DUST PREVENTION AND ROAD PRESERVATION, 1916. 53 
Section No. 1 — Refined water-gas-tar 'preparation. — Although it 
seemed, in February, 1916, that this experiment probably would not 
require a re-treatment in the summer, wear developed uniformly 
until the mat became so thin that it was thought best to re-treat. 
This was done by hand in October, and the quantities and costs 
appear in Table 58. The same type of bituminous material was used 
as in the original surface treatment and the covering was torpedo 
sand. Analysis of a sample of the bituminous material is shown in 
Table 56. At the time of last inspection, March 28, 1917, this exper- 
iment had a mat generally intact and uniformly worn. Near the 
north end there were a few small breaks in the surface near the center 
of the roadway. 
Table 56. — Analysis of water-gas tar preparation l used in re-treatment of experiment 
No. 1, Washington, D. C. 
Specific gravity 25°/25° C 1.117 
Specific viscosity, Engl er, 50° C, 50 c. c 18.5 
Per cent free carbon 2. 05 
Per cent Per cent 
Distillation : volume. weight. 
Water 0.0 0.0 
First light oils (to 110° C.) 1.0 .7 
Second light oils (110° to 170° C.) 5 .3 
Heavy oils (170° to 270° C.) 21. 19. 1 
Heavy oils (270° to 300° C.) 2 10. 9. 6 
Pitch residue 67. 5 70. 3 
Total 100. 100. 
During the autumn and winter of 1916 this experiment was sub- 
jected to a much heavier steel traffic than ever before, owing to con- 
struction operations on the department grounds. About 100 feet 
from the south end of the section a wide trench was cut through the 
roadway and was filled with cinders. A second trench, about 15 
inches wide, had been cut through at a point 275 feet from the south 
end, and when filled the surface treatment had been patched. At the 
time of inspection the fill had settled somewhat and probably will have 
to be repaired. Other than the repairs over these trenches, the surface 
needed slight repairs and a light re-treatment during the summer. 
Section No. 2—Aspkaltic petroleum, surface treatment. — As con- 
templated at the time of last inspection report, this experiment re- 
quired considerable patching and a re-treatment during the summer 
of 1916. The quantities and costs appear in Table 58, and the char- 
acteristics of the bituminous material used are given in Table 57. 
This was the same as used in the original treatment. 
» Fairly viscous fluids. 
2 The 270° to 300° C. portion showed 5 per cent insoluble in dimethyl sulphate. 
