86 M. C. Lea on the Platinum Metals. 
be worth working. 
For treating a mixture such as that which I have here desig- 
nated as (C) containing no platinum and ruthenium on ) 
NH,Cl, RuCl,, it is unnecessary to apply reducing agents, and 
the first method which I have described is the best. But if it 
- The action of oxalic acid on the platinum metals is interest- 
ing. Its reducing effect upon bichlorid of iridium at the boiling 
point is immediate. On bichlorid of ruthenium it seems to have 
no effect whatever, may be boiled with it fora length of time 
without sensible result. In a trial made with sesquichlorid of 
ruthenium and ammonium the oxalic acid was boiled with the 
metallic salt for a considerable time without any apparent effect 
becoming visible, but by long-continued boiling a gradual pre- 
cipitation took place. When platinum-salammoniac, NH Cl, 
Cl,, was boiled with oxalic acid, no effect was produced for a 
action upon the iridium was terminated. e difference between 
the time of action of the oxalic acid on the two bichlorids is s0 
very wide as to make it perfectly easy with proper care to effec 
tually reduce the one without acting upon the other, except 
where the platinum is present in very large excess. 
fi 
beni (1) ) 
reactions of the alkalies on the chlorids of iridium are 
er peculiar. Upon the bichlorid they exert a reducing 
