不溶性物质应根据本文件中描述的条件进行定义。目的不是溶解所有杂质，而是仅溶解用户感兴趣的杂质。本方法适用于在水介质或酸性介质中进行的分析。其原理是将试验部分溶解在水中，过滤、干燥并称量不溶性残留物。稀释滤液，形成主溶液，以进行其他测定。

Insoluble substances shall be defined by the conditions described in this document. The object is not to dissolve all the impurities but only those of interest to users. The method is applicable to the analysis, carried out inaqueous medium or in acid medium. The principle consists in solution of the test portion in water, filtration, drying and weighing of the insoluble residue. Dilution of the filtrate to form the main solution for carrying out other determinations.