The table below may prove useful as indicating the requirements to be exacted when the chemist is asked to give an opinion concerning the presence of facing admixtures or of exhausted or foreign leaves in a sample of tea: _Total ash_--should not be under 4.5% or over 7%. _Ash soluble in water_--should not be under 40% of total ash. _Ash insoluble in water_--should not be over 3%. _Ash insoluble in acid_--should not be over 1%. _Extract_--should not be under 30%. _Insoluble leaf_--should not be over 60%. NOTE.--The British Society of Public Analysts adopt: _Total Ash_ (dry basis)--not over 8% (at least 3% should be soluble in water). _Extract_ (tea as sold)--not under 30%. MILK. The chief constituents of milk are water, butter, caseine, lactose (milk-sugar), traces of albumen and mineral salts. Butter is present in the form of minute globules, held in suspension; the caseine, for the greater part, is in solution, only a small portion being present in an insoluble suspended condition. In milk only a few days old, the _colostrum_ (the milk secreted during the first few days after parturition) consists largely of rather voluminous cellular conglomerations, containing a sufficient quantity of albumen to coagulate upon heating. The normal density of milk is 1.030, water being 1.000; the density rising to 1.036, if the fluid has been skimmed. Good milk contains, on an average, 3.7 per cent. of butter; 5.7 per cent. of lactose, and leaves upon evaporation 12 to 14 per cent. of solid matters.[T] The most common adulteration of milk consists in the addition of water. This fraud is detected by means of an areometer (_lactodensimeter_) which gives directly the specific gravity of the fluid under examination. Should the density be much below 1.030, it is certain that water has been added. It does not, however, necessarily follow if it is about 1.030 that the milk is pure, since the gravity of the fluid, which would be increased upon skimming, could be subsequently reduced to 1.030 by the addition of water. The lactodensimeter, therefore, although useful in the detection of a simple admixture, fails to give reliable results if the fraud perpetrated is a double one; and a determination of the proportion of butter present is also usually necessary. Numerous methods have been proposed to accomplish this estimation. The most preferable of these, owing to the rapidity with which the operation is executed, is the use of the lactoscope (_galactoscope_). This instrument consists of a tube provided with a glass plate fitted at one end, and with a movable glass plate at the other extremity. A few drops of the milk to be tested are placed between the two plates, and the tube lengthened, by screwing out the movable plate, until the fluid no longer transmits the light of a candle placed at a distance of one metre. As the opacity of milk is due to the butter present, it is evident that the proportion of this substance contained