BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. G73 
Using the value for ethyl chloride calculated by Kopp from Pierre’s values for its 
thermal expansion, and the values obtained by Staedel, the following are the data 
which serve to establish the foregoing conclusion ;— 
Chlorethane. 
Differences in 
specific molecular 
volnm.e. 
Where R may be 
RCHg 
CHoCl, CHCQ, or CCI 3 . 
RCHoCl 
I4T ± -3 
CHg, CHXl, CHClo, or CCI. 5 . 
RCHCl, 
16-9 ± -4 
CH 3 , CH 2 CI, CHClo, or CCI 3 . 
RCC 1;5 
19-2 ± -4 
CH 3 , CHoCT, or CHClo. 
Here the effect of substituting chlorine, as in the case of the chlormethanes, is 
greater, according as the first, second, or third hydrogen atom in the original methyl 
group is replaced by the chlorine. 
The cause of the difference between the specific molecular volumes of ethylene 
chloride and ethylidene chloride is to be sought for in the fact that in the former 
substitution has taken place in two methyl groups, whereas in the latter it has only 
taken place in one methyl group. There is no doubt that the difference in the magni¬ 
tudes of the viscosity and other physical properties is to be ascribed to the same fact. 
Whether the magnitude of the effect of substituting chlorine in the case of these 
properties depends also on the nature of R, i.e., on the halogen contents of the other 
methyl group, can best be decided by investigations similar to those of Staedel. 
There is indication, however, that this effect is operative in the case of viscosity, as 
it appears that dihalogen derivatives of ethane give a smaller value for the atomic 
constant of the halogen than monohalogen compounds. If the effect of the nature 
of R were inoperative, the compound CHg.CHgCl should yield the same value for 
chlorine as CHgCl.CHgCl, for in each case the first hydrogen atom in a methyl group 
has alone been replaced. Indeed, it may be the case that specific molecular volume 
is also affected in the same way. The volume-change in passing from ethane itself, 
CH3.CH3, to ethyl chloride, CH3.CII2CI, may perhaps differ from the change 
produced in passing from CH3.CH2OI. to CHjCl.CHoCl. This point can only be 
settled when the specific molecular volume of ethane is determined. 
From a study of the chlorethanes and chlormethanes it is thus evident that, as in 
the case of specific molecular volume, the magnitude of the effect which is exerted on 
the molecular viscosity work when chlorine is united to carbon, hydrogen being 
expelled, depends on whether the first, second, or third hydrogen atom is replaced. 
Tetraclilorethylene .—The mean value of chlorine in tetrachlorethylene CC1.2;CCL 
is 74. 
4 R 
MDCCCXCIV.—A. 
