Nazira Mukhanbetova - Academia.edu (original) (raw)

Papers by Nazira Mukhanbetova

Л.Н. Гумилев атындағы Еуразия ұлттық университетінің хабаршысы, 2018

The study programs for scientific and technical degrees include classroom theoretical teaching, a... more The study programs for scientific and technical degrees include classroom theoretical teaching, analysis and resolution of real exercises, and some more practical teaching in the laboratory. The laboratory teaching focuses on the application of the theoretical concepts and principles to practical cases, in order to complement the theoretical classes and to reinforce the understandability of the main theoretical concepts.

This laboratory manual provides a one semester survey of basic analytical laboratory techniques, ... more This laboratory manual provides a one semester survey of basic analytical laboratory techniques, chemical methods of analysis and approaches to data analysis used in quantitative analytical chemistry. The new edition of the lab manual emphasises chemical principles as well as laboratory techniques. The manual helps students understand the timing and situations for the various techniques. Each experiment is presented with concise objectives, a comprehensive list of techniques, and detailed lab intros and step-by-step procedures. This is done in the introductory section of the manual, the individual lab introductions, and through extension questions requiring research about traditional, more hazardous experimental methods. Experimental laboratory manual is intended for students of specialties like «Food technology»,«Technology of processing production», and «Biotechnology».

EXPERIMENTAL LABORATORY MANUAL on discipline ANALYTICAL CHEMISTRY CHEMICAL METHODS OF ANALYSIS: TITRIMETRY and GRAVIMETRY (part 1), 2019

This laboratory manual provides a one semester survey of basic analytical laboratory techniques, ... more This laboratory manual provides a one semester survey of basic analytical laboratory techniques, chemical methods of analysis and approaches to data analysis used in quantitative analytical chemistry. The new edition of the lab manual emphasises chemical principles as well as laboratory techniques. The manual helps students understand the timing and situations for the various techniques. Each experiment is presented with concise objectives, a comprehensive list of techniques, and detailed lab intros and step-by-step procedures. This is done in the introductory section of the manual, the individual lab introductions, and through extension questions requiring research about traditional, more hazardous experimental methods. Experimental laboratory manual is intended for students of specialties like «Food technology»,«Technology of processing production», and «Biotechnology».

Refractometry method, 2018

Determination of sugar content

EXPERIMENTAL LABORATORY MANUAL by discipline GENERAL CHEMISTRY for students of technical specialties, 2015

The study programs for scientific and technical degrees include classroom theoretical teaching, a... more The study programs for scientific and technical degrees include classroom theoretical teaching, analysis and resolution of real exercises, and some more practical teaching in the laboratory. The laboratory teaching focuses on the application of the theoretical concepts and principles to practical cases, in order to complement the theoretical classes and to reinforce the understandability of the main theoretical concepts.

BULLETIN of the L.N. Gumilyov Eurasian National University. PEDAGOGY. PSYCHOLOGY. SOCIOLOGY Series, 2018

Purposes of Lab2: 1) Study the main methods of Gravimetry Analysis and the basic operations such ... more Purposes of Lab2: 1) Study the main methods of Gravimetry Analysis and the basic operations such as filtration, precipitation, drying, heating 2) Learn about the components, characteristics and best uses for the most common varieties of flour. 3) Determination of moisture of wheat flour based on air-oven method 4) Determination of alcoholic acidity of wheat flour based on acid-base titrimetry method Gravimetry based on measurement of weight of an analysed species or a compound containing the analysed species. Measuring mass is the most fundamental of all analytical measurements, and gravimetry is unquestionably the oldest analytical technique. Using Mass as a Signal: There are two ways to use mass as an analytical signal. We can, of course, measure an analyte's mass directly by placing it on a balance and recording its mass. For example, determination of the total suspended solids in water released from a sewage-treatment facility. Suspended solids are just that; solid matter that has yet to settle out of its solution matrix. The analysis is easy. A sample collects and passes it through a preweighed filter that retains the suspended solids. After drying to remove any residual moisture, the filter weighs. The difference between the filter's original mass and final mass gives the mass of suspended solids. It is a direct analysis because the analyte itself is the object being weighed. If the signal is the mass of a precipitate, the method calls precipitation gravimetry. Sometimes it is easier to remove the analyte and use a change in mass as the analytical signal. If thermal or chemical energy is used to remove a volatile species, the method calls volatilization gravimetry. For example, determine a food's moisture content by a direct analysis. One possibility is to heat a sample of the food to a temperature at which the water in the sample vaporizes. If we capture the vapor in a preweighed absorbent trap, then the change in the absorbent's mass provides a direct determination of the amount of water in the sample. An easier approach, however, is to weigh the sample of food before and after heating, using the change in its mass as an indication of the amount of water originally present. This technique calls an indirect analysis since we determine the analyte by a signal representing its disappearance. Volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample. The heating or chemical decomposition separates out any volatile compounds, which results in a change in mass that we can measure. Whether an analysis is direct or indirect, volatilization gravimetry usually requires that we know the products of the decomposition reaction. This is rarely a problem for organic compounds, which typically decompose to form simple gases such as CO 2, H2O, and N2. For an inorganic compound, however, the products often depend on the decomposition temperature. Depending on the method of analysis, the equipment for volatilization gravimetry may be simple or complex. In the simplest experimental design, we place the sample in a crucible and decompose it at a fixed temperature using a Bunsen burner, a Meker burner, a laboratory oven, or a muffle furnace. The sample's mass and the mass of the residue are measured using an analytical balance. Flour is the powdery substance created when a dry grain is pulverized. This is referred to as the milling process. The most common varieties of flour are made from wheat although any grain can be made into flour, including rice, oats, corn or barley. All-purpose flour is made from the endosperm of wheat. This flour is often bleached to give it a clean, white appearance and enriched to include nutrients that are lost due to the removal of the germ and bran. All-purpose flour has a medium balance of starch and protein so that it can be used in a wide variety of products without being too heavy or too delicate.

