10 BULLETIN 1216, U. S. DEPARTMENT OF AGRICULTURE. 
care being taken qoI to pour off any sand. This process shall he 
repeated until the wash water is clear, a glass rod being used 
to stir the material Cor the hist lew washings. The pan and 
washed sand shall he dried to constant weighl in an oven al a 
temperature between loo° and no C. (212° and 230° F.), 
weighed, and the net weight of sand determined. 
Calculation of 5. The percentage of clay and silt shall he calculated from the 
percentage. formula: 
Percentage of clay and siit= 
Original wei ght- - Weight a lter washin g 
Original weight ~ X 10 ° 
6. For a check on the results, the wash water shall he evapo- 
rated to dryness and the residue weighed : 
n 4. * i i -i t Weight of residue .. .,„ 
Percentage of clay and silt= ~ . . — ; -ttt" X 1<H) 
J Original weight 
TEST FOR QUANTITY OF CLAY AND SILT IN SAND FOR 
HIGHWAY CONSTRUCTION. 
(A. S T. M. standard method, serial designation 1» 74-21, slightly 
modified, i 
1. This is a test for the determination of the quantity of clay 
and silt in natural sand to he used in highway construction. 
Method of test. 2. The sample as received shall he moistened and thoroughly 
mixed, then dried to constant weight at a temperature between 
100° and 110° C. (212° and 230° P.). 
3. The pan or vessel to be used in the determination shall be 
substantially 9 inches (22.9 centimeters) in diameter by not less 
than 4 inches (10.2 centimeters) deep. II shall have vertical 
sides and shall he provided with a pouring lip. 
4. A representative portion of the dry material weighing 500 
grams shall he selected from the sample and placed in the pan 
which has been dried and accurately weighed. Sufficient water 
shall be poured into the pan to cover the sand (about 225 cubic 
centimeters) and agitated vigorously for 15 seconds. Alter it 
has settled for 15 seconds the water shall he poured off into a 
tared evaporating dish, care being taken not to pour off any sand.' 
This process shall he repeated until the wash water is clear, a 
glass rod being used to stir the material for the last tew washings. 
The pan and washed sand shall he dried to constant weight in 
an oven at a temperature between 100° and L10 c C. ( ii 1 *_' ° and 
230° P.), weighed, and the net weight of sand determined. 
Calculation of 5. The percentage of clay and silt shall he calculated from the 
percentage. formula I 
Percentage of clay and silt= 
Original weight — Weight after washing 
original weight' X 
6. For a check on (he results, the wash water shall he evapo- 
rated to dryness and the residue weighed. 
Weight of residue...^ 
Percentag clay and silt p^ weigfat X100 
TESTS FOR APPARENT SPECIFIC GRAVITY AND ABSORP- 
TION OF STONE OR OTHER COARSE MATERIALS. 
(1) The apparent specific gravity shall he obtained by weighing 
the water displaced hy a sample of the material weighing ap- 
proximately 1,000 grams, broken into pieces about 1 j inches iii 
diameter* The vessel to he used consists of a galvani/.ed-iron 
cylinder Closed at one end and measuring 5 inches in diameter 
hy 8 inches high. A hrass spout one-half inch in diameter is 
soldered into the side id' the cylinder 6 inches from the bottom. 
The spout is iucliued at an angle of 2° with the horizontal and 
