Page:The American Cyclopædia (1879) Volume XIII.djvu/618

 598 PLATED WARE PLATINUM made an unsuccessful attempt to seize Plataea ; and later the city, defended by 480 men, held out against the Lacedaemonians from 429 to the summer of 427, when want of provisions compelled a surrender, after which it was razed to the ground. It was rebuilt after the peace of Antalcidas, but was again destroyed by the Thebans in 374; was once more rebuilt by the Macedonians in 338, and is spoken of in the 6th century A. D. by Hierocles as one of the cities of Boeotia. Its ruins are still traced near the village of Kokla. PLATED WARE, articles of various kinds, consisting as a rule of a cheap metal as a base covered with one of more value, as britannia metal, nickel, copper, or brass covered with silver or gold, or iron with nickel. There are two distinct methods of plating : an older one by which the silver was either soldered or fused upon the foundation metal, and a newer one of depositing the coating from a solution of a metallic salt by electro-chemical decomposition. Attaching sheets of silver by means of solder was practised by the ancient Romans, and con- tinued in general use till the middle of the 18th century. The process is called by the French le double or lining, and the English call it French plating to distinguish it from the method which followed it, called the English method, which consisted in fusing a plate of silver upon an ingot of copper or brass without the intervention of solder, and then rolling the ingot into a sheet, This method is also called true plating, and was introduced into France about the year 1808. In 1839 it gave employ- ment to some 2,000 workmen, the products of whose labor amounted to about 8,000,000 francs. The metal to be plated may be either very fine copper or a brass containing a very large proportion of copper. The nickel alloys of copper, though preferred for electro-plating, do not answer for the older process because the surface is liable to oxidation, by which the silver is prevented from adhering. An ingot of copper or brass, or a mixture of the two, is cast about an inch thick, 3 in. broad, and 18 or 20 in. long. It must be free from holes or flaws, to insure which it is cast in an iron mould with rising mouthpieces to give pres- sure and allow impurities to float up. The surface of the ingot is smoothed with a file, and a plate of silver is laid upon the surfaces to be plated equal to -$ or -fa of the weight of cop- per for each side to be covered. The plate or plates are fastened on with iron wire and the edges sealed with a little borax. It is now placed upon burning coke in the plating fur- nace and watched by the workman through a small hole in the door. The proper tempera- ture of the ingot is indicated by the silver be- ing drawn into contact with the copper. It is then removed as quickly as possible, for the two metals are then just ready to run together and form an alloy, and in fact they do this at their surfaces of contact ; the rapid cooling of the surface which follows exposure to the air ar- rests the process. Being now cleaned, the ingot is reduced to a sheet of the required thickness by several rollings, between each of which the ingot must be annealed to preserve its ductility. After the last annealing the sheets are immersed in hot dilute sulphuric acid and covered with fine Calais sand. They are then ready to be formed into articles by raising with the ham- mer, spinning on the lathe, stamping, chasing, &c. The plated wire used for making bread baskets and other light open-work utensils is made by first fashioning silver tubes by lapping sheets around a rod, then placing the cleaned tubes upon clean copper rods and heating them in a furnace, whereby the surfaces of contact are united by the formation of a film of alloy, a burnisher being used to press them together, after which the plated rod is drawn into wire of the desired size. The newer process of elec- tro-plating has mostly superseded these older ones, and all housekeeping plated ware is now made by forming the articles in copper bronze, nickel, britannia, or white metal, and then de- positing upon them the silver or the gold, from a solution of cyanide of the metal, after which the surfaces may be burnished and otherwise embellished. This art is extensively practised in Europe and America. Some fine ware is made by depositing a thick coating of silver upon nickel, which, although much cheaper, has in every respect the appearance of real plate. The general principles of electro-plating and electro-gilding (as the covering with gold is technically called) are given in the article GALVANISM. The details of the operations vary with different cases, and can only be in- telligibly described or well understood in the work room. Nickel plating is described in the article NICKEL. PLATEN, August, count, a German poet, born in Anspach, Oct. 24, 1796, died in Syracuse, Sicily, Dec. 5, 1835. He served against France in the Bavarian army, and subsequently ac- quired celebrity as a poet, especially by his Polenlieder and by his dramas Die verhang- nissvolle Gabel and Der romantische Oedipus. His complete works have been published in 5 vols. (Stuttgart, 1847 and 1853), and his Poe- tischer und literarischer Nachlass, edited by Minckwitz, in 2 vols. (1852). PLATH, Johann Heinrieh, a German sinologue, born in Munich in 1807, died there, Nov. 16, 1874. In 1848 he became state librarian. His works comprise Confucius und seiner Schiller Leben und Lehren (2 vols., Munich, 1867-'72); Die Beschaftigungen der alien Chinesen (1869) ; China vor^WQ Jahren (1869); Die Quellen der alien chinesischen Geschichte (1870) ; and Geschichte der Volker der Mandschurei (4 vols., 1874), of which he left the fifth and last vol- ume in manuscript. PLATINUM (Sp. platina, little silver), a gray- ish white metal, distinguished by its great specific gravity and difficult fusibility, discov- ered by Wood, an assay er of Jamaica, in 1741. It occurs in the native state alloyed with pal-