26 BULLETIN- 407, U. S. DEPARTMENT OF AGRICULTURE. 
Experiment No. 2. — Residual Asphaltic Petroleum, Hot Application, Cor- 
responding to Experiment No. 5, on Rockville Pike. 
Location: Station 45+75 to station 89+61. 
Length: 4,386 feet. 
Total area: 7,310 square yards. 
Date of application: September 27 and 28. 
Temperature of bitumen: 180° F. 
Table 26. — Analysis of residual asphaltic petroleum used on experiment No. 2. 
Specific gravity, 25°/25° C 0. 981 
Viscosity engler, 100° C, 50 c. c, specific 16. 8 
Loss, 5 hours, at 163° C, 20 grams, per cent 5. 81 
Float test on residue at 50° C 2' 8" 
Per cent of total bitumen insoluble in 86° B. naphtha 17. 83 
Fixed carbon, per cent 10. 23 
Soluble in CS 2 (total bitumen) per cent 99. 93 
Organic matter, insoluble, per cent 07 
Inorganic matter, insoluble, per cent 00 
Total 100. 00 
The condition of the road surface was similar to that in section 
No. 1, except that the combined total length of areas in which the 
water bond was unbroken approximated 700 feet. In several places 
the foundation had failed, and extensive repairs and the digging of 
drainage ditches were necessary. The petroleum was delivered in 
a tank car in which it was heated by steam from a traction engine. 
Owing to the loose condition of the surface, practically three-quarters 
of a gallon of petroleum were applied per square yard. Much hand 
brooming of the petroleum was required to cause it to adhere to 
the dusty stone and produce uniform distribution. About three 
hours elapsed between spreading the oil and covering it with gravel. 
About 15 cubic yards of gravel were subsequently required on the 
firm portions of the road to take up the exuding bitumen. 
Experiment No. 3. — Coal-Tar Preparation, Cold Application, 
Location: Station 89+61 to station 169+02. 
Length: 7,941 feet. 
Total area: 13,235 square yards. 
Date of application: October 11, 12, and 13. 
Temperature of preparation: about 90° to 100° F. 
