Full Form of PH

PH stands for Potential of Hydrogen. It also stands for the Power of Hydrogen. A scale used to calculate the acidity or basicity of an aqueous solution is known as the pH. The pH values of acidic solutions are lower, while basic or alkaline solutions are higher.

In the beginning, a concentration cell with transference was used to determine the typical values of pH. In this method, the potential difference between a silver chloride electrode and a hydrogen electrode was measured. The pH of the aqueous solution can be measured by using a color-changing indicator or a glass electrode and a pH meter. The pH measurements are helpful in different applications in medicine, chemistry, water treatment, agronomy, etc.

A brief history of PH

  • In 1909, Søren Pender Lauritz Sørensen, a Danish chemist, first introduced pH at the Carlsberg Laboratory, Denmark. Later in 1924, the concept was amended to the modern pH.

Søren Pender Lauritz Sørensen

  • Initially, the H was written as a subscript to the lowercase p, i.e., pH, of the abbreviation.
  • At present, in chemistry, the p stated the “decimal cologarithm of.” It also stated the term pKa, which helps in acid dissociation constants and pOH (an equivalent for hydroxide ions).
  • In pH, the real meaning of p was not described by Sørensen. It is assumed that he used the term for the measurement by using potential differences.
  • As per the French, German, and Danish languages, the meaning of “p” could be puissance, Potenz, and Potens, respectively, which all means the power or potential. It is also assumed that Sørensen used the term “p” only to label the test solution and “q” for the reference solution (as these letters are often paired).
  • In the 1910s, Alice Catherine Evans, an American microbiologist, and bacteriologist developed pH measuring methods. She was famed for her dairying and food safety works. She credited William Mansfield and colleagues for this development which helped a lot in the laboratory and industrial use.
  • In 1934, the first electronic method for the measurement of pH came into existence. The credit of this introduction goes to a professor at the California Institute of Technology named Arnold Orville Beckman.

PH of Acid and Base

Every solution has a pH value between a scale of 0 to 14. This can be understand by the following information:

  • Acidic Solution: A solution with a pH value of more than 0 but less than seven contains acidic properties and hence, is known as an acidic solution.
  • Basic Solution: A solution with a pH value of more than seven and less than 14 contains basic properties and hence, is known as an alkaline solution.
  • Neutral Solution: The solution with a pH value equal to 7 is known as a neutral solution or it has neutral properties, for example, pure water.

Some Important Points About PH

  • The solution, which has a pH value of 0, is considered a highly acidic solution. As the pH value increases from 0 to 7, the acidity of a solution decreases continuously.
  • On the other hand, the solution which has a pH value of 14 is considered to be a highly basic or alkaline solution. As the pH value decreases from 14 to 7, the alkalinity of a solution decreases continuously.
  • A powerful acid may have a pH lower than 0, and a solid base may have a pH value of more than 14.

pH Scale

  • The number of H+ and OHions produced decides the intensity of acid and base of solution. The solution that produces more H+ ions is considered to be a strong acid, while the solution that produces more OHions is considered to be a strong base.

What is the Need For PH?

  • Only a limited range of pH changes can be borne by a living organism. In case of more pH adjustments, the life of an organism can come into danger. Take acid rain, for example. The acid rain has a pH value of less than 7. When this water flows into the river, it increases the pH of the river water. This affects marine life and makes their survival difficult.
  • There is also an acid present in the human stomach called hydrochloric acid, HCL, which helps in the digestion of food. A person can feel a lot of pain and discomfort in case of so much release of HCl as it causes indigestion. By using antacids, the release of HCl can be reduced.
  • The bee-sting may give a lot of pain and burning to a person. This happens because the bee injects the methanoic acid through its sting. In this situation, it is recommended to apply baking soda or other mild bases like calamine solution, which contains zinc carbonate, to the surface. This is helpful in reducing the acidity on the surface and maintaining the pH value.
  • An ant sting contains an acid known as formic acid. Therefore, it is recommended to apply baking soda or other mild bases in case of an ant sting.
  • Often, the degradation of food particles lowers the pH in the mouth of a person. This happens because of the presence of some bacteria in the mouth. That’s why it is advised to clean the mouth with toothpaste to maintain the pH because toothpaste contains the base that prevents the tooth from decay.

Universal Indicator

The universal indicator helps in the measurement of pH. The acidity or alkalinity of a solution can be easily understood by the changing color of the indicator. There is water, sodium hydroxide, bromothymol blue monosodium salt, 1-Propanol, methyl red, thymol blue monosodium salt, and phenolphthalein sodium salt composed in a universal indicator. The description of these colors is as under:

pH RangeDescriptionColor
Less than 3Strong AcidRed
3 to 6Weak AcidOrange or Yellow
7NeutralGreen
8 to 11Weak BaseBlue
More than 11Strong BaseViolet or Indigo

Types of Universal Indicator

A universal indicator is not just a single indicator but a mixture of two indicators. They include indicators in paper form and solution form. 

  • Paper Form: This form has a strip of colored paper. The strip can be placed on the wet substance, or with the help of a dropper, a few drops of the solution can be dropped onto the strip to check the solution. This strip turns red if the solution contains acidic properties and blue if the solution contains basic or alkaline properties. It is preferable to use this form of indicator if the color of the test solution is dark.

Universal Indicator in Paper Form

  • Solution: Thymol blue, bromothymol blue, methyl red, and phenolphthalein are the main components of the solution form of the universal indicator. It is advisable to use this universal indicator in a colorless solution to get the accurate result of indication.

Universal Indicator in Solution Form

pH Of Some Common Solutions

SubstancepH RangeType
Battery Acid<1Acid
Gastric Acid– 1.5Acid
Vinegar2.5Acid
Orange Juice3.3 – 4.2Acid
Black Coffee5.0 – 5.03Acid
Milk6.5 – 6.8Acid
Pure Water7Neutral
Sea Water7.5 – 8.4Base
Ammonia11.0 – 11.5Base
Bleach12.5Base
Lye13.0 – 13.6Base

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