Teaching Documents by Nazira Mukhanbetova

colorimetric determination of copper ions concentration in solution, 2018

Objective: colorimetric determination of copper ions concentration in solution with ammonium usin... more Objective: colorimetric determination of copper ions concentration in solution with ammonium using photometry analysis At the end of this unit, student should be able to: • Explain the meaning of spectroscopy; • Describe the nature of electromagnetic radiation; • Describe the interaction of radiation with matter; • Distinguish between absorption and emission spectroscopy; • State the different types of spectroscopy; and • Work on optical apparatus like photometer and determine concentration of ions in solution Many analytical techniques used in food chemistry are based on interaction between analyte and light. It can be change of colour or intensity of light, emission, luminescence, fluorescence, change of rotation of polarised light or light scattering. Electromagnetic radiation, or light, is a form of energy whose behavior is described by the properties of both waves and particles. The optical properties of electromagnetic radiation, such as diffraction, are explained best by describing light as a wave. Many of the interactions between electromagnetic radiation and matter, such as absorption and emission, however, are better described by treating light as a particle, or photon. The exact nature of electromagnetic radiation remains unclear, as it has since the development of quantum mechanics in the first quarter of the twentieth century. Nevertheless, the dual models of wave and particle behavior provide a useful description for electromagnetic radiation. Estimation of properties of a solution, e.g. concentration of certain compound, based on absorption of visible spectrum light of a certain wavelength is called photometry. The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 400 to 780 nm.

EXPERIMENTAL LABORATORY MANUAL by discipline GENERAL CHEMISTRY for students of technical specialties, 2015

The study programs for scientific and technical degrees include classroom theoretical teaching, a... more The study programs for scientific and technical degrees include classroom theoretical teaching, analysis and resolution of real exercises, and some more practical teaching in the laboratory. The laboratory teaching focuses on the application of the theoretical concepts and principles to practical cases, in order to complement the theoretical classes and to reinforce the understandability of the main theoretical concepts.

Lecture Notes in General and Inorganic Chemistry Part 2, 2017

In second part of Lecture notes in General and Inorganic Chemistry provides an introduction to th... more In second part of Lecture notes in General and Inorganic Chemistry provides an introduction to the chemistry of inorganic molecules. The emphasis is on basic principles of electrochemistry, redox equilibria, electrolysis and corrosion, properties of important metals and nonmetals.
Written primarily for use as a textbook for a university-level course, the topics covered here provide the fundamental tools necessary for an accomplished engineer.

Lecture Notes in General and Inorganic Chemistry, 2017

Lecture notes in General and Inorganic Chemistry provides an introduction to the chemistry of ino... more Lecture notes in General and Inorganic Chemistry provides an introduction to the chemistry of inorganic molecules. The emphasis is on basic principles of atomic and molecular structure, thermodynamics, chemical kinetics and catalysis, properties of solutions, acid-base equilibria, hydrolysis and buffer solutions, and coordination compounds.
Written primarily for use as a textbook for a university-level course, the topics covered here provide the fundamental tools necessary for an accomplished engineer.
Lecture notes is intended for students of specialty like «Transport, transport equipment and technology», «Machine engineering and Equipment», «Technology of processing production», «Standardization, metrology and certification», «Agriculture and grain processing machines».

