Calabar bean is a powerful poison. The antidotes are:—Diffusible stimulants; the hypodermic injection of the 1⁄50th of a grain of sulphate of atropia, to be repeated if necessary at the end of two hours; and artificial respiration. See Eserine.
CAL′AMINE. See Zinc (Carbonate of).
CALCINA′TION. The operation of burning or roasting any solid body to expel its more volatile parts, as the conversion of chalk into lime by the expulsion of carbonic anhydride. The roasting of the ores in the first stage of the Welsh process of copper smelting and in the Silesian mode of extracting zinc is technically termed CALCINATION.
The method of conducting the process of calcination depends on the nature of the body operated on. Many substances, for delicate experiments, are calcined over a spirit lamp in a platinum spoon or crucible; others, in iron vessels or earthen crucibles, placed in a common furnace. When the action of the air proves injurious, as in the manufacture of charcoal, the process is performed in close vessels or chambers. In some cases the fuel is mixed with the articles, and they are both burnt together, as in the manufacture of lime, the roasting of ores, &c. The process of drying
salts, or driving off their water of crystallisation by heat, is also frequently called CALCINATION; thus we have calcined copperas, alum, &c.
CAL′′CINER. A reverberatory furnace used for the calcination of metallic ores, particularly those of COPPER and ZINC (which see).
CAL′CIUM. [Eng., L.] Ca. The metal of which LIME is an oxide. Though it is a chemical curiosity when isolated, it is one of the most abundant substances in nature, forming a very large portion of the crust of the earth. It occurs in combination with fluorine as fluor-spar; with oxygen and carbonic acid as chalk, limestone, and marble; and with oxygen and sulphuric acid as gypsum. The metal was first obtained from lime by Sir H. Davy in 1808; but little was known of its properties until Dr Matthiessen formed it by the electrolytic decomposition of the chloride of calcium.
Prep. 1. By the action of a powerful voltaic current upon a paste of pure lime in contact with mercury, as in the original method of preparing barium.
2. By the electrolysis of chloride of calcium in a state of fusion.
3. (Caron.) Fused chloride of calcium in powder, 300 parts; distilled zinc, finely granulated, 400 parts; sodium, in small pieces, 100 parts; the whole placed in a crucible and heated to redness in an ordinary furnace. The action is very feeble at first, but after some time zinc flames arise. The heat must now be moderated to prevent the volatilisation of the zinc, but at the same time it must be maintained as high as possible. When the crucible has remained in this state for about a quarter of an hour it may be withdrawn. On cooling, a metallic button will be found at the bottom. This alloy of zinc and calcium, which generally contains from 10 to 15% of the latter metal, must be placed in a coke crucible and heated until the whole of the zinc is driven off. The alloy should be in pieces as large as possible. When proper precautions have been observed a button of CALCIUM is obtained, only contaminated with the foreign metals contained in the zinc.