quality control

B) Quantitative chemical test
In quantitative chemical test a number of tests used for evaluation of constituents e.g. fixed oils, volatile oils, fat, resin and wax.
The most important quantitative tests are:
1- acid value: organic acids are characterized by having one or more carboxyl group (R-COOH), these acids are neutralized by using alkaline to form salts, so acid value is the number of mg of KOH required to neutralized one gm of an acid.
This acid value is constant for each acid and depend on its molecular weight and on the number of carboxyl groups in its molecule.
e.g. acid value of official oleic acid (unsaturated fatty acid) is about 195-202.
e.g. acid value of colophony resin (الصنوبر) (drug containing unsaturated fatty acid) is 150-180.
2- iodine value: unsaturated bonds of fatty acids take up iodine under certain condition and this is called iodine value, so it’s a measure of unsaturatedness.
Iodine value: is the number of parts of iodine absorbed by 100 parts by weight of the substance.
Iodine value used for acids (fatty), fixed oils and waxes.
e.g. iodine value of castor oil is 82-90.
iodine value of linseed oilزيت بذور الكتان is over 175.