ISO 673:1981

The soap is dissolved in ethanol, filtrated and the undissolved residue is weighed. The constituents not dissolved correspond to the additives and foreign matter, of low solubility or insolubility in 95 % (V/V) ethanol, added to soaps and also to substances in all soap formulations, such as alkali carbonates and chlorides, borates, perborates, suphates, silicates, phosphates etc. It also may consist of organic substances like starches, dextrins, caseins, sugars, cellulose derivatives, alginates, etc.