In the precipitation of zinc with NH_4 CNS and methyl violet, when H_3PO_4 amounts to 4.5 ml in 50 ml, no dissolving of zinc is observed.

• 用NH_4CNs、甲基紫沉淀?时；H_3PO_4用量达4.；5毫升/50毫升时；尚不会使沉淀溶解。 当?含量大于?含量200时；仍能满意的??分离出来。