408 M. J. A. Groshans on the Specific Gravity of certain 



density, that with F or that with CI ? For this we have not 

 such a large number of examples as in the first case ; we 

 know that the greater part of the compounds of fluorine in 

 Table C are insoluble. 



We have come across Kohlrausch's researches on the 

 fluoride of potassium, KF ; and we have calculated, in round 

 numbers, from his experiments the densities for integral num- 

 bers of molecules of water. The results of these calculations 

 are in Table D ; and we have placed opposite to them the 

 observed densities of the solutions of KC1 of Thomsen, with 

 the same number of molecules of water. 



Table D. 



Comparison of the Densities of Solutions of KF and KCl 

 containing an equal number of molecules of water (n). 



n. 

 H 2 0. 



KF, 



Koklrausch, 



£=18°. 



Calculated 



density. 



KCl, 



Thomsen, 



*=18°. 



Observed 



density. 



Differences. 



15 



11560 



1-1468 



0-0092 



30 



1-0832 



1-0800 



00032 



50 



1-0515 



1-0496 



00019 



100 



1-0263 



1-0258 



0-0005 



200 



10133 



10136 



0-0003 



The densities here are d -$■ 



We see in this table that the two solutions have equal 

 densities when they are sufficiently dilute. 



This example proves that the densities of solutions does not 

 depend upon the greatness of the molecular weight of the 

 dissolved substance ; for the molecular weight of KCl is 

 greater than that of KF. 



On the Method employed in calculating the Densities of a Solu- 

 tion, with arbitrary numbers of Molecules of Water, taking 

 two experiments for the basis of the Calculation, 

 In explaining this method of calculation, it will be necessary 

 for us to touch upon some of the results of our researches upon 

 solution, which have been published elsewhere. 



We may regard a solution as a compound of one part (a 

 gramme) of the soluble substance with a variable number of 

 grammes of water ; this number we will call aq. We shall 

 show that the density of a solution can be represented with a 



