed at a high rate.

Sulfuric acid, H2SO4, 2 M solution.

Execution of the definition. Pour 20 ml of H2SO4 into a 100 ml titration flask and heat to 80-90°C. 10 ml of sodium oxalate solution is added to the hot solution with a pipette and titrated with a permanganate solution, and at the beginning of the titration, the next drop of KMnO4 solution is added only after the color from the previous drop has completely disappeared. Then, increasing the titration speed, titrate until a pale pink color appears, stable for 30 s.

Permanganometric determination of the oxidizability of water (or water extract from the soil) The oxidizability of water or soil is due to the presence of water-soluble organic substances capable of oxidation. The oxidizability of water or water extract from soils is determined by indirect redox titration, for which the excess of the oxidizing agent that has not reacted with organic substances is titrated. So, organic substances are oxidized with permanganate in an acidic medium, an excess of permanganate is reacted with sodium oxalate, and its excess is titrated with potassium permanganate. A noticeable release of manganese(IV) oxide interferes with the direct titration of excess permanganate with a precise volume of sodium oxalate.

Reagents Potassium permanganate, KMnO4, 0.05 M (1/5 KMnO4) solution.

Sodium oxalate, Na2C2O4, 0.05 M (1/2 Na2C2O4) solution.

Sulfuric acid, H2SO4, 1 M solution.

Execution of the definition. An aliquot of the analyzed solution (10 ml) is transferred into a conical titration flask, 20 ml of sulfuric acid is added, heated to 70-80°C, and 10 ml of the KMnO4 standard solution is introduced from the burette. The solution must remain colored. If the solution becomes discolored, another 5 ml of KMnO4 solution should be added. into a heated solution

– – –

where c1 is the concentration of the 1/5 KMnO4 solution, M c2 is the concentration of the 1/2 Na2C2O4 solution, M V1 is the volume of the KMnO4 solution added to the aliquot part, ml, V2 is the volume of the KMnO4 solution used for titration of excess Na2C2O4, ml, V3 is volume of Na2C2O4 standard solution added, ml.

Sometimes oxidizability is expressed in carbon units: 3n(mol)/1000 (g).

– – –

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We are all constantly confronted with chemical analysis. For example, in a clinic or, alas, in a hospital. If you think about it, other examples of analysis will come by themselves. In order for tap water to be potable, its composition is carefully controlled. Determine the acidity of the soil. Assess the blood sugar content of diabetics. And the detection of alcohol vapors in the air exhaled by the driver? What about chlorine control in a swimming pool? All these are examples of important and necessary chemical analyses.

Millions of these tests are being done. In principle, mass tests of this kind can be done by not very qualified people. But under one obvious condition: you need to have the appropriate methods and means for analysis (means here do not mean money at all, but instruments, reagents, utensils, etc.). But methods and means are invented and developed by specialists of a completely different level, analysts. These specialists are trained by the best universities.

The Department of Analytical Chemistry of Moscow State University is one of the most famous centers for such training. But it is also a major scientific center, where very interesting research is being carried out. The department is popular among students of the Faculty of Chemistry. The demand for graduate analysts is very high.

Among the staff of the department is the head of the department, academician Yu.A. Zolotov, Deputy Head, Corresponding Member of the Russian Academy of Sciences O.A. Shpigun, eight more professors. All of them are leading scientists in their fields, well-known specialists. At the department there is the Analytical Center of the Faculty, the All-Russian Environmental Analytical Association, three small enterprises, joint laboratories with instrument-making firms. The department teaches analytical chemistry at 8 faculties.

But the most important, the most interesting thing is the scientific problems solved at the department. Here original methods of chemical analysis are successfully developed, problems of analysis of ecological, biomedical, technical objects are solved. There are a lot of modern devices in the laboratory, which are used by graduate and postgraduate students, and often by undergraduate students, not to mention staff members.

Isn't it interesting to create methods that make it possible to detect harmful elements in natural water, to separate the most complex mixtures of organic compounds into separate components, or to diagnose lung diseases by the composition of exhaled air? Much is being done at the department in the chemical analysis of various kinds of materials, especially semiconductor ones.

Groups of scientists led by young doctors and candidates of sciences work at the forefront of science, in a businesslike, creative, friendly environment.

Head of Department: Academician

The staff of the department includes 80 employees, including 17 doctors and 30 candidates of sciences. The department has six research laboratories and a workshop in analytical chemistry.

