适用于测定氟化钠/三氟化铝摩尔比在3和1,7之间的天然和合成材料。该方法适用于铁含量等于或大于0020%（m/m）的产品。其原理是通过碱性或酸性熔融溶解试验部分。在pH值介于3,5和4,2之间的缓冲介质中，用氯化羟胺还原铁（III），形成复合铁（II）-1,10-苯并诺林。在约510 nm波长下对有色络合物进行光度测量。适用ISO建议R 1694-1970。

Applies for the determination of natural and synthetic materials having a molar ratio sodium fluoride/aluminium trifluoride between 3 and 1,7 approximately. The method is applicable to products having an iron content equal to or greater than 0,020 % (m/m). The principle consists in dissolution of a test portion by either alkaline or acid fusion. Reduction of iron(III) with hydroxylammonium chloride, formation of the complex iron(II)-1, 10-phenathroline in a buffered medium at pH value between 3,5 and 4,2. Photometric measurement of the coloured complex at a wavelength of about 510 nm. Applies ISO Recommendation R 1694-1970.