用达旦黄──溴百里酚蓝混合指示剂测定RSO_3Na型表面活性剂

在单相体系中 ,以十六烷基三甲基溴化铵为滴定剂 ,达旦黄 -溴百里酚蓝混合物作指示剂 ,测定了RSO3Na型表面活性剂。通过对影响滴定因素的考察 ,确定了滴定分析条件。结果表明 :当达旦黄与溴百里酚蓝的质量比为 5∶ 2 ,配成含有 0 .1 %达旦黄和 0 .0 4 %溴百里酚蓝的混合指示剂溶液 ,加量在 4滴～ 6滴 ,在p H值为 1 0 .0 0～ 1 1 .0 0的碱性介质中进行滴定较适宜。此时 ,以十六烷基三甲基溴化铵为滴定剂作空白滴定时 ,滴加 2滴～ 3滴 7.875× 1 0 - 4mol/L的滴定液即可明显地观察到终点颜色由绿色到紫色的转变 ;测定样品时 ,2滴～ 4滴滴定剂可清楚地判断终点 ,用该方法测定文中所选样品的相对平均偏差小于 1 .0 %。

A Mixed Indicator of Titan Yellow-bromothymol Blue for Determination of Anionic Surfactants

CTMAB was used for determining some anionic surfactants with a mixed indicator of titan yellow bromothymol blue. Titrating condition was determined by the investigated of the affecting factors of titration, the better condition of titrimetric analysis is dropwise 4~6 drops the mixed indictor of 0.1% titan yellow and 0.04% bromothymol blue, pH at 10.00~11.00. At this point, the color of end point was distinctness observed in blank titration with 2~3 drops 7.875×10 -4 mol·L -1 CTMBA; The end point was judged with 2~3 drops 7.875×10 -4 mol·L -1 CTMBA in the taken measure of samples, and it has better repeatability and degree of accuracy.