494 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
Concentration 
25 Per Cent 
CdBr 2 
NaBr 
Temperature 
13° C 
Test No. 1 
.12916 
.07610 
Duration of Test 
45 Minutes 
Test No. 2 
.12480 
.07052 
It is readily noted that the 25 per cent solution with the same 
time duration and the same temperature has diffused a much 
larger amount of the salt. We found this true in each case 
with this salt. 
Concentration 
25 Per Cent 
CdBr 2 
NaBr 
Temperature 
13 °C 
Test No. 1 
.13094 
.08861 
Duration of Test 
45 Minutes 
Test No. 2 
.14458 
.08690 
This test serves only to verify the foregoing one. 
Concentration 
2U Per Cent 
CdBr, 
NaBr 
Temperature 
Room Temp. 
Test No. 1 
.40921 
.19392 
Duration of Test 
24 Hours 
Test No. 2 
.36731 
.17313 
We made an analysis of the contents of the cup also and 
found that even in the twenty-four hours the solution had not 
reached its equilibrium, that is, the solution within the cup con- 
tained more of the salt per cc. than did the solution surround- 
ing the cup within the beaker. 
Conclusions : sodium cadmium bromide dissociates when dis- 
solved in water. 
Sodium bromide diffuses faster than cadmium bromide. 
THE DOUBLE BROMIDE OF AMMONIUM AND ZINC. 
3NH 4 Br. ZnBr,. 
We added the ammonium bromide to the zinc bromide in the 
proportion of three to one, multiplied by 'their molecular weights, 
to form the salt : 3NH 4 Br. ZnBr 2 . There separated out a large 
amount of the salt which we analyzed with the following re- 
sults : 
Br. Zn. Ammonium Total 
P'er Cent P*er Cent P*er Cent P*er Cent 
77.19 12.60 10.40 100.19 
