26 BULLETIN 555, U. S. DEPARTMENT OF AGRICULTURE. 
I. Chemical Peopebties. 
limits. 6 M * (2) The following limits shall not be exceeded : 
Per cent. 
Loss on ignition 4. 00 
Insoluble residue . 85 
Sulphuric anhydride (S0 3 ) 2.00 
Magnesia (MgO) 5.00 
II. Physical Pkopeetles. 
it). 
Specific grar- 
Fineness. 
Soundness. 
Time 
ting. 
ef set- 
Ten 
strength. 
8 1 1 e 
(3) The specific gravity of cement shall be not less than 3.10. 
Should the test of cement as received fall below this requirement, 
a second test may be made upon an ignited sample. The specific- 
gravity test will not be made unless specifically ordered. 
(4) The residue on a standard 200-mesh sieve shall not exceed 
22 per cent by weight.* 
(5) A pat of neat cement shall remain firm and hard, and show 
no signs of distortion, cracking, checking, or disintegration in the 
steam test for soundness. 
(6) The cement shall not develop initial set in less than 45 
minutes when the Yicat needle is used, or 60 minutes when the 
Gillmore needle is used. Final set shall be attained within 10 
hours. 
(7) The average tensile strength in pounds per square inch of 
not less than three standard mortar briquets composed of 1 part 
cement and 3 parts standard sand, by weight, shall be equal to or 
higher than the following : 
Age at 
test 
Storage of briquets. 
Tensile 
strength 
per square 
inch. 
Days. 
1 day in moist air, 6 days in water. . 
1 day in moist air, 27 days in water. 
Pounds. 
200 
300 
(8) The average tensile strength of standard mortar at 28 
days shall be higher than the strength at 7 days. 
III. Packages, Marking, and Storage. 
Packages and 
marking. 
Storage. 
(9) The cement shall be delivered in suitable bags or barrels 
with the brand and name of the manufacturer plainly marked 
thereon, unless shipped in bulk. A bag shall contain 94 pounds 
net. A barrel shall contain 376 pounds net. 
(10) The cement shall be stored in such a manner as to permit 
easy access for proper inspection and identification of each ship- 
ment, and in a suitable weather-tight building which will pro- 
tect the cement from dampness. 
* The United States Government specification requires that on and 
after July 1, 1918, the residue on the 200-mesh sieve shall not exceed 
20 per cent by weight. 
