20 Mr. William Sutherland on the 







Table XIII. 



{continued). 











K. 







Rb. 









F. 



Cl. 



Br. 



I. 



F. Cl. 



Br. 



T. 



T 



1060 



1007 



972 



907 



983 



956 



915 



M/p 



28-2 



383 



44 6 



54-3 



326 54 8 



59-5 



70 3 



MH 



. 327 



46-0 



55-7 



667 



69-2 



76-9 



90-8 



(M 2 /)* 



5-7 



68 



75 



8-2 



83 



8-8 



95 



(M^from] 

 Table IX. , 



► 5-1 



63 



69 



7-8 









The general agreement between the two sets of values of 

 (M 2 /) 5 is surprisingly good, the values found by (9) being on 

 the average about 7 per cent, larger than those found from 

 surface-tensions. The data for the haloid compounds of the 

 other metal of this family, namely Cs, are incomplete, at least 

 I have failed to find data for the densities of Cs compounds ; 

 but the following considerations give us the molecular domains 

 of Cs compounds in a satisfactory manner ; the mean differ- 

 ence in the molecular domains of the corresponding Na and 

 Li compounds is 5'4, for K and Na it is 11*2, and for Kb 

 and K 15*8, numbers which are closely .1 x 5*4, 2 x 5*4, and 

 3 X 5'4. Consequently for Cs and Rb compounds we should 

 expect a difference 4x 5*4 or 21*6, which when added to the 

 domains for the Rb compounds gives the domains tabulated 

 hereunder with the melting-points taken from Carnelley's 

 diagram : — 



Table XIII. {continued). 



Cs. 



01. Br. I. 



T 904 879 869 



M/p 76 81 92 



M 2 l 938 100 7 116-4 



(M 2 J)* 9-7 10-0 108 



The simplest way to deal with compounds of the type RC1 2 , 

 RC1 3 , and RCI4 is to replace kMc/6'4: in equation (13) by 1, 

 as we have done with the type RC1, and then ascertain what 

 values must be assigned to &Mc/6*4 to make the results con- 

 sistent with one another; then, having the value of Mc for 

 each type, we can assign the value of k for each. As the 

 event proves that kMc/6'4: is 1, or nearly 1, for the simple 

 types RC1, RC1 2 , RCI3, and RC1 4 , we can proceed to tabulate 

 values of (M 2 /)^ from (9), namely, 



M 2 /=5-8xlO- 4 (M//>)TM*, .... (9) 



