Mg 1-naphthy amine-8-sulfonateによる海かん水中のナトリウムの重量分析

概要

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Sodium salt of 1-naphthylamine-8-sulfonic acid (Peri Acid) is sparinglly soluble in cold water while magnesium salt is easily soluble. Sodium ion is then determined with magnesium 1-naphthylamine-8-sulfonate solution. This method was applied for sea water and brine. 10ml. of the reagnt solution, 12% in concentration, was added slowly to a neutralized sample solution containing 40-80 mg. of Na+, and the mixture was kept at 10-15° for 30 minutes. The precipitate was then filtered off and washed with 3 portions of 2-3 ml. of saturated alcoholic solution of sodium 1-naphthylamine-8-sulfonate followed by 2 portions of 1 ml. of absolute alcohol. The precipitate was heatresistant and nonhygroscopic. Heating to 105° was suitable for drying the precipitate. Effects of coexistence of cations were examined in the determination of about 70 mg. of Na+. K+ and NH+4 did not inte-rfere when presented in amounts not exeeding 10 and 60 mg., respectively. Even about 2mg. of Ca++ gave the positive error, but 10 mg. of Ca++ did not interfere when 300 mg. of Mg-EDTA was added. Analytical procedures for sea water and brine were established Potassium contents were too small to affect the analytical results, and the interference of calsium was prevented by the addition of Mg-EDTA. About 5 hours were needed for total operations, and results obtained were satisfactory.
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