4 BULLETIN 314, XJ. S. DEPARTMENT OF AGRICULTURE. 



SPECIFIC GRAVITY DETERMINATION. 



HYDROMETER METHOD USED FOR THIN FLUID BITUMENS. 



- EQUIPMENT. 



1 hydrometer jar approximately 35 centimeters long and 5 centimeters in diameter. 



(Fig. 1-a.) 

 1 1-pint tin cup, seamless type. (Fig. 1-6.) 



1 enamel-ware dish approximately 2 inches deep and 9 inches in diameter. (Fig. 1-c.) 

 1 chemical thermometer reading from — 10° 0. to 110° C. (Fig. 1-d.) 

 1 set of hydrometers — those with a double scale at 15.5° C. (60° F.), one foi Baume 

 and one for a direct specific gravity reading to the third decimal place are used 

 by the Office of Public Roads and Rural Engineeiing. (Fig. 1-e.) 

 1 hydrometer reading from 0.800 to 0.900 specific gravity. 

 1 hydrometer reading from 0.900 to 1.000 specific gravity. 

 1 hydrometer reading from 1.000 to 1.200 specific gravity. 

 1 hydrometer reading from 1.200 to 1.400 specific gravity. 



METHOD. 



The specific gravity of thin fluid bituminous road materials is de- 

 termined at 25° C. as compared with water at tliat temperature. 



Fig. 1. — Hydrometer method of determining specific gravity. 



This may be done with the above-mentioned apparatus by first pour- 

 ing a sufficient quantity of the material into the tin cup, which is then 

 placed in the large dish containing cold or warm water as occasion 

 may require. The material in the cup should be stirred with the 

 thermometer until it is brought to a temperature of 25° C, after 

 which it should be immediately poured into- the hydrometer jar and 

 its gravity determined by means of the proper hydrometer. In case 



