ELECTROTYPING is One of the most important applications of electrochemistry. For repro ducing printing-type the process is as follows; An impression of the type is taken in wax, which is then brushed with a coating of black lead and suspended as the cathode in a bath of sulphate of copper; a copper bar or plate is used for the anode. By passing a current through the cir cuit a thin film of copper is deposited in the wax. and when thick enough this is removed and backed with type-metal. The pages of this En eyclopatd ia and practically all hooks are printed from plates made substantially in this manner. Sometimes the article itself. as for example a medal, is used as a cathode to receive the copper coating. This coating. when removed. forms a negative. which is made the cathode to receive another plating of copper, forming the positive or true reproduction. A of methods of eleetrotyping, dithering chiefly in the details of the process. are employed.
Turning now to the production of chemical compounds by electrical action. we may notice. first, the manufacture of alkalis and chlorine from common salt. Chlorate of potash is now
produced in large quantities by electrolysis, as arc calcium carbide (q.v.) and carhorundum. (See ABRASIVES. ) Phosphorus ) is now made electrolytically in large quantities. and artificial graphite is now being made directly from eon I in the same way. Among the lesser applications of eleetro-chemistry may be men tioned the purification of sewage, the tanning ()f hides. the aging of wines, and the production of ozone, while ea•borundum and graphite, and even rubies and small diamonds are prepared by this means. Consult : Moissan. /.c fou•c flue 1 ; Borchers, Do ktrooietallii•gie (Brunswiek. 1896) ; Haber. Grand•iss der techni schen. Elatrock•inic oaf theory tischIT v;runfllage (Munich and Leipzig. 1S9S) ; Gore. Thr Art of Electrolytic ;;•paration of Mc tals (London, 189-t); (lore. TI. dr! of Electro-lletallaryy, ineluditul all kaoicn processes of Elretro-Deposition (New York, DM)) : Ahrens. Handbuch der Ma trochrmic (Stuttgart. 18961; also The Electro Chemi•al Industry ( Philadelphia. current ).