EXPERIMENTAL LABORATORY MANUAL on discipline ANALYTICAL CHEMISTRY CHEMICAL METHODS OF ANALYSIS: TITRIMETRY and GRAVIMETRY (part 1), 2019

This laboratory manual provides a one semester survey of basic analytical laboratory techniques, ... more This laboratory manual provides a one semester survey of basic analytical laboratory techniques, chemical methods of analysis and approaches to data analysis used in quantitative analytical chemistry.
The new edition of the lab manual emphasises chemical principles as well as laboratory techniques. The manual helps students understand the timing and situations for the various techniques. Each experiment is presented with concise objectives, a comprehensive list of techniques, and detailed lab intros and step-by-step procedures. This is done in the introductory section of the manual, the individual lab introductions, and through extension questions requiring research about traditional, more hazardous experimental methods. Experimental laboratory manual is intended for students of specialties like «Food technology»,«Technology of processing production», and «Biotechnology».

Refractometry method, 2018

Determination of sugar content

Mohr Method, 2018

Objective: Determination of chloride in solid and liquid samples by the Mohr Method Learning Outc... more Objective: Determination of chloride in solid and liquid samples by the Mohr Method Learning Outcome: • Students understand the terms volumetric analysis, morarity, molality normality and redox titration. • Students acquire the skill to prepare standard solutions of silver nitrate and sodium chloride. • Students understand the apparatus used for a titration. • Students acquire the skill to perform the precicpitation-titration in the real lab after understanding the different steps. Titration is a process by which the concentration of an unknown substance in solution is determined by adding measured amounts of a standard solution that reacts with the unknown. Then the concentration of the unknown can be calculated using the stoichiometry of the reaction and the number of moles of standard solution needed to reach the so called end point. Precipitation titrations are based upon reactions that yield ionic compounds of limited solubility. Classification of methods precipitation titration (on titrant): 1.

Objective: • Determination of table salt content in food by the argentometric titration. Titratio... more Objective: • Determination of table salt content in food by the argentometric titration. Titration is a process by which the concentration of an unknown substance in solution is determined by adding measured amounts of a standard solution that reacts with the unknown. Then the concentration of the unknown can be calculated using the stoichiometry of the reaction and the number of moles of standard solution needed to reach the so called end point. Precipitation titrations are based upon reactions that yield ionic compounds of limited solubility. The most important precipitating reagent is silver nitrate. Titrimetric methods based upon silver nitrate are sometimes termed argentometric methods. The most popular are three methods from this group, named as their inventors: Mohr, Volhard, Fajans. All these methods use AgNO 3 solution of known concentration, the Volhard one also solution of KSCN or NH 4 SCN. The sodium chloride content is determined by the well-known Volhard method. This method uses a back titration with 2 titrants like silver nitrate and potassium thiocyanate to determine the concentration of chloride ions in a solution. Before the titration an excess volume of a silver nitrate solution must be added first, followed by the concentrated HNO 3 , to the solution containing chloride ions, forming a precipitate of silver chloride. This order of addition is critical to ensure complete precipitation of the chlorides. The term 'excess' is used as the moles of silver nitrate added are known to exceed the moles of sodium chloride present in the sample so that all the chloride ions present will react. Ag + (aq) + Cl-(aq)-> AgCl(s) + Ag + (excess) titrant analyte white ppt The indicator Fe 3+ (ferric ion) is then added and the solution is titrated with the potassium thiocyanate solution. The titrate remains pale yellow as the excess (unreacted) silver ions react with the thiocyanate ions to form a silver thiocyanate precipitate. Ag + (excess) + SCN-(aq)-> AgSCN(s) titrant-2 Once all the silver ions have reacted, the slightest excess of thiocyanate reacts with Fe 3+ to form a dark red complex: Fe 3+ (aq) + SCN-(aq)-> [FeSCN] 2+ (aq) ind titrant-2 red complex The concentration of chloride ions is determined by subtracting the titration findings of the moles of silver ions that reacted with the thiocyanate from the total moles of silver nitrate added to the solution. This method is used when the pH of the solution after the sample has been prepared is acidic. If the pH is neutral or basic, Mohr's method or the gravimetric method should be used. The method is illustrated below by using the procedure to determine the concentration of chloride (from sodium chloride) in cheese.

