The methods of titrimetric analysis are divided according to the variant of titration and those chemical reactions that are selected to determine the substance (component). In modern chemistry, quantitative and qualitative analysis is distinguished .
Classification Types
The methods of titrimetric analysis are selected for a specific chemical reaction. Depending on the type of interaction, there is a division of the titrimetric determination into separate species.
Analysis Methods:
- Redox titration; the method is based on a change in the oxidation state of elements in a substance.
- Complexation is a complex chemical reaction.
- Acid-base titration involves the complete neutralization of interacting substances.
Neutralization
Acid-base titration allows you to determine the amount of inorganic acids (alkalimetry), as well as calculate the base (acidimetry) in the desired solution. By this method, substances reacting with salts are determined. When using organic solvents (acetone, alcohol), it became possible to determine more substances.
Complexation
What is the essence of titrimetric analysis method? It is assumed that substances are determined by precipitation of the desired ion as a sparingly soluble compound or its binding to a poorly dissociated complex.
Redoximetry
Redox titration is based on reduction and oxidation reactions. Depending on the titrated reagent solution used in analytical chemistry, there are:
- permanganatometry, which is based on the use of potassium permanganate;
- iodometry, which is based on oxidation by iodine, as well as reduction by iodide ions;
- bichromatometry using potassium dichromate oxidation;
- bromatometry based on potassium bromate oxidation.
Redox methods of titrimetric analysis include such processes as cerimetry, titanometry, and vanadometry. They suggest the oxidation or reduction of ions of the corresponding metal.
By titration method
There is a classification of methods of titrimetric analysis depending on the method of titration. In the direct embodiment, the ion being determined is titrated with the selected reagent solution. The titration process in the substitution method is based on determining the equivalence point in the presence of unstable chemical compounds. Residual titration (the inverse method) is used when it is difficult to select an indicator, as well as when the chemical reaction is slow. For example, when determining calcium carbonate, a sample of the substance is treated with an excess of titrated hydrochloric acid solution.
Analysis value
All methods of titrimetric analysis suggest:
- accurate determination of the volume of one or each of the reacting chemicals;
- the presence of a titrated solution, due to which the titration procedure is performed;
- identification of analysis results.
Titration of solutions is the basis of analytical chemistry, so it is important to consider the basic operations performed during the experiment. This section is closely related to everyday practice. Having no idea about the presence in the raw material or product of the main components and impurities, it is difficult to plan the technological chain in the pharmaceutical, chemical, metallurgical industries. Fundamentals of analytical chemistry are used to solve complex economic issues.
Research Methods in Analytical Chemistry
This branch of chemistry is the science of determining the component or substance. The basics of titrimetric analysis are the methods used to conduct the experiment. With their help, the researcher draws a conclusion about the composition of the substance, the quantitative content of individual parts in it. It is also possible in the course of analytical analysis to identify the degree of oxidation in which the component of the substance under study is located. When classifying analytical chemistry methods , it is taken into account which action is supposed to be performed. A gravimetric research method is used to measure the mass of the resulting sediment. When analyzing the intensity of a solution, photometric analysis is required. The magnitude of the EMF by potentiometry determine the components of the study drug. Titration curves clearly demonstrate the experiment.
Analytical Methods Division
If necessary, analytical chemistry uses physicochemical, classical (chemical), as well as physical methods. By chemical methods it is customary to understand titrimetric and gravimetric analysis. Both methods are classic, well-established, widely used in analytical chemistry. The weight (gravimetric) method involves determining the mass of the desired substance or its constituent components, which are isolated in a pure state, as well as in the form of insoluble compounds. The volumetric (titrimetric) analysis method is based on the determination of the volume of reagent spent on a chemical reaction taken in a known concentration. There is a division of chemical and physical methods into separate groups:
- optical (spectral);
- electrochemical;
- radiometric;
- chromatographic;
- mass spectrometric.
Specificity of titrimetric research
This section of analytical chemistry involves measuring the amount of reagent required to carry out a complete chemical reaction with a known amount of the desired substance. The essence of the method is that a reagent with a known concentration is added dropwise to a solution of the test substance. Adding it continues until its amount is equivalent to the amount of the analyte that reacts with it. This method allows quantitative calculations in analytical chemistry to be carried out with high speed.
As the founder of the methodology, the French scientist Gay-Lusac is considered. A substance or element defined in a given sample is called a defined substance. Among them may be ions, atoms, functional groups, bound free radicals. Reagents are gaseous, liquid, solid substances that react with a specific chemical substance. The titration process consists in adding one solution to another with constant mixing. A prerequisite for the successful implementation of the titration process is the use of a solution with a fixed concentration (titrant). For calculations, the normality of the solution is used, that is, the number of gram equivalents of the substance contained in 1 liter of solution. Titration curves are built after calculations.
Chemical compounds or elements interact with each other in well-defined weight quantities corresponding to their gram equivalents.
Options for the preparation of a titrated solution by a weighed portion of the starting material
As the first method for preparing a solution with a given concentration (a certain titer), one can consider dissolving a weighed portion of the exact mass in water or another solvent, as well as diluting the prepared solution to the required volume. The titer of the resulting reagent can be set according to the known mass of the pure compound and the volume of the finished solution. This technique is used to prepare titrated solutions of those chemicals that can be obtained in pure form, the composition of which does not change during prolonged storage. For weighing the substances used, containers with closed covers are used. This method of preparation of solutions is not suitable for substances with increased hygroscopicity, as well as for compounds that enter into chemical interaction with carbon monoxide (4).
The second technology for the preparation of titrated solutions is used in specialized chemical enterprises, in special laboratories. It is based on the use of solid pure compounds weighed in exact quantities, as well as on the use of solutions with a certain normality. Substances are placed in glass ampoules, then they are sealed. Those substances that are inside glass ampoules are called fixals. In a direct experiment, the ampoule with the reagent breaks over the funnel, which has a punching device. Next, the entire component is transferred to a volumetric flask, then by adding water, the required volume of the working solution is obtained.
A certain algorithm of actions is also used for titration. The burette is filled with the finished working solution to the zero mark so that there are no air bubbles in its lower part. Next, the analyzed solution is measured with a pipette, then it is placed in a conical flask. A few drops of the indicator are added to it. Gradually, the working solution is added dropwise to the finished solution from the burette, and the color change is monitored. When a stable color appears that does not disappear after 5-10 seconds, the completion of the titration process is judged. Then they proceed to the calculations, the calculation of the volume of the consumed solution with a given concentration, and conclusions are drawn from the experiment.
Conclusion
Titrimetric analysis allows you to determine the quantitative and qualitative composition of the analyte. This method of analytical chemistry is necessary for various industries, it is used in medicine, pharmaceuticals. When choosing a working solution, its chemical properties, as well as the ability to form insoluble compounds with the studied substance, must be taken into account.