36 BULLETIN 555, U. S. DEPARTMENT OF AGRICULTURE. 
the plates. The moist clay covers the wire on one plate, and the other plate is 
squeezed down tightly on the wire. After drying, the one plate being held firmly 
against cleats, wire slings are run symmetrically from the ends of the upper 
plate to one arm of a beam balance, and the tension necessary to separate the 
plates is given by shot or weights in the other pan of the balance. This test is 
tedious and is of service chiefly on low-grade samples which are of doubtful 
efficiency, but which represent the only available material for local construction. 
( d ) Approximate tests for tenacity of mixture can be made as follows : 
Make cylinders from the material passing the 10-mesh sieve, 25 mm. by 25 mm. 
The material is worked into a stiff mud and molded under 132 kg. per sq. cm. 
pressure. Dry thoroughly at 100° G. (212° F.) and break by the small Page 
impact machine for testing cementing value, using a 1 kg. hammer and 1 cm. 
drop. Record the number of strokes as the relative measure of tenacity. 
Mix 50 grams of the material passing the 10-mesh sieve with grams 
of water and knead with the hands into a spherical ball. Measure the diameter. 
Let this ball drop from a height of cm. on a flat slab. Measure and 
record the reduction in diameter and examine the surface for cracks. 
Usually the plastic character and adhesiveness of a good road soil can be 
judged by the feeling of the mud made from this material, its adherence to 
the hands, and its stretch under light pulling. 
TESTS OF PHYSICAL AND CHEMICAL PROPERTIES OF BITUMINOUS 
MATERIALS. 
(13) Specific Gravity: Standardized hydrometers or pycnometers. U. S. 
Department of Agriculture Bulletin 314, pp. 4 to 7. 
(14) Flash Point (Open Cup) : U. S. Department of Agriculture Bulletin 
314, p. 17. 
(15) Melting Point: A. S. T. M. tentative standard D36-16T ; Proc. A. S. 
T. M. 1916, p. 549. 
(16) Ductility: A. S. C. E. 1914 Proceedings, p. 3047. 
(17) Penetration: A. S. T. M. standard test D5-16. 
(18) Float Test: U. S. Department of Agriculture Bulletin 314, p. 9. 
(19) Specific Viscosity (on First 50 c.c.) : U. S. Department of Agriculture 
Bulletin 314, p. 7. 
(20) Total Bitumen and Organic and Inorganic Matter Insoluble in 
Carbon Disulphide : U. S. Department of Agriculture Bulletin 314, p. 25. 
(21) Bitumen Insoluble in Naphtha: U. S. Department of Agriculture Bul- 
letin 314, p. 28. 
(22) Volatilization Test (Loss at 163° C. or Other Temper atuke) : U. S. 
Department of Agriculture Bulletin 314, p. 19, except that a 50-gram sample is 
used in a flat-bottom box 55 mm. diameter by 35 mm. deep (Gill style, 3-ounce 
deep pattern box). 
(23) Distillation Test: A. S. T. M. standard test D20-16. 
(24) Fixed Carbon: U. S. Department of Agriculture Bulletin oil. p. 30. 
(25) Dimethyl Sulphate Test: U. S. Department of Agriculture Bulletin 
314, p. 25. 
(26) Percentage of Residue of Penetration: 
Fifty grams of the oil. are placed in a 3-ounce deep, seamless tin box ; the 
box is placed in a sand bath and heated over a Bunsen burner. A thermom- 
eter is suspended in the oil, the bulb not touching the bottom of the box. The 
temperature of the oil is kept at from 249° C. (480° F.) to 260° C. (500° P.), 
and the oil is stirred from time to time with the thermometer to prevent over- 
