For the purpose of estimating the percentage of tannin contained in tea, the simplest method is to make an infusion of the leaves and pour it into a cup or glass and add to it a small quantity of a standard solution of plumbic acetate. The acetate will cause the tannin to form a precipitate, which must be removed and weighed in a small scale fitted for the purpose; then by taking the nominal percentage of tannin contained in pure teas at 12 in Green and 10 in Black and 2 per cent. in Spent or exhausted leaves, the difference will be the percentage of adulteration, the extent being indicated by the lessened proportion of tannin in the same ratio. The presence of Catechu (soluble salts of iron) is best ascertained by making an ordinary infusion of the leaves, allowing the liquor to cool and pouring it into a cup or glass. Next add a preparation of neutral plumbic acid and separate the precipitate formed by the introduction of the chemical by filtration, and adding a little argentic nitrate to the filtrate. If catechu be present the residue will turn a dark-brown, the liquid meanwhile acquiring a deep yellow hue, while under the same conditions the liquor of pure tea will remain unaffected. But if the cosmetic be extensively employed, a weak solution of ferric-chloride will cause the precipitate to turn light-green or it may be detected under the microscope if heavily coated. Spent and spurious leaves may also be readily detected by the “ash test,” through the following deductions: Pure teas, as shown above, contain from 5 to 6 per cent. of ash on incineration, 2 per cent. of this being soluble in boiling water; any increase of these parts is a certain indication of the presence of foreign or exhausted leaves in the sample treated. The percentage of ash contained in spent leaves, ranging from 10 to 30, and in spurious leaves from 40 to 50, in many instances, while the residue of teas adulterated with mineral matter have been known to reach as high as 75 to 80 per cent. of the incinerated sample. The presence of logwood is best exposed by the addition of a few drops of sulphuric acid to an infusion made with the leaves in the ordinary way. If any of the dye be present this acid will cause the liquid to turn a deep red, but if the tea be uncolored the liquor will remain entirely unaffected. Graphite being visible to the naked eye is easily distinguished by its characteristic glossy nature, or can be separated by treating the leaves with boiling water in the usual manner and evaporating the infusion. The substance, if present, will form a deposit at the bottom of the vessel or will be found adhering to its sides if used in large quantities. While Silica is readily recognized by the increased amount of ash insoluble in the water obtained by calcimining a sample of the tea so adulterated, as above described. SAND AND MINERAL MATTER IN TEAS