Mar. i, 1934 
Movement of Water in Irrigated Soils 
689 
extracted from this soil required less acid to neutralize it than the solu¬ 
tion from the original soil by 6.7 units. From this it may be inferred 
that of the 12.1 units of S 0 4 added to the solution, 6.7 units displaced 
CO ? by combining with the bases already in the solution and that the re¬ 
maining 5.4 units were united with bases newly brought into solution from 
the soil. Of the 5.4 units of newly dissolved bases calcium constituted 
1.45 units. 
In the sample to which 50 units of sulphur were added the solution was 
enriched by 46.7 units of S 0 4 , of which 9.4 units were absorbed in replac¬ 
ing C0 3 already in the solution, while of the remaining 37.3 units 6.35 may 
be assigned to the newly dissolved calcium and 31 units to other bases 
brought into solution from the soil. 
It is clear from these results that of the sulphuric acid formed in 
this soil by the oxidation of sulphur only a part reacted to displace the 
dissolved carbonate, or, in other words, to neutralize the soil solution. 
The conditions of this experiment were such that the carbon dioxid, 
liberated either from the solution directly or from the soil carbonates as a 
result of reaction with S 0 4 , could escape from the solution into the air. 
The solution and doubtless the soil also actually lost C0 2 . 
In another experiment Kelley and Thomas used sulphuric acid on the 
same soil, but instead of leaving the soil exposed to the air at optimum 
moisture content for 15 weeks they digested the soil samples for one hour 
by shaking them with five times their weight of water after adding sul¬ 
phuric acid. After this digestion the solutions were analyzed for CO s , 
HC 0 3 , and calcium. The results of these analyses are shown in Table 
XXXI computed as reacting values. This table also shows the quantity 
of acid added to each soil sample and the increase in calcium and other 
bases brought into solution by the acid, all expressed as reacting values 
per million of dry soil. 
Tabi <3 XXXI .—Effect of sulphuric acid on alkali soil , the acid used and the solution 
constituents being expressed as reacting values based on the dry soil 0 
Soil No. 
r Add 
added. 
r Acid 
required. 
Gain. 
r Ca. 
Gain. 
r SO*. 
♦ 
00 q. 
None. 
12. 5 
< 2 5 - 0 
33-3 
5 °. 0 
100. 0 
17. 0 
21. 0 
25.° 
29. 0 
38.5 
55 - 0 
4. O 
8.0 
12. 0 
21. 5 
38. O 
1 
0. 25 
5. 00 
12. 50 
15. IO 
28. 10 
65.80 
4-75 
12. 2q 
14. 85 
2 7 - 85 
65 - 55 
74.0 
y d . * * 
a From Kelley and Thomas. 
In this experiment the results show that the addition of acid to the 
soil solution did not decrease the carbonates, but instead the solution 
was actually more alkaline after the acid treatment than before. With 
the first sample reported in the table to which 12.5 units of acid were 
added, it is to be inferred that the solution was enriched in bases not 
only by the 12.5 units equivalent to the acid used but also by 4 units 
more combined as carbonates. This further increase of 4 units of dis¬ 
solved bases may be explained by assuming that when the acid dissolved 
the soil carbonates, such as calcium carbonate, the replaced carbonate 
enriched the soil solution and thus brought still more calcium carbonate 
into solution. 
