630 
AJESSRS. T. E. THORPE AND ,T. W. RODGER ON THE RELATIONS 
Viscosity Coefficients at Slope 
{■q in dynes per sq. centim. X 10^.) 
As already stated, it was impossible to compare all the liquids at the same slope. 
The previous comparisons made at the slope •O 4323 include all the liquids except 
bromine and the alcohols. The next step was to choose another value of the slope so 
that these outstanding liquids might be included in the comparison. In the case of 
the alcohols, the slope, even at the boiling-point, has a value which is larger than that 
given by many of the liquids at the lowest temperatures of observation. Obviously, 
therefore, in order that as many compounds as possible might be compared with the 
alcohols, the smallest possible value of the slope at which the alcohols could be com¬ 
pared had to be chosen. The value which satisfied this condition was 'O 4987 , which 
happens to be the value possessed by isopropyl alcohol at its boiling-point. Besides 
the alcohols, it was found that 33 of the liquids, which were compared at slope '04323, 
could be compared at this new value of the slope, and the first point to decide was 
whether the same relations existed between the magnitudes of the various viscosity 
constants at this new value of the slope as we had established at the previous value. 
This point was easily ascertained in the following way:— 
On finding the value of the ratio. 
Viscosity coefficient at slope ’O^OSZ 
Viscosity coefficient at slope '04323 ’ 
a number was obtained which was practically the same for all the 33 liquids The 
mean value of the ratio was 2'03 ; the average divergence from the mean being '036, 
or about I'Z per cent. 
Making due allowance for experimental errors, and especially for imperfections in 
Slotte’s formula, the constancy of the ratio is satisfactory, as it shows that the 
relationships established between the viscosity coefficients at slope '04323 remain 
practically the same at slope '04987, and indicates that the method of comparison is a 
general one, and is independent of the particular value of the slope at which the com¬ 
parisons are made. 
It is also noteworthy that the acids and water, the complexity of which is 
supposed to increase as temperature falls, give values of the ratio which do not 
differ more widely from the mean ratio than the values given by other types of 
substances such as the dibromides. 
The values given by the alcohols and bromine which, of course, could not be 
compared at slope '04323, ai'e given below^:— 
