EXAMINATION OF BITUMINOUS ROAD MATERIALS, 35 
then poured into a weighed platinum or glass crystallizing dish and 
the petroleum ether evaporated off over a steam bath. The dish is 
then placed in a drying oven maintained at 105° C. until the lass 
traces of petroleum ether have been removed and the paraffin scale 
has attaimed a constant weight, after cooling in a desiccator. 
The weight of the par ae scale so obtained, divided by the weight 
of the distillate taken and multiplied by the percentage of the total 
distillate obtained from the original sample, equals the percentage 
of the paraflin scale. 
USE OF PARAFFIN SCALE ENE a ane 
The paraffin scale determination may be made on all native bitu- 
mens and their products which are suspected of being of a paraffin 
nature. itis not an extremely accurate determination, however, and . 
is seldom employed by the Office ef Public Roads and Rural Engi- 
neering. 
THE EXTRACTION OF BITUMINOUS AGGREGATES. 
EQUIPMENT FOR RECOVERING AGGREGATE: ONLY 
1 centrifuge extractor, complete with moter, speed regulator, and electrical connec. 
“tions: (Hig. 18.) . 
T hot plate. 
1 enamel-ware dish approximately 2 inches deep and 9 inches in diameter 
1 hammer. : 
- i three-fourths-inch cold chisel. 
I large metal kitchen spoon. 
1 square foot of one-sixteenth-inch. deadening felt paper. 
1 i}-inch stiff flat brush. 
1 500-cubic-centimeter bottle or flask. 
1 balance, capacity 1 kilogram, sensitive to @.1 gram 
 Lsheet of heavy manila paper. 
ADDITIONAL EQUIPMENT FOR RECOVERING BITUMEN, 
liyon ring support (ring 10 centimeters in diameter). 
Tiron ring support with condenser clamp. 
Lround tin can, 10 by 12 centimeters, cevered with asbestos paper. 
1 100-waitt incandescent carbon-filament lamp, with socket and connections. 
I asbestos hood. (Fig. 19-c.) 
1 1,000-cubic-centimeter round-botiom flask, with cork. 
1 pon condenser, length of body 25 centimeters, with cork te fit, and rubber-tubing 
connections. 
50 centimeters of glass tubing, 8 millimeters bore. 
1 1,000-cubic-centimeter flat-bottom flask. 
1 porcelain evaporating dish, 11 centimeters in diameter. 
i watch glass, 20 centimeters in diameter. 
1 steam bath. 
