Prof. Graham on the Diffusion of Liquids, 185 



contain the solutions, and to form what I shall call the Solu- 

 tion phials or cells. They were of the same make and selected 

 from a large stock, of the common aperture of 1*175 inch. 

 Both the mouths and bottoms of these phials were ground 

 flat. The mode of making an experiment was first to fill the 

 phial to the base of the neck, or rather to a constant distance 

 of 0-6 inch below the ground surface of the lip. A little disc 

 of cork, provided with a slight upright peg of wood, was then 

 floated upon the solution in the neck, after having been first 

 dipt in water. The neck itself was now filled up with pure 

 water by means of a pointed sponge, the drop suspended from 

 the sponge being made to touch the peg of the float, and water 

 caused to flow in the gentlest manner, by slightly pressing the 

 sponge. The only other part of the apparatus, the water-jar, 

 was a plain cylindrical glass jar, of which the inner surface of 

 the bottom was flat or slightly concave, to give a firm support 

 to the phial. The phial, with its solution only, was first 

 placed in this jar partly filled with distilled water, and the 

 neck of the former was then filled up with distilled water in 

 this position, as before described, to avoid any subsequent 

 movement. The phial was ultimately entirely covered to the 

 depth of an inch with water, which required about 30 ounces 

 of the latter, fig. 2. The saline solution in Fig. 2. 



the diffusion cell or phial thus communicated 

 freely with about five times its volume of pure 

 water, the liquid atmosphere which invites 

 diffusion. Another modification of this pro- 

 cedure was the substitution of phials cast in 

 a mould, of the capacity of 4 ounces, or more 

 nearly 2080 grs., which were ground down 

 to a uniform height of 3'8 inches. The neck 

 was 1*25 inch in diameter and 0*5 inch in 

 depth ; and the phial was filled up with the 

 solution to be diffused to that point. The solution cell or 

 phial and the water-jar form together a diffusion cell. 



The diffusion was stopt, after twenty-seven days in the pre- 

 sent experiments, by closing the mouth of the phial with a 

 plate of glass, and then raising it out of the water-jar. The 

 quantity of salt or of acid which had found its way into the 

 water-jar, — the diffusion product as it may be called, — was then 

 determined by evaporating to dryness for the salts, and by 

 neutralizing the same liquid with a normal alkaline solution 

 for the acids. The quantities of the acids diffused are esti- 

 mated at present as protohydrates for the sake of comparison 

 with the salts. 



