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在Mg、Zn、Cd及Mn测定中,于Al存在下用Ⅲ号错合剂(E.D.T.A.二钠盐)溶液及铬黑T指示剂滴定时,加入纯三乙醇胺N(CH_2CH_2OH)_3(Ⅰ)遮蔽Al。测定Mn~(2+)时向溶液中加入少量的NH_2OH·HCl以防Mn~(3+)的错合物与Ⅰ氧化为Mn~(3+)(绿色的错合物与Ⅰ能氧化指示剂)。当有≤10毫克的Fe~(3+)时加入Ⅰ和KCN也能遮蔽Fe~(3+)。将含Mg~(2+)和(至多)120毫克的Al的溶液冲淡到至250—300毫升。加入0.5～1克的
In the determination of Mg, Zn, Cd and Mn, pure triethanolamine N (CH 2 CH 2 OH) _3 (Ⅰ) was used to mask the concentration of Al in the presence of Al with titration of complexing agent Ⅲ (disodium EDTA) and chrome black T indicator . In the determination of Mn ~ (2+), a small amount of NH 2 OH · HCl was added to the solution to prevent the Mn 3+ complex from being oxidized to Mn 3 + (green complex and Ⅰ oxidation indicator Agent). Fe (3+) can also be masked by addition of Ⅰ and KCN when there are ≤10 mg of Fe ~ (3+). The solution containing Mg ~ (2+) and (up to) 120 mg of Al is diluted to 250-300 ml. Add 0.5 to 1 gram