SAMPLING AXD TESTING HIGHWAY MATERIALS. 
77 
(a) liquid fractions. 
13. The Westphal balance may be used. 
14. If the fraction to be tested is liquid at a temperature not Specific 
exceeding 60° C, the Westphal balance can be used with con- gravity liquid 
venience and rapidity. A special type of Westphal balance is fractions. 
obtainable, designed for testing very small quantities. However, 
the ordinary type of Westphal balance can be adapted to testing 
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 the balance be accurately made. The 
plummet can readily be made in the laboratory from a piece of 
ordinary glass tubing 7 millimeters outside diameter, sealed at 
the end, and melting into the glass where sealed a short platinum 
wire. After cooling, place 9 to 10 grams of mercury in the tube, 
making a column 35 to 40 millimeters high. Seal off the tube 
within 20 millimeters of the top of the mercury column with a 
blowpipe flame. The plummet shall have a length of about 55 to 
60 millimeters over all, and shall weigh between 10 and 12 grams. 
■Thermometer 
Shield- 
Retorts 
Condenser 
Fig. 12. — Assembled apparatus for distillation test. 
IB) SOLID AXD SEMISOLID FRACTIONS. 
15. A pan having the following approximate dimensions may 
be used. 
Diameter of base : 20 millimeters. 
Diameter of top : 25 millimeters. 
Depth: 12 millimeters. 
Diameter of wire: 1 millimeter. 
Total weight : 7 grams. 
The pan and wires are made of platinum or nickel. 
16. Solid or semisolid fractions of oil which can not be readily 
liquefied can be rapidly and accurately tested in this apparatus 
by the usual method of weighing in air and in water. The usual 
precautions of igniting the pan before use. and avoiding the in- 
cisure of air or water in the sample, should be observed. 
Note. — The mrthod for liquid fractions is usually applicable to 
the fractions 235° to 315° C, and the method for solid and semi- 
solid fractions to the fraction 315° to 355° C. 
Specific 
gravity solid 
and semisolid 
fractions. 
