3844. Decoloration

3844.    Decoloration. The blanching or loss of the natural color of any substance. Syrups, and many animal, vegetable, and saline solutions, are decolored or whitened by agitation with animal charcoal, and subsequent subsidence or filtration. Many fluids rapidly lose their natural color by exposure to light, especially the direct rays of the sun. In this "way, castor, nut, poppy, and several other oils are whitened. Fish oils are partially deodorized and decolored by filtration through animal charcoal. (See No. 3839 (Filtering Powders).) By the joint action of light, air, and moisture, cottons and linens are commonly bleached. The peculiar way in which light produces this effect has never been satisfactorily explained. The decoloration of textile fabrics and solid bodies, generally, is called bleaching.

3845. Defecation

3845.    Defecation. In chemistry, the separation of a liquid from its Iees, dregs, or impurities. This is usually performed by subsidence and decantation, and is commonly applied to the purification of saline solutions, on the large scale, in preference to filtration, than which it is both more expeditious and inexpensive.

3846. Neutralization

3846.    Neutralization. The admixture of an alkali or base with an acid in such proportions that neither shall predominate. A neutral compound neither turns turmeric paper brown, nor litmus paper red. The term saturation is also applied to complete neutralization (see No. 27 (Saturation)); but saturation has two distinct meanings; chemically, it denotes that a given alkali has been neutralized completely by an acid, or vice versa. Pharmaceutically, it implies that a given solvent is charged to its utmost capacity with an active ingredient; this point is, however, so difficult to determine, that the term is scarcely ever applied accurately.

3847. Edulcoration

3847.     Edulcoration. The affusion of water on any substance for the purpose of removing the portion soluble in that fluid. Edulcoration is usually performed by agitating or triturating the article with water, and removing the latter after subsidence, by decantation or filtration. It is the method commonly adopted to purify precipitates and other powders which are insoluble in water.

3848. Rectification

3848.    Rectification. A second distillation of a fluid, for the purpose of rendering it purer. In rectifying alcohol containing water, the distillation is conducted at a temperature high enough to evaporate the alcohol and cause it to distill over into the receiver, but not high enough to boil the water, the greater part of which, therefore, remains behind in the body of the still. It is difficult to obtain an anhydrous product without employing some agent having a strong affinity for water.

3849. Calcination

3849.    Calcination. The separation or expulsion, by heat, of volatile from fixed matter. By this means crystalline salts are obtained in a dry or anhydrous form, by depriving them of their water of crystallization; in this particular, the process is similar to desiccation. (See No. 12 (Desiccation).) Calcination is also employed for the ignition of silica, etc., in order to render it more easily reducible to fragments or powder.

The operation of calcining is conducted on the small scale in platinum spoons or crucibles, and heat applied by the flame of a spirit lamp, or other appropriate means. When large quantities of matter are calcined, metal or earthenware crucibles and the heat of a furnace are employed. Charcoal is thus obtained from wood, bone-black from bones, etc..