DUST PREVENTION" AND ROAD PRESERVATION, 1916. 23 
Table 27.— Analysis of coal-tar preparation ! used on experiment No. 1 and for first 
application on experiment No. 3. 
Specific gravity, 25°/25° C 1.145 
Specific viscosity, Engler, 40° C, 50 c. c 14.4 
Per cent free carbon 6. 24 
Distillation: 
Per cent Per cent 
by volume, by weight. 
Water 0.0 0.0 
First light oils (110° C.) 0.4 0. 3 
Second light oils (110-170° C.) 1.7 1.0 
Heavy oils (170°-270° C.) 24. 6 21. 1 
Heavy oils (270°-300° C.) 9. 2 8. 
Pitch residue 64. 1 69. 6 
Total 100. 100. 
It had been planned to allow the tar to stand for several hours 
after it had been applied to the road before covering it with the 
gravel top-dressing, but the tendency of the material to run off the 
road was so great that it was found necessary to cover it immediately 
after the distributor had finished applications. The gravel was 
spread at a fairly uniform rate of 1 cubic yard to 78 square yards of 
surface. 
The only noticeable lack of uniformity in the workmanship on this 
experiment is where the cut-off valve of the distributor failed to 
work properly on a return trip, with the result that a double appli- 
cation of tar was made on the west half of the road from station 13+50 
to station 15+00. It also was necessary, of course, to increase the 
amount of gravel top-dressing on this part of the experiment. 
Experiment No. 2. — Surface Treatment with Asphaltic Oil, Applied Hot, and 
Clay Gravel. 
Location, station 23+55 to 85+45. 
Total length, 6,140 feet. 
(Equality station decreases length of section 50 feet.) 
Total area, 10,915 square yards. 
The bituminous material used in this experiment was shipped to 
Alexandria in tank cars. At the Alexandria siding the oil was 
heated and pumped into the auto distributor, in which it was hauled 
7 miles to the road. The material was heated to a temperature of 
about 200° F. and there was no appreciable loss of temperature dur- 
ing the haul. The analysis of the oil is shown in Table 28. 
i Fairly thin fluid. 
