The measurement of pH is one of the most widely performed tests in laboratories and industries. This is because many physical properties, chemical and biological process are dependent on pH. For example, the following are all influenced by pH:
Solubility of many chemicals
Bio-availablity of drug moelcules
Rates of chemical reactions
Physiological chemistry of living organisms
pH measurement is so common that almost everything we use everyday was tested for pH at one point: the shampoo and soap used to keep our bodies clean, the water used to take shower and to brush teeth, drinks to quench our thirst, food we eat, medicines we take, to name a few.
The most accurate way of measuring pH is by using a pH meter. It is based on the difference of potential between two electrodes, one of them being a reference electrode. An approximate measure of pH may be obtained by using a pH indicator, a substance that changes color around a particular pH value. Universal indicators may also be used. They consist of a mixture of indicators such that there is a continuous color change from about pH 2 to pH 10. They also come in paper form, the universal indicator paper, which is a simple paper that has been impregnated with universal indicator.
A buffer is a solution that maintains its pH after the addition of a small amount of an acid or a base. Buffers are widely used in laboratories since pH influences the rate of many chemical and enzymatic reactions. Buffers and solutions used in pH measurements are usually prepared with high-purity water in order to minimize the risk of contamination from water impurities.
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