14 Mr. William Sutherland on the 



equivalents. In the case of the K and Na compounds of the 

 dibasic acids in Table IX., we will reduce the value of (M 2 /)* 

 to that for equivalents not by dividing by the theoretical 2* 

 but by the empirical 1*6 : for convenience the value of (M 2 /)* 

 thus reduced to the value for equivalents will be denoted by 

 2F e , the relation between the two being as a rule 



tF e =(M.H)i/ni, 

 though in the present case we are taking 1*6 in place of 2* 

 in order to allow for a slight difference in equation (2) as 

 applied to the compounds of the dibasic acids ; so also in 

 Na 4 P 2 7 1-6 \/2 will be used instead of #. 



Table X. 



Compounds of Potassium K. 

 CO,. S0 4 . Or0 4 . Cr 2 7 . Cr 3 O I0 . P 2 G . 

 2F e 76 8-2 79 11-1 14-1 109 



Compounds of Sodium Na. 



C0 3 . S0 4 . Cr0 4 . Cr 2 7 . B 4 7 . W0 4 . P 2 6 . P 2 T . 

 2F e 6-4 71 7 9-9 103 7*8 9 9 10-3 



Thus the additive principle holds throughout the values of 

 (M 2 Z)* in Table IX. for the K and Na compounds of the 

 monobasic acids, and in Table X. for equivalents of their 

 compounds with dibasic acids ; and if we knew the values of 

 F for K and Na, we could at once obtain the values for the 

 other atoms and radicals and equivalents involved. We 

 might adopt the values already found for F for the halogens 

 in the organic compounds, but seeing that we do not know 

 yet how far the absolute values given by equation (2) are to 

 be relied on, the following process is safer. From the 

 potassium compounds we get that in (M 2 /)*, CI — F = l*2, 

 Br — F = l*8, and I — F=2*7; while in the molecular volumes 

 M/p, which in solids is very nearly the same as M/3, we have 

 Cl-F = 13-9, Br-F = 20 : 5,andI-F = 3Ol; or, using mean 

 values obtainable from data for the haloid compounds of 

 Li, Na, K, and Rb given later on in Table XIII. from C. W. 

 Clarke (Phil. Mag. ser. 5, iii.), we have CI- F = 10*3, 

 Br-F = 16'7, and I-F = 26'8. It will be seen that these 

 two series of differences in M/p are about ten times the cor- 

 responding differences in (M 2 Z)% and 10 was the value that 

 we found for the ratio of B the atomic volume to F for the 

 halogens in organic compounds : thus then it happens that 

 equation (2), in spite of the roughnesses in it, gives values of 



