The distillate is concentrated and after treatment with animal charcoal and filtration should conform to the requirements of the British Pharmacopoeia. These are specified as follows: Specific gravity at 15.5 deg. C., 1.260. It should yield no characteristic reaction with the tests for lead, copper, arsenium, iron, calcium, potassium, sodium, ammonium, chlorides, or sulphates. It should contain no sugars and leave no residue on burning. _Animal Charcoal for Decolorisation._--The application of animal charcoal for decolorising purposes dates back a century, and various are the views that have been propounded to explain its action. Some observers base it upon the physical condition of the so-called carbon present, and no doubt this is an important factor, coupled with the porosity. Others consider that the nitrogen, which is present in all animal charcoal and extremely difficult to remove, is essential to the action. Animal charcoal should be freed from gypsum (sulphate of lime), lest in the burning, sulphur compounds be formed which would pass into the glycerine and contaminate it. The "char" should be well boiled with water, then carbonate of soda or caustic soda added in sufficient quantity to give an alkaline reaction, and again well boiled. The liquor is withdrawn and the charcoal washed until the washings are no longer alkaline. The charcoal is then separated from the liquor and treated with hydrochloric acid; opinions differ as to the amount of acid to be used. Some contend that phosphate of lime plays such an important part in decolorising that it should not be removed, but it has, however, been demonstrated that this substance after exposure to heat has very little decolorising power. Animal charcoal boiled with four times its weight of a mixture consisting of equal parts of commercial hydrochloric acid (free from arsenic) and water for twelve hours, then washed free from acid, dried, and burned in closed vessels gives a product possessed of great decolorising power for use with glycerines. A good animal charcoal will have a dull appearance, and be of a deep colour; it should be used in fine grains and not in the form of a powder. The charcoal from the filter presses is washed free from glycerine (which is returned to the treated lyes), cleansed from foreign substances by the above treatment and revivified by carefully heating in closed vessels for twelve hours. _Glycerine obtained by other Methods of Saponification._--French saponification or "candle crude" glycerine is the result of concentration of "sweet water" produced in the manufacture of stearine and by the autoclave process. It contains 85-90 per cent. glycerol, possesses a specific gravity of 1.240-1.242, and may be readily distinguished from the soap-crude glycerine by the absence of salt (sodium chloride). This glycerine is easily refined by treatment with charcoal.