1825.] Analpi$ of an Alloy of Gold and Rhodium, 251 



Akticle III. 



Analysis of an Alloy of Gold emd Rhodium from the Farting 

 House, at Mexico.^ By M. Andre Del Rio, Professor at the 

 College of Mines, and Member of the Institution of Sciences 

 at Mexico. t 



In the year 1810, M. Cloud, Chemical Director at the Mint 

 in Philadelphia, discovered an alloy of gold and palladium in 

 two ingots of g^old from Brazil. I have found another alloy 

 here, containing rhodium, which, as yet, is unknown in Europe. 

 At this favourable era we may expect an infinite number of 

 discoveries, as the careful e"Xamination of a country so vast and 

 richly endowed by nature as this is, proceeds. I am surprised 

 that M. Cloud has not given in his analysis, either the specific 

 gravity of his alloy, nor the proportions of the metals of which 

 it is composed. 



1. 199*2 grains of an alloy of gold, of this Parting House, of 

 the specific gravity, according to Citizen Jean Mendez, of 15*4, 

 left, after the action of aqua regia 1*28 of chloride of silver, 

 = 0'97 silver. The gold of one-fourth part of the solution was 

 separated by ether, when a galvanic current was observed, 

 which occasioned the ether sometimes to swim on the surface 

 of the aqua regia, as it naturally would do, and at others to 

 assume a position below it ; a phenomenon deserving closer 

 investigation. Convinced that the gold was still alloyed with 

 some other metal, a brittle button was obtained by means of 

 borax which weighed 45*5 grains. This lost no weight by being 

 boiled with nitric acid ; when fused with nitre in a small platina 

 crucible, a large quantity of the gold attached itself to the 

 platina, and, besides, an efflorescence, formed of very small 

 grains of a tin-white colour. The whole was treated with hot 

 water, which being decanted off", and the residuum washed, a 

 very heavy black powder remained, partly composed of very 

 short and thin needles, and also another lighter powder of an 

 olive-green colour. The filtered solution was yellow and black- 

 ened the filter, but on dying the colour became a clear olive- 

 green. The yellow solution, saturated with nitric acid, left a 

 cherry-coloured deposit, and gave with tincture of galls a dark 

 yellowish-brown precipitate ; a proof that it was not osmium. 



The black powder being separated from the gold by quick- 



* 



From the Annales de Chimie. i rt i ? ' 



^ -j- This Memoir was communicated to M. de Humboldt, by M. Lucas Alartian, whose 

 singular merit is duly appreciated by the savans of Europe, and who is at present 

 Minister of the Interior of the Confederation of the Mexican States. M. del Rio, who 

 studied at Paris, Freiberg, and Schemnitz, is well luiown by his labours in analytical 

 chemistry, and by his Treatise, on Mineralogy and Geognostic Tables.— iV;«><e by the 

 French Editor. fij,,,,^ \:dZ. ^.,,.Ai. , .. fci ...j..4ifju. .. j ii« .. > |fS. 



