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



of which 610 milligrammes, or 95 3 per cent., were chloride of 

 potassium. It is obvious that by repeating this diffusive recti- 

 fication a sufficient number of times, a portion of the more 

 diffusive salt might be obtained at last in a state of sensible 

 purity. 



The preceding example illustrates the separation of unequally 

 diffusive metals or bases; the following example, on the other 

 hand, the separation of unequally diffusive acids united with a 

 common base. Chloride of sodium and sulphate of soda diffuse 

 separately in the phial experiments in the proportion of 1 to 

 0-707. 



Table VII. — Diffusion of 5 per cent, of Chloride of Sodium 

 and 5 per cent, of anhydrous Sulphate of Soda, for seven days, 

 at 10° to 10°-75. 



Number of 



Chloride of 



Sulphate of 



Total diffu- 



stratum. 



sodium, in 



soda, in 



sate, in 



grammes. 



grammes. 



grammes. 



1 



•009 





•009 



2 



•013 



"ooi 



•014 



3 



•024 



•002 



•026 



4 



•038 



•003 



•041 



5 



•060 



•006 



•066 



6 



•095 



•012 



•107 



7 



•141 



•029 



•170 



8 



•203 



•059 



•262 



9 



•278 



•115 



•393 



10 



•360 



•205 



•565 



11 



•473 



•317 



•790 



12 



•560 



•507 



1-067 



13 



•637 



•694 



1-331 



14 



'718 



•909 



1-627 



15 and 16 



1-390 



2-141 



3-531 





4-999 



5-000 



9-999 



Here the separation is still more sensible than before with the 

 bases. The six upper strata contain 263 milligrammes of salt, 

 of which 239 milligrammes, that is 90*8 per cent., are chloride 

 of sodium. The salt of the upper eight strata amounts to 695 

 milligrammes, of which 583 milligrammes, or 83*9 per cent., 

 are chloride of sodium. 



How long the diffusion should be continued in a liquid column 

 of limited height, such as in these experiments, so as to produce 

 the greatest separation, is a question of some interest, which can 

 only be answered by experiment. The last diffusion was ac- 

 cordingly repeated, with the difference that it was continued for 

 double the former time. 



