24 Mr. William Sutherland on the 



and XV. In the haloid compounds of the Li family the mean 

 difference in (M 2 /)* for the chlorides and fluorides (CI — F) 

 is l'l, for Br-F 1*8, and for I-F 2*5; which are a little 

 smaller than the 1*2, I'S, and 2*7 which we got before, although 

 the values of (M 2 lf in Table XIII. are larger than those in 

 Table IX. 



Similarly we have the average values Na — Li =1*1, 

 K-Li = 2 : 2, Rb-Li = 3-6, and Cs-Li = 4'9, which go 

 nearly as 1,2, 3, and 4, The corresponding differences in 

 the molecular domains with Clarke's values given in Table 

 XIII., are Na-Li = 5'4, K-LI=166, Rb-Li = 32'4. The 

 same molecular domains taken in conjunction with Thorpe's 

 values for the halogens in organic compounds lead, as has 

 been already shown, to the domains 9 for F, 19 for CI, 26 for 

 Br, and 36 for I, which lead to a mean value 2*0 for Li ; so 

 that the molecular domains of the metals of the Li family in 

 the compound state are 2'0 for Li, 7*4 for Na, 18*6 for K, 

 34'4 for El), and probably 56 for Cs. To obtain the values 

 contributed to (M 2 /) 5 by these atoms, it must be remembered 

 that from the results in Table IX. we found that the value 

 for fluorine might be taken as 9, so for the numbers in 

 Table XIII. it should be taken as about *9, gi v ing for the 

 halogens the values *9 for F, 2*0 for CI, 2'7 for Br, and 3*4 

 for 1, nearly the same as the former values "9, 2*1, 2*7, and 

 3*6 ; which will be retained and lead to the values 2*4 for Li, 

 3-5 for Na, 4*6 for K, 60 for Rb, and 7'3 for Cs, which go 

 very nearly as 2, 3, 4, 5, and 6. 



To complete the data for the Be family we require the 

 densities of the haloid compounds of Be, but as these appear 

 to be wa iting we must approximate to the molecular volumes 

 of the Be compounds by means of the fact that the molecular 

 volume of BeO is 5 Jess than that of MgO ; subtracting then 

 5 from the molecular volumes of MgCl 2 , MgBr 2 , and Mgl 2 , 

 we can supply the following 



Supplement to Table XIV. 

 Be. 



Cl 2 . Br 2 . I 2 . 



T 870 870 770 



M/p 39 51 66 



(M. 2 lf 6-4 7-8 3-6 



On passing from the haloid compounds of the monad 

 metals in Table XIII. to the compounds of the dyads, triads, 

 and tetrads in Tables XIV. and XV., the first point to arrest 

 attention is that the values for I 2 — Cl 2 , 1 ? — Cl 3 , I 4 — Cl 4 are 



