Power ” Potential ” of hydrogen ( hydrogen ion concentration ) pH

Power ” Potential ” of hydrogen

It is a measurement determining the concentration of hydrogen ion (H+) in the solution and whether the solution is basic , acidic or neutral , You can determine pH of any solution by using the pH indicators ,The acid is the substance that can give up a hydrogen ion (H+) and the base is the substance that can accept H+ .

If  the potential of hydrogen ( pH ) is :

Less than 7 , the solution is acidic ( pH < 7 ) .

Greater than 7 , the solution is basic ( pH > 7 ) .

Equals 7 , the solution is neutral ( pH = 7 ) .

The neutral potential of hydrogen ( pH = 7 ) equals pH of pure water at 25 degree Celsius , The values of power of hydrogen of solutions are ranged between ( Zero : 14 ) depending on their positive hydrogen ion concentration (H+) .

pH is the numeric scale used to specify the acidity or basicity of the aqueous solution , It is the negative of logarithm to base 10 of the molar concentration , It is measured in units of moles per liter of hydrogen ions , It is the negative of the logarithm to base 10 of the activity of the hydrogen ion .

The solutions with the pH less than 7 are acidic and the solutions with the pH greater than 7 are basic , The pure water is neutral , being neither an acid nor a base , The pH value can be smaller than 0 or bigger than 14 for strong acids and bases .

PH scale

PH scale

The pH measurements are important in the agronomy , the medicine , the biology , the chemistry , the agriculture , the forestry , the food science , environmental science , oceanography , civil engineering , chemical engineering , nutrition , the water treatment and the water purification , as well as many other applications .

The pH scale is traceable to the set of standard solutions whose pH is established by international agreement , The pH of aqueous solutions can be measured with the glass electrode and the pH meter , or the indicator .

The primary pH standard values are determined using the concentration cell with transference , by measuring the potential difference between the hydrogen electrode and the standard electrode such as the silver chloride electrode .

PH in the human body

The pH is used as the measure of whether the body is maintaining the normal acid-base balance , The favorable pH is important in the function of the enzymes and the other biochemical systems , The fluids of the body are normally somewhat alkaline , The pH being between 7.35 and 7.45 , The pH above 7.8 or below 6.8 is generally fatal .

The symbol for the negative logarithm of the H+ ion concentration ( measured in moles per liter) , The solution with pH 7.00 is neutral at 22°C , one with the pH of more than 7.0 is alkaline , and one with the pH lower than 7.00 is acid , At the temperature of 37°C , neutrality is at a pH value of 6.8 .

The measurement of the acidity or the alkalinity of the solution based on the amount of hydrogen ions available , Based on the scale of 14 , The pH of 7.0 is neutral , The pH below 7.0 is an acid , the lower the number, the stronger the acid , The pH above 7.0 is the base , when the number is higher , The base is the stronger , Blood pH is slightly alkaline (basic) with the normal range of 7.36-7.44 .

Relation between pH and enzyme activity

Enzymes are affected by changing pH values because they are protein substances that contain acidic carboxyl groups ( COOH ) and Basic amino group ( NH2 ) , Each enzyme has an optimal pH value at which it works with a maximum efficiency .

If the pH is lower or higher than the optimal pH of the enzyme , The enzyme activity decreases until it stops working , Optimal pH of enzyme is the potential of hydrogen ( pH ) at which the enzyme works with a maximum efficiency .


Pepsin works at acidic pH value

Trypsin works at basic pH value .

Most enzymes work at pH value equals 7.4 ( neutral medium ) due to the amino acid molecules that forming the enzyme contain an acidic carboxyl group and a basic amino group .


They are biological macromolecules ( proteins ) that are produced and used in treating some diseases in the human body .


It is difficult to carry on the medicine directly to the target parts or cells in the body like several medicines .

The method to avoid these disadvantages

After the enormous development resulted by the nanotechnology , many trials are conducted to carry on the medicine to the infected cells in the body using nanoparasites .

These trials have led to the arising of a new field called nanobiopharmaceutics and the products used in this field are called nanobiopharmaceuticals .

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