About 100 articles are published annually in domestic and international (about 20%) journals, more than 120 abstracts. Employees of the department make presentations (more than 100 per year) at Russian and international (about 30%) conferences.

The course of analytical chemistry at the Faculty of Chemistry is studied in the 3rd-4th semester (2nd year), includes lectures, seminars, practical classes. At the end of the 3rd semester, a test task is submitted, at the end of the course (4th semester) - an exam and the defense of a term paper. According to the results of the rating, it is possible to get an "automatic" - excellent and good.

From the history of the department

In connection with the reform of higher education, on August 13, 1929, a resolution was adopted by the Council of People's Commissars of the USSR on the reorganization of the chemical departments of the physics and mathematics faculties of universities into independent chemistry faculties. In fact, the Faculty of Chemistry was formalized in 1930, and among the first five departments it included the Department of Analytical Chemistry. The head of the department was prof. A.E. Uspensky, who headed the department until 1931. Within the framework of the department, a laboratory of analytical chemistry was formed, headed by Associate Professor E.S. Przhevalsky.

Many outstanding scientists worked at the Department of Analytical Chemistry. Professor K.L. Malyarov, who was engaged in microanalysis back in the recovery period and in the early years of industrialization. Microanalysis was also carried out by E.S. Przhevalsky and V.M. Peshkov. Since 1934, Peshkova began research on the use of new organic reagents in analytical practice (in particular, she developed a method for the quantitative determination of nickel by reaction with dimethylglyoxime). Z.F. Shakhova expanded research on the use of complex compounds in chemical analysis. V.M. Shalfeev conducted research on electroanalysis.

Fully educational and scientific work at the department unfolded after moving in 1953 to a new building. I.P. was invited to head the department. Alimarin. Since 1989 Yu.A. Zolotov. Yu.A. Zolotov is a recognized expert in the field of analytical chemistry and metal extraction. He introduced (1977) the concept of hybrid methods of analysis. In 1972 he was awarded the State Prize for the development of the theory and new physical and chemical methods for the analysis of high-purity metals, semiconductor materials and chemical reagents. In the 1980s, he was the first in the country to develop work on ion chromatography (the most important result was the use of amphoteric amino acids as eluents (1985) and a decrease in the detection limit due to the use
conductometric detector).

Heads of the department:
1929-1931 - prof. A.E. Uspensky
1933-1953 - prof. E.S. Przhevalsky
1953-1989 - acad. I.P. Alimarin
since 1989 - acad. Yu.A.Zolotov

Department laboratories:

concentration laboratory
academician, prof. Yu.A. Zolotov

senior researcher group G.I. Cizina
group of prof. E.I. Morosanova
group of prof. S.G. Dmitrienko
senior researcher group I.V. Pletnev

Chromatography laboratory
corresponding member RAS, prof. O.A. Shpigun

Assoc. E.N. Shapovalova
senior researcher group A.V. Pirogov
senior researcher group A.V. Smolenkov
educational work of the laboratory of chromatography

Laboratory of Spectroscopic Methods of Analysis
d.h.s., prof. M.A. Proskurnin

Assoc. A.G. Borzenko
group of prof. V.M. Ivanova
group of senior researcher N.V. Alova
group of prof. M.A. Proskurnina
Assoc. A.V. Garmash

Laboratory of Electrochemical Methods
d.h.s., prof. A.A. Karyakin

group of prof. A.A. Karjakin
Assoc. A.I. Kamenev
Assoc. N.V. Sweden

Laboratory of Kinetic Methods of Analysis
d.h.s., prof. T.N. Shekhovtsova

group of prof. T.N. Shekhovtsova
senior researcher group M.K. Beklemisheva

Academician Yu.A.Zolotov

ABOUT THE DEPARTMENT OF ANALYTICAL CHEMISTRY

The department was established together with the Faculty of Chemistry in 1929 on the basis of the Laboratory of Organic and Analytical Chemistry of the Faculty of Physics and Mathematics, which existed at Moscow University since 1884. The department was headed by: in 1929 - 1931. - Professor A.E. Uspensky, in 1931-1953. - Professor E.S. Przhevalsky, in 1953-1989. - Academician I.P. Alimarin. Since 1989, the department has been headed by Academician Yu.A. Zolotov.
Currently, the staff of the department has over 80 employees (6 doctors, 42 candidates of sciences).

