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The Titration Process Titration is a technique for measuring chemical concentrations using a reference solution. Titration involves dissolving a sample using an extremely pure chemical reagent, also known as a primary standards. The titration technique involves the use an indicator that changes color at the endpoint of the reaction to indicate completion. Most titrations are performed in an aqueous solution, however glacial acetic acids and ethanol (in the field of petrochemistry) are used occasionally. Titration Procedure The titration method is well-documented and a proven method of quantitative chemical analysis. It is employed by a variety of industries, such as food production and pharmaceuticals. Titrations can take place manually or with the use of automated equipment. Titration involves adding a standard concentration solution to an unknown substance until it reaches its endpoint or the equivalence. The most common titration is the acid-base titration. These are usually performed to determine the strength of an acid or the concentration of a weak base. To do this, a weak base is converted into its salt and then titrated by an acid that is strong (such as CH3COONa) or an acid that is strong enough (such as CH3COOH). The endpoint is usually identified with an indicator such as methyl red or methyl orange that transforms orange in acidic solutions and yellow in basic or neutral ones. Another titration that is popular is an isometric titration, which is generally used to measure the amount of heat produced or consumed during a reaction. Isometric measurements can be done by using an isothermal calorimeter or a pH titrator which measures the temperature change of a solution. There are a variety of factors that can cause failure of a titration, such as improper handling or storage of the sample, incorrect weighting, irregularity of the sample as well as a large quantity of titrant added to the sample. The best method to minimize these errors is through an amalgamation of user training, SOP adherence, and advanced measures to ensure data integrity and traceability. This will dramatically reduce the chance of errors in workflows, particularly those resulting from the handling of titrations and samples. This is because titrations are typically performed on small volumes of liquid, which makes these errors more obvious than they would be with larger quantities. Titrant The titrant is a solution with a concentration that is known and added to the sample substance to be determined. It has a specific property that allows it to interact with the analyte through an controlled chemical reaction, resulting in the neutralization of the acid or base. The endpoint can be determined by observing the color change, or using potentiometers that measure voltage with an electrode. The volume of titrant dispensed is then used to determine the concentration of the analyte present in the original sample. Titration can be done in a variety of ways, but the majority of the analyte and titrant are dissolved in water. Other solvents, like glacial acetic acid, or ethanol, could be used for special purposes (e.g. the field of petrochemistry, which is specialized in petroleum). The samples should be in liquid form for titration. There are four types of titrations: acid-base, diprotic acid titrations and complexometric titrations as well as redox. In acid-base titrations an acid that is weak in polyprotic form is titrated against a strong base and the equivalence point is determined through the use of an indicator like litmus or phenolphthalein. In laboratories, these types of titrations are used to determine the concentrations of chemicals in raw materials like petroleum-based products and oils. Titration can also be used in manufacturing industries to calibrate equipment as well as monitor the quality of products that are produced. In the food and pharmaceutical industries, titration is used to determine the acidity and sweetness of foods and the amount of moisture contained in drugs to ensure they will last for an extended shelf life. The entire process can be controlled by the use of a the titrator. The titrator will automatically dispensing the titrant, observe the titration process for a visible signal, recognize when the reaction has completed, and then calculate and keep the results. It can detect that the reaction hasn't been completed and prevent further titration. It is simpler to use a titrator instead of manual methods, and requires less training and experience. Analyte A sample analyzer is a system of pipes and equipment that collects a sample from a process stream, conditions the sample if needed and then delivers it to the appropriate analytical instrument. The analyzer is able to test the sample using a variety of principles such as electrical conductivity, turbidity fluorescence or chromatography. A lot of analyzers add reagents into the sample to increase its sensitivity. The results are stored in the log. The analyzer is usually used for liquid or gas analysis. Indicator An indicator is a substance that undergoes an obvious, visible change when the conditions in its solution are changed. The change is usually a color change but it could also be bubble formation, precipitate formation or temperature changes. Chemical indicators are used to monitor and control chemical reactions, including titrations. They are typically found in chemistry labs and are useful for demonstrations in science and classroom experiments. The acid-base indicator is an extremely popular kind of indicator that is used for titrations as well as other laboratory applications. It consists of a weak acid which is combined with a conjugate base. The indicator is sensitive to changes in pH. Both bases and acids have different colors. An excellent indicator is litmus, which changes color to red in the presence of acids and blue in the presence of bases. Other types of indicators include phenolphthalein and bromothymol blue. These indicators are used to observe the reaction between an acid and a base, and they can be very useful in determining the precise equilibrium point of the titration.
Indicators have a molecular form (HIn) and an ionic form (HiN). The chemical equilibrium that is formed between the two forms is influenced by pH which means that adding hydrogen ions pushes the equilibrium toward the molecular form (to the left side of the equation) and gives the indicator its characteristic color. Additionally, adding base shifts the equilibrium to the right side of the equation, away from the molecular acid, and towards the conjugate base, which results in the characteristic color of the indicator. Indicators are most commonly used for acid-base titrations, however, they can also be employed in other types of titrations, like Redox titrations. Redox titrations are a little more complicated, but they have the same principles like acid-base titrations. In a redox test the indicator is mixed with an amount of acid or base in order to adjust them. If the indicator's color changes during the reaction to the titrant, it indicates that the process has reached its conclusion. The indicator is removed from the flask and washed off to remove any remaining titrant. |
