544 [April 30, 



in accordance with the principles already described. I also give them 

 in the case of water, calculated from Thomson's experiments, assu- 

 ming that, when ice melts and mixes with water, it may be looked 

 upon as dissolving in it ; and, as will be seen, the mechanical force 

 thus deduced is of the same general order of magnitude as that gene- 

 rated by the crystallization of salts. 



I. II. III. IV. V. 



1. Chloride of Sodium 13-57 97 '407 '419 157 



2. Sulphate of Copper. ... 4'83 60 1-910 3-183 7 



3. Ferridcyanide of Potas- 



sium 2-51 86 -288 '335 42 



4. Sulphate of Potash.... 31-21 63 1-840 2'914 42 



5. Ferrocyanide of Potas- 



sium 8-90 66 1-640 2-485 20 



6. Water 8'93 .. .. -991 106 



Nos. 2 and 5 are calculated as hydrated crystals. 



Column I. gives the expansion of each salt in crystallizing from a 

 nearly saturated solution in water, the volume in a crystalline state 

 being taken at 100. 



Column II. gives the actual pressure in atmospheres in the ex- 

 periment. 



Column III. gives the increased solubility due to the pressure 

 given in column II., the total amount of salt dissolved without pres- 

 sure being taken at 100. 



Column IV. gives the increase in solubility that would be produced 

 by a pressure of 100 atmospheres, as calculated in accordance with 

 the principles already described, the same unit being taken as in 

 column III. 



Column V. gives the value of the mechanical work that could be 

 done, or, so to speak, the amount of mechanical force set free when 

 the various substances crystallized from a solution containing 1 per 

 cent, more than would be dissolved without pressure, as measured 

 by the number of times its own weight which any unit of the 

 various salts could raise to the height of 1 metre in the act of cry- 

 stallization. Conversely, it is the amount of mechanical force which 

 becomes latent in the act of solution ; and in the case of a still more 

 supersaturated solution it would be greater, and vice versd, in accord- 

 ance with the fact of the increased solubility varying with the pressure. 