Prehistory

Chemical analysis was introduced into curricula at least throughout the 19th century. In 1827, a university employee A.A. Iovsky published the book "Chemical Equations with a description of various ways to determine the quantitative content of chemicals." Analytical chemistry before the revolution was taught at the university by outstanding chemists: V.V. Markovnikov, M.M. Konovalov, I.A. Kablukov, N.M. Kizhner, N.A. Shilov, N.D. Zelinsky. However, the training of professional analytical chemists began later, the first thesis in analytical chemistry was defended in 1928 by V.V. Ipatiev.

Scientific service in the field of chemical analysis was carried out from the first years of the existence of Moscow University; the first chemical laboratory opened in 1760. At the end of the 18th century, much attention was paid to the detection and determination of precious metals ("assay chemistry"), then to the analysis of mineral waters (F. Schmidt, 1807-1882). In the second half of the 19th century, analyzes for industry began to be carried out frequently at the university, mainly on orders from Moscow manufacturers.

Of the works of a later period, which can already be considered scientific, it should be noted urine analysis (book by V.S. Gulevich, 1901). After the revolution, a lot of effort was spent on the analysis of chemical reagents, the production of which was being established in the country. These works were carried out for a long time in cooperation with the Institute of Reagents (IREA). The future leading employees of the department, E.S. Przhevalsky, V.M. Peshkova and others. Professor K.L. Malyarov carried out work on microchemistry and analytical hydrochemistry.

At the end of the 20s, when the department was created, analytical chemistry used mainly chemical ("wet") methods - gravimetric (then they were called gravimetric), titrimetric (volumetric), classical methods of gas analysis. On a very small scale, some physicochemical and physical methods were used - conductometry, potentiometry, colorimetry, spectral analysis. True, mass spectroscopy, polarography, micromethods of organic elemental analysis were already known (the Nobel Prize in 1923 to the Austrian scientist F. Pregl), even chromatography, but they were not widely used.

It is very significant that at the end of the last - the beginning of this century the theoretical basis of "solution", "wet" analytical chemistry was formed. The beginning was laid by W. Ostwald in his book (1894) "Scientific Foundations of Analytical Chemistry". This theoretical foundation was based mainly on the doctrine of chemical equilibrium in solutions (the law of action of masses, electrolytic dissociation, solubility product, etc.).

From the history of the department

After the department was formed, the Faculty of Chemistry, the entire university, and the entire system of higher education in the USSR underwent various restructurings and reorganizations for some time. However, in the prewar years, the situation stabilized.

An important place in the department in the pre-war, war and first post-war years was occupied by its head Evgeny Stepanovich Przhevalsky, who for some time was also the dean of the Faculty of Chemistry and director of the Scientific Research Institute of Chemistry of Moscow University, which existed until 1953. Other leading employees and teachers of those times - V.M. Peshkova, N.V. Kostin (also a dean), P.K. Aghasyan. Teaching work was done well, but in the scientific sense, the department, perhaps, did not occupy a leading place at that time.

In 1953, Professor Ivan Pavlovich Alimarin, who later became an academician, was invited to head the department. Under his leadership, and Ivan Pavlovich was in the position of head for 36 years, the department became one of the leading research centers in the field of analytical chemistry.

Academician Alimarin (1903-1989) was the most famous analytical scientist in our country. He contributed to the analysis of mineral raw materials, radiochemical analytical methods, new methods for the separation of substances; paid much attention to organic analytical reagents. IP Alimarin for a long time headed the Scientific Council of the USSR Academy of Sciences on Analytical Chemistry, was the editor-in-chief of the "Journal of Analytical Chemistry", worked in the International Union of Theoretical and Applied Chemistry. Three foreign universities elected the academician as their honorary doctor, he was a foreign member of the Academy of Sciences of Finland (see the book: Ivan Pavlovich Alimarin. Articles. Memories. Materials. M .: Nauka, 1992).

The main directions of scientific work of the department in the 50-80s. - determination of impurities in inorganic substances, including high-purity ones; organic analytical reagents; extraction of metal ions; ion-exchange, then extraction chromatography; polarography, potentiometry; atomic emission analysis, later laser spectrometry, kinetic methods, partly gas analysis.

