278 Notice of some Recent [April 



that a saturated solution of gold does not dissolve a notable 

 quantity of chloride of silver ; the second, on the contrary, 

 deposits a considerable quantity of this substance. When 

 the whole chloride has been deposited it should be filtered 

 and weighed, after being dried and fused in a porcelain 

 crucible. Evaporate the liquid in a porcelain crucible, to 

 drive off the excess of chlorine, and when fumes cease to be 

 given off, treat it with oxalic acid. Place the liquid in a 

 glass defended by a convex cover, in order that no gold may 

 be mechanically removed with the carbonic acid, and allow 

 the glass to remain for 24 hours in a warm place. Filter 

 the liquid, evaporate to dryness, and pass a stream of sul- 

 phuretted hydrogen through the solution of the residue in 

 muriatic acid. A trace of copper is thus separated, and the 

 iron may be removed by hydro-sulphuret of ammonia. 



When the gold contains more than 20 per cent, of silver, 

 the correct plan is to assay the alloy in a cupel with lead 

 and silver, and to treat the new alloy with nitric acid, which 

 takes up the silver only. Gay Lussac shewed that a loss of 

 silver is sustained to a small extent in, this way, and G. 

 Rose, to obviate the inadequacy of this plan, tried a num- 

 ber of others, and at last hit upon one which he considers 

 better than any other yet devised. Fuse the native gold 

 in a small porcelain crucible with lead, by means of a lamp 

 supplied with a double current of air. Digest the mass in 

 nitric acid ; detach it from the crucible, and place it in a 

 glass vessel, adding a new portion of nitric acid diluted 

 with water, in order to dissolve the nitrate of lead ; wash 

 the residue ; dissolve it in aqua regia ; precipitate the chlo- 

 ride of silver dissolved, diluting the liquid with water ; fil- 

 ter the liquor and evaporate to dryness. Dissolve in water, 

 and precipitate the gold by means of muriate of iron. Sul- 

 phated protoxide of iron does not answer for the precipita- 

 tion, because the gold in solution may still contain a little 

 lead. Dilute the nitric acid solution with much water; then 

 treat it with chloride of lead, and not with muriatic acid, 

 which may precipitate part of the lead in the state of 

 chloride. Place the liquid in a warm place, to favour the 

 precipitation of the chloride of silver, and when the solution 

 has become clear, collect the chloride upon the filter which 

 was used to filter the solution of gold. The minute portion 



