I5« 
Journal of Agricultural Research 
Vol. XI, No. 4 
EFFECT OF GREAT FLUCTUATIONS IN THE TEMPERATURE OF THE ROOM 
To obtain some idea as to how great a fluctuation in temperature is 
permissible we exposed soil F for 17 hours simultaneously in a labora¬ 
tory and in a greenhouse as well as in the basement room used regularly 
for such work. In the plant house where the range of temperature was 
greatest the amount of moisture absorbed (Table VII) was the highest. 
In the laboratory where the temperature was much higher during the 
day than during the night the amount of moisture absorbed was lower 
than in the constant temperature room. 
Table VII .—Influence of variations in the temperature oj the room of exposure upon 
the amount of moisture absorbed 
Hygroscopic coefficient. 
Determination. 
In constant 
temperature 
room ( ii ° 
to ix® C.). 
In laboratory 
(9® to 16° C.). 
In plant house 
(23 s to a9°C.). 
17.4 
16. 5 
19.7 
17. 0 
16.5 
20.1 
EFFECT OF OVEN DRYING 
In field moisture studies it is usually much more convenient to deter¬ 
mine the total moisture content of the sample and then to use a portion 
of this dried material for the determination of the hygroscopic coefficient 
than to air dry a portion of the original sample. If the previous drying 
should appreciably alter the value of the coefficient, it would become 
* necessary to air dry a separate portion of the sample. 
With four subsoils (Table VIII) we determined the coefficient, using 
the air-dried form of each, as well as portions dried at ioo°, no°, 150°, 
and 175 0 C. 
Table VIII .—Effect of drying soils at different temperatures previous to their exposure 
in the absorption boxes 
Hygroscopic coefficient. 
Air-dried. 
Dried at 
ioo° C. 
Dried at 
no 0 C. 
Dried at 
150° c. 
Dried at 
175 ° C. 
0. 7 
0.7 
O.7 
5-6 
5-3 
5-2 
5-2 
5*4 
12. 0 
22. 3 
11. 6 
11. 7 
12. I 
21*3 
20. 8 
