On the Aimhjsis of Soils. 
619 
in w ater, be gently calcined, to insure the expulsion of every particle of 
ammoniacal salt, otherAvise the precipitate afforded by soda-chloride of 
platinum would be fallacious. 
Another peculiar research of great importance is that which deter- 
mines the amount of ammonia in a soil ; and which may exist either 
ready formed, or in its element?, capable of afiFording a portion of the 
azotic food so indispensable to vigorous vegetation. The actual am- 
monia is easily obtained by distilling the soil along with some milk of 
lime. The distilled water will contain all the volatile alkali, which may 
be measured by the number of drops of a standard dilute acid, which it 
will saturate. 
The potential ammonia, slumbering, so to speak, in its embryo ele- 
ments, may be estimated by igniting 200 grains of the soil with its own 
■weight of a mixture of hydrate of soda and quicklime, as described in 
my memoir on 'The Analysis of Guano,' in the last number of this 
Journal, page 296, § 16. 
I have subjected the soil of Dr. Kerrison's farm to the various 
modes of research above enumerated, and have obtained the following 
results : — 
1. By the application of my limestone-meter I obtained carbonic acid 
gas, equivalent to 9 grains of carbonate of lime. 
2. By igniting 200 grains of the soil along with 200 grains of mixed 
quicklime and hydrate of soda, in the appropriate apparatus, I obtained 
0'34 grains of ammonia, or O'lT per cent, of the weight of the soil. 
Hence 600 grains of the soil contain the azotic equivalent of one grain 
of ammonia. This remarkable fact reveals most plainly one secret source 
of the uninterrupted production of rich crops of cereals and other plants 
from it, without receiving any manure. How appropriate to such land 
is Virgil's beautiful title of the subject of his ' Georgics,' jitstissima 
tellus I 
3. By the process of cohobation for 8 hours, with dilute muriatic 
acid, as also by the process of fusion with alkalis in a platinum crucible, 
and the subsequent treatment above detailed, I obtained — 
1. 
Silica ..... 
56 
0 
2. 
Alumina ..... 
8 
0 
3. 
Oxide of iron .... 
5 
5 
4. 
Carbonate of lime .... 
9 
0 
5. 
Sub-phosphate of lime 
0 
4 
6. 
Magnesia (carbonate) 
0 
5 
7. 
Moisture separable by steam heat 
11 
3 
8. 
Organic matter, chiefly vegetable mould 
6 
6 
9. 
Moisture separable at a red-heat 
2 
7 
100 
0 
Besides traces of muriate of soda, and muriate of lime (chlorides of 
sodium and calcium). The iron exists mostly in the state of protoxide, 
a circumstance owing, probably, to exhalations from the subsoil of sul- 
phuretted, phosphuretted, and carburettcd hydrogen. The fresh soil is 
of a grey colour, but becomes ochrey-red by calcination. 
