130 
Journal of Agricultural Research 
Vol. VII, No. 3 
EFFECT OF HEATING ON THE HYDROGEN-ION CONCENTRATION 
In order to ascertain the effect of heating upon the H-ion concentra¬ 
tion, several soils were subjected to the heating treatments indicated in 
Table IV. 
Tabi<e; IV .—Effect of heating on H~ion concentration of soil suspensions 
Soil No. 
*5 
16 
17 
i 7 
i 7 
i 7 
19 
19 
20 
20 
20 
Quantity 
of soil. 
Water. 
Method of heating. 
Time of 
heating. 
Voltmeter 
reading. 
H-ion concentra¬ 
tion (gram mole¬ 
cules per liter). 
Gm. 
C. c. 
Hours. 
2 
5 ° 
Oven 140° C. 
3 
0 .578 
0.6X10- 4 
2 
5 ° 
.do. 
3 
. 621 
. iXict 4 
2 
5 ° 
.do. 
3 
.583 
.5X10- 4 
5 
50 
Muffle below red 
1 
. 652 
. 3Xxo _s 
heat. 
2 
50 
.do.... 
1 
• 730 
• iXicf^ 
2 
So 
Blasted. 
1 
. 812 
. 6X10"" 8 
2 
50 
Oven 140° C. 
3 
. 603 
. 2XlO~‘ 
2 
50 
3 
• 598 
.3XIO- 4 
2 
50 
.do.. 
3 
. 672 
.2XIO- 5 
2 
5 ° 
Muffle below red 
3 
.678 
.iXict* 
heat. 
2 
50 
Blasted. 
3 
. 803 
.8X10- 8 
The data of Table IV confirm the views of Connor (8), in that the 
intensity of acidity decreases when the soils are heated at high tempera¬ 
tures. The insufficiency of the data concerning heating at 140° C. does 
not admit of positive conclusions, though there is indication that the 
H-ion concentration may be slightly increased by this treatment. 
ESTIMATION OF THE LIME REQUIREMENT BY THE ELECTROMETRIC 
METHOD 
The rational treatment of acid soils requires that sufficient lime be 
added to bring the soil to a neutral or slightly alkaline reaction. The 
attainment of this point may be definitely determined by the method 
described in this paper. Many empirical methods have been suggested 
for the determination of the lime requirement, but the inaccuracy of 
these methods is indicated by the enormous variations in results, as 
shown in the comparative tests reported by Ames and Schollenberger (1) 
and others. These findings are also confirmed by data obtained in this 
laboratory. 
An attempt was made to determine more precisely the lime require¬ 
ment of soils by a method of electrometric titration with calcium hydroxid, 
Ca(OH) 2 , in which a standard calcium-hydroxid solution was added to 
the soil suspensions until a definite alkaline reaction was obtained. The 
data were supplemented by pot and beaker studies. Tables V and VI 
present the results of these experiments. 
