THE PLATINUM METALS 373 



as spongy platinum or platinum black. If this powder of platinum be 

 heated and pressed, or hammered in a cylinder, the grains aggregate or 

 forge together, and form a continuous, though of course not entirely 

 homogeneous, mass. Platinum was formerly, and is even now, worked 

 up in this manner- The platinum money formerly used in Russia was 

 made in this way. Sainte-Claire Deville, in the fifties, for the first 

 time melted platinum in considerable quantities by employing a special 

 furnace made in the form of a small reverberatory furnace, and com- 

 posed of two pieces of lime, on which the heat of ^the oxyhydrogen flame 

 has no action. Into this furnace (shown in fig. 34, Vol. 1. p. 175) or, 

 more strictly speaking, into the cavity made in the pieces of lime the 

 platinum is introduced, and two orifices are made in the lime ; through 

 one, the upper, or side orifice, is introduced an oxyhydrogen gas burner, 

 in which either detonating gas or a mixture of oxygen and coal-gas is 

 burnt, whilst the other orifice serves for the escape of the products of 

 combustion and certain impurities which are more volatile than the 

 platinum, and especially the oxidised compounds of osmium, ruthenium, 

 and palladium, which are comparatively easily volatilised by heat. In 

 this manner the platinum is converted into a continuous metallic form 

 by means of fusion, and this method is now used for melting consider- 

 able masses of platinum 4 and its alloys with iridiura. 



about the same time Tennant Distinguished iridium and osmium in it. Professor Glaus, 

 of Kazan, in his researches on the platinum metals (about 1840) discovered ruthenium 

 in them, and to him are due many important discoveries with regard to these elements, 

 such as the indication of the remarkable analogy between the series Pd Rh Rn and 

 Pt-Ir-0*. 



The treatment of platinum ore is chiefly carried on for the extraction of the platinum 

 itself and its alloys with iridium, because these metals offer a greater resistance to the 

 action of chemical reagents and high temperatures than any of the other malleable and 

 ductile metals, and therefore the wire so often used in the laboratory and for technical 

 purposes is made from them, as also are various vessels used for chemical purposes in 

 the laboratory and in works. Thus sulphuric acid* is distilled in platinum retorts, and 

 many substances are fused, ignited, and evaporated in the laboratory in platinum 

 crucibles and on platinum foil. Gold and many other substances are dissolved in dishes 

 made of iridium-platinum, because the alloys of platinum and iridium are but slightly 

 attacked when subjected to the action of aqua regia. 



The comparatively high density (about 21'5), hardness, ductility, and infusibility (it 

 does not melt at a furnace heat, but only in the oxyhydrogen flame or electric furnace),, 

 as well as the fact of its resisting the action of water, air, and other reagents, renders an 

 alloy of 90 parts of platinum and 10 parts of iridium (Deville's platinum-iridium alloy) a 

 most valuable material for making standard weights and measures, such as the metrej 

 kilogram, and pound, and therefore all the newest standards of most countries are made 

 of this alloy. 



1 This process has altered, the technical treatment of platinum to a considerable 

 extent. It has in particular facilitated the manufacture of alloys of platinum with 

 Iridium and rhodium from the pure platinum ores, since it is sufficient to fuse the 

 ore in order for the greater amount of the osmium to burn off, and for the mass to fuse 

 Into a homogeneous, malleable alloy, which can be directly made use of. There is very 

 little ruthenium in the ores of platinum. If during fusion lead be added, it dissolves 



