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钢铁中铅的测定方法虽较多,但容量法和萃取比色法因干扰多,需经麻烦的分离手续,且常用氰化物作掩蔽剂。极谱法也要沉淀干扰离子。本文拟定在聚乙二醇(PEG)存在下,用氟硼酸根PVC膜电极作指示电极,四苯硼酸钠(NaTPB)为滴定剂,测定钢铁中铅。结果表明,当铅含量不低于0.02%时,不需任何分离和掩蔽手续,只需调节酸度,便可直接测定,试验中,酸度在pH1.5～6范围内,滴定曲线基本一致,但常选用pHl.5～2.5,如pH值太高,有Fe(OH)_3沉淀析出,PH值太低,滴定终点不明显。在滴定时,NaTPB的浓度不宜小于0.01M,实验中选用0.02M。大多数常见阳离子不干
Although there are many methods for the determination of lead in steel, the volumetric method and the extraction colorimetric method are often disturbed by troublesome separation procedures, and cyanide is often used as a screening agent. Polarography also precipitates interfering ions. In this paper, the fluoroborate PVC membrane electrode was used as indicator electrode in the presence of polyethylene glycol (PEG), and sodium tetraphenyl borate (NaTPB) was used as titrant to determine lead in steel. The results showed that when the content of Pb was not less than 0.02%, no separation and masking procedures were needed. Only the acidity was adjusted, the titration curve was basically the same in the range of pH1.5 ~ 6 Often use pHl.5 ~ 2.5, such as the pH value is too high, Fe (OH) _3 precipitate precipitation, PH value is too low, titration end point is not obvious. In titration, the concentration of NaTPB should not be less than 0.01M, the experiment used 0.02M. Most common cations do not work