界面活性剤の定量 (第4報)

ニュートラルレッドを用いるラウリル硫酸ナトリウムの比色定量法について

抄録

By the use of the properties of Neutral Red to react with sulfate-type and sulfonate-type anionic surface active agents to forma complex compound sparingly soluble in water but easily soluble in organic solvents, various conditions were examined for the determination of sodium laurylsulfate. The method thereby established was as follows: A sample solution containing 5-100γ/cc. of sodium laurylsulfate, 1cc. of buffer solution (pH 5), and 2cc. of 0.01M Neutral Red solution, measured accurately, are placed in a glass-stoppered test tube and shaken for about 1 minute. To this mixture, 10cc. of dichloroethylene is added, the mixture is shaken for 2 minutes, and centrifuged. The supernatant is filtered through a cotton plug and absorbance of the filtrate is measured at 530mμ. A blank test is carried out with the same quantity of the same reagents, using 1cc. of distilled water in place of the sample solution. This method can be used to a certain extent in the presence of potassium stearate and nonionic surface active agents, and the presence of sodium sulfate does not interfere in this reaction. If 10cc. of the sample solution is used, this method can be applied to solutions of 1/10 the concentration. The accuracy of this method is below 1%.