Para-anisidine is a reagent that reacts with aldehydes to give products that absorb at 350 nm (Fig. 7.5). The p-anisidine value is defined as the absorbance of a solution resulting from the reaction of 1g fat in isooctane solution (100 ml) with p-anisidine (0.25% in glacial acetic acid).

P-anisidine is a substituted aniline that is aniline in which the hydrogen para to the amino group has been replaced by a methoxy group. It is used as a reagent for the detection of oxidation products such as aldehydes and ketones in fats and oils.

(1 mole) of p-anisidine (Note 1), 300 ml. of glacial acetic acid, and 217 ml. of water. 

p-Anisidine, also known as 4-methoxyaniline or p-aminoanisole, belongs to the class of organic compounds known as aminophenyl ethers. These are aromatic compounds that contain a phenol ether, which carries an amine group on the benzene ring. p-Anisidine is a very strong basic compound (based on its pKa).

P ANISIDINE 98%