Dec. i7, 1917 
Soil Acidity and the Hydrolytic Ratio in Soils 
661 
The results given in the foregoing table do not show striking differences 
except that the calcium-oxid content of the acid solutions from the 
alkaline soils is somewhat greater than in the case of the add soils; 
but, when ratios between the soluble calcium oxid and iron oxid and 
aluminium oxid are determined, an interesting relationship is exposed. 
Table II gives these ratios. 
Table II.— Ratios between soluble calcium oxid and iron oxid and aluminium oxid 
ACID SOILS 
2 
6 
7 
9 
10 
13 
14 
16 
17 
20 
21 
22 
23 
24 
27. 
28, 
Laboratory No. 
Iron oxid. 
Aluminium 
oxid. 
Iron oxid 
and 
aluminium 
oxid. 
o. 70 
i- 55 
1. 03 
i- 05 
2. 85 
1. 74 
1. 36 
1. 77 
•43 
2.05 
i -35 
.72 
i- 54 
.69 
i* 33 
•65 
1.25 
i- 95 
1.63 
3- iS 
.90 
i- 93 
1.65 
2. 70 
4.75 
7. 60 
•94 
2. 68 
1. 30 
2.66 
2. 53 
4 - 30 
•99 
1.42 
2-37 
4. 42 
*• 55 
2. 90 
•74 
1. 46 
1. 67 
3.21 
•95 
1. 64 
• 94 
2. 27 
.89 
i- 54 
ALKALINE SOILS 
3 
4 
5 
8 
11 
12 
15 
18 
19 
25 
26 
29 
0. 26 
o- 55 
0. 81 
•30 
.38 
.68 
.78 
. 11 
.89 
•65 
. 11 
• 76 
•59 
. 62 
1. 20 
•43 
•53 
96 
.46 
•57 
1.03 
.48 
• 5 ° 
.98 
•43 
.46 
.89 
•32 
•30 
. 62 
. 11 
. 26 
•37 
•25 
.44 
.69 
.38 
.58 
.96 
These results show that, although the quantities of calcium, iron, and 
aluminium soluble in Nj 5 hydrochloric acid under the conditions of the 
method vary considerably in the several soils, there is a marked rela¬ 
tionship between the ratios of calcium oxid and iron oxid and aluminium 
oxid as expressed in Table II and the soil reaction. Considering the 
ratios CaO: (Fe 2 0 3 -f*Al 2 0 8 ), we find the lowest ratio for an add soil is 
1.42 and the highest ratio for an alkaline soil, 1.20. A neutral ratio 
may then be approximated by averaging these two numbers, and it is 
