METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS O 
Dilute ammonium hydroxide shall be added dropwise until the color of the 
solution changes to a distinct yellow. The solution shall be boiled for one or 
two minutes and filtered at once. The beaker and precipitate shall be washed 
slightly with a hot 2 per cent solution of ammonium chloride (or ammonium 
nitrate) . Setting aside the filtrate, the precipitate shall be transferred by a jet 
of hot water to the precipitating vessel and dissolved in 10 cubic centimeters of 
hot hydrochloric acid. The paper shall then be extracted with acid, the solution 
and washings being added to the solution of the precipitate. The aluminum 
and iron shall then be reprecipitated at boiling heat by ammonium hydroxide as 
before in a volume of about 100 cubic centimeters and the second precipitate 
shall be collected and washed with a hot 2 per cent solution of ammonium 
chloride (or ammonium nitrate) on the filter used in the first instance, if this 
is still intact. To the combined filtrates from the hydroxides of iron and 
aluminum, reduced in volume if need be, 1 cubic centimeter of ammonium 
hydroxide shall be added, the solution brought to boiling, 25 cubic centimeters 
of a saturated solution of boiling ammonium oxalate added, and the boiling 
continued until the precipitated calcium oxalate has assumed a well-defined 
granular form. The precipitate after one hour shall be filtered and washed, 
and the filtrate set aside. The filter shall be placed wet in a platinum crucible, 
and the paper burned off over a small flame of a Bunsen burner : after ignition 
it shall be cautiously moistened with water, redissolved in hydrochloric acid, 
and the solution diluted to 100 cubic centimeters : ammonia shall be added in 
slight excess, the liquid boiled, and filtered if a precipitate appears. The lime 
shall then be reprecipitated by ammonium oxalate, allowed to stand till settled, 
filtered and washed. The combined filtrates from the calcium precipitates shall 
be acidified with hydrochloric acid, concentrated on the steam bath to about 
150 cubic centimeters and made slightly alkaline with ammonium hydroxide, 
boiled and filtered (to remove a little iron and aluminum, and perhaps calcium). 
When cool, the solution shall be acidified with hydrochloric acid, "10 cubic 
centimeters of saturated solution of sodium-ammonium-hydrogen phosphate 
added, and ammonia drop by drop, with constant stirring. When the crystallin 
ammonium-magnesium orthophosphate has formed, 5 cubic centimeters excess 
ammonia shall be added. The solution shall be set aside for not less than four 
hours, preferably overnight, in a cool place, filtered and washed with water 
containing 2.5 per cent NIL. The precipitate shall be dissolved in a small 
quantity of hot hydrochloric acid, the solution diluted to about 100 cubic 
centimeters. I cubic centimeter of a saturated solution of sodium-ammonium- 
hydrogen phosphate added, and ammonia drop by drop, with constant stirring. 
until the precipitate is again formed as described and the ammonia is in 
moderate excess. The precipitate shall then be allowed to stand about two 
hours, filtered and washed as before. The paper and contents shall be placed 
in a weighed platinum crucible, the paper slowly charred, and the resulting 
carbon carefully burned off. The precipitate shall then be ignited to constant 
weight over a Meker burner or a blast not strong enough to soften or melt the 
pyrophosphate. The weight of magnesium pyrophosphate obtained multiplied 
by 72.5 gives the percentage of magnesia. The precipitate so obtained always 
contains some calcium and usually small quantities of iron, aluminum, and 
manganese as phosphates. 
28. A permissible variation of 0.4 will be allowed, and all results in excess of 
the specified limit but within this permissible variation shall be reported as 
5.00 per cent. 
DETERMINATION OF FINENESS 
29. Wire cloth for standard sieves for cement shall be woven (not twilled) 
from brass, bronze, or other suitable wire and mounted without distortion on 
frames about 2 inches below the top of the frame. The joint between the cloth 
and frame shall be smoothly filled with solder to prevent lodging of the cement. 
The sieve frames shall be circular, approximately 8 inches in diameter, and 
may be provided with a pan and cover. 
30. A standard No. 200 sieve is one having nominally a 0.0029-inch opening, 
certified by the United States Bureau of Standards, and conforming to the 
specifications for this sieve in the Standard Specifications for Sieves for 
Testing Purposes (serial designation : E 11) of the American Society for Testing 
Materials (3). The correction to the sieving value of the sieve shall be 
determined by sieving tests made in conformity with the standard specifications 
