188 Prof. Graham on the Diffusion of Liquids. 



and as far as can be determined by three observations, in 

 direct proportion to the temperature. The diffusion-product 

 from the 4 per cent, solution increases from 10 grs. to 13*60, 

 with a rise of temperature of 27°*4, or rather more than one- 

 third. Supposing the same progression continued, the diffu- 

 sibility of chloride of sodium would be doubled by a rise of 

 84< or 85 degrees. 



(3.) The progress of the diffusion of chloride of sodium in 

 such experiments as have been narrated, was further studied 

 by intercepting the operation after it had proceeded for dif- 

 ferent periods of 2, 4, 6 and 8 days. The solution employed 

 was that containing 4 parts of salt to 100 water. Two of the 

 six-ounce phials were diffused at the same time for each 

 period. The temperature given is the mean of the tempera- 

 tures of a water-jar observed each day of the period. The 

 daily fluctuation was not more than two or three-tenths of a 

 degree Fahr. 



In 2 days, temperature 63°*7; the salt diffused was 4*04 

 and 3*86 grs. ; mean 3*95 grs. 



In 4 days, temperature 63°*7 ; the salt diffused was 6*78 

 and 7*12 grs. ; mean 6*95 grs. 



In 6 days, temperature 63 0, 8 ; the salt diffused was 10*02 

 and 9*70 grs. ; mean 9*86 grs. 



In 8 days, temperature 64°; the salt diffused was 13*00 and 

 13*25 grs.; mean 13*12 grs. 



The proportion diffused in the first period of two days is 

 given directly in the first experiments. The proper diffusion 

 for each of the three latter periods of two days is obtained by 

 deducting from the result of each period the result of the 

 period which precedes it : — 



Diffused in 1st two days . . 3*95 grs. 



Diffused in 2nd two days . . 3*00 grs. 



Diffused in 3rd two days . . 2*91 grs. 



Diffused in 4th two days . . 3*26 grs. 



The diffusion appears to proceed pretty uniformly, if the 

 amount diffused in the first period of two days be excepted. 

 Each of the phials contained at first about 108 grs. of salt, of 

 which the maximum quantity diffused is 13*12 grs. in eight 

 days, or ^ of the whole salt. Still the diffusion must neces- 

 sarily follow a diminishing progression, which would be 

 brought out by continuing the process for longer time, and 

 appear at the earliest period in the salt of most rapid diffusion. 



All the experiments which follow being made like the pre- 

 ceding on comparatively large volumes of solution in the phial, 

 and for equally short periods of seven or eight days, may be 

 looked upon as exhibiting pretty accurately the initial diffusion 