Л.Н. Гумилев атындағы Еуразия ұлттық университетінің хабаршысы, 2018

The study programs for scientific and technical degrees include classroom theoretical teaching, a... more The study programs for scientific and technical degrees include classroom theoretical teaching, analysis and resolution of real exercises, and some more practical teaching in the laboratory. The laboratory teaching focuses on the application of the theoretical concepts and principles to practical cases, in order to complement the theoretical classes and to reinforce the understandability of the main theoretical concepts.

This laboratory manual provides a one semester survey of basic analytical laboratory techniques, ... more This laboratory manual provides a one semester survey of basic analytical laboratory techniques, chemical methods of analysis and approaches to data analysis used in quantitative analytical chemistry. The new edition of the lab manual emphasises chemical principles as well as laboratory techniques. The manual helps students understand the timing and situations for the various techniques. Each experiment is presented with concise objectives, a comprehensive list of techniques, and detailed lab intros and step-by-step procedures. This is done in the introductory section of the manual, the individual lab introductions, and through extension questions requiring research about traditional, more hazardous experimental methods. Experimental laboratory manual is intended for students of specialties like «Food technology»,«Technology of processing production», and «Biotechnology».

EXPERIMENTAL LABORATORY MANUAL on discipline ANALYTICAL CHEMISTRY CHEMICAL METHODS OF ANALYSIS: TITRIMETRY and GRAVIMETRY (part 1), 2019

This laboratory manual provides a one semester survey of basic analytical laboratory techniques, ... more This laboratory manual provides a one semester survey of basic analytical laboratory techniques, chemical methods of analysis and approaches to data analysis used in quantitative analytical chemistry. The new edition of the lab manual emphasises chemical principles as well as laboratory techniques. The manual helps students understand the timing and situations for the various techniques. Each experiment is presented with concise objectives, a comprehensive list of techniques, and detailed lab intros and step-by-step procedures. This is done in the introductory section of the manual, the individual lab introductions, and through extension questions requiring research about traditional, more hazardous experimental methods. Experimental laboratory manual is intended for students of specialties like «Food technology»,«Technology of processing production», and «Biotechnology».

Refractometry method, 2018

Determination of sugar content

EXPERIMENTAL LABORATORY MANUAL by discipline GENERAL CHEMISTRY for students of technical specialties, 2015

The study programs for scientific and technical degrees include classroom theoretical teaching, a... more The study programs for scientific and technical degrees include classroom theoretical teaching, analysis and resolution of real exercises, and some more practical teaching in the laboratory. The laboratory teaching focuses on the application of the theoretical concepts and principles to practical cases, in order to complement the theoretical classes and to reinforce the understandability of the main theoretical concepts.

BULLETIN of the L.N. Gumilyov Eurasian National University. PEDAGOGY. PSYCHOLOGY. SOCIOLOGY Series, 2018

Purposes of Lab2: 1) Study the main methods of Gravimetry Analysis and the basic operations such ... more Purposes of Lab2: 1) Study the main methods of Gravimetry Analysis and the basic operations such as filtration, precipitation, drying, heating 2) Learn about the components, characteristics and best uses for the most common varieties of flour. 3) Determination of moisture of wheat flour based on air-oven method 4) Determination of alcoholic acidity of wheat flour based on acid-base titrimetry method Gravimetry based on measurement of weight of an analysed species or a compound containing the analysed species. Measuring mass is the most fundamental of all analytical measurements, and gravimetry is unquestionably the oldest analytical technique. Using Mass as a Signal: There are two ways to use mass as an analytical signal. We can, of course, measure an analyte's mass directly by placing it on a balance and recording its mass. For example, determination of the total suspended solids in water released from a sewage-treatment facility. Suspended solids are just that; solid matter that has yet to settle out of its solution matrix. The analysis is easy. A sample collects and passes it through a preweighed filter that retains the suspended solids. After drying to remove any residual moisture, the filter weighs. The difference between the filter's original mass and final mass gives the mass of suspended solids. It is a direct analysis because the analyte itself is the object being weighed. If the signal is the mass of a precipitate, the method calls precipitation gravimetry. Sometimes it is easier to remove the analyte and use a change in mass as the analytical signal. If thermal or chemical energy is used to remove a volatile species, the method calls volatilization gravimetry. For example, determine a food's moisture content by a direct analysis. One possibility is to heat a sample of the food to a temperature at which the water in the sample vaporizes. If we capture the vapor in a preweighed absorbent trap, then the change in the absorbent's mass provides a direct determination of the amount of water in the sample. An easier approach, however, is to weigh the sample of food before and after heating, using the change in its mass as an indication of the amount of water originally present. This technique calls an indirect analysis since we determine the analyte by a signal representing its disappearance. Volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample. The heating or chemical decomposition separates out any volatile compounds, which results in a change in mass that we can measure. Whether an analysis is direct or indirect, volatilization gravimetry usually requires that we know the products of the decomposition reaction. This is rarely a problem for organic compounds, which typically decompose to form simple gases such as CO 2, H2O, and N2. For an inorganic compound, however, the products often depend on the decomposition temperature. Depending on the method of analysis, the equipment for volatilization gravimetry may be simple or complex. In the simplest experimental design, we place the sample in a crucible and decompose it at a fixed temperature using a Bunsen burner, a Meker burner, a laboratory oven, or a muffle furnace. The sample's mass and the mass of the residue are measured using an analytical balance. Flour is the powdery substance created when a dry grain is pulverized. This is referred to as the milling process. The most common varieties of flour are made from wheat although any grain can be made into flour, including rice, oats, corn or barley. All-purpose flour is made from the endosperm of wheat. This flour is often bleached to give it a clean, white appearance and enriched to include nutrients that are lost due to the removal of the germ and bran. All-purpose flour has a medium balance of starch and protein so that it can be used in a wide variety of products without being too heavy or too delicate.

