EXAMINATION OF BITUMINOUS HO AD 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 last 

 traces of petroleum ether have been removed and the paraffin scale 

 lias attained a constant weight, after cooling in a desiccator. 



The weight, of the paraffin, 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 

 cf the paraffin scale. 



USE OF PARAFFIN SCALE DETERMINATION. 



The paraffin scale determination may be made on all native bitu- 

 mens and their products which are suspected of being of a paraffin 

 nature. It is not an extremely accurate determination, however, and 

 is seldom employed by the Office of Public Roads and Rural Engi- 

 neering. 



THE EXTRACTION OF BITUMINOUS AGGREGATES. 



EQUIPMENT FOR RECOVERING AGGREGATE ONLY. 



1 centrifuge extractor, complete with motor, .speed regulator, and electrical connec- 

 tions. (Fig. 18.) 

 lliot plate. 



3 enamel-ware dish approximately 2 inches deep and 9 inches in diameter. 

 1 hammer. 



1 three-f ourths-inch cold chisel. 

 1 large metal kitchen spoon. 



1 square foot of one-sixteenth-inch deadening felt paper. 

 3 ll-isich. stiff flat brush.. 

 1 500-cubic-centimeter bottle or flask. 

 1 balance, capacity 1 kilogram, sensitive to 0.1 gram. 

 1 sheet of heavy manila paper. 



ADDITIONAL EQUIPMENT FOR RECOVERING BITUMEN. 



3 iron ring support (ring 10 centimeters in diameter). 



3. iron ring support with condenser clamp. 



3 round tin can, 10 by 12 centimeters, covered with asbestos paper. 



3 100-watt i eat carbon-filament lamp, with socket and connections. 



Iiood. (Fig. 19 r.) 

 3 1,000-cubIc-centimeter round-bottom flask, with cork. 



ral conden er, length of body 25 centimeters, with cork to fit, and rubber-tubing 

 connections. 



bing, 8 millimeters bore. 

 1 1,000-cubic-centimeter fiat-bottom flask. 

 3 porcelain evaporating dish, 1 1 centimeters in diameter. 



1 1 entimetei i in di uneter. 

 3 steam bath. 



