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硫醇的测定一般采用碘量法,基于硫醇被碘氧化生成二硫醚。该法操作简便,但反应速度慢,并受烯烃、胺、酚等物质的干扰。也有人采用汞量法(或银量法),基于硫醇与可溶性汞盐(或银盐)形成硫醇盐的反应: RSH+HgCl_2=RSHgCl+HCl此法可按电流滴定、电位滴定或库伦滴定等方式进行,烯烃、胺、酚等物质无干扰,但仪器设备较复杂。也可利用上述反应中释放出来的等当量盐酸,以甲基橙或甲基红作指示剂,用标准碱溶液进行滴定。但结果往往偏低,其原因是终点时pH值太小,这是为了防止因二氯化汞水解而引起的干扰作用。本文提出如下方法:在滴定前加入足够量的碘化钾,与剩余的二氯化汞作用生成稳定的碘汞络离子,从
The measurement of mercaptans generally uses iodometry, based on the oxidation of mercaptans to iodides to form disulfides. The method is simple, but the reaction is slow, and by olefin, amine, phenol and other substances interfere. Others use the mercury method (or silver method) based on the reaction of mercaptans with soluble mercury salts (or silver salts) to form thiolates: RSH + HgCl 2 = RSHgCl + HCl This method can be performed by current titration, potentiometric titration or coulometry Titration and other ways, olefin, amine, phenol and other substances without interference, but more complicated equipment. Equivalent hydrochloric acid released from the above reaction can also be used to titrate with a standard alkali solution using methyl orange or methyl red as an indicator. However, the results tend to be low because the pH at the end point is too small in order to prevent the interference caused by the hydrolysis of mercury dichloride. This paper proposes the following method: adding a sufficient amount of potassium iodide before titration, with the remaining mercuric chloride to form a stable iodine mercury complex ions from