DECOCTION, (Eng. and Fr.; Abkochung, Germ.) means either the act of boiling a liquid along with some organic substance, or the liquid compound resulting from that act.
DECOMPOSITION, (Eng. and Fr.; Zersetzung, Germ.) is the separation of the constituent principles of any compound body. The following table, the result of important researches recently made by M. Persoz, Professor of Chemistry at Strasburgh, shows the order in which decompositions take place among the successive substances.
| Nitric Acid. | Muriatic Acid. |
|---|---|
| Oxide of Magnesium | Oxide of Magnesium |
| Ox— of Silver | Ox— of Cobalt |
| Ox— of Cobalt | Ox— of Nickel |
| Ox— of Nickel | Protox. of Mercury |
| Protox. of Cerium | Pro—. of Cerium |
| Oxide of Zinc | Oxide of Zinc |
| Protox. of Manganese | Protox. of Manganese |
| Oxide of Lead | Pro—. of Iron |
| Ox— of Cadmium | Pro—. of Uranium |
| Ox— of Copper | Pro—. of Copper |
| Ox— of Glucinum | Pro—. of Tin |
| Ox— of Alumium | Oxide of Glucinum |
| Ox— of Uranium | Ox— of Alumium |
| Ox— of Chromium | Ox— of Uranium |
| Protox. of Mercury | Ox— of Chromium |
| Oxide of Mercury | Ox— of Iron |
| Ox— of Iron | Ox— of Tin |
| Ox— of Bismuth | Ox— of Bismuth |
| Ox— of Antimony |
By means of the cupric oxide we may separate, 1, the ferric oxide from the manganous oxide; 2, the cobaltic, nickelic, zincic and cerous oxides from the uranic, ferric, chromic, and aluminic oxides; 3, the ferrous oxide from the chromic oxide, when dissolved in the muriatic acid.
In boiling a muriatic solution of the cobaltic, nickelic, and manganous oxides, with the mercuric oxide, the first two oxides alone are precipitated. Alumina separates the cadmic oxide from the bismuthic oxide, the stannous oxide from the stannic oxide, and the stannous oxide from the antimonic acid. The cupric oxide separates also by precipitation, the aluminic, uranic, chromic, titanic, and vanadic oxides from all the oxides which are precipitable in the state of sulphuret, by hydrosulphuret of ammonia.
As an example of this mode of analysis—
Dissolve pech-blende in aqua regia, precipitate its copper by sulphuretted hydrogen, boil the liquid along with nitric acid, in order to transform all the uranium into uranic acid. Next boil it along with cupric oxide, which precipitates only the uranic and ferric oxides. Redissolve the precipitate in nitric acid, and boil the solution with mercuric oxide, which does not precipitate the ferric oxide. Finally, separate the copper and the mercury from the uranium, by means of sulphuretted hydrogen. In this process we may substitute plumbic oxide for the cupric oxide, and succeed equally well.
Knowledge, like the above, of the elective affinities and habitudes of chemical bodies, simple and compound, imparts to its possessor an irresistible power over the unions and disunions of the elements, which he can exercise with certainty in effecting innumerable transformations in the arts.
DECREPITATION, (Eng. and Fr.; Verknistern, Germ.) is the crackling noise, attended with the flying asunder of their parts, made by several salts and minerals, when heated. It is caused by the unequal sudden expansion of their substance by the heat. Sulphate of baryta, chloride of sodium, calcareous spar, nitrate of baryta, and many more bodies which contain no water, decrepitate most violently, separating at the natural joints of their crystalline structure. Some chemists have preposterously enough ascribed the phenomenon to the expansion of the combined water into steam. What a specimen of inductive philosophy!
DEFECATION, (Eng. and Fr.; Klaren, Germ.) the freeing from dregs or impurities.