Titrations in Industry
A standard solution is a solution with an accurate known concentration (mol dm-3) of a substance. It is made by dissolving a primary standard in distilled water. A primary standard is a substance with high purity, so that when it is weighed the number is moles calculated in the substance is accurate.
The precise volumes and masses of water and the primary standard should be used and transferred to a volumetric flask. When its concentration has been determined with titration the solution can be used as a standard solution.
Standard solutions can be used to investigate unknown concentrations of chemicals by being titrated against one another. Different solutions differ in light absorbency at certain wavelengths. A sample can be compared to the light absorbency of a standard solution to determine its concentration using Beer’s Law.
In industry, standard solutions may be supplied by a company, or prepared by a technician where they will then be tested to ensure they are accurate before use. An example of a chemical supplier is Sigma-Aldrich. https://www.sigmaaldrich.com/united-kingdom.html
In industry, standard solutions are prepared quickly without observation, unlike our standard solution which was observed and checked by staff to ensure they are accurate and properly made. Industry uses extremely accurate class A glassware and equipment, unlike a school setting which uses class B glassware such as volumetric flasks and pipettes due to expenses. Industry is able to use machines to measure and analyse data, whereas a school setting cannot afford to do so, leaving a large margin for error.
Acid-base titration is an experiment used to determine the unknown volume of a substance. This is done by titrating a known standard solutions against the unknown substance of a different pH until they reach equilibrium. A pH indicator may be added to indicate the end-point with a change of colour.
There are 3 methods of carrying out a volumetric titration
• Direct Titration Method
• Indirect titration Method
• Back Titration Method
A standard solution is placed in a burette and is titrated into the conical flask containing unknown solution. The amount of standard solution needed to reach equilibrium is known as the titrant.
An indicator is a compound that changes colour at a certain pH, indicating when the solutions have reached equilibrium- this is described as the end-point of the reaction. The indicator must have a pH close to the titrations endpoint, and is only needed in small amounts, or else it will affect the pH of the reactants and will lower the accuracy of the experiment.
Acid-base can be used to test unknown concentrations of substances, to test the acidity of foods, identifying amino acids, and test water hardness. Waste Vegetable Oil (WVO) is titrated to determine its acidity so that the appropriate neutralisation can be done by removing free fatty acids (FFA), making it appropriate for use as Biodiesel. FFA makes oil acidic, and reacts with lye (NaOH or KOH) to make soap which prevents all of the lye from reacting with oil to make biodiesel. A lye/FFA titration is performed and phenolphthalein is used to detect the end-point. This tells us how much FFA there is and how much extra lye must be added to complete the reaction.
Redox titrations are based on redox-reduction reactions between oxidising and reducing agents. The end-point is determined using a redox indicator which changes colour, but some redox titrations don’t require an indicator as the reaction itself provides a change in colour.
Redox titrations can be used to determine the amount of a substance in food. An example of this would be iodine molecules reacting with sodium thiosulphate in the presence of starch. This causes iodine to be converted to iodide which shows a colour change of blue/black to white.
Photometric titration involves the formation of a metal complex between the titrant and analyte. This leads to a change in light absorbency in the titrated solution.
Complexometric titration uses colour change as an indication of end-point. It is based on the formation of a complex to detect metal ions. A complex is formed
Titrations in Industry
Industrial titration has the same principal as the titrations performed in task 2. The scale on which they are performed is much higher than that of a college setting.
Automated titration systems are widely used in industry. These systems perform the titration as well as collecting and computing results, meaning there is little need for intervention. This makes the titrations more time effective. Human error is greatly reduced and machines are able to precisely measure the end point, so results are more accurate. Examples of titration machines includes an Automatic, Karl Fischer, Pontentiometric, and Thermometric Titrator. In our task we manually performed our titration using class B glassware (volumetric flasks, pipettes, burette), which is much less accurate than the machines and class A glassware used in industry. Machinery is able to measure the exact end-point of titrations accurately unlike the practical where end-point was detected with a colour change and is read on a burette meaning it depends on an individual’s perspective.