CALCIUM CARBIDE 286 CALCULATING MACHINE ness. It is a white, earthy, infusible powder, phosphorescent at high temper- atures; it is strongly alkaline, and readily absorbs carbonic anhydride. It unites vigorously with water, throwing out great heat, and forms a hydrate, CaOH^O, which is slightly soluble in cold water; it is used in medicine as lime-water. Impure lime mixed with sand forms mortar. Calcium sulphate, CaS04, found as hy- dride of gypsum, CaS042H20, and sele- nite and alabaster. The water is given off by heating it, and a white powder is left, which dissolves in 500 parts of cold water. Mixed with water, it sets in a hard substance; it is used under the name of plaster of Paris for making casts of medals and statues, etc. Calcium carbonate, CaCOs, forms the chief constituent of limestone, marble, chalk, etc. It occurs crystallized as calc- spar and aragonite. Calcium carbonate is insoluble in water, but is dissolved by water containing carbonic acid gas; it is deposited from this solution by boil- ing, hence boiler deposits. Calcium phosphates occur in the bones of animals and are native in Apatite. Calcium chloride, CaCl.., is obtained by dissolving the carbonate in hydrochloric acid. It crystallizes in white prismatic crystals; it is very deliquescent. Fused calcium chloride is used to dry gases, etc. It absorbs ammonia gas. Calcium fluoiide, CaFli, occurs as fluor spar. Calcium sulphides and phosphides have been obtained. Salts of calcium are not precipitated by H2S, either in an acid or alkaline solution. Alkaline carbonates and ammonia carbonate give a white precipitate insoluble in excess; oxalate of ammonia gives a white pre- cipitate from a neutral solution ; the pre- cipitate is not soluble in acetic acid._ A solution of sulphate of calcium gives no precipitate. The chloride gives an orange-red flame with alcohol. The spectrum of calcium gives several char- acteristic lines, especially an orange-red and a green line. Chloride of lime, or bleaching powder, is a mixture of cal- cium chloride and calcium hypochlorite. CALCIUM CARBIDE, a chemical compound of calcium and carbon, symbol CaC... It is a hard, bluish-black, clear crystalline body, and is impervious to light, insoluble in all known solvents, and with a sp. gr. of 2.22. Although calcium carbide has been known for many years, it did not come into promi- nence until 1894, when Moissan pro- duced it by heating 120 grains of oxide of calcium and 70 grains of sugar char- coal in an electric furnace. The furnace was heated to 3,500° C. by an electrical current of 350 amperes and 70 volts for 20 minutes. This produced about 150 grains of carbide. Dry carbide is not affected by heat in an ordinary atmos- phere, but when heated in an excess of oxygen it burns and forms calcium car- bonate. When exposed to damp air for a short time it disintegrates and gives off a peculiar odor resembling garlic. When calcium carbide comes in contact with water. Acetylene Gas (q. v.) is produced and calcium hydroxide thrown down (CaC2+2H:.0=CzH,+Ca(OH).). It is used generally for the production of acetylene and the reduction of iron. CALCIUM LIGHT, a brilliant light produced by directing the flame of an oxy-hydrogen blow-pipe against a block of compressed quicklime. It has been used on the stage for many years, and by the aid of colored glasses very charm- ing effects are produced. More recently it was employed in lanterns for project- ing photographic and biographic pic- tures on a screen. It has now been su- perseded by electric light. CALCULATING MACHINE, a piece of mechanism for assisting the human intellect in the performance of arithmet- ical operations. The system of loga- rithms. Invented by the celebrated Napier of Merchistoun, in 1614, which is of the greatest assistance to mathematicians and others in the computation of figures, by shortening the ordinary operations, seems to have been instrumental in di- recting attention to the construction of an instrument by which arithmetical re- sults could be produced by mechanical means, although the abacus had been long used in Europe and Asia for effect- ing calculations; anj Napier himself had produced what may be termed an elementary calculating machine, consist- ing of rods with four faces, known as Napier's Bones. The first instrument which can be justly called a calculating machine, was invented by Blaise Pascal, in 1642. It was more especially con- trived for the calculation of sums of money, although it would also perform the ordinary operations of arithmetic with numbers on the common, or decimal scale of notation. It consisted of a set of cylinders, with numbers marked on their external surface, moving on axles to which wheels were attached, with a certain number of notches cut in their circumference. Among the various ma- chines of later invention, the two de- vised by Mr. Babbage, but never fully executed, are by far the more elaborate. The invention of the brothers Scheutz was based on the description of Mr. Babbage's difference machine, and is A
