Ash (chemistry)

Ash is one of the components in the proximate analysis of biological materials, consisting mainly of salty, inorganic constituents.

It includes metal salts which are important for processes requiring ions such as Na+ (sodium), K+ (potassium), and Ca2+ (calcium).

It is defined as the inorganic residue that remains after combustion of the oil in air at specific high temperature.

Some of the ash forming constituents occur naturally in crude oil; others are present as a result of refining or contamination during storage or distribution.

Ashing is also performed prior to chemical analysis by inductively coupled plasma emission spectrometry.