This method describes a procedure for determining the acid-insoluble ash content of cellulose samples. The sample is dry-ashed and the residue treated with hydrochloric acid. The insoluble residue is filtered, washed, ignited, and weighed. This method measures all acid insoluble material. For a more accurate but time-consuming wet-ash procedure for determining the silicates and silica content of pulp, see TAPPI T 245 "Silicates and Silica in Pulp (Wet Ash Method)."