1909-10.] Solutions of Tetra-propyl-ammonium Chloride. 519 
Concen- 
tration 
gms. per 
100 gms. 
Solution. 
1-73 
10-90 
15-69 
23-98 
27-70 
3 ) 
Tempera- 
ture 
t° C. 
0 
25 
0 
25 
0 
25 
0 
25 
0 
25 
Density 
gms. per 
c.c. 
•9995 
•9964 
•9992 
•99465 
•99965 
•9940 
1-0030 
•99465 
1-0055 
•9959 
Yol. of 1 
gm. Solu- 
tion at 
t° 
1-0005 
1-0036 
1-0008 
1-0054 
1-0004 
1-0060 
•9970 
1-0054 
•9945 
1-0041 
Vol. of 
Water 
in 1 gm. 
Solution. 
•9828 
•9856 
•8911 
•8936 
•8432 
•8456 
•7603 
•7624 
•7231 
•7250 
Yol. of 
Solid 
in 1 gm. 
Solution. 
•0167 
•0169 
•1054 
T063 
T517 
T530 
•2319 
•2338 
•2679 
•2701 
Yol. of 
Water 
+ Yol. of 
Solid 
in 1 gm. 
Solution 
v 2 . 
•9995 
1-0025 
•9965 
•9999 
•9949 
•9986 
•9922 
•9962 
•9910 
•9951 
Expansion 
on 
Solution 
v x -y 2 . 
•0010 
•0011 
•0043 
•0055 
•0055 
•0074 
•0048 
•0092 
•0035 
•0090 
The figures in the last column of the table show that in all cases there 
is expansion on solution, i.e. the volume of solution is greater than the 
combined volumes of the solid and water in that solution. It will also be 
noticed that at 0 C C. the expansion at first increases with concentration and 
then decreases. Generally when a solid dissolves in water there is a slight 
contraction, i.e. the volume of the solution is greater than the volume of 
water in that solution, but less than the combined volumes of water and 
solid. There are, however, a few exceptions, of which the present case is 
one. Braun * mentions the chloride, bromide, and iodide of ammonium, 
VOL. xxx. 
* Zeit.f. physik. Chem ., i. p. 259 (1887). 
34 