colorimetric determination of copper ions concentration in solution, 2018

Objective: colorimetric determination of copper ions concentration in solution with ammonium usin... more Objective: colorimetric determination of copper ions concentration in solution with ammonium using photometry analysis At the end of this unit, student should be able to: • Explain the meaning of spectroscopy; • Describe the nature of electromagnetic radiation; • Describe the interaction of radiation with matter; • Distinguish between absorption and emission spectroscopy; • State the different types of spectroscopy; and • Work on optical apparatus like photometer and determine concentration of ions in solution Many analytical techniques used in food chemistry are based on interaction between analyte and light. It can be change of colour or intensity of light, emission, luminescence, fluorescence, change of rotation of polarised light or light scattering. Electromagnetic radiation, or light, is a form of energy whose behavior is described by the properties of both waves and particles. The optical properties of electromagnetic radiation, such as diffraction, are explained best by describing light as a wave. Many of the interactions between electromagnetic radiation and matter, such as absorption and emission, however, are better described by treating light as a particle, or photon. The exact nature of electromagnetic radiation remains unclear, as it has since the development of quantum mechanics in the first quarter of the twentieth century. Nevertheless, the dual models of wave and particle behavior provide a useful description for electromagnetic radiation. Estimation of properties of a solution, e.g. concentration of certain compound, based on absorption of visible spectrum light of a certain wavelength is called photometry. The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 400 to 780 nm.

EXPERIMENTAL LABORATORY MANUAL by discipline GENERAL CHEMISTRY for students of technical specialties, 2015

The study programs for scientific and technical degrees include classroom theoretical teaching, a... more The study programs for scientific and technical degrees include classroom theoretical teaching, analysis and resolution of real exercises, and some more practical teaching in the laboratory. The laboratory teaching focuses on the application of the theoretical concepts and principles to practical cases, in order to complement the theoretical classes and to reinforce the understandability of the main theoretical concepts.

Lecture Notes in General and Inorganic Chemistry Part 2, 2017

In second part of Lecture notes in General and Inorganic Chemistry provides an introduction to th... more In second part of Lecture notes in General and Inorganic Chemistry provides an introduction to the chemistry of inorganic molecules. The emphasis is on basic principles of electrochemistry, redox equilibria, electrolysis and corrosion, properties of important metals and nonmetals.
Written primarily for use as a textbook for a university-level course, the topics covered here provide the fundamental tools necessary for an accomplished engineer.

Lecture Notes in General and Inorganic Chemistry, 2017

Lecture notes in General and Inorganic Chemistry provides an introduction to the chemistry of ino... more Lecture notes in General and Inorganic Chemistry provides an introduction to the chemistry of inorganic molecules. The emphasis is on basic principles of atomic and molecular structure, thermodynamics, chemical kinetics and catalysis, properties of solutions, acid-base equilibria, hydrolysis and buffer solutions, and coordination compounds.
Written primarily for use as a textbook for a university-level course, the topics covered here provide the fundamental tools necessary for an accomplished engineer.
Lecture notes is intended for students of specialty like «Transport, transport equipment and technology», «Machine engineering and Equipment», «Technology of processing production», «Standardization, metrology and certification», «Agriculture and grain processing machines».

