before.

With plenty of O and high enough temperature, all the C is burned
to CO2, whether in gas, candle, or wood. CO2 is an invisible gas.
The porcelain, when held in the flame, cools the C below the
point at which it burns, called the kindling-point, and hence it
is deposited. The greater part of smoke is unburned carbon.

Experiment 28.--Hold an inverted dry t.t. or receiver over the
flame of a burning candle, and look for any moisture (H2O). What
two elements are shown by these experiments to exist in the
candle? The same two are found in wood and in gas. Experiment
29.--Put into a small Hessian crucible (Fig. 18) some pieces of
wood 2 or 3 cm long, cover with sand, and heat the crucible
strongly. When smoking stops, cool the crucible, remove the
contents, and examine the charcoal. The gases have been driven
off from the wood, and the greater part of what is left is C.

Experiment 30.--Put 1 g. of sugar into a porcelain crucible, and
heat till the sugar is black. C is left. See Experiment 5. Remove
the C with a strong solution of sodium hydrate (page 208).

41. Allotropic Forms.--Carbon is peculiar in that it occurs in at
least three allotropic, i.e. different, forms, all having
different properties. These are diamond, graphite, and amorphous
--not crystalline--carbon. The latter includes charcoal, lamp-
black, bone-black, gas carbon, coke, and mineral coal. All these
forms of C have one property in common; they burn in O at a high
temperature, forming CO2. This proves that each is the element C,
though it is often mixed with some impurities.