电气石中亚铁的微量分析

The Micro Analysis of Tourmaline for Ferrous Iron

电气石是复杂的硼铝硅酸盐矿物,难溶于酸,电气石中亚铁的微量分析方法长期以来没有很好解决。WiJson曾在分解样品时,加入五价钒,用硫酸亚铁铵滴定测定亚铁、但不适于微量分析。本文试验了在五价钒存在下用氢氟酸—硫酸170℃增压分解电气石矿物,研究了V+FeV+Fe反应的可逆性。

The reaction was found to be highly dependent on the pH of the medium.The reaction goes to the right quantitatively in strong acid solution and can be forced to proceed to the left quantitatively at pH 68 at ambient temperature.A rapid spectrophotometric method for the determination of Fe(Ⅱ)in tourmaline is proposed on the basis of the above investigation.The mineral was opened up by pressure decomposition in a HF-H_(2)SO_(4)-V(V)mixture at 170℃in a teflon vessel and the resulted solution was poured into H_(3)BO_(3)to complex fluoride.The solution was brought to pH 6~8 by a suitable buffer,and the regenerated Fe(Ⅱ)was determined with o-phenanthro-line by photometry.