用EDTA微量滴定法测定了水中硫酸根及总硬度,测定过程在氨性缓冲介质中进行,采用络黑T作指示剂,用一种自制的聚乙烯微型毛细管滴定管进行滴定,滴定反应所耗的滴定剂用计滴法计数.从微滴管流出的每一小滴滴定剂的体积(通常在0.01~0.02 mL之间)用重量法校正,每次滴定所耗滴定剂一般在50~200小滴之间.此方法的扩展不确定度,对硫酸根测定为0.94%与重量法相当,而精密度则优于重量法,对总硬度测定为0.82%优于常量滴定法.此方法的特点为分析快速、准确,消耗试剂少且便于携带,适合于现场或野外分析应用.

Sulfate and total hardness of natural water were determined by EDTA micro titration in ammoniacal buffer solution with eriochrome black T as indicator.A self-made polythene microburette was used in the titration by counting the droplets used in the reaction.Volume of the droplet (ordinarity 0.01 to 0.02 mL per drop) from the microburette was calibrated by gravimetry.Amounts of titrant used in the titration were usually in the range of 50-200 droplets.Expanded uncertainty of this method was found to be 0.94% for SO2-4 determination which is equivalent to the uncertainty of the gravimetric method,while the precision is better than gravimetry.Expanded uncertainty for hardness determination was found to be 0.82%,which is also better than the macro titration method.The special features of this method were its rapidity and accuracy in analysis,less in consumption of reagent and portability.It is proved to be feasible in the worksite or field analys.s