Jan. is, 19x7 
Calcium Compounds in Soils 
69 
Tabl£ III .—Partial analytical examination of soils in Classes I to XII for calcium — 
Continued 
Class and No. 
Total 
calcium 
oxid. 
Water- . 
soluble 
calcium 
oxid. 
Add-soluble 
calcium oxid. 
Carbon 
dioxid. 
Water- 
soluble 
sulphur 
trioxid. 
Method 
A. 
Method 
B. 
Class VIII: 
Gm. 
Gm. 
Gm. 
Gm. 
Gm. 
Gm. 
53.. 
0, 61 
0. 01 
O. 20 
0. 17 
O. 12 
0. 02 
54 . 
• 59 
Trace... 
. 19 
. 16 
.07 
. OI 
Class IX: 
55 .. 
•6S 
~ *°5 
• 45 
.40 
• 36 
. or 
•43 
Trace... 
. IO 
. 06 
. 09 
Class X: 
57 . 
3 - °S 
Trace... 
•47 
•36 
•05 
Trace. 
r8. 
5. 57 
. 03 
3 - 04 
2. 50 
1. 97 
. 01 
. 
CJ(J,. 
5 - 44 
. 02 
3. 10 
2. 72 
2. 14 
. 02 
Class XI: 
60. 
4. 43 
. 01 
O *<t 
. IO 
. 09 
. 01 
^ J ,,,,T... 
4. 64 
Trace... 
• J 9 
•05 
Class XII: 
fa . 
.27 
. 37 
Trace ... 
. 02 
Trace ... 
.08 
fa . 
• °3 
. 01 
•05 
u 3 . 
INTERPRETATION OF THE ANALYTICAL DATA 
In interpreting the analytical data in terms of calcium compounds 
the following assumptions have been made and procedure followed: 
It has been assumed that leaching with 2 per cent hydrochloric acid 
(method B) decomposed all calcium carbonate and all combinations of 
calcium with humus bodies, and that such leaching and subsequent 
washing with water dissolved all calcium sulphate. The resulting solu¬ 
tion then obtained by method B would contain all the calcium present 
as carbonates, as so-called humates and as sulphates. 
Leaching with 4 per cent hydrochloric acid (method A) gave, without 
exception, more calcium in solution than did method B, and it has been 
assumed that this increase represented easily decomposable calcium 
silicates. 
Where the CaO equivalent of the C 0 2 found was less than the CaO 
leached by 2 per cent acid, the whole of the C0 2 was calculated to calcium 
carbonate, but when the CaO equivalent of the C 0 2 found was greater 
than CaO leached by 2 per cent acid, the whole of the CaO in the 2 per 
cent acid solution was calculated to calcium carbonate. 
When the CaO equivalent of the S 0 3 found was equal to or less than 
the water-soluble CaO found, the S 0 3 was calculated to CaS 0 4 ; but 
where such equivalent was greater than the water-soluble CaO, the water- 
soluble CaO was calculated to CaS 0 4 . 
The calcium present as difficultly decomposable silicates and that 
present combined with humus bodies was found by difference, as indi¬ 
cated in the following schematic presentation. 
