This section is from the book "The Manufacture Of Liquors, Wines, And Cordials, Without The Aid Of Distillation", by Pierre Lacour. Also available from Amazon: Manufacture of Liquors, Wines, and Cordials, Without the Aid of Distillation.
Owing to a variety of causes, - the fluctuations of the market, an over stock of one particular kind of unmerchantable liqour or a quantity of liquor too highly colored, or to point to the emergency that might arise, would be impossible; and hence the necessity of a knowledge of the articles used in decolorizing liquors, viz. animal charcoal or bone black. Animal charcoal by no means necessarily possesses the decolorizing property, as this depends upon its peculiar state of aggregation. If a piece of pure animal matter be carbonized, it usually enters into fusion, and from the gaseous matter which is extricated, becomes porous and cellular. The charcoal formed has generally a metallic lustre, and a color resembling that of black lead. It has little or no decolorizing power.
The most powerful of all the charcoals for discharging colors, are those obtained from certain animal matters, such as dried blood, hair, horns, etc, etc, by first burning them with carbonate of potassa, and then washing the product with water. The next most powerful decolorizer is bone black, in which the separation of the carbonaceous particles is effected by the phosphate of lime present in the bone. Vegetable substances may be made to yield a good charcoal for destroying color, provided before burning they be well mixed with pumice stone, chalk, flint, calcined bones, etc., etc.
It results from the foregoing facts that the decolorizing power of charcoal depends upon a peculiar mode of aggregation of its particles, the leading character of which is they are isolated from one another, and thus enabled to spread over a greater extent of surface. It is on this principle that certain chemical substances act in developing the property in question, when they are ignited in a state of intimate mixture with the substances to be charred. Thus it is perceived that there is no necessary connexion between animal charcoal and the decolorizing power; as this charcoal may or may not possess the peculiar aggregation of its particles, on which the power depends.
Bone black, for instance, has this property, not because it is an animal charcoal, but in consequence of the phosphate of lime present in the bone, the favorable state of aggregation is induced.
Animal charcoal will, by digestion and filtration, remove the bitter principles from infusions, etc., Its power of acting on chemical compounds and solutions is much more decided in its purified state.
Bone black is composed of phosphate and carbonate of lime, charcoal, and carburet of iron.
Bone black, when used for decolorizing, should be deposited in a filter to the depth of from five to fifteen feet. On a small scale, a common forty gallon barrel can be used for the same purpose. (For further particulars see Filtering Apparatus.)
Boiled Milk possesses decolorizing properties, and is very useful in wines. A pint of boiled milk added while warm to a pipe of red wine, will discharge the color completely, rendering it transparent. The action of the milk is mechanical; the particles of milk, combining with the minute particles that constitute the coloring, fall to the bottom or subside.