176 Process for procuring pure Platinum, Palladium, @c. 
of ammonia into the solution of crude platinum, has a reddish- 
brown colour, and contains all the ammonio-muriates of palia- 
dium 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 re- 
moved, after detaching from their surfaces the adhering powder. 
The liquor is decanted off, and thrown away. The black pre- 
cipitate 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 re- 
siduum is washed anew, and treated with nitro-muriatie acid, 
which dissolves all the platinum, palladium, rhodium, and re- 
mains of the iron ; but does not affect the iridium, which remains 
pure at the bottom of the solution in the form of a black pow- 
der, or metallic spangles. The iridium, being separated by the 
filter, is then washed, dried, and united to that formerly ob- 
tained (15). 
19. The liquors are now to be united, and evaporated to the 
consistence of syrup, to drive off the greater part of the acid ex- 
cess; then this is to be diluted with four or five times its weight 
of water, as cold as possible. Into this a solution of muviate of 
ammonia is to be poured, till it ceases to occasion a precipitate. 
What falls is an ammonio-muriate of platinum, which must be 
separated by filtration, The solution is then concentrated, and 
allowed to cool several times in succession, to separate all the 
ammoniacal salt of platinum which it may contain. When the 
liquid is completely deprived of platinum, or when it yields no 
longer the yellow precipitate, we dilute it with five or six parts 
of cold water; and it ought to have a sensible excess of acid. 
This, if wanting, may be supplied by adding a little of the mu- 
riatic. We then pour into it water of ammonia, drop by drop, 
but not so much as entirely to saturate the acid-excess. mme- 
* Or, during the precipitation had fullen down in alloy with these nietals. 
The original words are, “ fer, qui par leffet de la précipitation s’étoit allié 
avec ces métaux.” 
diately 
