[ 290 ] 



XLI. Liquid Diffusion applied to Analysis. 



By Thomas Graham, F.R.S., Master of the Mint. 



[Continued from p. 223.] 



3. Dialysis. 



PASSING from liquid diffusion in the water-jar, I may advert 

 first to the diffusion of crystalloids through a gelatinous or 

 colloid mass, the circumstances of the experiment being varied 

 as little as possible from those of jar diffusion. 



Ten grammes of chloride of sodium and 2 grammes of the 

 Japanese gelatine, or gelose of Payen, were dissolved together in 

 so much hot water as to form 100 cub. centims. of fluid. Intro- 

 duced into the empty diffusion-jar and allowed to cool, this fluid 

 set into a firm jelly, occupying the lower part of the jar, and 

 containing of course 10 per cent, of chloride of sodium. Instead 

 of placing pure water over this jelly, it was covered by 700 cub. 

 centims. of a solution containing 2 per cent, of the same gelose, 

 cooled so far as to be on the point of gelatinizing, — the jar at the 

 same time being placed in a cooling mixture, in order to expedite 

 that change. The jar with its contents was now left undisturbed 

 for eight days at the temperature 10°. After the lapse of this 

 time the jelly was removed from the jar in successive portions of 

 50 cub. centims. each from the top, and the proportion of chloride 

 of sodium in the various strata ascertained. The results were 

 very similar to those obtained in diffusing the same salt in a jar 

 of pure water. The diffusion in the gelose appeared more ad- 

 vanced in eight days than diffusion in water for seven days, as 

 will be seen by comparing the gelose experiment below with a 

 water experiment on chloride of sodium, which had been con- 

 ducted at nearly the same temperature (Table III.). 



Table XI. — Diffusion of a 10 per cent, solution of Chloride 

 of Sodium in the jelly of gelose, for eight days, at 10°. 



No. of stratum. 



Diffusate, in grammes. 



1 



•015 



2 



•015 



3 



•026 



4 



•035 



5 



•082 



6 



•130 



7 



•212 



8 



•350 



9 



•486 



10 



•630 



11 



•996 



12 



1-172 



13 



1-190 



14 



1-203 



15 and 16 



3-450 





9-992 