The works of professors A.I. Buseva, V.M. Peshkova, V.M. Ivanov and others on organic analytical reagents, professors P.K. Aghasyan, associate professors E.N. Vinogradova, Z.A. Gallay on electrochemical methods, associate professor N.I. Tarasevich on spectral analysis. Professor Yu.Ya. Kuzyakov, N.E. Kuzmenko and F.A. Gimelfarb, who headed after N.I. Tarasevich Laboratory of Spectroscopic Methods, brought - each - something new to this area.

Many tutorials and manuals have been published.

Graduates of the department have occupied and continue to occupy leading positions in research institutes, universities, and partly in enterprises of the country; some of the graduates also work abroad.

Analytical chemistry of our days

At present, analytical chemistry as a field of science is no longer just a part of chemistry, it is turning into a large independent mega-discipline. This is mainly due to the powerful expansion of the arsenal of analysis methods, including chemical, physical, biological. A new general theory is being developed, including, for example, the metrology of analysis.

The possibilities of chemical analysis have sharply increased in terms of sensitivity and speed. Many methods allow you to simultaneously determine several dozen components. Analyzes without destroying the analyzed sample, at a great distance, in a stream, at a single microscopic point or on a surface, are becoming common. Mathematization and computerization have significantly expanded the capabilities of known methods and made it possible to create fundamentally new ones.

Analytical chemistry, analytical service solve, or must solve, many vital tasks in the state and society. This is the control of production processes, diagnostics in medicine (blood, urine, etc.), monitoring of environmental objects, meeting the needs of the military, forensics, and archaeologists.

The main areas of research at the department

If we talk about the objects of analysis, about the sphere of application of methods and means of chemical analysis, now environmental objects, primarily water, are in the first place. Many studies of the department are aimed at creating new and effective methods for assessing water quality, methods for determining impurities in natural or waste water. Attention is also paid to other objects - biological, technological and others; for example, methods are being developed for the analysis of semiconductor substances.

Almost all modern methods of analysis are presented at the department. The main methods being developed are sorption and extraction preconcentration of inorganic and organic micro- and ultramicro-components, including methods carried out automatically in a stream; chromatographic methods for the separation of substances and their determination with various detectors, including mass spectrometric (liquid, including ion, gas chromatography); spectroscopic methods of analysis - spectrophotometric in the visible and ultraviolet regions of the spectrum, including the reflective version; luminescent; thermal lens spectrometry, etc.; electrochemical methods, especially voltammetry and direct potentiometry (ion-selective electrodes); kinetic and enzymatic methods.

The department is well equipped. There are more than two hundred instruments in the general workshop, and about a hundred in special workshops. The equipment park of scientific laboratories is very diverse and rich. So, among the spectral instruments are laser installations for thermal lens measurements by Coherent (USA), an electronic spectrometer by Leybold (Germany), X-ray fluorescence analyzers Spark and Spectroscan (Russia), a laser microprobe analyzer LAMMA (Germany), etc. The department has excellent chromatographic equipment, for example capillary gas chromatographs, gas chromatography mass spectrometer, supercritical fluid chromatograph, ion chromatographs of two companies, various liquid chromatographs. At the modern level, there are also electrochemical devices - voltammetric analyzer, polarographs and others, for example, installations for electrochemical research made in the USA and Switzerland. Other instruments for chemical analysis include a supercritical fluid extractor (Italy), a device for capillary electrophoresis (USA) and isotachophoresis (Slovakia-Russia).

Some scientific problems solved at the department

Consider, as an example, several works performed at the department in more detail.

Test methods. For centuries, since the time of the alchemists, chemical analysis has been carried out in laboratories. And now hundreds of thousands, millions of analyzes are carried out in the conditions of analytical laboratories, and now not only chemical ones. However, recently the situation has changed: chemical analysis is gradually moving to the places where the analyzed object is located - in the field, in the workshop, at the airport, at the patient's bedside, even in ordinary apartments. The fact is that there is a huge need for out-of-lab analysis, and that now there are opportunities to create effective tools for such analysis "on the spot". These tools include tools for test methods of chemical analysis.

Test methods of analysis are express, simple and relatively cheap methods for detecting and determining substances, which usually do not require significant sample preparation, the use of complex stationary instruments, laboratory equipment and laboratory conditions in general, and most importantly, do not require qualified personnel.

The department develops purely chemical and enzymatic test methods. Specially selected reactions and reagents are used in "ready" forms - on indicator papers, in the form of tablets, powders, indicator tubes, etc. By the intensity or tone of the color that appears during the analysis, or by the length of the colored layer in the tube, the desired component can be detected and quantified. Not only visual registration is possible, but also using the simplest pocket-type devices.

