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DAMASSIN.
or strokes across the iron, &c. with a cutting knife, such as is used in making of smallfiles. As to the first, it is necessary for the gravings or incisions to he made in the dove-tail form; that the gold or silver wire, which is thrust forcibly into them, may adhere themore strongly. As to the second, which is the more usual, the method is this :—Havingheated the steel till it changes to a violet, or blue color, they hatch it over and acrosswith the knife; then draw the ensign or ornament intended, upon this hatching, with afine brass point or bodkin. This done, they take fine gold wire, and conducting or chasingit according to the figures already designed, they sink it carefully into the hatches of themetal with a copper tool.
DAMASSIN is a kind of damask, with gold and silver flowers, woven in the warp andwoof; or occasionally with silk organzine.
DAMPS, in mining, are noxious exhalations, or rather gases, so called from the Germandamp/, vapor. There are two principal kinds of mine gases, the fire-damp, or carburetedhydrogen, and t^ choke-damp, or carbonic acid gas. See Mines.
DAPHNINE ; the bitter principle of the Daphne Mpina.
DATOLITE. A mineral composed of silica, lime, and boracic acid.
DECANTATION (Eng. and Fr.; Abgiessen, Germ.) is the act of pouring off the clearsupernatant fluid from any sediment or deposite. It is much employed in the chemicalarts; and is most conveniently effected by a syphon.
DECOCTION (Eng. and Fr.; Mlcochung, Germ.) means either the act of boilinga liquid along with some organic substance, or the liquid compound resulting from thatact.
DECOMPOSITION (Eng. and Fr.; Zerselzung, Germ.) is the separation of the con-stituent principles of any compound body. The following table, the result of importantresearches recently made by M. Persoz, Professor of Chemistry at Strasburgh, shows theorder in which decompositions take place among the successive substances.
of Magnesium
— Silver
— Cobalt
— Cobalt
— Nickel
— Nickel
Protox. of Mercury
Protox. of Cerium
— Cerium
of Zinc
Protox. of Manganese
Protox. of Manganese
Oxyde of Lead
— Iron
— Cadmium
— Uranium
— Copper
— Copper
— Glucinum
— Tin
— Alumium
Oxyde of Glucinum
— Uranium
— Alumium
— Chromium
— Uranium
Protox. of Mercury
— Chromium
Oxyde of Mercury
— Iron
— Iron
— Tin
— Bismuth
— Bismuth
— Antimony
By means of the cupric oxyde we may separate, 1,
, the ferric oxyde from the
, n ganous
oxyde; 2, the cobaltic, nickelic, zincic and cerous oxydes from the uranic, ferric, c J'^° n Jj ] eand aluminic oxydes; 3, the ferrous oxyde from the chromic oxyde, when dissolved mmuriatic acid. .. t be
In boiling a muriatic solution of the cobaltic, nickelic, and manganous oxydes, wimercuric oxyde, the first two oxydes alone are precipitated. Alumina separates themic oxyde froA the bismuthic oxyde, the stannous oxyde from the stannic oxyde, aa . ; ta .stannous oxyde from the antimonic acid. The cupric oxyde separates also by P re w bichtion, the aluminic, uranic, chromic, titanic, and vanadic oxydes from all the oxydesare precipitable in the state of sulphuret, by hydrosulphuret of ammonia.
As an example of this mode of analysis— , j ro gen,
Dissolve pech-blende in aqua regia, precipitate its copper by sulphurated hy ur ^ n j cboil the liquid along with nitric acid, in order to transform all the uranium m t0 ^ f trr icacid. Next boil it along with cupric oxyde, which precipitates only the uranic aa rcur j coxydes. Iledissolve the precipitate in nitric acid, and boil the solution with 1,1 ^oxyde, which does not precipitate the ferric oxyde. Finally, separate the copper ^ ma ymercury from the uranium, by means of sulphureted hydrogen. In this processsubstitute plumbic oxyde for the cupric oxyde, and succeed equally well. , bodies*
Knowledge, like the above, of the elective affinities and habitudes of | mI un ; on s andsimple and compound, imparts to its possessor an irresistible power over the