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IN connexion with work in progress in this laboratory on tea fermentation; a volumetric method for the determination of tea tannin has been dev'ised, which is free from many of the disadvantages attending other methods in common use. This method has already enabled us to confirm some of our findings on the extent of oxidation of tea tannin in tea fermentation. It also makes it possible to estimate the amount of tannin in black tea with much greater precision than was formerly possible, and it is hoped that it will facilitate any work oh made tea that may be undertaken in the home country. The method mayvalso prove to be of use to biochemists who are interested in tannins other than those obtained from tea. In the absence of any specific volumetric reagent for tea tannins, these substances are determined in tea infusions by an oxidimetric titration of the infusion followed by a similar determination on another portion of the solution from which tannin has been quantitatively removed. The difference between the "total" and the "non-tan" titres gives the tannin titre. The infusion is prepared by boiling 5 g. tea or 20 g. fresh green leaf with 400 ml. water for 1 hr., cooling and making up the volume of the extract to 500 ml. Fresh green leaf contains from 75 to 80% -moisture so that the above quantities are approximately equivalent to each other. The separation into tannins and non-tans is usually effected by gelatin. The following reagents are required. Gelatin solution. 25 g. gelatin are soaked fbr 1 hr. in saturated NaCl solution. The mixture is then warmed until the gelatin has dissolved and after cooling the solution is made up to 11. with saturated NaCl. Acid NaCl. 25 ml. of conc. H2SO4 are added to 975 ml. saturated NaCI solution. 100 ml. of a tea infusion are mixed with 50 ml. of the gelatin solution, 100 ml. of acid NaCl and 20 g. of powdered kaolin. After shaking for several min. and allowing to settle, the mixture is ifitered and an aliquot of the filtrate withdrawn for titration. 25 ml. of the non-tan filtrate are equivalent to 10 ml. of the original infusion. The Lowenthal and alkaline iodine methods

Methods for the volumetric estimation of tea tannin in green-leaf and black tea. A new alkaline permanganate method