806 
PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
1. Hydrochloric Acid. 
The period of diffusion arbitrarily chosen for this acid was five days. The diffusate, 
or quantity of acid diffused, was determined by precipitating the liquid of the ex- 
ternal reservoirs with nitrate of silver, and weighing the chloride of silver formed. 
In the 1 and 2 per cent, solutions, the liquids of two jars were generally mixed and 
precipitated together. 
(1.) Hydrochloric acid, 0’99 per cent.; density 1'0043. Diffused at 53°‘5, in six 
cells, 7*52, 7*52, 7*42 ; mean 7*49 grs. for two cells. Calculated for 1 per cent., 7*56 grs. 
at .53°'5 for two cells, or 7*41 grs. at 51°, when corrected for that temperature. 
(2.) Hydrochloric acid, T92 per cent.; density 1*009. Diffused at 51°, in eight 
cells, 14*71j 14*05, 14*54, 14*47 ; mean 14*44 grs. for two cells. Calculated for 2 per 
cent., 15*04 grs. at 51° for two cells. 
(3.) Hydrochloric acid, 1*993 per cent.; density 1*0094. Diffused at 62°*8, in six 
cells, two experiments on one-sixth part of the mixed jars gave 8*203, 8*198; mean 
8*20 grs. for one cell, or 16*40 grs. for two cells. Calculated for 2 per cent., 16*46 grs. 
at 62°*8 for two cells. 
(4.) Hydrochloric acid, 3*90 per cent.; density 1*0190. Diffused at 51°, in eight 
cells, 29*18, 30*70, 30*70, 29*26; mean 29*96 grs. for two cells. Calculated for 4 per 
cent., 30*72 grs. at 51° for two cells. 
(5.) Hydrochloric acid, 7*90 per cent. ; density 1*0380. Diffused at 51°, in four cells, 
32*71, 33*64, 33*64, 33*74 ; mean 33*43 grs. for one cell. Calculated for 8 per cent., 
33*84 grs. at 51° for one cell. 
Comparing the diffusibilities of the 2 per cent, solutions (2 and 3) at 51° and 62°*8, 
an increase is observed from 15*04 to 16*40 grs., or from 100 to 109*1, which gives an 
increase of 0*77 pet* cent, for 1°. This method of estimating the effect of temperature 
is not exact, as the times only in which an equal diffusion at the different temperatures 
takes place are truly comparable. We may deduce from it, however, the effect of 
the small difference of temperature of 2°*5 of the 1 per cent, solution from the 
others, as has bqen done, without sensible error. The diffusatesat the same tempera- 
ture would then be as follows *. — 
Diffusion of Hydrochloric Acid in five days at 51° Fahr. ; two cells. 
Grs. 
Ratio. 
From 1 per cent, solution . 
.... 7*41 
0*97 
From 2 per cent, solution . 
.... 15*04 
2*00 
From 4 per cent, solution . 
.... 30*72 
4*08 
From 8 per cent, solution . 
.... 67*68 
9*00 
The increasing diffusibility with the larger proportions of acid here observed is 
unusual, at least in the degree exhibited by the 8 per cent, solution. Other substances, 
as will be immediately observed of nitric acid, appear to lose proportionally in diffu- 
sibility as their solutions are concentrated. 
