832 
PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
the excess of chlorine was removed by agitation of the solution with air. The pro- 
portion of salt present was thus increased in weight from 1 to TSG per cent. The time 
of diffusion was 11*43 days, and the temperature 53°. 
2. Chloride of copper diffused from a 1*36 per cent, solution of the salt in hydro- 
chloric acid, 5*83, 5*66, and 5*30 grs. in two cells ; mean 5*60 grs. 
The corresponding diffusion from a 1 per cent, solution may be supposed to be less 
than 5*6 grs., in the proportion of 1*36 to 1, without any great error. The results 
thus become chloride of copper diffused, 3*98, 3*85 and 3*58 grs. ; mean 3*80 grs. in 
two cells. 
It hence appears that the diffusion of chloride of copper is much diminished by the 
presence of a great excess of hydrochloric acid in the same solution. Different causes 
suggest themselves for this result, such as the possibility of a combination existing of 
chloride of copper with chloride of hydrogen, in the acid solution ; or the influence 
which must be admitted of the more soluble substance, in a mixture of two similar 
substances, in repressing the diffusion of the less soluble. The present result, how- 
ever, is entirely opposed to the idea that the high diffusibility of the dichloride of 
copper, observed before, is due to the hydrochloric acid present. 
3. The diffusion of chloride of sodium also appears to be repressed by contact with 
a large excess of hydrochloric acid. One per cent, of chloride of sodium raised the 
density of dilute hydrochloric acid from 1*035 to T0408. Diffused into pure water 
for seven days at 52°*9, in eight cells, the diffusates of chloride of sodium were 
3*80, 3*87j 4*00 and 3*86 grs. ; mean 3*88 for two cells. The diffusion of chloride of 
sodium is thus reduced in a corresponding measure with that of chloride of copper 
by association with seven times its weight of hydrochloric acid. 
These results are interesting in a very different point of view. I have always 
watched for the appearance of some absorbent or imbibing power on the part of the 
acids, more analogous to an endosmotic attraction for water, as usually conceived. If 
such an attraction existed, it would complicate the phenomena of diffusion, for the 
volume of water absorbed by the acid would displace and project a portion of the 
latter into the reservoir, the phial not being extensible. The high diffusibility of 
hydrochloric and nitric acids would be thus explained. But by such a mechanical 
displacement the chloride of sodium would be thrown out in the preceding experi- 
ment, as well as the hydrochloric acid, which is not the case. 
4. Even in hydrochloric acid of density TT24 (25 per cent.), the diffusion of 1 per 
cent, of chloride of sodium for seven days, at 56°’6, was found to amount to 4*7 grs. 
only in two cells, and is less than from a solution in pure water. 
5. In comparing the influence of nitric acid with that of hydrochloric acid upon 
the diffusion of chloride of sodium, it was found that in a 7 percent, solution of nitric 
acid, the chloride of sodium (1 per cent.) was entirely decomposed in the diffusive 
process, at 56°*6, and gave hydrochloric acid in the full diffusive equivalent of that 
acid, together with nitrate of soda. 
