フッ素イオン電極と塩化アルミニウム分解を利用する無機化合物中フッ素の迅速分析  [in Japanese] Rapid analysis of various inorganic fluorides with a fluoride ion-selective electrode after attack with aqueous aluminum chloride.  [in Japanese]

種々の無機フッ素化合物試料の分解法として、塩化アルミニウム水溶液を用いて、加熱溶解する方法を検討した。 加えるアルミニウム量は、試料中のフッ素量に対してモル比で約1以上あれば十分であり、加熱時間は約 15 分でよい。 ほたる石、氷晶石、フッ化第一スズ、フッ化バリウム、フッ化第ニクロム、ヘキサフルオロチタン酸カリウム、ヘキサフルオロジルコニウム酸カリウム、フッ化ランタン、テトラフルオロホウ酸第二銅、テトラフルオロホウ酸第一スズは完全に分解された。 アルミニウムのマスキング剤としてクエン酸を用い、既報^<1)> の希釈法を応用して、フッ素イオン電極で定量した。 定量に要する時間は約30分で、迅速分析法として有用である。 フッ化アルミニウム、フッ化第一セリウム、フッ化トリウムは分解不十分のため、フッ化ベリリウムはベリリウムのマスキングが不十分なため、低い分析結果を得た。

Fluorite, cryolite, barium, stannous, chromic, and lanthanum fluorides, potassium hexafluorotitanate and hexafluorozirconate, cupric and stannous tetrafluoroborattes(commercial, each 45% aqueous) were digested with aqueous alumnum chloride at pH 2. It was necessary to maintain a ratio of Al/F to be more than unity. Fifty maintain of the sample (10mg of lanthanum fluoride and the hexafluoro complexes, and 1Oml of the tetrafluoroborates after 100-fold dilution) was added to lOml of 2.5% AlCl_3 solution. The digestion completed in 15 min. by gentle boiling. Two to six% losses of fluorine were observed when a reflux condenser was not used. As pH of the solution increased to 2.6〜2.7 during the heating, (4〜5) drops of (1 : 1) HCl was added to ajust pH to 2. After cooling, 50 ml of the 1 M citrate buffer of pH 6 was added and the solution was diluted to 500ml. A lO ml aliquot was mixed with 1O ml of the citrate buffer and another lO ml with 20 ml of the buffer and 1O ml of water. The potential of a fluorid ion-selective electrode was measured in each solution. When both data did not coincide with each other, the potential in the latter solution was taken as a correct value. The dilution method previously suggested can thus be applied. It took about half an hour to analyze a sample. The prsent method is not applicable to beryllium, cerous, and aluminum fluorides.