#2 HOW CROPS GROW. 
Hydrogen forms with carbon a large number of com. 
pounds, the most common of which are the volatile oils, 
like oil of turpentine, oil of lemon, ete. The chief illumi- 
nating ingredient of coal-gas (ethylene or olefiant gas,) 
the coal or rock oils, (kerosene,) together with benzine 
and paraftine, are so-called hydro-carbons. 
Sulphur is a well-known solid substance, occurring in 
commerce either in sticks (brimstone, roll sulphur,) or as 
a fine powder (flowers of sulphur), having a pale yellow 
color, and a peculiar odor and taste. 
Uncombined sulphur is comparatively rare, the com- 
mercial supplies being almost exclusively of voleanic ori- 
gin; but in one or other form of combination, this element 
is universally diffused. 
Sulphur is combustible. It burns in the air with a pale 
blue flame, in oxygen gas with a beautiful purple-blue flame, 
yielding in both cases a suffocating and fuming gas of 
peculiar nauseous taste, which is called sulphurous acid. 
Exp. 15.—Heat a bit of sulphur as large as a grain of wheat on a slip 
of iron or glass, in the flame of a spirit lamp, for observing its fusion, 
eymbustion, and the development of sulphurous acid. Further, scoop 
out alittle hollow in a piece of chalk, twist a wire around the latter to 
serve for a handle, as in fig. 3; heat the chalk with a fragment of sulphur 
upon it until the latter ignites, and bring it into a bottle of oxygen gas. 
The purple flame is shortly obscured by the opaque white fume of the 
sulphurous acid. ‘ 
Sulphur forms with oxygen another compound, which, 
in combination with water, constitutes common sulphuric 
acid, or oil of vitriol. This is developed to a slight ex- 
tent by the action of air on flowers of sulphur, but is pre 
pared on a large scale for commerce by a complicated 
process. 
Sulphur unites with most of the metals, yielding com- 
pounds known as sulphides or sulphurets. These exist in 
nature in large quantities, especially the sulphides of iron, 
copper, and lead, and many of them are valuable ores. 
