PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
37 
the former series, although the circumstances were more than usually unfavourable 
to their success. To find whether the same relation existed between the salts through a 
considerable range of temperature, an opportunity was taken during cold weather to 
repeat the experiments at a low temperature. 
(4.) Solutions of 1 salt in 100 water were diffused from eight solution cells, for 
each salt. The times were increased, but the same ratio of 1 to 1'4142 was pre- 
served between them. The liquids of the cells were found to retain a temperature 
ranging slowly between 41° and 38°'8 during the whole period of the observations. 
Sulphate of potash was substituted for the carbonate, as of these two equi-diffusive 
salts the former had been found to be least in accordance with nitrate of potash, in 
the 4 per cent, solutions, and appeared therefore to afford the severest test of the 
relation. 
For nitrate of potash, at a mean temperature of 39°'7, during nine days, the diffu- 
sion product of two cells together was 6’97, 6*93, 6’77 and 6‘64 grs. ; mean 6*83 grs. 
for two cells. 
For sulphate of potash, at the same mean temperature of 39°'7, during 12*728 days 
(twelve days, seventeen hours, twenty-eight minutes), the diffusion product of two 
cells together was 7‘05, 6*93, 7'28 and 6*90 grs. ; mean 7'04 grs. for two cells. 
The general results are — 
Nitrate of potash in nine days at 39°*7 . . 6*83 grs. . . 100 
Sulphate of potash in 12*728 days at 39°*7 7'04 grs. . . 103*07 
(5.) Solutions of 2 salt in 100 water were diffused simultaneously with the pre- 
ceding experiments, and in precisely the same conditions of time and temperature. 
The diffusion product of nitrate of potash during nine days, at a mean temperature 
of 39°*7, was 7‘03, 6*63, 6*83 and 6*83 grs. for one cell ; mean 6*83 grs. for one cell, 
or the same number as for two cells with the 1 per cent, solution. 
The diffusion product of sulphate of potash during 12*728 days was 6*84, and 6*80 ; 
mean 6*82 grs. for one cell. These experiments almost coincide with the number for 
nitrate of potash. 
Nitrate of potash, 6*83 grs 100 
Sulphate of potash, 6*82 grs 99*85 
(6.) The existence of the relation in question was also severely tested in another 
manner. Preserving the ratio in the times of diffusion for the two salts, the actual 
times were varied in duration, in three series of experiments, as 1, 2 and 3. The ex- 
periments were made in the vault, with a uniformity of temperature favourable to 
accuracy of observation. Eight cells of the 1 per cent, solution of each salt were 
always diffused at the same time. 
(a.) Nitrate of potash diffused for 3*5 days, at 47°'2, gave for two cells, 3*55, 3*63, 
3*33 and 3*51 grs. ; mean for two cells, 3*50 grs. 
Sulphate of potash diffused for 4*95 days, at 47°*3, gave for two cells, 3*54, 3*31, 
