氨硫脲的三种容量测定法的比较

关于氨硫脲即对乙酰氨基苯甲醛縮氨硫脲的含量测定法文献的报导是很多的。重量法的原理是根据氨硫脲与硝酸銀生成銀盐的作用。在容量法中有日本藥局方注解追补的酸鹼滴定法;以及硝酸銀法、溴量法、碘量法和三氯化铁法。很多比色法是采用酸或鹼使氨硫脲的乙酰基脫下而形成游离氨基,再經重氮化反应和偶合反应成为有色物質而比色的。此外,还有使氨硫脲与-溴代苯乙酮及与Grote氏試剂作用而比色的方法。

A COMPARISON OF THREE VOLUMETRIC METHODS FOR THE DETERMINATION OF TIBIONE

The following three volumetric methods for the determination of Tibione (p-acetylaminobenzaldehyde thiosemicarbazone)when pure and in tablets were iuvestigated and compared. 1. Argentimetric method. Tibione dissolved in 95% ethanol was precipitated by excess 95% ethanolic AgNO₃. After standing at room temperature for 10 minutes, the precipitate was filtered and thoroughly washed with ethanol. The Ag~+ in the filtrate and washings were titrated with aqueous KSCN, using ferric alum as indicator. One mole of Tibione was equivalent to 2 moles of AgNO₃. Tablets were first extracted with ethanol and treated accordingly. 2. Iodimetric method. A 0.02 g sample of Tibione was dissolved in 20 ml water containing 4 ml 10% NaOH, to which standard I₂ solution was added. After 10 minutes, the solution was acidified with about 4 ml 3N HC1, and then titrated with Na₂S₂O₃. One mole of Tibione required 8 equivalents of iodine. Tablets were first extracted with ethanol, and the sample was treated as before after ethanol was removed. 3. For the determination by FeCl₃, the method of O. Wollenberg was followed. For assaying tablets, it was found unnecessary to extract Tibione from the tablets. The compound could be determined directly. All three methods gave accurate results. For pure samples, the iodine method was most suitable, whereas for tablets, the ferric chloride method was recommended.