Sulphated ash

Sulphated ash describes both a chemical-analytical process and its product (substance) and result (value).

Sulphated ash is a gravimetric method used to determine inorganic constituents in an organic sample. It differs from other incinerations in that sulfuric acid is added before glowing . This converts any alkali halides that may be present into less volatile alkali sulfates. This is to prevent, in addition to the desired volatilization of the organic constituents (see ash ), alkali halides also passing into the gas phase and thus no longer being detected. Any deviations can be caused by the formation of pyrosulphates . According to the European Pharmacopoeia, this problem is prevented by adding ammonium carbonate , which converts pyrosulphates back into sulphates.

Since the underlying chemical processes are complex and inconsistent, the analysis must follow a precisely defined procedure ( convention method ). Such methods for testing lubricating oils and greases are e.g. B. in DIN 51 575 (November 1984) and DIN 51 803 (March 1982) are described in detail.

Individual evidence

1. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 6: T-Z. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1988, ISBN 3-440-04516-1 , p. 4479.