Section VTTT. 
HUMUS AND ITS NITROGEN CONTENTS. 
M. Grandeau,of Paris, some time since suggested the use of dilute 
alkali as a solvent for humus in soil analysis, and the process, in an 
extended form, has been applied t<> the Investigation of a targe num- 
ber of soils in the United States by Professor Hilgard and Professor 
Jaffa, both for the extraction of humus and for the determination of 
soluble nil rogen. Papers on the subject have been published by both 
authors. 1 
The feature on which Professor Hilgard lays especial stress is not 
the actual percentage of humus or of nitrogen in the soil, but the 
rat io of "soluble " nit rogen to "soluble " humus. 1 1 is invest igat ion, 
Up to the time of publishing the papers referred to, led him to the con- 
clusion that if the "soluble" nitrogen was less than -2.-") parts per 100 
parte of "soluble" humus, the conditions were probably so unfavor- 
able to nitrification that the soil might be regarded as suffering 
practically from "nitrogen hungriness." 
The process used is described by Professor Jaffa on page 35 of the 
report referred to, and is briefly as follows: 
Hil</<ir<r.s method. — The soil (5 grains or 1<> grams) is extracted in a 
funnel, first with dilute hydrochloric acid, then with water to remove 
the acid, and lastly with dilute caustic soda in the experiment for 
determining soluble nitrogen or with dilute ammonia for the deter- 
mination of soluble organic matter. Professor Hilgard uses a -t per 
cent solution of caustic soda and a <*> to 7 per cent solution of ammonia. 
The soil is extracted as long as the filtrate remains colored. 
The process was subsequently slightly modified at an annual con- 
vention of the Association of Official Agricultural Chemists of the 
United States. 
The process as used earlier by Professor Hilgard, without the just- 
mentioned modifications as to the strength of alkali, has been applied 
in the Kothamsted laboratory by Dr. X. II. J. Miller to the investiga- 
tion of a large number of the Kothamsted soils, and also of a sample 
1 California Station Rpt. 1894-95, pp. 23, 35. 
• The process as thus modified is described in U. S. Dept. Agr. , Division of Chem- 
istry Bui. 46, revised, p. ?r». 
9385— Xo. 106—02 12 
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