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含硼试样中氟的测定存在一定困难。当使用氟硼酸根电极时,其困难在于:试样中B∶F ≠1:4,而且硼和氟形成多种形式的络合物;当使用氟电极时,其困难在于:试样中B-F紧密的化学键结合,致使直接电位法所测得游离氟离子的浓度远远小于试样中总氟的含量。本文介绍了三氯化铝回流法及碳酸钠熔融法两种破坏B-F键的方法。释放出的氟离子采用氟电极直接电位法或硝酸钍电位滴定法测定。讨论了滴定剂和介质对滴定的影响。
Determination of fluorine in boron-containing samples there are some difficulties. When using a fluoroborate electrode, the difficulty lies in: the sample B: F ≠ 1: 4, and boron and fluorine form various forms of complexes; when using a fluorine electrode, the difficulty lies in the sample BF Tight chemical bond, resulting in the direct fluorine method to determine the concentration of free fluoride ions is far less than the total fluoride content of the sample. This article describes the aluminum trichloride reflux and sodium carbonate melting two methods to destroy the B-F bond. Fluoride released by the fluorine electrode direct potentiometry or thorium nitrate potentiometric titration. The effect of titrant and media on titration is discussed.