688 
SIMPLE SUBSTANCES IN CHEMISTRY EXPLAINED. 
spirits, and . hence it has been popularly 
named intoxicating or laughing gas. Nitro- 
gen enters largely into the composition of 
most kinds of animal matter. 
Hydrogen is likewise a gas, being that 
which when combined with oxygen forms 
water, as its name, which is derived from 
the Greek, implies. It was, when first dis- 
covered, called phlogiston, and inflammable 
air. The former of these terms was attach- 
ed to it in consequence of an erroneous opi- 
nion, at one period generally adopted by 
chemists, that all metals were composed of 
various kindvS of calces or earths, each res- 
pectively united to an inflammable principle 
named phlogiston. Now as it was observed 
that when any metal becomes dissolved in 
a diluted acid as when iron or zinc are thus 
treated with sulphuric acid and water, in- 
flammable air was always given off during 
the process, it was conjectui’ed that the air 
in question was derived from the metal ; 
though it is now known that, in the case 
proposed, it arises from the decomposition 
of the water with which the acid is diluted, 
and that this sort of air never makes its ap- 
pearance in the course of such metallic 
solutions, unless water or some other body 
containing hydrogen be present. This gas, 
though highly inflammable when mixed with 
oxygen, and some other simple and com- 
pound gases, yet is incapable of supporting 
combustion, for if a burning body, as a 
lighted candle or match, be introduced into 
it, the flame will be immediately extin- 
guished. 
Hydrogen enters into combination with 
most other substances, producing many 
remarkable compounds, among which may 
be mentioned that formed by its union with 
nitrogen ; the result of which is an alkaline 
gas, formerly called volatile alkali, and now 
ammonia. This compound, which at com- 
mon temperatures exists only in the state of 
gas, is rapidly absorbed by water or spirit 
of wine, communicating to it a peculiar 
pungent odour, with which most persons are 
familiar, as belonging to spirit of hartshorn 
and smelling salts. 
Chlorine is the last of the simple bodies 
existing in a gaseous state at common tem- 
peratures ; but,while those already mention- 
ed are not only transparent but colourless, 
this gas exhibits a yellowish-green tint, 
whence its name chlox’ine.* It was origin- 
ally obtained, by Scheele, from the decom- 
position of muriatic acid, or spirit of salt, 
in which he found it combined with hydro - 
* Chlore in French— from the Greek chloros 
the green colour of sioung hertage. 
gen, then called phlogiston ; and therefore 
he gave to the newly-obtained gas the name 
of dephlogisticated marine acid. It was 
subsequently supposed to be a compound 
of muriatic acid, and oxygen ; but Sir. H. 
Davy ascertained its real nature, and gave 
it its present name. 
Chlorine unites with many other simple 
and compound bodies, forming with several 
of them acids ; and in other respects it ex- 
hibits chemical properties analogous to 
those of oxygen, being like that gas a 
supporter of combustion. It is largely dis- 
persed throughout nature, but always in a 
state of combination, as in sea-water and 
rock-salt, or that procured from brine 
springs, in which it is united with the metal 
sodium. This gas is by no means adapted 
for respiration, and when mixed with much 
atmospheric air it still proves highly irritat- 
ing, provoking cough and defluxion from 
the nostrils. As it combines rapidly with 
many other gases, it has been found useful 
to purify air loaded with infectious mias- 
mata. It is on this account that the chlo- 
ride of lime, in solution, is used to sprinkle 
the floors and walls of rooms, and to purify 
clothes and other articles, which have been 
tainted by putrid or infectious vapoui's. 
Chlorine has alsoa powerful effect in de- 
stroying vegetable colours, and the chloride 
of lime is therefore extensively used in the 
process of bleaching linen cloth and other 
substances. 
The four preceding bodies, o.xygen, hy- 
drogen, nitrogen, and chlorine, exist at 
common temperatures and pressures only 
as gas. There are other substances, as, for 
instance, carbon (charcoal), and the more 
rare bodies, called silicon and boron, which 
are found only in the solid state ; and some, 
like iron and most of the metals, though 
usually solid, become liquefied at respec- 
tively various temperatures ; and there is 
still another class of bodies capable of ex- 
isting under the three several forms of 
aggregation. Among these last are sulphur, 
phosphorus, and the substances called bro- 
mine, iodine, and selenium, which are of less 
frequent occurrence. 
Carbon is a solid body, hitherto unde- 
composed and therefore supposed to be 
elementary, which enters largely into the 
composition of most substances belonging 
to the animal and vegetable kingdoms, and 
which also forms the basis of many of the 
combustible minerals, as bitumen, coal, 
plumbago, and amber. In the form of 
charcoal, procured by charring, or distilling 
without the access of air, wood and some 
other substances, carbon is obtained in a 