For example, an exceptionally sensitive enzymatic method for the determination of mercury has been developed, especially in environmental objects. Or you can name a series of works in which indicator tubes are proposed for the determination of other heavy toxic metals in natural and drinking waters. Another simple tool is polyurethane foam (foam rubber) tablets, on which analytical reagents are pre-applied or which can absorb the resulting colored reaction products from solution. The appearance or color change on the tablets is compared with the scale. It is possible to determine phenols, surfactants, a number of metal ions.

Methods for implementing test methods, as already mentioned, are very simple. However, this simplicity does not come cheap: its achievement requires good science to create the appropriate means. Here, as always, the inverse proportionality rule applies: to develop the simplest and most effective test tool, you need to invest maximum creative energy, ingenuity, knowledge, and a lot of money.

New approaches to the determination of organic toxicants in environmental objects. In natural waters, the content of more than a thousand substances is normalized, among which there are many toxic and carcinogenic. If the concentration of a substance is normalized, it must be controlled. This means that there must be reliable methods for such control for all these substances and the appropriate means - instruments, reagents, reference materials, etc. This is an almost unrealistic task - the list of "controlled" components is too long. Indeed, in real practice, the analysis is carried out for a maximum of 100-150 substances, and usually for a smaller number of components.

How to be?

The department develops the idea of changing the very methodology of analysis. It is about abandoning attempts to follow the approach of "each substance - its own methodology" in favor of systematic analysis with a wide use of generalized indicators. For example, such generalized indicators can be the content of organic chlorine, phosphorus or sulfur in the analyzed object. It makes no sense to test water separately for dozens of possible toxic organochlorine compounds, if the primary experiment showed that there is no organic chlorine in the sample at all. New methods of such "gross" analysis are being created, and they are very sensitive.

The best method for the determination of anions. This method is ion chromatography. The department was the first center in the former USSR, where they began to develop this effective method of analysis. Now the relevant laboratory has a large fleet of state-of-the-art ion chromatographs. Accelerated methods are being developed for the simultaneous determination of 10-12 anions, the simultaneous determination of cations and anions in environmental objects, in food products and other samples. A school of specialists in ion chromatography was formed, the first domestic symposium on this method was held, and books were written.

Ion-selective electrodes (ISE). A feature of the department's work in this direction is the creation of ISE for organic substances using complex formation according to the "guest-host" or "key-lock" scheme.

X-ray fluorescent analysis with concentration. RFA is a wonderful method. It allows you to determine simultaneously a large number of elements, with the exception of the elements of the beginning of the periodic system, and without destroying the analyzed sample. But the method is not very sensitive, it is difficult to determine concentrations below 0.01 percent. Sorption preconcentration on cellulose filters comes to the rescue, moreover, complexing atomic groups are grafted onto cellulose. In this case, the detection limits are very significantly reduced, and the method of X-ray fluorescence spectrometry acquires a new sound.

The use of enzymes. Immobilized enzymes are special and very effective analytical reagents: they provide high selectivity of interaction with the components to be determined. Using the peroxidase enzyme, a very sensitive and selective method for the determination of mercury has been developed.

Thermal lens spectroscopy. The setup used in this method takes up a lot of space and is by no means easy to use. However, the efforts to create a setup and maintain it in working condition are quite justified: in comparison with conventional spectrophotometry, the limits of detection of substances can be reduced by 2-3 orders of magnitude!

Microwave sample preparation and other applications of microwave radiation. It is very interesting that such radiation makes it possible to significantly speed up many slow chemical-analytical reactions. An example is the complex formation reactions of platinum metals: it is known that these metals often form kinetically inert complexes, the substitution of ligands in them is very slow. In the microwave, the picture changes dramatically; this is of great importance for the practice of analysis.

Educational and methodical work

The staff of the department teaches analytical chemistry to students of the chemical, geological, geographical, biological, soil faculties, the faculty of fundamental medicine, the Higher Chemical College of the Russian Academy of Sciences, the Higher College of Materials Sciences, as well as students of schools with a chemical bias. This is a huge and very responsible job, excellent teachers who know their job have grown up on it, among them there are many young ones. The workshop in analytical chemistry is one of the best at the Faculty of Chemistry, students are interested in completing numerous educational tasks, term papers, and participating in the annual Olympiads in analytical chemistry. During the year, about a thousand students of chemical and related faculties pass through the general practicum, more than fifty students of the 4th and 5th courses of the chemical faculty go through special practicums.

