for procuring pure Platinum. 247 



water is decanted off, and it is then exposed in a crucible to 

 a red heat during a quarter of an hour. The whole mercury 

 is thus volatilized, when we can readily distinguish the spangles 

 of alloy of gold and copper by their colours. 



3. The calcined ore being introduced into a tubulated retort, 

 we pour over it half its weight of nitro-muriatic acid (aqua 

 regia) composed of one part of nitric acid, at 25° Baume (1.210 

 sp. gr.) and three parts of muriatic acid, at 18° (1.14), and heat 

 the mixture for half an hour. Such acid dissolves all the gold, 

 all the lead, the greater part of the copper, and a very small 

 quantity of platinum, palladium, and iron, while the silver is con- 

 verted into a chloride, which remains mingled with the ore not 

 attacked. After decanting the acid liquor, the ore is thrown on 

 a filter, and washed with a sufficient quantity of water. The 

 filter-funnel being transferred to another vessel, the filter is to 

 be washed with a very weak water of ammonia. By this means 

 we dissolve all the chloride of silver, which is recovered by 

 saturating the filtered liquor with muriatic acid. 



4. The solution which contains the gold, lead, copper, and iron, 

 with a small quantity of palladium and platinum, being added to 

 the water which has served for the washings,. the whole is now 

 evaporated to the consistence of syrup, which is diluted with 

 thrice its volume of water, and treated with sulphuric acid, 

 drop by drop, to precipitate the lead in the state of sulphate, 

 to be afterwards separated by the filter. 



5. Into the filtered liquor a solution of proto-sulphatc of iron 

 must be poured, which throws down the gold and palladium in 

 the metallic state. We decant the liquor, wash and dry the 

 precipitated metals. The platinum remains in the liquor with 

 the iron and copper. We concentrate this liquor by evapora- 

 tion, then pour into it a sufficient (juantity of a saturated solu- 

 tion of muriate of ammonia, which throws down the platinum 

 in the state of ammonio-muriate. This must be washed on a 

 filter and dried. 



6. The gold may be very easily separated from the palladium 

 by nu'lling these metals with four times their weiglit of silver, 

 and acting on the alloy willi concentrated nitric acid, which 



