DUST PEEVENTION AND ROAD PRESERVATION, 1915. 27 
Table 27. — Analysis of coal-tar preparation l used on experiment No. 3. 
Specific gravity, 25°/25° C 1. 144 
Viscosity, Engler, 50 c. c. at 40° C, specific 10. 4 
Free carbon (insoluble in CS 2 ) per cent 5. 53 
_. .... . Percent Percent 
Distillation: by volume, by weight. 
Water 2 1. 8 1.6 
First light oils (to 110° C) 3 .7 .4 
Second light oils (110° to 170° C.) 3 1.0 .6 
Heavy oils (170° to 270° C.) 3 23. 2 20.1 
Heavy oils (270° to 315° C.) ^ 10. 2 8.9 
Pitch residue 4 63. 1 68. 3 
Total 100.0 99.9 
All but 500 linear feet of the road surface near the south end of 
the section was in excellent condition to receive the surface treat- 
ment. The section was thoroughly swept with horse-drawn rotary 
sweepers, and the tar adhered uniformly to the surface rock without 
the aid of hand brooming. After about 500 linear feet of surface 
had been sprayed, the distributor was stopped and the gravel was 
spread immediately to prevent the tar from flowing off the surface 
over the shoulders. The tar preparation was shipped in a tank car, 
which was placed 2J miles from the near end of section 3. 
Experiment No. 4. — Refined Water-Gas Tar, Cold Application, Similar to 
Experiment No. 2 on Rockville pike. 
Location: Station 169+02 to station 226+20. 
Length: 5,718 feet. 
Total area: 9,530 square yards. 
Date of application: September 22 and 23. 
Temperature of tar: About 130° F. 
Table 28. — Analysis or refined water-gas tar used on experiment No. 4. 
Specific gravity, 25°/25° C 1. 132 
Viscosity, Engler, 50 c. c. at 50° C, specific 16. 2 
Free carbon (insoluble in CS 2 ), per cent 0. 64 
_^ . . Percent Percent 
Distillation: by volume, by weight. 
Water 0.0 0.0 
First light oils (to 110° C) .0 
Second light oils (110° to 170° C.) 2 1. 5 1. 
Heavy oils (170° to 270° C.) 3 21. 5 18. 9 
Heavy oils (270° to 315° C.) 2 15. 13. 4 
Pitch residue 4 62. 66. 6 
Total 100. 99. 9 
The surface of this section was in excellent condition and no repairs 
were required. The experiment was conducted in all respects like 
experiment No. 3. The tar when delivered in the distributors from 
1 Thin fluid. 2 Clear. 3 Cloudy. * Hard, glossy, semisolid. 
