Laws of Molecular Force. 9 



radicals CH 2 and NH 3 . The values of (WVf for benzene and 

 its monohalogen substitution compounds are : — 



C 6 H 6 . O fl H 6 01. 6 H 5 Br. C e H 6 I. 



6-6 7-6 8-2 9-0 



which give for CI — H the value 1*0, for Br— H 1*6, and for 

 I— H 2*4 ; and these, with the values found for the halogens, 

 give for H in benzene the values 1*2, *9, and *8, the mean of 

 which is 1*0; still a large value and nearly equal to the l'l 

 belonging to each CH in benzene, which, it should be noticed, 

 is larger than the *9 for CH 2 . Strictly speaking, all that the 

 last numbers really show is that the difference between the 

 halogens and hydrogen in benzene is about the same as the 

 difference between the halogens and the terminal hydrogen 

 in paraffins. The following values form the beginning of a 

 series which, if extended, would illustrate the transition from 

 one type to the other : — 



C 2 H 6 . C 2 H 5 01. C 2 H 4 Cl a . C 2 H 3 C1 3 . 



(Wl)i 4-0 5-1 67 7-6 



They give C1-H = M, 2(Cl-H) = 2-7, and 3(Cl-H) = 3-6, 

 which are in fair enough agreement. In the following cases 

 we have only CH 2 groups and halogens. 



C 2 H 4 C1 2 . C 3 H 6 C1 . C a H 4 Br 2 . 3 H 6 Br 2 . 



Mj3...= 68 76 91 



(M 2 0* 6-7 7-5 71 7-8 



With '9 for CH 2 in (M 2 /)*, these give for CI the values 2'45 

 and 2*4, and for Br 2 # 65 and 2*55, which are a little larger 

 than those adopted from the series, namely 2*2 and 2*5. 



The data of table xxv. of the " Laws of Molecular Force " 

 furnish values of (M 2 /) 3 " for the elements H 2 , 2; and N 2 , and 

 for CH 4 , which are gathered into 



Table VIII. 



H 2 . 2 . N a . CH 4 . 



M/3 8-6 193 22-7 25 



(M 2 0* 47 108 1-11 15 



Eatio 18 18 20 17 



To these may be added an uncertain set of values for Cl 2 , 

 namely M/3 = 34 and (M 2 rp=2'4, their ratio being 14; 

 excepting this, we see that the element gases and CH 4 have 

 nearly a constant value 18 for the ratio M/3/(M 2 Z)*, a value 

 which is nearly double the 10 for atoms in the combined 

 state. It should be noticed that the ratio 19 for CH 2 in the 

 carbon series ranges itself along with the values for the 