EXPERIMENTAL LABORATORY MANUAL on discipline ANALYTICAL CHEMISTRY CHEMICAL METHODS OF ANALYSIS: TITRIMETRY and GRAVIMETRY (part 1), 2019

This laboratory manual provides a one semester survey of basic analytical laboratory techniques, ... more This laboratory manual provides a one semester survey of basic analytical laboratory techniques, chemical methods of analysis and approaches to data analysis used in quantitative analytical chemistry.
The new edition of the lab manual emphasises chemical principles as well as laboratory techniques. The manual helps students understand the timing and situations for the various techniques. Each experiment is presented with concise objectives, a comprehensive list of techniques, and detailed lab intros and step-by-step procedures. This is done in the introductory section of the manual, the individual lab introductions, and through extension questions requiring research about traditional, more hazardous experimental methods. Experimental laboratory manual is intended for students of specialties like «Food technology»,«Technology of processing production», and «Biotechnology».

Refractometry method, 2018

Determination of sugar content

Mohr Method, 2018

Objective: Determination of chloride in solid and liquid samples by the Mohr Method Learning Outc... more Objective: Determination of chloride in solid and liquid samples by the Mohr Method Learning Outcome: • Students understand the terms volumetric analysis, morarity, molality normality and redox titration. • Students acquire the skill to prepare standard solutions of silver nitrate and sodium chloride. • Students understand the apparatus used for a titration. • Students acquire the skill to perform the precicpitation-titration in the real lab after understanding the different steps. Titration is a process by which the concentration of an unknown substance in solution is determined by adding measured amounts of a standard solution that reacts with the unknown. Then the concentration of the unknown can be calculated using the stoichiometry of the reaction and the number of moles of standard solution needed to reach the so called end point. Precipitation titrations are based upon reactions that yield ionic compounds of limited solubility. Classification of methods precipitation titration (on titrant): 1.

Objective: • Determination of table salt content in food by the argentometric titration. Titratio... more Objective: • Determination of table salt content in food by the argentometric titration. Titration is a process by which the concentration of an unknown substance in solution is determined by adding measured amounts of a standard solution that reacts with the unknown. Then the concentration of the unknown can be calculated using the stoichiometry of the reaction and the number of moles of standard solution needed to reach the so called end point. Precipitation titrations are based upon reactions that yield ionic compounds of limited solubility. The most important precipitating reagent is silver nitrate. Titrimetric methods based upon silver nitrate are sometimes termed argentometric methods. The most popular are three methods from this group, named as their inventors: Mohr, Volhard, Fajans. All these methods use AgNO 3 solution of known concentration, the Volhard one also solution of KSCN or NH 4 SCN. The sodium chloride content is determined by the well-known Volhard method. This method uses a back titration with 2 titrants like silver nitrate and potassium thiocyanate to determine the concentration of chloride ions in a solution. Before the titration an excess volume of a silver nitrate solution must be added first, followed by the concentrated HNO 3 , to the solution containing chloride ions, forming a precipitate of silver chloride. This order of addition is critical to ensure complete precipitation of the chlorides. The term 'excess' is used as the moles of silver nitrate added are known to exceed the moles of sodium chloride present in the sample so that all the chloride ions present will react. Ag + (aq) + Cl-(aq)-> AgCl(s) + Ag + (excess) titrant analyte white ppt The indicator Fe 3+ (ferric ion) is then added and the solution is titrated with the potassium thiocyanate solution. The titrate remains pale yellow as the excess (unreacted) silver ions react with the thiocyanate ions to form a silver thiocyanate precipitate. Ag + (excess) + SCN-(aq)-> AgSCN(s) titrant-2 Once all the silver ions have reacted, the slightest excess of thiocyanate reacts with Fe 3+ to form a dark red complex: Fe 3+ (aq) + SCN-(aq)-> [FeSCN] 2+ (aq) ind titrant-2 red complex The concentration of chloride ions is determined by subtracting the titration findings of the moles of silver ions that reacted with the thiocyanate from the total moles of silver nitrate added to the solution. This method is used when the pH of the solution after the sample has been prepared is acidic. If the pH is neutral or basic, Mohr's method or the gravimetric method should be used. The method is illustrated below by using the procedure to determine the concentration of chloride (from sodium chloride) in cheese.