198 
ME. T. GE^mAM ON LIQUID DIFFUSION APPLIED TO ANALYSIS. 
The preceding experiments were made by diffusing a 2 per cent, solution 
of hydrochloric acid from wide-mouth phials immersed in a jar of water, 
as in my former experiments*. The times were observed in which an 
equal amount of the acid (0-777 gramme from three phials) was diffused 
out. These times of equal diffusion were 72 hours at 15°'55 (60° F.); 
53-15 hours at 26°-66 (80° F.); 40-6 hours at 37°-77 (100° F.); and 33 
hours at 48°-88 (120° F.). 
The diffusate from a 2 per cent, solution of chloride of potassium in 
similar circumstances was 0-6577 gramme, 
In 101-75 hours, at 15°-55 (60°F.); and 
In 41-93 hours, at 48°-88 (120° F.). 
The diffusate from a 2 per cent, solution of chloride of sodium was 0-6533 gramme. 
In 124-75 hours, at 15°-55 (60° F.) ; 
In 49-60 hours, at 48°-88 (120° F.). 
In equal times the diffusate would be 
For chloride of potassium at 15°-55 ( 60° F.), 1 
„ „ at 48°-88 (120° F.), 2-426 
For chloride of sodium at 15°-55 ( 60° F.), 1 
„ „ at 48°-88 (120° F.), 2-5151. 
As the ratio between the diffusates of hydrochloric acid, at the same two temperatures, 
was 1 to 2-1812, it appears that the acid is less increased in diffusibility than the salts 
at the higher temperature; chloride of sodium also is slightly more increased than 
chloride of potassium. The more highly diffusive the substance the less does it appear 
to gain by heat. Chloride of sodium appears to be sensibly 2^ times more diffusible at 
48°-88 (120° F.) than at 15°-55 (60° F.): this gives an average increase of 0-014, or 
for 1 degree (0-025 for 1°F., or ^). The inequality of diffusion which the three sub- 
stances referred to exhibit at a low temperature, becomes therefore less at high tempe- 
ratures ; and it would appear to be the effect of a high temperature to assimilate diffusi- 
bilities. Heat, then, although it quickens the operation of diffusion, does not appear 
otheiwise to promote the separation of unequally diffusive substances. 
The results in such experiments are less disturbed by changes of temperature, if at all 
gradual, than might be supposed. A sensible separation was obtained of hydrochloric 
acid and chloride of sodium from each other, in a solution containing 2 per cent, of each 
substance, when the water-jar was heated up from 15°-55 to 95° C. in two hours, and 
maintained at the latter temperature during four hours more. Diffusion appeared to be 
accelerated about six times at the higher temperature. 
At low temperatures, again, diffusion is proportionally slow. The ratio of diffusibility 
* Philosophical Transactions, 1850, p. 25. 
