Methods of titrimetric analysis are subdivided according to the titration option and according to those chemical reactions that are selected to determine the substance (component). In modern chemistry, quantitative and qualitative analysis are distinguished.
Types of classification
Titrimetric analysis methods are selected for a specific chemical reaction. Depending on the type of interaction, there is a division of titrimetric determination into separate types.
Analysis methods:
- Redox Titration; the method is based on the change in the oxidation state of the elements in the 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 bases (acidimetry) in the desired solution. This method is used to determine substances that react with s alts. Atthe use of organic solvents (acetone, alcohol) made it possible to determine more substances.
Complex formation
What is the essence of the method of titrimetric analysis? It is supposed to determine substances by precipitation of the desired ion as a poorly soluble compound or its binding into a poorly dissociated complex.
Redoximetry
Redox titration is based on reduction and oxidation reactions. Depending on the used titrated reagent solution in analytical chemistry, there are:
- permanganatometry, which is based on the use of potassium permanganate;
- iodometry, which is based on iodine oxidation and iodide reduction;
- bichromatometry, which uses oxidation with potassium dichromate;
- bromatometry based on potassium bromate oxidation.
Redox methods of titrimetric analysis include such processes as cerimetry, titanometry, vanadometry. They involve the oxidation or reduction of ions of the corresponding metal.
By titration method
There is a classification of titrimetric analysis methods depending on the titration method. In the direct variant, the ion to be determined is titrated with the selected reagent solution. The titration process in the substitution method is based on the determination of the equivalence point in the presence ofunstable chemical compounds. Residue titration (reverse method) is used when it is difficult to select an indicator, as well as when the chemical interaction is slow. For example, when determining calcium carbonate, a sample of a substance is treated with an excess amount of a titrated solution of hydrochloric acid.
Analysis Meaning
All methods of titrimetric analysis assume:
- precise determination of the volume of one or each of the reacting chemicals;
- presence of a titrated solution, thanks to which the titration procedure is performed;
- revealing 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 daily practice. Having no idea about the presence of main components and impurities in a raw material or product, it is difficult to plan a technological chain in the pharmaceutical, chemical, and metallurgical industries. Fundamentals of analytical chemistry are applied to complex economic issues.
Research methods in analytical chemistry
This branch of chemistry is the science of determining a component or substance. Fundamentals of titrimetric analysis - 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 during the analytical analysis to identifythe oxidation state in which the component of the substance under study is located. When classifying methods of analytical chemistry, they take into account exactly what action is supposed to be performed. To measure the mass of the resulting sediment, a gravimetric research method is used. When analyzing the intensity of a solution, photometric analysis is necessary. The magnitude of the EMF by potentiometry determines the constituent components of the study drug. Titration curves clearly demonstrate the experiment.
Analytical Methods Division
If necessary, in analytical chemistry, physical-chemical, classical (chemical), as well as physical methods are used. Under chemical methods, it is customary to understand titrimetric and gravimetric analysis. Both methods are classical, proven, and 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) method of analysis is based on determining the volume of the reagent consumed in 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 spectrometry.
Titrimetric study specifics
This section of the analyticalChemistry involves measuring the amount of a reagent that is required to carry out a complete chemical reaction with a known amount of the desired substance. The essence of the technique is that a reagent with a known concentration is added dropwise to a solution of the test substance. Its addition continues until its amount is equivalent to the amount of the analyte reacting with it. This method allows high-speed quantitative calculations in analytical chemistry.
The French scientist Gay-Lusac is considered as the founder of the technique. The substance or element determined in a given sample is called the substance being determined. 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 process of titration consists in adding one solution to another while constantly mixing. A prerequisite for the successful implementation of the titration process is the use of a solution with a specified concentration (titrant). For calculations, the normality of the solution is used, that is, the number of gram equivalents of a substance that is contained in 1 liter of the 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 preparing a titrated solution according toweighed starting material
As the first method of preparing a solution with a given concentration (a certain titer), one can consider dissolving a sample 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 determined from the known mass of the pure compound and from the volume of the prepared 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 long-term storage. For weighing the substances used, bottles with closed lids are used. This method of preparing 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 at 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 the glass ampoules are called fixanals. During the direct experiment, the ampoule with the reagent is broken over a 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.
Titration also uses a specificaction algorithm. The burette is filled with ready-made 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. Add a few drops of indicator 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, which 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 spent solution with a given concentration, draw conclusions 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 must be taken into account, as well as the ability to form insoluble compounds with the substance under study.
