Oct. 22, 1917 
Direct Determination of the Hygroscopic Coefficient 165 
more than 24 hours gives higher values in the case* of only very fine 
textured soils. 
A soil containing the amount of moisture corresponding to its hygro¬ 
scopic coefficient loses water very rapidly when exposed to an ordinarily 
dry atmosphere, but in determining the hygroscopic coefficient the time 
necessary to transfer the soils from the absorption boxes to weighing 
bottles is so brief that the loss during the transfer is too small to appreci¬ 
ably affect the accuracy of the results. 
Hilgard’s method for the determination of the hygroscopic coefficient, 
carried out exactly as he describes it, gives reliable results. However, 
the loose sheets of glazed paper thus involved are very inconvenient 
when many determinations are to be made and may advantageously be 
replaced by shallow trays, either of aluminum or of copper. Trays of 
glass, graniteware, and vulcanized rubber give satisfactory results, but 
are less convenient, while those of tin plate or zinc, although satisfactory 
at first, soon corrode. Pasteboard trays lined with glazed paper give 
results much too low, unless the period of exposure be greatly prolonged, 
and even those of paraffined pasteboard lined with glazed paper give 
somewhat low results. Any considerable increase in the size of the 
absorption boxes over that recommended by Hilgard or the use of a 
larger number of exposed samples within the boxes of the same size 
cause too low results, unless the time of exposure be greatly increased. 
LITERATURE CITED 
(1) Alway, F. J. 
1906. STUDIES ON THE SOILS OF THE NORTHERN PORTION OF THE GREAT PLAINS 
region: the second steppe. In Amer. Chem. Jour., v. 36, no. 6, 
p. 580-594. 
( 2 ) - 
1908. STUDIES OF SOIL MOISTURE IN THE “GREAT PLAINS 1 * REGION. In JOUT. 
Agri. Sci., v. 2, pt. 4, p. 333-342. 
(3) - 
1913. STUDIES ON THE RELATION OF THE NON-AVAILABLE WATER OF THE SOIL TO 
THE hygroscopic coefficient. Nebr. Agr. Kxp. Sta. Research Bui. 
3, 122 p., 37 fig. 
(4) -and Clark, V. L. 
1916. USE OF two indirect methods for the determination of the hygro¬ 
scopic coefficients of soils. In Jour. Agr. Research, v. 7, no. 8, 
p. 345~359> 1 Literature cited, p. 359. 
(5) -and McDolE, G. R. 
1907. STUDIES ON THE SOILS FROM THE NORTHERN PORTION OF THE GREAT PLAINS 
region: The distribution of carbonates on the second steppe. 
In Amer. Chem. Jour., v. 37, no. 3, p. 275-283. 
(6) Ammon, Georg. 
1879. UNTERSUCHUNGEN #BER DAS CONDENSATIONSVERMdGEN DER BODEN- 
constituenten FtfR gasB. In Forsch. Geb. Agr. Phys., Bd. 2, p. 1-46. 
(7) Briggs, L. J., and McLane, J. W. 
1911. MOISTURE EQUIVALENT DETERMINATIONS AND THEIR APPLICATION. In 
Proc. Amer. Soc. Agron., v. 2, 1910, p. 138-147, pi. 6. 
