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合金中磷的测定,一般采用重量法或酸碱容量法,这些方法的手续复杂,时间冗长且不易掌握,钨、钒、砷、钛、硅等常见共存元素均干扰测定,有时需预先分离。以络合滴定法间接测定磷已有报导,如借滴定MgNH_4PO_4沉淀中的 Mg~(2+),MnNH_4PO_4沉淀中的 Mn~(2+)或滴定母液中过量的 Mg~(2+)以测定 PO_4~(3-),及借滴定 Zn_2P_2O_7沉淀中的 Zn~(2+)和Mn_2P_2O_4沉淀中的 Mn~(2+)测定 P_2O_7~(4-)。近来亦有在金属指示剂存在下,以鉍(Ⅲ)标准溶液直接滴定 PO_4~(3-)
The determination of phosphorus in alloy usually adopts gravimetric method or acid-base volume method. The procedures of these methods are complex, time-consuming and difficult to grasp. Common coexisting elements such as tungsten, vanadium, arsenic, titanium and silicon all interfere with the determination and sometimes need to be separated in advance. Indirect determination of phosphorus by complexometric titration has been reported. For example, Mg2 + in titration of MgNH4PO4 precipitation, Mn2 + in precipitation of MnNH4PO4 or excess Mg2 + in titration mother liquor can be measured PO_4 ~ (3-), and determination of P_2O_7 ~ (4-) by titration of Zn ~ (2+) in precipitation of Zn_2P_2O_7 and Mn ~ (2+) in precipitation of Mn_2P_2O_4. Recently there is also a metal indicator in the presence of bismuth (Ⅲ) standard solution titration PO_4 ~ (3-)