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在NH_4Ac底夜中,MO(Ⅵ)可直接用标准Pb~2+滴定,利用Pb~2+切口产生指示终点,若是Cd-Mo混合溶液,还能连续测定。先用EGTA滴定Cd~2+,然后用Pb~2+直接滴定Mo。W-Mo合金中Mo的测定也只需将W(Ⅵ)沉淀为钨酸,用干过滤法分离部分滤液,直接测Mo,可得满意结果。在同样底液条件下。W(Ⅵ)则需要加过量标准Pb~2+生成PbWO_4沉淀,过量Pb~2+再用标准EDTA反滴定,以Pb~2+切口消失指示终点。用此法作了纯钨粉及钨铁合金标样测定。
In the NH_4Ac night, MO (Ⅵ) can be titrated directly with standard Pb ~ 2 +, using Pb ~ 2 + incision to produce the end point, if the Cd-Mo mixed solution, but also continuous determination. Titrate Cd ~ 2 + with EGTA and titrate Mo directly with Pb ~ 2 +. The determination of Mo in W-Mo alloy also only needs to precipitate W (Ⅵ) as tungstic acid, and part of the filtrate is separated by dry filtration to directly measure Mo, thus obtaining satisfactory results. Under the same conditions at the end of liquid. W (Ⅵ) requires the addition of Pb2 + in an excess amount to form PbWO4 precipitates. Excess Pb2 + is then back titrated with standard EDTA and the end point is indicated by the disappearance of Pb2 + incisions. This method was made pure tungsten powder and tungsten iron alloy standard determination.