24 BULLETIN" 586, U. S. DEPARTMENT OF AGRICULTURE. 
Table 28. — Analysis of residual asphaltic petroleum 1 used on experiment No. 2. 
Specific gravity, 25°/25° C 0.995 
Specific viscosity, Engler. 100° C, 50 c. c 17. 5 
Float test, 50° C. (seconds) 36 
Loss, 163° C, 5 hours. 20 grams, (per cent) 13. 56 
Float test on residue, 50° C. (seconds) 232 
Per cent of total bitumen insoluble in 86° B naphtha 20. 12 
Fixed carbon (per cent) 10. 79 
Soluble in CS 2 (total bitumen per cent) 99.87 
Organic matter insoluble (per cent) 11 
Inorganic matter insoluble (per cent) 02 
Total 100.00 
The first tank car of oil delivered at Alexandria was found to be 
low in viscosity and was rejected as not conforming to the specifica- 
tion. This rejection occasioned a delay of about two weeks in secur- 
ing the oil for experiment No. 2, during which time experiment No. 3 
was completed. When the contractor was ready to resume work on 
experiment No. 2, bad weather had set in and further delay was 
occasioned. Finally, it was deemed expedient to' complete the experi- 
ment, although the weather conditions were not altogether favorable, 
because it was feared that long-continued bad weather might make 
it necessary to postpone the work until the next season. The oil 
accordingly was applied on the first warm day, regardless of the fact 
that the road surface was damp. The oil was applied 0.53 gallon 
per square yard, while the rate for gravel top-dressing was the same 
as in experiment No. 1, or 78 square yards to 1 cubic yard. No 
lack of uniformity in the distribution of either the oil or the gravel 
was noticed. Where successive distributor loads of oil joined, care 
was exercised to prevent overlapping, and there was no unevenness 
at any of the joints. From station 85 + 00 to 85+45, however, 
the gravel surface on the east side, of the road was not very well 
bonded when the work was done. 
Experiment No. 3. — Surface Treatment Using Two Applications of Tar. 
First application of coal-tar preparation applied cold; second application refined 
coal tar, applied hot. 
Location, station 85+45 to 109+00. 
Total length, 2,355 feet. 
Total area, 4,187 square yards. 
Both kinds of tar for this experiment were hauled in the distributor 
from Washington, about 15 miles, to the road. The first applica- 
tion was of the same material as used on experiment No. 1, analysis 
of which is shown in Table 27. This application was made in a 
1 Viscous, sticky fluid. 
