毛细滴管称量滴定法测定水中溶解氧

Determination of Dissolved Oxygen in Water by Micro-Weighing-Titration with a Polythene Capillary Burette

将微量称量滴定法应用于硫代硫酸钠-碘量法测定水中溶解氧的含量。在滴定中采用自制的聚乙烯毛细滴定管代替了国标GB10738～1989中所规定使用的结构复杂精细的称量滴定装置。操作时，在聚乙烯毛细滴定管中吸满了Na2S2O3标准溶液，在精密电子天平上称得滴定前后（以淀粉为指示剂）毛细滴定管及滴定剂的总质量。从滴定中所耗Na2S2O3标准溶液的质量按文中所给出的公式即可计算水样中的溶解氧含量，所制作的毛细管滴定管每滴滴定剂的质量要求控制在0．005-0．010g之间，滴定过程的相对偏差可控制在1．0％左右。由于滴定系在微量水平上进行，因此方法具有消耗试剂少，操作快速而方便，且能取得优于国标方法的准确度和精密度，对4个水样进行分析，测得结果的相对标准偏差值（n=7）在0．18％-0．66％之间，明显小于国标方法测定结果的相对标准偏差（0．43％～1．26％）。

In the iodometric titration of dissolved oxygen in water, weighing titration with Na2S2O3 standard solution was applied. A self-made polythene capillary burette was used in the titration instead of the complex and precise weighing titration deviced specified in the standard GB 10738-1989. The polythene capillary burette was filled with standard solution of Na2S2O3, and the total mass of the burette and titrant was weighed on a precise elec- tronic balance before and after the titration using starch as indicator. Amount of dissolved oxygen in the sample was calculated from the mass of Na2S2O3 standard solution according to the formula given in the paper. One drop of titrant from the capillary burette was qualified to have the mass in the range from 0. 005-0. 010 g. Relative deviation of the titration process was controlled around 1.0%. Titration of the proposed method was made on a micro scale, thus resulting less comsuption of reagents, more rapid and convenient in operation, as well as better accuracy and precision than the GB standard method. Values of RSD＇s （n= 7） obtained in analysis of 4 water samples were ranging from 0. 18%-0. 66% which were smaller than those obtained by the GB method （0. 43%-1. 26%）.