CHEMISTRY OF HORTICULTURE. 
165 
111 our notice of oxygen gas, it was stated that its combining or single equivalent 
number is always represented by 8, the atomic weight being so many times heavier than 
that of hydrogen (the unit of English chemistr}^). Now, the combining number of nitrogen 
was, till lately, represented by 14, indicating that it was fourteen times more ponderous 
than hydrogen. Modern researches appear to have decided that its equivalent is 14y|-y-ths. 
Hence, the construction of the above table, wherein one proportional of each element com- 
bines to produce an oxide of nitrogen in its first or lowest condition, and so on, till with 5 
of oxygen, 8 X 5 = 40, and one of nitrogen, we obtain the strongest Nitric Acid — one of the 
most energetic acids that has ever been discovered by chemical research, and which some 
of our readers will be astonished to find is produced by the electric union of those elements 
that constitute the bland and wholesome air that sustains animal respiration. 
Nitric Acid, combined to saturation with potash, forms the common Nitre or Saltpetre of 
commerce. This salt is a natural production (though perfectly imitable by art) of India, 
and other dry countries ; there " the soil is occasionally covered by a saline efflorescence 
like that sometimes seen on plastered walls. This substance collected, dissolved in hot 
water, the solution filtered, and left to crystallise, furnishes the saltpetre, enormous 
quantities of which were imported during the war by the East India Company. 
Is nitrogen a simple element or a compound ? This important question has not yet been 
satisfactorily answered. It has not been decomposed, yet there are facts which have 
induced chemists to consider it a compound. Among others, one described by Dr. Faraday 
may be cited ; " An empty tube was filled with hydrogen gas, zinc foil, and a piece of 
caustic potash (called Hydrate of Potass, because it contains water in the solid form) ; it 
is evident that the only elements present were the metals, zinc and potassium, with oxygen 
and hydrogen which form the water contained in the hydrate ; yet, on the application of 
heat, ammonia was evolved, as indicated by its action on moistened turmeric paper, placed 
in the upper part of the tube." 
Admitting the correctness of the experiment, and that its phenomena could be borne out 
by repetition, under precisely similar circumstances, we should infer, 1st, that the change 
of colour produced in the turmeric paper, from orange yellow to a dingy red, must result 
from the extrication of some alkaline gas ; 2nd, that either a minute portion of the 
potassa itself was volatilised by the heat ; or that ammoniacal gas had been developed. Now, 
as we shall soon perceive, ammonia is composed of three proportionals of hydrogen gas, 
and one proportional of nitrogen gas : the question therefore arises, whence the required 
nitrogen, and what its source ? Our authority does not enlighten us ; neither does it say 
whether or not the pungent odour of ammonia was observed ; it merely states that the 
nitrogen must have been derived from the combination of some of the elements 
enumerated ! " If this were the fact, we can only infer, that nitrogen is either a compound 
of oxygen and hydrogen in some undiscovered proportions ; or, that the presence of a 
metal is required to produce it. Here, however, we are in the dark, and therefore we 
must be content with the only fact which cannot, I think, be contested, namely, that since 
nitrogen, as it exists in the atmosphere, and when developed from its combinations, is an 
aerial fluid or gas, its particles — in common with those of all other gases — being separated, 
and kept apart in a state of minute division, by electric repulsion ; therefore it is to be 
considered a compound of some peculiar base, with a certain definite quantity of electric 
matter. Again, this gas can be condensed, and made to exist in the solid form, as in the 
Salts of Ammonia, and many other compounds, by the abstraction of that agent which had 
retained it in the gaseous condition. Upon these and similar facts is based that Electrical 
Theory which it is the leading object of these articles to establish. 
Ammonia, of which so much has lately been written in our modern works upon 
agriculture, furnishes several proofs corroborative of the attractive energy that is exerted 
between gaseous bodies, during which their form and qualities are materially altered. 
Ammonia, in the pure and natural state, is a gas ; it is prepared in our chemical labora- 
tories with great facility from sal-ammoniac and quick-lime; but nature produces it 
abundantly during the putrefaction of animal matter, by the combination of the two 
elements, hydrogen and nitrogen gases, at the moment they are extricated by the heat thus 
