iiETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 67 5 
The effect of introducing chlorine increases as N increases, and, N remaining the 
same, it is greatest in an ethylene compound and least in a methane compound. Here, 
as is always the case, the direction of the change in specific molecular volume is the 
reverse of that exhibited in the case of molecular viscosity work. 
It is evident that the condition of chlorine in carbon tetrachloride is different from 
that in tetrachlorethylene. Indeed, CClj, is hardly comparable with the other 
substances where substitution in methyl groups is considered. 
On comparing the physical properties of these two substances with those of 
compounds which are related in the same way so far as chemical composition goes, in 
all cases, as the following table shows, the behaviour of these chlorine compounds is 
peculiar. 
The peculiarity is doubtless to be attributed to the different conditions of chlorine in 
the two compounds, a difference which is ignored when the compounds are simply 
regarded as differing in chemical nature by an atom of carbon and a double linkage. 
Molecular 
Difference. 
Difference. 
Surface tension 
Difference. 
viscosity 
work. 
point. 
i Molecular weight 
at b.p. 
Ethyl bromide . 
282 
45 
38-4 
32-1 
20-5 
- 1-7 
Ally! bromide . 
327 
70'5 
18-8 
Ethyl iodide . . 
341 
56 
72-4 
30-4 
14-7 
- 1-7 
Allyl iodide . . 
397 
102-8 
13-0 
Tetrachlormetbane 
406 
91 
76-8 
43-9 
13-3 
1 
1 
•1 
Tetrachlorethylene 
497 
120-7 
13-4 
Specihc 
Heat of 
combustion. 
Difference. 
molecular 
volume at 
Difference. 
b.p. 
i 
1 
Ethyl bromide . . 
341-8 
120-3 
77-5 
1 
13-0 
Allyl bromide . 
462-1 
90-5 
Ethyl iodide . . 
85-8 
15-1 
Allyl iodide. . 
•" 
•• 1 
100-9 
Tetrachlormetbane 
75-9 
103-7 
i 
1 
• 
119-2 
10-9 
T e trachlorethy lene 
195-1 
114-6 
j 
4 R 2 
