论文部分内容阅读
目前测定锌化合物中重金属铅的含量,一般仍用氰化物掩蔽铜、镉等,但氰化物有剧毒。和氰化物一样,氨水能和许多金属离子形成氨络合离子,例如:Zn(NH_3)_4~(2+),Cu(NH_3)_6~(2+)等,pb~(2+)不被络合。在碱性溶液中,加入硫化物,即形成黑色不溶性PbS的悬浊溶液,可借此测定微量铅。在氯化锌中,Fe~(2+),Fe~(3+),Mn~(2+)是主要干扰元素,现加入酒石酸盐,硝酸铵掩蔽效果良好。含有小于万分之一的下列元素之一者,均不受影响,Fe~(2+),Fe~(3+),Mn,Cd,Cu,Co Ni,Sn~(2+). 一试剂酒石酸钾钠-硝酸铵混合液:将50%酒石酸钾钠溶液230毫升与70%硝酸铵溶液400毫升混匀。氨水-硫化钠混合液:取氨水(1+2)100毫升加硫化钠溶液(5%)10滴。铅标准溶液:称取0~1599克Pb(NO_3)_2,溶于少
The current determination of the content of heavy metals in zinc compounds, the general still use cyanide to cover copper, cadmium, etc., but cyanide is highly toxic. Like cyanide, ammonia can form ammonia complex ions with many metal ions such as Zn (NH 3) 4 ~ (2 +), Cu (NH 3) _6 ~ (2+), etc. pb 2+ Complex. In alkaline solution, adding sulfide, that is, the formation of black insoluble PbS suspended solution, which can be used to measure trace lead. In ZnCl2, Fe2 +, Fe3 + and Mn2 + are the main interference elements. Tartrate is added to the zinc chloride and the masking effect is good. Fe 2+, Fe 3+, Mn, Cd, Cu, Co Ni, Sn 2+ with less than 1/10000 of one of the following elements: Potassium tartrate - ammonium nitrate mixture: 50% sodium potassium tartrate solution 230 ml and 70% ammonium nitrate solution 400 ml mix. Aqueous ammonia - sodium sulfide mixture: Take ammonia (1 +2) 100 ml sodium sulfide solution (5%) 10 drops. Lead standard solution: Weigh 0 ~ 1599 grams of Pb (NO_3) _2, soluble in less