The general course of analytical chemistry, given to 2nd year students of the Faculty of Chemistry, is accompanied by seminars and extensive, rich and very interesting laboratory work. In 1999, the second edition of a two-volume textbook written by the staff of the department - "Fundamentals of Analytical Chemistry" was published. A variety of manuals, manuals, problem books are constantly published.

Many chemistry students choose analytical chemistry as their area of specialization; in terms of the number of accepted students, the department occupies one of the first places in the faculty (from 20 to 40 third-year students annually). The training of analysts includes listening to a large number of special courses, performing practical work, speaking at seminars and conferences. Students receive good training in the methods of concentration of substances, in spectroscopic, electrochemical, chromatographic and other methods of analysis, get acquainted in detail with the metrology of chemical analysis, listen to lectures on general issues of analytical chemistry.

Every year, 10-15 graduates of Moscow State University and other universities enter the postgraduate course of the department. Special courses are taught for graduate students, including elective courses.

The department annually awards graduate students and students with an award or scholarship named after I.P. Alimarina.

External relations of the department

The department closely cooperates with the institutes of the Russian Academy of Sciences, especially with the Institute of General and Inorganic Chemistry. N.S. Kurnakov and the Institute of Geochemistry and Analytical Chemistry. IN AND. Vernadsky. In 1996, the Scientific and Educational Center for Analytical Chemistry of the Moscow State University was established. M.V. Lomonosov and the Russian Academy of Sciences; the center is based at the department.

The department is also the base of the All-Russian Environmental Analytical Association "Ecoanalytics"; through the association, numerous contacts are made in the field of analysis of environmental objects. The department, for example, actively participated in the implementation of projects under the program "Ecological Safety of Russia" and other environmental programs, and is one of the organizers of all-Russian conferences on the analysis of environmental objects.

Numerous joint scientific works are being carried out with a number of industry research institutes and universities in Russia. So, for example, for a long time the department has been closely cooperating with NPO Burevestnik (St. Petersburg) in the field of X-ray spectral and electrochemical equipment.

International relations are carried out in several directions. There are joint research projects carried out within the framework of the INTAS program, as well as on the basis of bilateral agreements. Contracts are being implemented with instrument-making firms, as a result of which the department gets the opportunity to have modern instruments without buying them. We can name contacts with Carlo Erba (Italy) and Biotronik (Germany) in the field of chromatography and chromato-mass spectrometry, with Milestone (Italy) in the field of microwave technology, with Intertech (USA) by spectroscopic instruments.

In 1995, the department held the V International Symposium on Kinetic Methods of Analysis, in 1997 - the International Congress on Analytical Chemistry.

ZOLOTOV YURI ALEKSANDROVICH (b. 1932). Head of the Department of Analytical Chemistry (since 1989), Full Member of the Russian Academy of Sciences (1987), Professor (1970), Doctor of Chemical Sciences (1966). Director of the Institute of General and Inorganic Chemistry of the Russian Academy of Sciences (since 1989), Head of the Laboratory of Analytical Chemistry of Platinum Metals of this Institute. President of the Russian Chemical Society. DI. Mendeleev (1991-1995).

Areas of scientific research. Extraction of inorganic compounds, concentration of trace elements, flow analysis, test methods of analysis. Methodological problems of analytical chemistry.

Major scientific achievements. Developed the theory of extraction of metal chelates and complex acids; discovered, investigated and put into practice the phenomenon of suppression of the extraction of one element by another; proposed a number of new effective extractants; created a large number of extraction methods for the separation of complex mixtures of elements for the purposes of analytical chemistry and radiochemistry. Developed a general methodology for the concentration of trace elements, proposed a number of concentration methods and used them in the analysis of high purity substances, geological objects and environmental objects; together with employees created new sorbents for concentration purposes. Introduced the concept of hybrid methods of analysis (1975), developed a large number of such methods. He formed a broad scientific direction - the creation of test methods and appropriate means of chemical analysis. Organized research on ion chromatography and flow-injection analysis.

The head of the department is a member of several international organizations, was or is a member of the editorial boards of major international journals in analytical chemistry, and is invited as a speaker at international conferences.