この論文を読む／探す
抄録
二ケイ化モリブデン及びフェロシリコン中のケイ素の定量にフッ化物イオン選択性電極を使用した電位差滴定法を確立した.試料を硝酸及びフッ化カリウムを含むフッ化水素酸で分解後,低温維持漏斗を使用してヘキサフルオロケイ酸カリウムを沈殿分離した.それを硝酸ナトリウム温溶液に溶解し,一定量に希釈後,その一部を採取し,全イオン強度調整緩衝溶液を加えてpHを5.3〜5.4に調整した.硝酸ランクン標準溶液で電位差滴定を行い,滴定曲線から,作図法により当量点を求めた.対象としたケイ素濃度範囲(20〜80%)で合成試料(モリブデン+ケイ素)を調製し,回収率を求めたところ,平均99.98±0.03%となった.更にフェロシリコン標準試料(JSS720-3,SI:75.94%)の定量結果は75.94%{n=6,R.S.D.(相対標準偏差)=0.054%}と精度,正確さともに良好な結果が得られた.実試料では,本法によると36.64%(n=7,R.S.D.=0.065%)となった.なお,中和滴定法によると36.4%(n=7,R.S.D.=1.26%)であった.
A hundred mg of a sample was dissolved with 10 ml of conc. nitric acid and 50 ml of the mixture of hydrofluoric acid and potassium fluoride (200 ml+30 g), the sample solution was then cooled to below 10℃ to precipitate the potassium hexafluorosilicate. The precipitate was filtered using funnel cover in order to maintain a low temperature and then dissolved in a hot sodium nitrate solution (5w/v%). After the solution was adjusted to pH 7〜8 with a sodium hydroxide solution (0.2 M), it was diluted to 500ml with the sodium nitrate solution, and a 50 ml aliquot was exactly transferred to a polyethylene beaker (200 ml). Three ml of the total ionic strength adjustment buffer was added to adjust the pH of the solution to pH 5.3〜5.4 and to promote the dissociation of the fluoride ion from hexafluorosilicate ion. The fluoride ions were titrated against a standard lanthanum nitrate solution (1/30 M). The analytical concentration range was 20〜80% of silicon. The recovery of silicon(Si : 20, 40, 60, 80 mg) when analyzing synthesized samples (molybdenum powder+standard solution of silicon) was 99.98±0.03% (n=5). The maximum permissible amounts of interfering elements in determining 40 mg of silicon were 2.0 mg for Al, 2.5 mg for Ga and 3.0 mg for Mg. However, the analytical values were not affected because molybdenum disilicide does not contain these element. The analytical value for ferrosilicon of Japanese Standards of Iron and Steel JSS 720-3 (Si : 75.94%), was 75.94% (n=6, R. S. D.=0.054%). The analytical value of silicon in molybdenum disilicide was 36.64% (n=7, R. S. D.=0.065%), while the analytical result by the neutralization titration was 36.4% (n=7, R. S. D.=1.26%).
