Improvement in the Pretreatment Method of Samples for the Determination of Sulfides in Wastewater
废水中硫化物测定样品预处理方法的改进

The pretreatment method of samples, known as Nz-blowing method , for the determination of sulfides in wastewaer has been further studied and improved. The improvement includes the test apparatus,pretreatment procedure,acidity and temperature used in the pretreatment,and the volume of reaction bottle. Particularly,a multihole blowing ball was used to replace the sigle hole blowing pipet.and a mixture of NaOH,EDTA and TEA was used as the blowing-absorbing solution instead of ZnAc2-NaAc. Then a step-wise pressure procedure has been suggested. The studies on the recovery and precision of the improved method and the comparative determination of six different kinds of industrial wastewater show that the improvement has seen an obvious effectiveness and the recovery increases from 40% for the original method to over 95% for the improved method. The blowing time is shortened by 25%. The apparatus is easy to operate.