156 
earthy salts. See Urine, Guano, and Manurzs. 
Even plants, such as tobacco, goosefoot, borage, 
and sunflower, which require nitrates as neces- 
sary constituents, owe their nitric acid to the 
transformation of ammonia, and thrive only when’ 
they are fed with large supplies of ammonia, and 
when the action of the sun’s rays is sufficiently 
powerful so to disengage oxygen within their 
leaves and stem that it may combine with the 
ammonia to form nitric acid. 
Ammonia, in its ordinary form of carbonate, is 
exceedingly volatile, and makes a gradual and 
constant escape from all such animal manure as 
lies on the surface of the ground, or is otherwise 
exposed to the open air. All the pungent por- 
tion of the odour from stables and dung-heaps 
consists wholly of particles and volumes of am- 
monia, in the act of escaping and of becoming 
diffused through the atmosphere. If any quan- 
tity of animal manure lie for a sufficient time 
either in a heap or distributed over the mere 
surface of soil, it will lose all its ammoniacal 
matter, and become a mere carbonaceous residue 
closely similar in nature to charcoal. But, on 
the contrary, when the ammonia yielded by any 
substance is either evolved in the form of a sul- 
phate, a phosphate, a muriate, or an oxalate, or 
is reduced by foreign combination from a volatile 
to a fixed condition, it is a permanent or insep- 
arable constituent of manure, and is expended, 
without one particle of loss, in stimulating, nour- 
ishing, and maturing the processes of vegetation. 
Sal ammoniac or muriate of ammonia is a famil- 
lar instance of a fixed salt of ammonia, possess- 
ing full ammoniacal influence upon plants, and 
yet perfectly free from both volatility and am- 
moniacal odour; and a soluble sulphate of am- 
monia of precisely kindred properties to this salt 
is, jointly with carbonate of lime, formed by the 
combination of gypsum with carbonate of ammo- 
nia, either as existing in rain-water or as imme- 
diately evolved out of animal decomposition. 
The strewing of stables and the sprinkling of 
dung-heaps with gypsum, therefore, are practices 
which both prevent the disagreeable odours of 
putrefaction and save a large proportion of the 
most valuable manure; and the strewing of gyp- 
sum upon a meadow so completely fixes the por- 
tion of carbonate of ammonia in rain-water which 
would otherwise go off in evaporation, as to ren- 
der the grasses both luxuriant in growth and 
eminently nutritious in constitution.* “In order 
* When putrid urine or the draining of dunghills, 
in a state emitting an ammoniacal smell, is distributed 
over an arable field for manure, a sprinkling of gyp- 
sum or of chloride of calcium ought to be made upon 
the field to convert the ammonia into a fixed salt. 
But a better practice is to fix all the ammonia, by 
means of gypsum, chloride of calcium, superphos- 
phate of lime, muriatic acid or sulphuric acid, in the 
stable, in the water-closet, and in all other places 
_ where the ammonia is generated. A basin of con- 
centrated muriatic acid, properly situated in a water- 
_ closet, will prevent disagreeable odours, and convert 
_ all the ammoniacal gases of the place into sal-ammo- 
Ui oe 
AMMONIA. 
to form a conception of gypsum,” says Dr. Lie- 
big, “it may be sufficient to remark that 100 lbs. 
of burned gypsum fixes as much ammonia in the 
soil as 6,250 lbs. of horse’s urine would yield to 
it, even on the supposition that all the nitrogen 
of the urea and hippuric acid + were absorbed by 
the plants without the smallest loss, in the form 
of carbonate of ammonia. If we furnish to a 
field 40 lbs. of gypsum, and if we suppose that 
the tenth part of this enters into plants in the 
form of sulphate of ammonia, we would actually 
supply nitrogen sufficient for 100 lbs. of hay, 50 
Ibs. of wheat, or 60 Ibs. of clover. Water is ab- 
solutely necessary to effect the decomposition of 
the gypsum, on account of its difficult solubility, 
(one part of gypsum requires 400 parts of water 
for solution,) and also to assist in the absorption 
of the sulphate of ammonia by the plants: hence 
it happens that the influence of gypsum is not 
observable on dry fields and meadows; while the 
gaseous carbonate of ammonia formed by the 
decay of animal manures on such fields, on the 
other hand, does not fail in producing a favour- 
able effect. The decomposition of gypsum by 
carbonate of ammonia does not take place in- 
stantaneously ; on the contrary, it proceeds very 
gradually ; and this explains why the action of 
the gypsum lasts for several years.” See Gypsum. 
Alumina and peroxide of iron form solid com- 
pounds with ammonia; salts of alumina or iron 
combine with ammonia to form true ammoniacal 
salts; and minerals containing alumina or oxide 
of iron attract ammonia from the atmosphere and 
retain it. Soils, therefore, which contain burnt 
clay or oxides of iron absorb ammonia from both 
the atmosphere and rain-water, make such chem- 
ical combinations with it as to constitute fixed 
salts, contribute it in these combinations to act | 
manurially upon plants, and thus perform the 
same fertilizing office as a mineral acid would do, 
if extensively spread over their surface. Coal 
soot, as is well known, exerts a highly beneficial 
action as a top-dressing, when not employed in 
a greater proportion than about 20 or 25 bushels 
per acre, and is apt to stunt and scorch and kill 
vegetation when employed in excessive quantity ; 
and it owes both its beneficial and its mischie- 
vous power to the presence of a large proportion 
of sulphate of ammonia,—this salt acting fertiliz- 
nia; and any of the other substances which we have 
named—and which are both low in price and easy of 
being procured—will collect and concentrate the am- 
moniacal gases of the stable, the cow-house, the pig- 
gery, the poultry-yard, and every other part of the 
farmery. The ammonia which usually escapes in 
the form of gas in the stable is not only lost to the 
farmer, and noxious to the eyes of horses, but it 
works a slow and steady destruction of the walls of 
the edifice, combining with the lime of the mortar 
to form nitric acid, and converting the whole cement 
of the lime into the condition of soluble nitrate. This 
mischievous chemical precess in stables is known in 
Germany by the special name, salpeterfrass. 
+ Hippuric acid is a constituent of the urine of 
herbivorous animals; and, during putrefaction, is de- 
composed into benzoic acid and ammonia. 
