254 MM. C. Lea on the Platinum Metals. 
add excess of potash. The liquid should be perfectly clear and 
very nearly colorless. The addition of a single drop of dilute 
solution of sesquichlorid of iridium communicates a yellow color, 
2) 
@ 
Qu 
ie, 
Le | 
oO 
gs, 
ce) 
me 
oo 
= 
@ 
oy 
— 
rs 
v4 
| 
: 
c 
mS 
7) 
bg 
oS 
ie) 
cr 
Qu 
oO 
ie) 
o 
al 
2) 
a 
N 
» 
or 
pet 
° 
Bp 
° 
ar) 
> 
oO 
(VIL) 
REACTIONS WITH AMMONIO-CHLORID OF ZINC. 
A solution of clorid of zinc in excess of ammonia gives an 
interesting and beautiful series of reactions with the metals of 
the platinum group. The metallic solutions, which are to be 
subjected to this test, must be either neutral or slightly acid. 
The presence of alkali in excess, or of acid in large excess, nat- 
y interferes with these reactions, 
To obtain the zine solution in proper condition, chlorid of 
zine must be added to ammonia until the smell of ammonia be- 
comes tolerably faint, and a considerable proportion of zine 
ne remains undissolved. The liquid is then to be filtered off, 
and should be used without too much delay. In this condition 
the affinities are in a state of very unstable equilibrimn. The 
itat 
tion , the precipitate which falls carries 
with it a part or the whole of the platinum metal, which imparts 
to it a characteristic coloration. 
The following are the reactions: 
Ru,Cl, a brown precipitate: the solution becomes colorless. 
RuCl, a rose-colored precipitate: the solution becomes color- 
ess. 
Ir, Cl, a pale buff precipitate: the solution becomes colorless, 
or nearly so. 
IrCl, a fire-red precipitate: solution decolorized. . 
_ With platinum and palladium the tendency of ammonia t0 
m double salts, interferes, and prevents any characteristic Te 
action from the zinc solution : 
* 
(VIIL) 
ACTIONS WITH SOLUTION OF FERRIDCYANID OF POTASSIUM IN CAUSTIC 
it SODA. 
When this solution is added to ruthenium and iridium solu- 
