^52 Af. Andre del Rio's Anali^sis of [Oct. 



silver, was dissolved in muriatic acid, and the solution assumed 

 by boiling a fine orange colour. Citizen Mendez was unable to 

 reduce the green powder before the blowpipe, but he observed 

 that some specks detonated like nitre ; a property of rhodium. 

 This green powder, which I wished to treat separately, by 

 transferring it with water from a capsule to a matrass, became 

 black a second time, and I added it to the red solution, and 

 boiled the whole afresh ; although it appeared brown whilst hot 

 it resumed its red colour on coolmg. Sal ammoniac threw down 

 from the concentrated solution, an orange-coloured powder, 

 which, separated by decantation and sufficiently washed, was 

 soluble in cold water, and still more so in hot, and gave by care- 

 ful evaporation an infinite number of orange-coloured crystals. 

 Being reduced alone, in the same crucible that was employed 

 before, the gold was covered with a tin-white, blistered coating 

 of rhodium.* By twice boiling potash and nitre in the same 

 crucible, with the addition of water, the whole of the gold was 

 exposed, and the lixivium saturated with sulphuric acid, gave 

 16 grains of the dark reddish brown deutoxide of rhodium, 

 from which deducting 2*14 for oxygen, there remain 13-86 

 grains of rhodium for tlie 45*5 grains of alloy employed, or 30-4 

 per cent. I must not omit to state that the potash made very 

 small holes in the crucible, and 131 grains of protoxide of pla- 

 tina were extracted from it, which were reduced in another 

 crucible of earthenware, as perfectly as the nature of the cru- 

 cible allowed. 



The black powder was insoluble both in muriatic acid, and 

 aqua regia; solution of potash dissolved it in part, and the 

 residium gave many white metallic points by being heated with 

 tallow in a small crucible. As all the points were not equally 

 brilliant, the weight of the residuum was not added to the former 

 product ; I afterwards reflected that I had not employed suffi- 

 cient heat, and that I ought to have added it just the same as 

 that which was dissolved by the potash. 



2, The greater part of the acid of the remaining three-fourths 

 oJT tlie solution was distilled off, and the rest saturated with 

 amptt(6ma,' not added in excess. The orange-coloured precipi- 

 t{)i^ liost its red tint, and acquired a slight yellow ochre hue; 

 "iyherefdre, and because it became greenish by washing with 

 -(varm \v'ater, I concluded, although it detonated like fulminating 

 gold,' that it was not absolutely pure. In fact, 10 grains mixed 

 witKipil, and fused with borax, gave a little white button t which 

 wa»/tDpt)rittle for pure gold, and internally had a whitish 



♦ 1 1 was afterwards discovered that the blistered appearance was owing to the gold, 

 «-* it' it had endeavoured ta quit the platina to combine with the rhodium. The latter 

 always remained white — was that owing to the platina ? I believe it to be eminently 

 galvanic. 



f This tendency of rhodium to cover the surface of the gold is very singular. 



