PAINTS, VITRIFIABLE

See Porcelain , Pottery , and Stained Gla . PALLADIUM; a rare metal, po e ed of valuable properties; was discovered in 1803, by Dr. Wollaston, in native platinum. It constitutes about 1 per cent. of the Columbian ore, and from 1 ⁄ 4 to 1 per cent. of the Uralian ore of this metal; occurring nearly pure in loose grains, of a steel-gray colour, pa ing into silver white, and of a specific gravity of from 11·8 to 12·14; also as an alloy with gold in Brazil, and combined with selenium in the Harz near Tilkerode. Into the nitro-muriatic solution of native platinum, if a solution of cyanide of mercury be poured, the pale yellow cyanide of palladium will be thrown down, which being ignited affords the metal. This is the ingenious proce of Dr. Wollaston. The palladium present in the Brazilian gold ore may be readily separated as follows: melt the ore along with 2 or 3 parts of silver, granulate the alloy, and digest it with heat in nitric acid of specific gravity 1·3. The solution containing the silver and palladium, for the gold does not di olve, being treated with common salt or muriatic acid, will part with all its silver in the form of a chloride. The supernatant liquor being concentrated and neutralized with ammonia, will yield a rose-coloured salt in long silky crystals, the ammonia-muriate of palladium, which being washed in ice-cold water, and ignited, will afford 40 per cent. of metal. The metal obtained by this proce is purer than that by the former; and if it be fused in a crucible along with borax, by the heat of a powerful air-furnace or forge, a button of malleable and ductile palladium will be produced. When a slip of it is heated to redne , it takes a bronze-blue shade of greater or le intensity, as the slip is cooled more or le slowly; but if it be suddenly chilled, as by plunging it into water, it resumes instantly its white lustre. This curious phenomenon depending upon oxidize ment and de-oxidize ment, in different circumstances, serves at once to distinguish palladium from platinum. Pure palladium resembles platinum, but has more of a silver hue; when planished by the hammer into a cup, such as that of M. Bréant, in the museum of the Mint at Paris, it is a splendid steel-white metal, not liable, like silver, to tarnish in the air. Another cup made by M. Bréant, weighing 2 lbs. (1 kilogramme), was purchased by Charles X., and is now in the garde-meuble of the French crown. The specific gravity of this metal, when laminated, is stated by Dr. Wollaston at 11·8, and by Vauquelin at 12·1. It melts at from 150° to 160° Wedge wood; and does not oxidize at a white heat. When a drop of tincture of iodine, is let fall upon the surface of this metal, and di ipated over a lamp flame, a black spot remains, which does not happen with platinum. A slip of palladium has been used with advantage to inlay the limbs of astronomical instruments, where the fine graduated lines are cut, because it is bright, and not liable to alteration, like silver. There are a protoxide and peroxide of palladium. The proto-chloride consists of 60 of metal and 40 of chlorine; the cyanide, of 67 of metal, and 33 of cyanogen. PALM OIL ( Huile de pal me , Fr.; Palmöl , Germ.); is obtained, in Guinea and Guyana, by expre ing, as also by boiling, the fruit of the avoira elais . It has an orange colour, a smell of violets, a bland taste, is lighter than water, melts at 84° Fahr., becomes rancid and pale by exposure to air, di olves in boiling alcohol, and consists of 69 parts of oleine, and 31 of stearine, in 100. It is employed chiefly for making yellow soap. It may be bleached by the action of either chlorine or oxygen gas, as also by that of light and heat. Palm oil, quantity of, | Imported. | Retained for consumption. | Exported. | | Year. | Cwts. | Cwts. | Cwts. | | 1835. | 260,151 | 242,733 | 30,915 | | 1836. | 277,017 | 234,357 | 34,379 | | 1837. | 223,329 | 214,000 | | Duty, 1 s. 3 d. per cwt.