ELECTRO-CHEMISTRY. 781 ELECTRO-CULTURE OF PLANTS. copper or aluminium bronze iu an alkaline cyanide hath: (3) platini; with copper in an acid >ul]iliate bath : |4) jilaling willi aluiuinium. In tlie tiiial operation the bath was a concen- trated solution of aluminate of soda, cyanide of potassium, and stannate of soda lieated to 130" F. by a steam coil. The anode of pure alumin- iimi was ■}i inch thick. 10 inches wide, and 4 feet long, and the cathode was of course the column or plate to be coated. The current was of 2500 amperes at 5 volts, and was supplied by a d iamo. A coating about -^K inch thick, or 2 to 3 ounces per square foot, was deposited in 4S hours. Electrically deposited copper is now largely used to protect and ornament architectural iron- work, the coating varying from 8 to 10 ounces per square foot for smooth plates, to 1-1 to 16 ounces for rough cast-iron. l"or interior orna- ment electro-bronzing is often employed, using a coating of from 2 to 3 ounces per square foot. In Europe it is common practice not to deposit the plating directly on the iron, but on a suitably prepared varnish, thus avoiding the necessity of cleaning, but at the same time giving a plating which is easily knocked off; in the United States the iron is very carefully cleaned and the copper deposited directly upon it, and so firmly that the original metal with its coating may be bent or twisted without rupturing the plating. The electro-deposition of nickel, or nickel-plat- ing, is employed in manufacturing a multitude of useful and ornamental articles familiar to every one. The bath consists of nickel-ammo- nium sulphate dissolved in boiling water. The articles to be plated are first cleaned with abrasives or acids, and after the plating is finished are polished. Gold and silver plating are employed in making jewelry, ornaments, and tableware of all descriptions. In silver-plating the bath used is a solution of chloride of silver, cyanide of potash, and water. In gold-plating either a hot or a cold solution may be used, and each is variously compounded, according to the result which it is desired to obtain. After the plating has been deposited the article is suitably polished. See article Electropl.tixg. Electbotypi:»g is one of the most important applications of electro-chemistry. 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- cvclopa"dia and practically all books 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 variety of methods of electrotyping, difl'oring 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 are calcium carbide (q.v.) and carborundum. (.See Abrasives.) Phosphorus (q.v.) is now made elcctrolytically in large quantities, and artificial graphite is now being made directly from coal in the same way. Among the lesser applications of electro-chemistry may be men- tioned the purification of sewage, the tanning of hides, the aging of w-ines, and the production of ozone, while carborundum and graphite, and even rubies and small diamonds are prepared by this means. Consult: Moissan, Le foure clcc- triquc{ Paris, 1807 ) ; Horchers, Elektromefallurgic (Brunswick, ISOO) ; Haber. Grundiiss der tcchiti- schen Elrhlruchcmie uuf theoretischer Grundlage (Munich and Leipzig, I89S) ; Gore. The Art of Electrolytic Reparation of Metals (London, 1894) ; Gore, The Art of Electro-iletalluryy, in- cluding all kiiotrn processes of Electro-Deposition (New York. 1900) : Ahrens. Handhiich der Elek- trochemic (Stuttgart. 1896) ; also The Electro- chemical Indutitry (Philadelphia, current). ELECTRO-CULTURE OF PLANTS. The culture of plants under electric stimulus. It has long been known that plants respond to electric stimuli, and many investigations have been made to ascertain practical means of realiz- ing the benefits of this force. The subject naturally divides itself into the direct use of the current when applied to the seed, plant, or soil, and the use of the electric light. The Abb6 Xollet seems to have been the first to notice that the germination of seeds could be hastened by electrifying them before planting. Later, Specnew stimulated, for a few minutes, moist seed of beans, peas, barley, and sunflower, after which they were planted. Such seed germinated in half the time required for untreated seed. His experiments were repeated at the Massachusetts Hatch Experiment Station, where the germina- tion was accelerated and the total germinations increased. Direct experiments upon the growth of plants have been made, in which zinc and copper plates, connected by wires, were placed in the soil in which the plants were grown, or wires were run through the soil and connected with a battery or electric machine of some sort. The first method has been successfully tried in Eng- land and Germany with the result that larger crops of peas, barley, and grass were obtained from electrified plots of ground. The second method has been tried many times, the experi- ments of Warner at the Massachusetts Hatch Experiment Station being of this class. In 1893 he grew parsnips, lettuce, carrots, turnips, beets, salsify, onions, peas, and tomatoes. The seed of most varieties germinated sooner, developed bet- ter, and the tomatoes ripened earlier, where the soil was subjected to the electric current. The nearer the plants were to the electrodes the bet- ter was the growth. Various forms of accumu- lators of atmospheric electricit.v have been tried, with greater or less success. That atmospheric electricity influences growth is shown by the experiments of Grandeau. who grew maize inside an insulated cage. The stalks were nuicli smaller than those receiving the eft'ect of the electricity of the air. The effect or advantage secured is explained by the fact that the electric current induces more rapid changes in the seed and soil, or that electrified plants are enabled to take up carbon dioxide more rapidly owing to the treat- ment. The effect of the electric light has been very
