ON THE SOLUBILITY OF SALTS. 309 



water added to a mixture of alcohol and ether increased the tension of the 

 mixed vapours and lowered the boiling-point of the mixture. In the same 

 manner common salt considerably increases the ten-ion of the vapour which 

 rises into a closed space from a mixture of alcohol and water, and diminishes 

 the boiling-point. Pliicker did not experimentally determine the relative 

 proportions of each vapour before and after the addition of the salt. It 

 would not be easy to do so ; but if it could be accurately done, it would be 

 of great importance, for it seems to me to be necessary in order to control 

 the calculated determinations, and help to give a correct explanation of the 

 phenomenon. From some experiments made with mixtures of other sub- 

 stances, I have found that the relative proportion of each liquid which distils 

 over from a mixture of two or more fluids, before and after the addition 

 of a salt, is very different, but I have not yet determined the influence of 

 temperature, relative proportions of the fluids forming the mixture, and of 

 the mass of the salt, upon the proportions. The action of chloride of calcium 

 upon a mixture of methylic alcohol, acetone, and a number of other liquids, 

 the alcohol being in largest quantity, throws much light upon the phenomena 

 observed by Pliicker. 



The mixture alluded to dissolves fused chloride of calcium with great 

 facility ; when a lar»e quantity has been added, the fluid suddenly splits 

 into two layers, the heavier of which contains the whole of the chloride 

 of calcium, the lighter none. All the fluids of low boiling-points happened 

 to separate from the chloride of calcium in the cases which I happened to 

 observe. On heating the chloride of calcium solution in a retort, a large 

 portion of the liquid distilled over ; on adding water to the residue, and ap- 

 plying heat, another separation took place of some oily compounds, which 

 distilled over along with water. If the mixture was distilled in the first 

 instance before sufficient chloride of calcium had been added to cause the 

 separation of the fluids, we should have an excellent example of the case de- 



H 1 C H 1 



scribed by Pliicker. The molecular union of the atoms „ > 2 and 4 j, 5 > O a 



may be assumed to have been disturbed by the atom of NaCl, which had a 

 stronger affinity for the water than the latter had for the alcohol ; the alcohol 

 was accordingly set free and lowered the boiling-point. The separation of 

 the liquid into two parts does not always take place so evidently as in the 

 case which I have above described, but it is probable the effect is essen- 

 tially the same. If this explanation be true, certain salts ought to produce 

 a diminution of tension, and the boiling-point ought to rise ; thus, if we add 

 a large quantity of salts which are more soluble in ether than in alcohol to 

 a mixture of those fluids, the boiling-point ought to rise, unless the adhesion 

 of the salt and ether be so much diminished by the heat, that the ether should 

 separate again in part and distil over. I had an opportunity of observing an 

 example of this kind in the case of some very volatile, oleaginous bodies, 

 some of which combined with CaCl. Generally speaking, however, the heat 

 required to vaporize the denser oils was sufficient to decompose the molecular 

 combination with the CaCl, although it was sometimes possible to produce 

 the splitting into two fluids. The whole subject is evidently one well worth 

 further investigation, as I have no doubt that very great light would thereby 

 be thrown upon the nature of solution. It also affords a measure of the 

 comparative forces by which different salts are held by water and other 

 solvents, and which I propose to make full use of for that purpose. 



The diathermancy of solutions, which has been made the subject of inves- 

 tigation by Frantz, may likewise be made use of hereafter, as also the optical 

 properties, such as their refractive and dispersive powers, &c. Krcmers has 



