植物鞣质的测定方法研究——络合量法在鞣质含量测定中的应用

植物鞣质(tannin)的含量测定自十九世纪初至今,大都应用皮粉吸附法(Hidepowder method),并以其为国际公定法,但该法十分冗长繁复,不能满足当前生产实际的需要.为寻求简便、快速、准确且能较广泛应用的方法,本文据鞣质能与金属离子生成络合物沉淀的原理,研究络合量法应用于植物鞣质的含量测定.研究本法的结果与国际皮粉法比较无显著差异;并较他法精密,简捷,应用范围亦较广泛;本法误差不超过2%,完成测定只需40分钟.

STUDIES ON THE METHOD OF DETERMINATION OF VEGETABLE TANNINS, THE COMPLEXOMETRY USED FOR QUANTITATIVE DETERMINATION OF TANNIN

A method is described which is based upon the formation of a precipitate of poly- nucleus complex compound between the tannins and metallic ions, and estimation of the complexed quantity of metallic ions by complexometric titration for the determination of vegetable tannins. The tannin is precipitated completely by Zn⁺⁺ at pH 11±0.2, 35±2℃, and afterwards EDTA is used to titrate back the excess of Zn⁺⁺. By comparison made with the official method (the Hide powder method) as standard, we obtained the relation between the complexed quantity of Zn⁺⁺ and the percentage content of tannin: Tannin%=(0.1556×1M Zn⁺⁺ required (ml))/(W (sample, g))×100. This method is more accurate than L?wenthal's. It is more simple, precise and widely applicable than the Hide powder method and L?wenthal's method. The average deviation is not over 2%. It is very rapid and the whole determination can be finished within 40 minutes.