ISO 5985:1978

Depending on the nature of the samples are specified two procedures. Procedure A consists in decomposing of organic matter in a test portion by incineration, then treating with hydrochloric acid if the ash obtained, and filtration, followed by drying, incineration and weighing of the residue. Procedure B consists in treating of a test portion with hydrochloric acid, filtration, followed by drying and incineration. and treating of the ash as in procedure A.