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在测定含卤化物药品含量时,一般常采用银量法测定。由于此法在滴定过程中产生多量絮状沉淀,振摇均匀费时,同时硝酸银标准液不易保存,因此我们改用了汞量法测定含卤化物的药品。汞量法的优点是标准溶液稳定,操作简单迅速。在滴定中不产生沉淀;硝酸汞的价格也比硝酸银便宜。汞量法测定原理主要利用卤化物溶于水中,离解成气溴离子,它们与汞离子化合,生成相当的卤化汞。过多一点的汞离子和苯肼羧基偶氮苯或二苯胺基脲作用,生成深紫色化合物为终点。Roberts 找出须将欲滴定溶液 pH 值维持在1.5和2.0之间,才可以得到较好结果。上述指示剂是弱酸,能用作酸-硷指示剂,可能只有硷型与汞成紫色。若溶液中酸度不足时则终点出现太早,而酸度过高时则终点太迟。现以我们两院药房常用的几种合卤化合物制剂,用汞量法与银量法进行比较,其结果如下:
Determination of the content of the halide-containing drugs, the general method is often used silver determination. Because this method produces a large amount of flocculent sedimentation in the titration process, shaking evenly and time-consuming, while the silver nitrate standard solution is not easy to preserve, so we use the mercury content method to determine the halide-containing drugs. Mercury method has the advantage of standard solution stability, simple and rapid operation. No precipitation occurs in the titration; the price of mercury nitrate is also cheaper than silver nitrate. Mercury quantitative determination of the principle of the main use of halide dissolved in water, dissociated into gas bromine ions, which combine with the mercury ion to generate a comparable mercury halide. A little too much mercury ion and phenylhydrazine carboxy azobenzene or diphenylaminyl urea role, generating dark purple compounds as the end point. Roberts found that the pH of the solution to be titrated should be maintained between 1.5 and 2.0 to get better results. The above indicator is a weak acid, can be used as an acid-base indicator, may only be alkaline and mercury purple. If the acidity of the solution is low, the end point appears too early, while the acidity is too high, the end point is too late. Is now our hospital pharmacy commonly used several halogen compound preparation, with the amount of mercury method and the amount of silver compared, the results are as follows: