672 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
influences, and conform to the general rule that the extent to which the magnitude 
of a property is affected by the displacement of one atom of hydrogen by one atom of 
halogen is not constant, but varies in a regular way according as the first, second, 
third, or fourth hydrogen atom is replaced. 
Chlorethanes .—The molecular viscosity work of ethylene chloride is distinctly 
greater than that of ethyl id ene chloride. 
Ethylene chloride. 
326 
14 
Ethylidene chloride. 
.312 ■ 
With the exception of heats of combustion, where it has to be noted that chlorine 
takes no part in the chemical change, the magnitudes of several of the other physical 
properties of these metamers exhibit similar striking differences, as the following 
table shows :— 
Boiling- 
point. 
Surface tension 
Molecular 
magnetic 
rotation. 
Heat of 
comhustion. 
Specific 
molecular 
volume 
at b.p. 
1 
Molecular | 
refraction. ! 
1 
1 
Molecular weight 
at b.p. 
Ethylene chloride . 
Ethylidene chloride. 
840 
57-5 
24-6 
20-8 
5-485 
5-.335 
•272 
272 
85-0 
89-3 
20- 92 
21 - 08 
Difference .... 
26-5 
3-8 
•150 
0 
-4-3 
I 
-16 
Here again the change in specific molecular volume and molecular refraction is in 
the opposite sense to the change in the other properties. 
The cause of these remarkable differences is no doubt to be traced to the fact that 
the effect of introducing chlorine in place of hydrogen into ethane varies according as 
it is the first, second, or third atom of chlorine which is united to the same carbon 
atom. Thus the effect of substituting hydrogen by chlorine in the compounds, 
KCHg, HCHgCl, RCHClg, is doubtless different in each case. 
Moreover, it is also conceivable that the effect may depend on the nature of R, i.e., 
whether it be CHg, CH3CI, CHCL, or CCI3. To test these two points it would be 
necessary to investigate as many of the various chlorraethanes as possible. 
This has only been done in the case of specific molecular volumes, and here the results 
clearly point to the conclusion that if we start with ethyl chloride the nature of R is 
inoperative, and that the effect of introducing Cl into ethyl chloride, or its chlorine 
derivatives, simply depends on whether it is the first, second, or third chlorine atom 
which has been introduced into a particular methyl group. 
