PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
45 
and of course at the same temperature of 53°‘7- Two cells, evaporated two together, 
gave 17*40 and 17*36 grs. of ignited sulphate of zinc ; mean 17*38 grs. The salt re- 
mained, after ignition, entirely soluble. This is a diffusion of 8*69 grs. for one cell, 
while the sulphate of magnesia gave 9*05 grs. ; or of 100 sulphate of zinc to 104' 14 
sulphate of magnesia. This result is interesting, as we here find two salts which 
are isomorphous, and of which the equi-diffusion is on that account in a high degree 
probable, differing between themselves so much as 4 per cent. 
Another numerous series of experiments vv^as made at a considerably lower tempe- 
rature, with the view of testing several of the same relations. The temperature in 
commencing the diffusion was 41°, but fell in the course of three days to 38°*8, and 
afterwards rose to 39°, from which it never varied afterwards more than a degree 
during the diffusion of the salts of potash and soda. The mean temperature for their 
periods did not vary above 0°'l or 0°*2 from 39°*7, so that it may be supposed the 
same for all these salts. For the sulphates of magnesia, the mean temperature was 
38°*9, or 0°’8 lower. The times chosen are as the square-roots of 2, 3, 6 and 16. 
Table XV. — Solutions of 1 and 2 Salt to 100 Water, at 39°'7- 
Time in 
days. 
Square of 
times. 
Diffusion product of two cells in 1 per cent, solutions, 
and one ceU in 2 per cent, solutions. 
Sol. density. 
Exp. I. 
Exp. II. 
Exp. III. 
Exp. IV. 
Mean. 
Chloride of potassium, 2 per cent.... 
9 
2 
6*58 
6*79 
6*82 
6*73 
Nitrate of soda, 2 per cent 
11*022 
3 
6*66 
6*98 
6*63 
6*79 
6*81 
Chloride of sodium, 1 per cent. ... 
11*022 
3 
6*33 
6*73 
7*06 
6*69 
Chloride of sodium, 2 per cent. ... 
11*022 
3 
6*50 
6*60 
6*64 
6*74 
6*62 
Sulphate of soda, 1 per cent 
15*589 
6 
6*60 
6*56 
6*56 
6*50 
6*55 
Sulphate of soda, 2 per cent 
15*589 
6 
6*50 
5*43 
6*33 
6*42 
Sulphate of magnesia, 1 per cent.... 
25*456 
16 
6*36 
6*20 
6*86 
6*59 
6*50 
Sulphate of magnesia, 2 per cent.... 
25*456 
16 
6*42 
6*78 
6*50 
6*84 
6*63 
Several other salts were diffused in the same circumstances as the preceding, of 
which the diffusion products have been previously given. Of these salts, both the 1 
and 2 per cent, solutions of nitrate of potash gave 6*83 in nine days, or in the same 
time as chloride of potassium in the table. The latter salt maintains a sensible 
equality of diffusion with the present series at the low, as well as it was found to do 
at the former high temperature. Chloride of sodium is here introduced for the first 
time : it appears to be equi-diffusive with nitrate of soda. If the sulphate of mag- 
nesia diffused be increased by 0'07, for its lower temperature, this salt will be in close 
accordance with the salts of potash and soda. 
Taking nitrate of potash 6*83, as 100, for a standard, the salt which deviates most 
considerably is sulphate of soda, which for the 1 per cent, solution is 6'55, or 95*9. 
A low temperature, however, must be unfavourable to diffusion experiments, from 
inereasing the tendency of salts to crystallize. 
In conclusion, I may sum up the results of most interest which this inquiry re- 
specting liquid diffusion has hitherto furnished. 
