180 Mr. W. W. J. Nicol on the Molecular 



dilute (less than one equivalent of salt to 100 molecules of 

 water) and of the same strength. The cause of any slight 

 variation in the constants was shown to lie in the concen- 

 tration of the solution : this must be such that the molecules 

 of salt are without an appreciable influence upon one another; 

 for the molecular volume of all salts increases with the con- 

 centration of the solution, but more rapidly the less soluble 

 the salt (loc. cit.). 



I purpose in the following pages to endeavour to prove 

 that the conclusions arrived at in my previous paper hold good 

 for all elements or groups of elements. I had hopes of being 

 able to employ for this purpose the numerous determinations 

 of the density of various salt-solutions to be found in the 

 papers of Kremers, Schiff, Grerlach, and others, but soon 

 found that these were of little value for my purpose, for 

 without interpolation it is seldom possible to obtain the 

 density of solutions of the same strength ; even where it is 

 so, the determinations were made at different temperatures, 

 or the density referred to water at different temperatures as 

 unity. Only in a few cases can these old results be employed 

 without involving considerable calculation, leading to figures 

 which are in too many instances evidently erroneous. How- 

 ever, I have arranged in Table I. the apparent molecular 



volumes ( — j of some of the more important chlorides, bro- 

 mides, and iodides, calculated by means of the following 

 formulae from the results of former investigators. 



Where the quantity of salt is expressed in percentage, 



:^™) ,„i,„. 



1 Pg x 100 



Yw 



When in parts per 100 of water, 



/P + 100 



-100)xM.W. 



Ps = per cent, of salt, Pw = per cent, of water, 



8 = density, M.W. = mol. wt. in grams. 



P= parts per 100 of water. 



