キシリジルブルー(II)による火成岩中のマグネシウムの吸光光度定量

概要

論文の詳細を見る
A rapid and sensitive method for the determination of magnesium in silicate rocks is proposed. Reproducibility of the photometric method is improved by using a pH 10.0 buffer solution (borax-sodium carbonate) on the color development. Iron, aluminum, titanium, and manganese are separated from magnesium as the hydroxides by adding sodium hydroxide solution. Calcium up to 50 μg can be masked as the sulfate. The procedure is as follows: A powdered sample (0.050.2 g) is decomposed with a hydrofluoric-sulfuric acid mixture and evaporated to fumes, then dissolved in hot water and make to 25 or 50 ml. An aliquot of the solution is neutralized by dropping 0.2 N sodium hydroxide solution followed by 0.02 N solution (indicator; p-nitrophenol), then is added one drop of 30% hydrogen peroxide. After dilution to about 10 ml, the solution is heated for a few minutes and centrifuged. A supernatant is transferred to a 50 ml volumetric flask. A precipitate is dissolved in a small amount of hydrochloric acid and then reprecipitated as above. The supernatant is combined into the volumetric flask. To an aliquot of the solution is added sodium sulfate solution so that the amount of sulfate in the solution may be 10 mg. The solution is diluted to 5 ml accurately and mixed with 15 ml of ethanolic solution of Xylidyl Blue (II) (25 mg/l) and with 0.5 ml of the buffer solution. The absorbance is measured at 505 nm against water.
社団法人日本分析化学会の論文