272 Prof. Graham on the Diffusion of Liquids, 



Thus while the 4 per cent, solutions range from 10*27 to 

 11*49 grs., or from 100 to 111*8, the 2 per cent, solutions 

 range from 5*45 grs, to 5*85 grs., or from 100 to 107*3. 



As it appeared to be in dilute solutions that the greatest 

 uniformity of diffusion is to be expected, a series of experi- 

 ments was instituted upon the preceding salts, with the ad- 

 dition of acetate of potash, which appeared to belong to the 

 same class, the solution employed being that of 1 salt to 100 

 water. The experiments were made in a vault, of which the 

 temperature was nearly uniform, falling in a gradual manner 

 from 59° to 58°, with a mean of 58°*5 during the period of 

 seven days which the diffusion lasted. Eight phials of each 

 salt were diffused, and the liquids of four water-jars evaporated 

 together. 



Carbonate of potash gave 10*42 and 1059 grs. of salt dif- 

 fused: mean 10*51 grs., or 2*63 grs. for one cell. 



Sulphate of potash gave 10*72 and 10*78 grs. of salt dif- 

 fused: mean 10*75 grs., or 2*69 grs. for one cell. 



Acetate of potash, its diffusion product being treated with 

 an excess of hydrochloric acid, gave 8*30 and 8*0 h grs. of 

 chloride of potassium, equivalent to 10*91 and 10*57 grs. of 

 acetate of potash; mean 10*74 grs. of acetate of potash, or 

 2*68 grs. for one cell. The diffusion of these three salts is 

 therefore remarkably similar: — 



Diffusion of 1 per cent, solutions at 58°*5. 



Carbonate of potash .... 2*63 grs. 

 Sulphate of potash .... 2*69 grs. 

 Acetate of potash .... 2*68 grs. 



The 1 per cent, solution of neutral or yellow chromate of 

 potash in good crystals gave 11*28 and 11*35 grs.; mean 

 11*31 grs., or 2*83 grs. for each cell. It was remarked of the 

 diffused chromate in this experiment, that it contained a sen- 

 sible quantity of green oxide of chromium. The diffusion of 

 a salt appears indeed to try its tendencies to decomposition 

 very severely. 



The bicarbonate of potash gave 8*83 and 8'35 grs. of chlo- 

 ride of potassium, the diffusion product being neutralized with 

 hydrochloric acid; equivalent to 11*25 and 11*21 grs. of bi- 

 carbonate of potash ; mean 11*23 grs., or 2*8 1 grs. for one cell. 



The bichromate of potash gave 11*54 and 11*49 grs. of salt 

 diffused; mean 11*51 grs., or 2*88 grs. for one cell. These 

 last three salts give all a larger diffusion product than the 

 preceding three, while they agree well together. It is doubtful 

 whether this excess in their diffusion is occasioned by a par- 

 tial decomposition in the act of diffusion, which might be of 



