规定了氟化钠/三氟化铝摩尔比约在3和1,7之间的天然和合成材料的测定方法。其原理是将试样与碳酸钠熔融，用硫酸或高氯酸蒸馏分离氟。以茜素磺酸钠/亚甲基蓝为指示剂，硝酸钍溶液滴定。或者，硝酸钍滴定可仅使用茜素磺酸钠进行，终点在525 nm处通过分光光度法测定。

Specifies the determination for natural and synthetic materials having a molar ratio sodium fluoride/aluminium trifluoride between 3 and 1,7 approximately. The principle consists in fusion of a test portion with sodium carbonate, separation of fluorine by distillation with sulphuric acid or perchloric acid. Titration with thorium nitrate solution in presence of sodium alizarinsulphonate/methylene blue as indicator. Alternatively, the thorium nitrate titration may be made using only sodium alizarinsulphonate, the end-point being*spectrophotometrically determined at 525 nm.