492 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
THE DOUBLE BROMIDE OF SODIUM AND CADMIUM. 
2 NaBr, 3CdBr 2 + 6 H 2 O. 
We brought together the constituent bromides in the propor- 
tion two to three to form the salt 2NaBr. 3CdBr 2 -j-6H 2 0 which 
was first made by Jones and Knight and described in “ Aqueous 
Solutions of Double Salts.” 9 The salt crystallized out in long 
narrow plates with tapering mitre-like ends. We dried the salt 
and made two analyses of it with the following results : 
Cd. 
Per Cent 
32.60 
32.77 
Br. 
E'er Cent 
46.51 
46.50 
H 2 0 
Per, Cent 
21.00 
20.90 
Total 
Per Cent 
100.11 
100.17 
Since the total per cent of the elements of this salt is 100 it is 
evident that no sodium salt was present in the compound. By 
calculation we found that the result from the above salt corre- 
sponds to the formula CdBr 2 -f-4H 2 0 which has the composi- 
tion : 
Cd. Br. H 2 0 Total 
Per Cent Per Cent Per Cent Per Cent 
32.56 46.51 20.93 100.00 
The cadmium bromide which crystallized out of this mixture 
of salts resembled the original cadmium bromide very closely 
and when a microscopic examination was made of the two salts 
it was noted that the two were identical in crystalline form. 
The cadmium bromide which we had obtained was returned 
and redissolved in the mother solution. More of the sodium 
bromide was added until the amount of the two bromides was 
proportional to their molecular weights. From this mixture 
there separated out a salt made up of small six sided plates 
about the thickness of a ten cent coin. 
Analysis of this salt gave the following results: 
Cd. H 2 0 Br. 
Per Cent Per Cent Per Cent 
30.00 10.09 56.47 
This corresponds to the formula 2NaBr. 3CdBr 2 +6H 2 0 
which has the percentage composition : 
Cd. H 2 0 Br. 
29.80 9.55 56.59 
9 American Chemical Journal, Vol. XXII, No. 2, August, 1899. 
