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.