THE DISSOCIATION OF DOUBLE SALTS 
495 
This compares favorably with the calculated results which 
are : 
Br. 
Per Cent 
77.07 
Zn. 
Per Cent 
12.52 
Ammonium 
F’er Cent 
10.40 
Total 
P*er Cent 
99.99 
With the use of the same method employed in the examina- 
tion of the preceding salt, we diffused the salt and found the 
following results : 
Concentration 
5 Per Cent 
ZnBr 2 
NH 4 Br 
Temperature 
Room Temp. 
Test No. 1 
.43537 
.78583 
Duration of Test 
24 Hours 
Test No. 2 
.42142 
.77359 
In the double bromide the ratio between the constituent bro- 
mides is one of the zinc to 1.3 of the ammonium bromide. Un- 
less it is dissociated by water the diffusate should contain these 
elements in the same ratio one to the other. We find, however, 
on analysis that the ammonium bromide is much in excess of 
this ratio. The results show that the ammonium bromide is 
to zinc bromide as 1 :1.8. 
Concentration 
2 % Per Cent 
ZnBr 2 
NH 4 Br 
5 Per Cent 
ZnBr 2 
NHJBr 
Temperature 
Room Temp. 
Test No. 1 
.30132 
.35455 
Room Temp. 
Test No. 1 
.2856'8 
.83258 
Duration of Test 
24 Hours 
Test No. 2 
.32412 
.37241 
12 Hours 
Test No. 2 
.31271 
.84781 
It appears from the results that during the first twelve hours 
the ammonium bromide goes through the porous cup much faster 
than during the second twelve hours. In the twenty-four hour 
test the ammonium was not present in large excess but in this 
analysis of the twelve hour test we find that the ammonium 
bromide is. present in much larger proportions. 
Concentration 
5 Per Cent 
ZnBr, 
NHJ3r 
Temperature 
55°C 
Test No. 1 
.04428 
.26310 
Duration of Test 
1 Hour 
Test No. 2 
.04947 
.29190 
