Rhodium

in: mineralogy, one of the metals lately discovered by Dr. Wollaston in erude platina: for the mode by which it may be procured, see the article PLATINUM. It is of a white colour: specific gravity something more than 11. No degree of heat hitherto applied is capable of fusing it. We do not. know therefore whether it be malleable: but as it forms malleable alloys with other metals, it is probable that it would not be destitute of malleability if it could be fused into a button. The following are the results of the experiments made by Dr. Wollaston to alloy rhodium with other metals. <¢ It unites readily with all the metals tiat have been tried, except mercury; and with gold and silver it forms very malleable alloys, that are not oxydated by a high degree of heat, but become incrusted with a black oxyd when very slowly cooled. ‘* When four parts of gold are united with one of rhodium, although the alloy may a ume a rounded form under the blowpipe, yet it seems to be more in the state of an amalgam than in complete fusion. When six parts of gold are alloyed with one of rhodium the compound may be perfectly fused, but requires far more heat than fine gold. There is no circumstance in which rhodium differs more from platina than in the colour of this alloy, which might be taken for fine gold by any one who is not very much accustomed to discriminate the different qualities of gold. On the contrary, the colour of an alloy containing the same proportion of platina differs but little from that of latina. «¢ When I endeavoured,” continues Dr. Wollaston, ‘¢ to di olve an alloy of silver or of gold with rhodium, the rhodium remained untouch« ed by either nitric or nitro-muriatic acids; and when rhodium had been fused with arsenic or with sulphur, or when merely heated by itself, it was reduced to the same state of insolubility. But when one part of rhodium had been fused with three parts of bismuth, of copper or of lead, each of these alloys could be di olved completely in a mixture of two parts, by measure, of muriatic acid with one of nitric. With the two former metals the proportion of the acids to each other seemed not to be of so much consequence as with lead; but the lead appeared on another account preferable, as it was most easily separated when reduced to an insoluble muriat by evaporation. The muriat of rhodium had then the same colour and properties as when formed from the yellow oxyd precipitated from the original salt.”