96 DEPARTMENT BULLETIN 1216, TJ. S. DEPT. OF AGRICULTURE 
SPECIFIC GRAVITY 
-J— 
ycbmrn. 
8. (a) Hydrometer. — The hydrometer shall be of the form shown in Figure 40. 
It shall have the following dimensions : 
Length of stem 125 millimeters ; permissible variation, 12.5 millimeters. 
Length of bulb 105 millimeters ; permissible variation, 10.5 millimeters. 
Length of scale 80 millimeters ; permissible variation, 8.0 millimeters. 
Diameter of stem millimeters ; permissible variation, 0.5 millimeters. 
Diameter of bulb 22 millimeters ; permissible variation, 2.0 millimeters. 
A set of two hydrometers with ranges 1 to 1.08 and 1.07 to 1.15 will suffice. 
(&) Cylinder. — The cylinder shall be of the form shown in Figure 41. It 
shall have the following dimensions : 
Length 300 millimeters; permissible variation, 30 millimeters. 
Diameter 32 millimeters; permissible variation, 3 millimeters. 
9. The oil shall be brought to a temperature of 38° 
C. (100° F.), and the determination shall be made at 
that temperature unless the oil is not entirely liquid at 
38° C. In case the oil requires to be brought to a 
higher temperature than 38° C. in order to render it 
completely fluid, it shall be tested at the lowest tempera- 
ture at which it is completely fluid, and a correction 
made by adding 0.0008 to the observed specific gravity 
for each degree centigrade above 38° C. at which the test 
is made. This correction factor does not apply with 
equal accuracy to all oils, but serious error due to its 
use will be avoided if the foregoing precaution is ob- 
served, with respect to avoiding unnecessarily high tem- 
perature. Before taking the specific gravity the oil in 
the cylinder should be stirred thoroughly with a glass 
rod, and this rod when withdrawn from the liquid should 
show no solid particles at the instant of withdrawal. 
Care should be taken that the hydrometer does not touch 
the sides or bottom of the cylinder when the reading 
is taken, and that the oil surface is free from froth 
and bubbles. 
DISTILLATION 
Fig. 40. — Hydrometer 10. The distillation of creosote oil 
shall be determined in accordance 
with the tentative method of test for distillation of creosote 
oil (serial designation D 246-27 T) of the American Society 
for Testing Materials (5). (See p. 98.) 
SPECIFIC GRAVITY OF FRACTIONS 
11. As specific gravity is an absolute physical determina- 
tion, any recognized method which can be applied to the 
quantity and quality of material at hand to be tested must 
be considered satisfactory. The following methods are 
convenient and accurate means for the relatively small 
amounts of oil available in determining specific gravity of 
fractions to be tested. 
(a) LIQUID FRACTIONS 
12. The Westphal balance may be used. 
13. If the fraction to be tested is liquid at a tempera- 
ture not exceeding 60° C, the Westphal balance can be used ^ ^ 
with convenience and rapidity. A special type of Westphal fig. 41. — Cylinder 
balance is obtainable, designed for testing very small quan- 
tities. However, the ordinary type of Westphal balance can be adapted to test- 
ing small fractions by the" use of a special plummet. When using the ordinary 
balance with the special plummet, extra care is needed that the adjustment of 
Y\ 
mm. 
12 •-> 
