42 PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
Carbonate of soda, diffused for 9‘9 days at a mean temperature of 53°'4, gave 9'93, 
9‘54 and lO'lO grs. in three experiments; mean 9‘86 grs. But the latter amount is 
to be increased by 0'09 gr. to bring it to the diffusion of 54°'3. We have then for the 
diffusion product of the two salts at the same temperature of 54°-3 — 
Nitrate of soda, in 7 days, 10' 10 grs 100 
Carbonate of soda, in 9'9 days, 9'95 grs. . . . 98’51 
The difference is again small, namely. O' 15 gr., or per cent., and within the 
limits of unavoidable error. 
It appears therefore that the times of equal diffusion of the nitrate and carbonate 
of soda are related like those of the nitrate and carbonate of potash, or as the square 
root of 1 and 2, that is, as 1 to T4142. 
Relation of Salts of Potash to Salts of Soda. 
It appeared probable, from many of the experiments already recorded, that if any 
relation, in the times of equal diffusibility, existed between the corresponding salts of 
potash and soda, it was that of the square root of 2 to the square root of 3. They 
were accordingly diffused for times having this ratio ; namely, the nitrate of potash 
for seven days, the nitrate of soda for 8'57325 days ; the sulphate and carbonate of 
potash for 9'9 days, and the sulphate and carbonate of soda for 12' 125 days. If these 
times are rightly chosen, the eventual diffusion products of all the experiments should 
be equal. The 1 per cent, solution was selected, and the number of experiments 
simultaneously made on each salt was eight or six. The liquids of two water-jars 
were evaporated together, so that each of the results in the table below represents the 
diffusion of two cells. These experiments also afford another opportunity of testing 
the assumed relation between the nitrates and sulphates of the same base. 
Table XIV. — Solution: 1 Salt to 100 Water, at 55°'4 — 56°' 1. 
Tempe- 
rature. 
Time in 
days. 
Square of 
times. 
Sol. density. 
Diffusion product of two cells in grs. 
Esp. I. 
Exp. IL 
Exp. III. 
Exp. IV. 
Mean. 
Nitrate of potash 
56*1 
7 
2 
6-67 
6-87 
6-90 
6-57 
6-75 
Nitrate of soda 
55-7 
8-57 
3 
6-59 
6-80 
6-94 
6-57 
6-78 
Sulphate of potash 
55-4 
9-90 
4 
6-73 
6-77 
6-96 
6-68 
6-78 
Sulphate of soda 
55-4 
12-125 
6 
6-43 
6-94 
6-80 
6-68 
6'72 
Carbonate of potash 
55-4 
9'90 
4 
6-54 
6-b4 
6-40 
6-67 
6-56 
Carbonate of soda 
53-4 
12-125 
6 
6-40 
6-63 
6-60 
6-67 
6-54 
The range of temperature during the period of these experiments rather exceeded 
3 degrees, so that they cannot be considered as fortunate in that respect ; but still the 
similarity between the different sets of experiments, and the near equality of their 
means, is very remarkable. The two nitrates and the two sulphates may be said 
to coincide, the extreme difference of the means of the four salts not being quite so 
much as 1 per cent. The two carbonates fall about 3'4 per cent, below the sul- 
