662 
Journal of Agricultural Research 
Vol. XI, No. 12 
i.31, or 1.3 nearly. From this standpoint we have a condition in which 
the ratios CaO : (Fe 3 0 3 -f-Al 2 0 3 ) for the acid soils are all greater than 
1 :1.3, without exception. A similar relationship exists in case of the 
ratios CaO : A 1 2 0 3 , the lowest ratio for an add being 0.74 and the highest 
ratio for an alkaline soil 0.62, giving as an average 0.68 for a neutral 
ratio also without exception. The ratios CaO rFegOg, however, can not 
be placed in like order without having several exceptions, but if the 
other ratios can be considered correct because of the absence of excep¬ 
tions, the correct ratio CaO:Fe 2 O s can be computed and is 1.31 — 0.68, 
or 0.63. Three exceptions to this ratio are still apparent—namely, 
alkaline soils 4 and 5 have ratios greater than 0.63, and the acid soil 17 
has a considerable lower ratio. It can be seen, however, that the two 
alkaline soils mentioned gave exceptionally low quantities of soluble 
aluminium oxid and the acid soil gave a very high quantity of soluble 
aluminium oxid. This point is also generally true in case of other 
soils—that is, alkaline soils having high CaO : Fe 2 0 3 ratios gave low 
quantities and acid soils with low Ca0:Fe 3 0 3 ratios gave high quanti¬ 
ties of soluble aluminium oxid with few exceptions. Therefore these 
exceptions can not be considered as invalidating the other results but 
rather tend to show the close relationship between soluble iron and 
aluminium in the soils and the soil reaction. There are no exceptions 
in the ratios between calcium oxid and iron oxid plus aluminium oxid. 
The relationship between total calcium, iron, and aluminium was 
studied by making total analyses in duplicate of the soils for these 
elements. Ten gm. of soil ground to pass a 100-mesh sieve and 25 gm. 
of sodium peroxid were fused together in a nickel crucible. After cooling 
the mass was transferred to a 500-c.c. volumetric flask by means of hot, 
distilled water, acidified with concentrated hydrochloric acid, and allowed 
to stand on a steam bath for several hours. The contents of the flask 
were then cooled to room temperature, brought to a volume of 500 c.c., 
well mixed, and filtered. The solution was then analyzed according to 
official methods. The results are given in Table III and the ratios in 
Table IV. 
Table III .—Total quantities of calcium , iron , and aluminium in soils 
[Estimated as oxids. Results expressed as pounds per 2,000,000 of soil] 
ACID SOILS 
Laboratory No. 
Total calcium 
oxid. 
Total iron 
oxid. 
Total alumin¬ 
ium oxid. 
2 ... 
17, 261 
16,154 
14, 042 
11,808 
9 ,553 
* 9>352 
13,079 
82,421 
45 >< 5 ° 1 
89 » 53 i 
39.647 
87,891 
74.087 
74.071 
120,984 
I 39 > 2 39 
99,167 
94,184 
99.977 
110,029 
136,349 
6 .. 
7 . 
T 2 , .... 
