1825.] an Alloy of Gold and Rhodium'* 253 



copper, or nickel colour ; the flux left a glass, partly of a leek 

 green, and partly of a cochineal red colour, and the little buttorf 

 weighed 5'9 grains. Its white surface soon changed tc a 

 tombac brown, and when fused with nitre it yielded a little buttoa 

 of pure gold, weighing 4*3 grains.* Other 10 grains, similarly 

 fused, gave also a brittle button, which left a scoria of a brigjiter 

 red colour, weighing 7-1 grains, and this by a second fusion, as 

 before, gave a button of pure gold, which also weighed 4*3 

 grains. Thus, as 100 parts of ammoniuret of gold gave 43 

 parts of gold, 212 parts, the weight of the whole precipitate^r 

 would have given 91*16. Three-fourths of the solution inust- 

 have contained 149*40 of the alloy, or deducting three-fourtlis 

 of a grain of silver, 148*65. \: 



Deducting the gold, there remain 57*49 parts of rhodium, or 

 38*6 per cent, of the alloy. The specific gravity of this alloy 

 should be 15*91, but as it was actually only 15*4 it must have 

 suffered expansion. , .. , ^ ,; ., . ^t 



The remainder of the solution was distilled to dryness, and a/ 

 dark brown residuum was obtained, which neither gave tliQ 

 changes of colour that characterise iridium by the action o^ 

 muriatic acid, nor red crystals with ammonia ; but it afibrded 

 an uncrystallizable double salt, of a flesh red colour, which, wheii 

 dried, resembled discoloured, brown, frothy iron (fer tcumeux); 

 Citizen Mendez could not reduce it before the blowpipe, an^, 

 obtained with borax only a yellowish green glass, ^ ^ 



Thus v/e see that neither ether nor ammonia afford the most 

 certain nor the most easy methods of separating rhodium. 

 From this consideration 1 had recourse to what Dr. WoUaston, 

 says on the subject, that it is not capable of forming _^namaJgj^m 

 with mercury. . ,^ .V ..(.fii ,» 



3. For this purpose, Citizen Mendez cupelled, at two opera-;! 

 tions, a very brittle alloy of gold with rhodium and copper, 

 weighing 133*7 grains, which gave him two little globules, one^ 

 of which weighed only 53*87 grains, and the other 66*13. I^ 

 treated the first with mercury and boihng water, and again by 

 trituration in an iron mortar, when the whole amalgamated,^ 

 except 2*5 grains of a bright olive green powder, which after- 

 wards darkened in water, and became greenish black. Can the. 

 green powder be a deutoxide, interaiediate between the blac^k 

 and the reddish brown, or puce coloured oxide, and the greenish 

 black povv^'der a hydrate ? I have the highest esteem fpr M. 

 Berzelius, but he himself desires that truth should be freely 

 sought. As to the small button of alloy, however carefully I 

 washed its amalgam, it always showed a black spot of rhodium 

 at the bottom {dans lefond) after having been heated to redness. 

 After fusion with nitre it weighed 49*7 grains, and its specific 



* On this account I lined the bottom and side^ 'of%e^crucilile'\^th an excei^s dif 

 borax, whidi has gre^t tendency, to vitrify rhodium. , . ,, , .-t; , 



^^ 



