BETWEEN THE VISCOSITY OF LIQUIDS AND THEIE CHEMICAL NATUBE. 89 
The comparison of the values given by these three samples with those given by 
the petroleum sample (A.) is contained in the following table. 
In the case of each sample two curves were plotted, and the coefficients were read 
off at every 5°. The means of these values are given in the table, which also shows 
at each temperature-interval the differences between the coefficients of samples II,, 
III., and A, and that of I. 
I. 
II. 
III. 
A. 
Temp. 
'?■ 
'/• 
Difference. 
V- 
Difference. 
'/• 
Difference. 
o 
0 
*002797 
•002769 
*000028 
*002776 
*000021 
*002726 
*000071 
O 
*002651 
■002624 
•000027 
*002627 
*090024 
*002583 
*000068 
10 
*002521 
*002494 
•000027 
•002495 
*000026 
•002456 
*000065 
15 
*002398 
■002371 
•000027 
*002375 
*000023 
*002340 
*000058 
20 
*002283 
*002255 
•000028 
•002264 
*000019 
*002233 
*000050 
25 
*002175 
•002149 
*000026 
■002158 
*000017 
*002130 
*000045 
The table shows that no two samples gave precisely the same values. No. I.—the 
isopentane derived from potato spirit, giving the largest, and A—the isopentane from 
petroleum, the smallest value. 
The values given by No. I. are about I’l per cent, larger than those given by 
No. II., and 0’9 per cent, larger than those given by No. III., whilst they are 2‘5 per 
cent, larger than those given by the petroleum hydrocarbon. It is evident, therefore, 
that the isopentane from petroleum was not a pure product, and further that on 
preparing the hydrocarbon from amyl alcohol in the manner just described, although 
the boiling-points and vapour-densities of the three samples are practically the same, 
yet, as regards their viscosities, slight differences can be detected, which can only be 
due to the difference in the origin of the samples. 
Apparently, the lower the boiling-point and the higher the viscosity the more 
likely is it that the substance is pure; we, therefore, regard the values for r) given 
by No. I. as nearest to the truth. It may be that isoamylene, wiiich is less viscous 
than isopentane, may be present to some extent in Nos. II. and III. 
In what follows we have used the coefficients given by No. I, sample. 
Taking 
7]^ = *002783 7]^ — *002172 (calculated) = *002458, 
= 0°*44 ^3 = 25*15 ^2 (from curve) = 12°*50, 
we obtain the formula 
391*101 
~ (208*6 + 02*2186 ’ 
which gives numbers in close agreement with those observed. 
MDCCCXCVII.—A. N 
