4 2 
our atmosphere. It is an elastic fluid, at all 
known temperatures. Its specific gravity is to that 
of air as 10967 to 10000. It supports combustion 
with much more vividness than common air ; so 
that if a small steel wire or a watch-spring, having 
a bit of inflamed wood attached to it, be intro- 
duced into a bottle filled with the gas, it burns 
with great splendour. It is respirable. It is very 
slightly soluble in water. The number represent- 
ing the proportion in which it combines is 15. It 
may be made by heating a mixture of the mineral 
called manganese and sulphuric acid together in 
a proper vessel, or by heating strongly red lead, 
or red precipitate of mercury. 
2. Chlorine , or oxymuriatic gas, is, like oxygene, 
a permanent elastic fluid. Its colour is yellowish 
green ; its smell is very disagreeable ; it is not 
respirable ; it supports the combustion of all the 
common inflammable bodies except charcoal ; its 
specific gravity is to that of air as 24677 to 10000 ; 
it is soluble in about half its volume of water, and 
its solution in water destroys vegetable colours. 
Many of the metals (such as arsenic or copper) 
take fire spontaneously when introduced into a 
jar or bottle filled with the gas. Chlorine may be 
procured by heating together a mixture of spirits 
of salt or muriatic acid, and manganese. The 
number representing the proportion in which this 
gas enters into combination is 67 . 
3. Fluorine , or the fluoric principle. This sub- 
stance has such strong tendencies to combination 
that as ye*t no vessels have been found capable of 
containing it in its pure form. It may be obtained 
