论文部分内容阅读
在铝的络合滴定法中,有关文献虽对各种指示剂有所介绍,但对最常见的紫脲酸铵却始终未被采用。本文提出在紫脲酸铵中混以萘酚绿B(naphtholgreen B),用铜离子反滴定,可以获得一个相当清晰的终点,使紫脲酸铵用作铝的络合滴定指示剂成为可能。本方法首先加过量的EDTA 以络合铝,用醋酸缓冲液控制pH5,使指示剂显暗紫红色,然后用硫酸铜回滴过量的EDTA。在滴定过程中,溶液逐渐变成蓝色,最后突然变成暗黄绿色即系终点。一、分析方法(一)试剂1.紫脲酸铵-萘酚绿B 混合指示剂3份紫脲酸铵,7份萘酚绿B 和200份硫酸钾混合研细备用。此混合物貯于干燥处可保存较长时间。2.pH 5 醋酸缓冲液27克结晶醋酸钠与60毫升1N 盐酸混和,加水稀释至1升。3.0.05M EDTA 溶液19克乙二胺四乙酸二钠盐溶解于水,稀释至1升。
In the complexation of aluminum titration method, although the literature on various indicators have been introduced, but the most common ammonium urethane has not been used. In this paper, it is proposed that ammonium thiocyanurate can be mixed with naphtholgreen B and back-titration with copper ions can obtain a fairly clear endpoint, making it possible to use ammonium urethane as a complexometric titration indicator for aluminum. In this method, an excess amount of EDTA is first added to complex aluminum. The pH5 is controlled with an acetate buffer to make the indicator dark purple and the excess EDTA is then back-titrated with copper sulfate. In the titration process, the solution gradually turns blue, finally suddenly turns yellowish green that is the end point. First, the analytical method (A) Reagents 1. Ammonium urea - naphthol green B mixed indicator 3 parts of ammonium urea, 7 parts of naphthol green B and 200 parts of potassium sulfate mixed fine preparation. Store this mixture in a dry place for longer periods of time. 2. pH 5 Acetic Acid Buffer 27 g Crystalline Sodium Acetate is mixed with 60 ml 1N hydrochloric acid and diluted to 1 liter with water. 3.0.05M EDTA solution Dissolve 19 g of disodium ethylenediaminetetraacetate in water and dilute to 1 liter.