Fifl. 2. 



222 Mr. T. Graham on Liquid Diffusion applied to Analysis. 



cent solution of hydrochloric acid from wide- 

 mouth phials immersed in a jar of water, as in 

 my former experiments*. The times were ob- 

 served 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 



c 





-^1 





~ 



: 



and 



1 

 2-426 



In 101*75 hours at 15°-55 (60° F.) ; 

 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.} 



at 48°-88 (120° F.] 



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 tem- 

 perature ; 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 ap- 

 pears to be sensibly 2± times more diffusible at 48°*88 (120° F.) 

 than at 15 0, 55 (60° F.) : this gives an average increase of 0*014, 

 or yV for 1 degree (0*025 for 1° F., or ^). The inequality of 

 diffusion which the three substances referred to exhibit at a low 

 temperature becomes therefore less at high temperatures ; and 

 it would appear to be the effect of a high temperature to assimi- 

 late diffusibilities. Heat, then, although it quickens the opera- 

 tion of diffusion, does not appear otherwise to promote the sepa- 

 ration 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 0, 55 



* Philosophical Transactions, 1850, p. 25. 



