364 Mr. W. W. J. Nicol on the 



to establish the relation between the force of molecular 

 attraction and "the repulsive force of heat," on which our 

 whole argument has been based. This relation is, as we have 

 seen, the expression of a relation between observed quantities, 

 and is one which we must suppose to hold good even in the 

 limit where the observed quantities are vanishingly small. 

 Laplace, by confining his attention to this limiting case, over- 

 looked the relation, and accordingly failed to perceive the 

 reality of the surface-tension ; and his theory is in consequence 

 absolutely inapplicable to the explanation of any of those 

 phenomena of horizontal motion on a liquid surface which are 

 due solely to variations of the surface-tension, and are not 

 necessarily accompanied by an elevation or depression of the 

 liquid. 



XXXVIII. The Nature of Solution. — Part II. Boiling-Points 

 of Salt-Solutions. By W. W. J. Nicol, M.A., B.Sc, 

 F.R.S.E., F.C.S., Sfc, Lecturer on Chemistry, Mason Col- 

 lege, Birmingham* . 



YEKY little indeed is known of the temperatures at which 

 salt-solutions of definite composition boil. Almost the 

 whole of our knowledge is confined to the boiling-points of 

 saturated solutions; and these have been determined in very 

 many cases with but little pretence to accuracy. With the 

 exception of the experiments made by Legrandf, nothing 

 has been done to determine the effect on the boiling-point 

 of water produced by the presence of various quantities 

 of salts dissolved in it. The vapour-pressure of water from 

 salt-solutions of various strengths has also received but little 

 attention; the results of Wtillnert ? Babo, and one or two 

 others comprising all that is known on this subject. 



From the time when I began first to work at the subject 

 of solution, it appeared to me that it was in this direction that 

 most knowledge of the nature of solution was to be gained ; 

 but it is only recently that I have been able to turn my attention 

 to this point. The following pages contain an account of my 

 experiments on the pressures under which saturated salt-solu- 

 tions boil at different temperatures. These experiments are 

 merely preliminary to a more extended and more accurate 

 series of determinations of the pressure of aqueous vapour 

 from such solutions. Still the results of these first attempts 



* Commimicated by the Author. 

 f Ann. Chim. et Phys. lix. p. 423. 

 X Pogg. Ann, ci. ? cy., ex. 



