For the estimation of tannin in tea various processes are in use, a tritration by means of a standard solution of gelatine, which depends upon the well-known property possessed by gelatine of forming insoluble compounds with tannin being the most effective, but tedious and difficult. A much more simple and promising method consists in tritrating by means of a standard solution of lead, the point of saturation being indicated by the red color struck by an ammoniacal solution of ferricyanide of potassium, one drop of this solution being capable of coloring one milligram of tannin dissolved in 100 parts of water, the exact strength of the solution of lead being ascertained with a standard solution of tannin. In using the solution of lead, 10 drops of it are first diluted with 9 times its volume in water, and the tea infusion dropped into it from a graduated burette until the indicator strikes a red with the drop of the indicator. The infusion of tea is made by boiling 2 grains of the leaves in water and afterwards diluting it to 250, it being understood that the smaller the quantity of this infusion required to saturate the 10 parts of the lead solution, the higher the percentage of tannin in the sample of tea treated. This test is specially applicable for ascertaining whether Black tea in particular has been mixed with spent leaves. By taking the normal percentage of tannin in pure Black tea at 10 and the percentage of tannin in spent tea as 2, the difference is the extent of adulteration. There is a great variability in the amount of tannin contained in the different varieties of tea, varying in quantity according to the country of production, kind, quality, and state of growth when picked. In six samples of China Oolong teas recently tested, the percentage of tannin extracted, after an infusion of thirty minutes, averaged only 7.44, an almost similar result being obtained from an examination of the finest Congou-China Green teas, ranging from 11.87 to 14.11 per cent., some Japan samples under the same conditions yielding on an average from 8 to 10. While with a sample of the finest Assam (India) a percentage of 17.73 of tannin by actual weight was extracted after an infusion of only fifteen minutes, two samples of India and Ceylon giving respectively 18.91 and 15.26, proving conclusively that India and Ceylon teas are much more heavily weighted with tannin than China and Japan teas. The percentage of tannin in the extract is also quite irregular, according to the quality of the tea, the ratio of tannin to the extract varying quite uniformly with the value of the tea, the percentage falling and rising with the percentage of the extract and cost of the tea.