252 M. Baruel on the Process 



which are fabricated the large alembics, destined for the con- 

 centration of sulphuric acid. 



18. The mother-water, from which have been precipitated 

 the ammonio-muriates of platinum and iridium by pouring mu- 

 riate of ammonia into the solution of crude platinum, has a 

 reddish-brown colour, and contains all the ammonio-muriates 

 of palladium and rhodium, as well as a certain quantity of the 

 ammonio-muriates of platinum and iridium; because, as we have 

 observed, these salts are not completely insoluble. It contains, 

 moreover, all the iron which was alloyed with the platinum, and 

 sometimes a little copper, which has escaped the action of the 

 first portion of nitro-muriatic acid which was poured on the ore 

 to dissolve the gold. This mother-liquor is put into matrasses, 

 and plates of iron are plunged into it. The iron precipitates all 

 the metals (except the oxide of iron) under the form of a black 

 powder. When the whole metallic matter is thrown down, 

 which is known by the liquor assuming a green colour, the plates 

 of iron are removed, after detaching from their surfaces the ad- 

 hering powder. The liquor is decanted off, and thrown away. 

 The black precipitate must be washed several times, till the water 

 employed passes off tasteless. The powder is then treated with 

 weak nitric acid, which dissolves the greatest part of the iron, 

 which, by the effect of the precipitation, had been alloyed with 

 these metals*, and which takes up also whatever copper may 

 remain. The residuum is washed anew, and treated with nitro- 

 muriatic acid, which dissolves all the platinum, palladium, rho- 

 dium, and remains of the iron ; but does not affect the iridium, 

 which remains pure at the bottom of the solution in the form of 

 a black powdc, or metallic spangles. The iridium, being se- 

 parated by the filter, is then washed, dried, and united to that 

 formerly obtained (15). 



19. The liquors are now to be united, and evaporated to 

 the consistence of syrup, to drive off the greater part of the 



* Or, during the precipitation had/alien down in alloy with these metals. 

 The original words are, " fer, qui par I'effet de la precipitation, s'etoit 

 alli6 avec ces nietaux." 



