164 
CHEMISTRY OF HORTICULTURE. 
nitrogen free. This experiment can be made with facility, thus : Mix together equal weights 
of the sulphur and filings, and put them into a glass-stoppered bottle, adding water 
sufficient to form the paste ; then close the bottle. In forty-eight hours the oxygen gas 
will be absorbed, leaving the nitrogen nearly pure. 
2. Brande says — " According to Berzelius, the purest nitrogen is obtained by filling a 
bottle about one-third full of a liquid amalgam of lead and mercury, carefully stopping it, 
and agitatmg it with the inclosed air for two hours or more ; the highly divided lead absorbs 
the oxygen and leaves pure nitrogen. On opening the bottle under water (the neck being, 
of course, held downward), the liquid rushes in, and thus shows the degree of absorption. 
3. A third process is the following : Put a small piece of phosphorus on a cork, or into a 
little porcelain saucer floating on water, and ignite it; then hold over it, inverted, a tall glass 
shade like that used by gardeners to shade and protect some tender exotic ; the edge dipping 
about a quarter of an inch into the water, so as to prevent the entrance or escape of air. 
During the combustion, the phosphorus will unite with the oxygen of the inclosed air, 
and form phosphoric acid ; but as phosphorus has no affinity with nitrogen, that gas 
remains nearly in a pure state in the glass, after it has stood over the water, at rest, so 
long as to permit the white vapour of phosphoric acid to disappear. 
4. The gardener can obtain nitrogen by adopting the following process, — not 
pure indeed — but sufficiently so, to ascertain its essential properties. He has only to 
substitute a short piece of wax-taper for the phosphorus, light its wick, and cover the 
burning taper with the tall bell-glass. This vessel, he is certain, must contain air only, 
and being made close at bottom by the water into which its edge is immersed, nothing 
extraneous can enter from without. 
For a short time the flame will remain bright ; very soon, however, its extent and 
brilliancy will decline, and finally be extinguished. During the combustion, the water 
will (after the first few moments) rise in the glass, and continue to do so till the flame 
expiree. The air then remaining above the water, will be chiefly nitrogen, contaminated 
with some carbonic acid, the greater part, however, of which has been absorbed by the water. 
We have said that the two words Azotic Gas and Nitrogen express the same thing ; but 
as Brande justly observes, every gas (excepting atmospheric air), even oxygen itself, fails 
to support life, whereas, "if we consider the term Nitrogen, namely, as implying a com- 
ponent of nitric acid, it is explicit and unobjectionable ; we therefore adopt it in preference 
to that of Azote." 
Properties. — These, as we find them described by the best authorities, are the following : 
— Nitrogen is lighter than atmospheric air, which, being taken as the unit 1, the specific 
gravity of nitrogen is estimated by Biot and Arago, as 0.969; Dr. Thompson, 0.972; 
Berzelius, 0.976 ; and if 100 cubic inches of atmospheric air weigh thirty-one grains, an 
equal volume of nitrogen under the same pressure and temperature should be (following 
the order above given) 30.04, 30.13, and 30.25 grains. 
Nitrogen gas is transparent, colourless, void of odour and flavour. 
It is fatal to animals when inspired by itself ; whence the name Azote, as before said ; 
and it instantly extinguishes flame ; but it enters into many combinations wherein its 
deadly properties are entirely changed, as in the instances of common air, and the highly 
nutritive qualities conferred by it on those animal and vegetable substances which 
contain it. 
With oxygen it produces five distinct and definite compounds, namely. Nitrous Oxide ; 
Nitric Oxide, or Nitrous Oas ; Nitrous Acid ; Per-oxide of Nitrogen ; and Nitric Acid. 
This nomenclature has been somewhat modified by Dr. Turner, as will appear by the 
annexed table extracted from p. 114 of Dr. Fownes' Manual of Chemistry. 
Composition by Weight. 
Nitrogen. Oxygen. 
1 Protoxide of Nitrogen ..... 14*06 8 
2 Deutoxide of Nitrogen 14-06 16 
3 Hyponitrous Acid 14-06 24 
4 Nitrous Acid (red fuming) 14-06 32 
5 Nitric Acid (white „ ) 14-06 40 
