696 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
at which drjjdt is the same for the different substances. Instead of comparing the 
values of the viscosity at these points wm may equally well deal with the magnitudes 
of the temperatures at which the slope is the same for the various substances. In 
what follows an attempt is made to show how the magnitudes of the temperatures of 
equal slope are related to the chemical nature of the substances, and, also, how the 
relationships obtained at any one slope are affected on passing to a new value of 
the slope. 
Temperatures = t' in degrees Centigrade at which the slope is ’0000323. 
Homologues. 
r. 
Difference. 
Pentane . 
o 
— 5'4 
1 
° I 
25-9 
Hexane. 
20-5 
20-6 
Heptane .. 
41T 
23-0 
Octane. 
64T 
Isopentane . 
- 4-4 
20-4 
Isoliexane. 
16-0 
19-7 
Isohej^tane. 
35'7 
Isopreue. 
- I2-I 
21-8 
Dialljl. 
9-7 
Methyl iodide .... 
42-9 
18-6 
Ethyl iodide .... 
61-5 
22-1 
Propyl iodide .... 
83-6 
Isopropyl iodide . . . . 
79'9 
17-7 
Isohutyliodide . . . . 
97-6 
Ethyl bromide .... 
26-9 
Propyl bromide . . . . 
64-7 
- / O 
Isopropyl bromide 
ol-6 
24-8 
Isobutyl bromide . . . . 
76'4 
Ethylene bromide. 
147-8 
- 3-2 
Propylene bromide . 
144-6 
