between the YtSCOSITY OE LIQUIDS AND THEIR CHEMICAL NATURE. 671 
Molecular 
viscosity-worh. 
Diffei'ence. 
Boiling-point. 
Diffei’ence. 
MetLyl cLloricIe .... 
(135) 
108 
o 
- 23-7 
63-9 
Methylene dichloricle 
243 
85 
40-2 
21-1 
Chloroform. 
328 
78 
61'3 
15-5 
Carbon tetrachloride. . . 
406 
76-8 
Molecular mag¬ 
netic rotation. 
Difference. 
Specific mole¬ 
cular volume at 
boiling-point. 
Difference. 
Methyl chloride .... 
50-8 
14-8 
Methylene chloride . . . 
4:313 
1-240 
65-6 
18-9 
Chloroform. 
5-559 
1-023 
84-5 
19-2 
Carbon tetrachloride. . . 
6-582 
103-7 
In all cases the differences are not constant, but alter progressively as substitution 
goes on; and for all the properties but specific molecular volume the differences diminish. 
Other properties, which are less influenced' by differences in constitution than those 
mentioned above, also give indication of effects of a simila.r kind. Observations on 
molecular refraction show, although not so definitely as the above properties, that as 
an element, or radicle, accumulates in a molecule the effect of each increment is not 
the same (Comp. Bruhl, ‘ Zeit. f physik. Chem.,’ 7, 178; Armstrong, ‘ Proc. Chem. 
Soc.,’ 1892-3, 57). 
In the case of specific molecular volume and molecular refraction, unlike what takes 
place in the case of molecular viscosity work, the value of chlorine, say, increases as 
successive atoms are linked to the same carbon atom. This difference is significant, 
as viscosity and boiling-point are doubtless to be referred to inter-molecular effects, 
whereas specific molecular volume, and, as there is reason to believe, refraction as well, 
are to be associated with intra-molecular effects (compare p. 549). 
The surface tensions of two only of the chlormethanes, viz., chloroform and carbon 
tetrachloride, have been determined by Schiff. He has shown that, according to his 
method of treating surface tension measured at the boiling-point, the value of chlorine 
in chloroform is the same as in carbon tetrachloride. It would thus appear that, as 
regards the surface tensions of these two substances, the effect of the accumulation of 
chlorine in the molecule is inoperative. 
The values for the molecular viscosity work of the chlormethanes are thus in 
harmony with those of all other properties which are largely affected by constitutive 
