DUST PREVENTION AND ROAD PRESERVATION, 1915. 25 
cessful. The condition of the surface of each section at the time of 
treatment is discussed in detail in connection with each experiment. 
The cost of this repair work was $70. 
Experiment No. 1 begins at the city limits of Rockville, and the 
remainder of the series follow in regular numerical order. The 
details of the work are subjoined. 
Table 24. — Mechanical analysis of gravel used on Rochville-Potomac Road. 
Per cent. 
Passing f -inch screen, retained on £-inch screen 9.8 
Passing J-inch screen, retained on +inch screen 62. 2 
Passing +inch screen, retained on |-inch screen 25. 2 
Passing |-inch screen 2.8 
Total 100. 
Experiment No. 1. — Asphaltic Petroleum, Cold Application, Corresponding 
to Experiment No. 3, on Rockville Pike. 
Location: Station 0+00 to station 4545+75. 
Length: 4,575 feet. 
Total area: 7,625 square yards. 
Date of application: September 23 and 24. 
Temperature of petroleum: About 90° to 100° F. 
Table 25. — Analysis of asphaltic petroleum used in Experiment No. 1. 
Specific gravity, 25°/25° C 0. 944 
Flash point, ° C 26 
Burning point, ° C 90 
Viscosity, Engler 50 c. c. at 25° C, specific 86. 6 
Loss, 5 hours at 163° C, 20 grams, per cent 26. 54 
Float test on residue at 50° C. (time) 2' 0" 
Per cent of total bitumen insoluble in 86° B. naphtha 13. 70 
Fixed carbon, per cent 7. 93 
Soluble in CS 2 (total bitumen), percent 99. 94 
Organic matter insoluble, per cent 06 
Inorganic matter insoluble, per cent .00 
Total 100. 00 
Except for a few short sections, the total length of which did not 
exceed 300 feet, the stone in the surface of Experiment No. 1 was loose 
and covered with a layer of dust. The surface was swept lightly to 
avoid displacing the stone, and masses of undesirable matter were 
removed with hoes and shovels. In order to facilitate the adhesion of 
the petroleum to the dusty stones, much hand-brooming was required. 
The oil was permitted to lie for about 2 hours before the gravel was 
applied. The oil was shipped in a tank car, which was placed about 
1 mile from the beginning of the section. 
52086°— Bull. 407—16 4 
