Laws of Molecular Force. 5 



same effect on the value of (M. 2 iy whatever may be the number 

 of CH 2 groups it is associated with. In the " Laws of Mole- 

 cular Force " it was shown that there is a striking parallelism 

 between the values of the dynic equivalents of the atoms and 

 of their refraction equivalents. I had a strong impression 

 that this must be due to the fact that both quantities were 

 nearly proportional to the volumes of the atoms, but was not 

 then able to test the idea through lack of values of the volumes 

 of the atoms. Bat by means of the characteristic equation for 

 liquids given in that paper, and an unpublished simplified 

 form of it, I have been able to get approximate values of the 

 limiting volumes of the members of a number of series of 

 compounds. Let ft be the limiting volume of a gramme of 

 substance of molecular mass (weight) M ; then the differences 

 in M/3 for a difference CH 2 in composition are as follows : — 

 paraffins 15*7, alkyl iodides 16"4, alkyl bromides 17, alkyl 

 chlorides 16, alkyl oxides 17*3, alkyl amines 17'3, esters 17*5, 

 and benzene series 16'8. The values of M/3 for the lowest 

 available members of these series are CH 4 25, CH 3 I 52, 

 CH 3 Br 46, C,H 5 C1 55-5, (C 2 H 5 ) 2 83, NH 3 20, C 3 H 6 3 64, 

 and C 6 H 6 75*5 ; so that for M/3 we have the scheme given 

 above with (Wl)K 



The following are the few data on which the numbers in 

 the scheme for the nitriles, sulphides, nitro-compounds, 

 nitrates, and sulphocyanates are founded, on the assumption 

 that in (M 2 Z)* CH 2 has a value '9 and in M/3 approximately 17. 



Table V. 



C 3 H 7 CN. (0 2 H 5 ) 2 S. CH 3 NO a . C 2 H 5 N0 3 . CH 3 CNS. C 2 H 5 CNS. 



(M.H)* 6-2 74 4-8 61 5-8 6*6 



M/3 75 94 46 70 59 75 



In Table IV. there are no values given for the olefine 

 series C n H 2n ; but the data for the olefines in table xxv. of 

 the " Laws of Molecular Force " show that (M 2 /)* for C„H 2ra is 

 practically identical with that for C n H 2 » +2 . On this account 

 the dynic equivalent of the two terminal hydrogens of a 

 paraffin C n H 2 »+ 2 was ; i n ^ ne " Laws of Molecular Force," said 

 to be negligible ; but the better mode of expression in accord- 

 ance with the usages of physical chemistry would be to say 

 that the double-bonded union of two carbon atoms in an 

 olefine changes the dynic equivalent of the two carbon atoms 

 by an amount equal to that of the two terminal hydrogen 

 atoms of the paraffin. The first point to be noticed about the 

 expressions for (M 2 /) 5 in Table IV. is that in the paraffins the 



