w the
source of paraffin for making candles, in which it is usually mixed with
substances like stearin in order to raise its melting-point.

Crude petroleum possesses a very repugnant odor; it varies in color from
yellow to black; and its specific gravity ranges from about 0.80 to
1.00, but commonly is between 0.80 and 0.90. Its chemical constitution
is chiefly of carbon and hydrogen, in the approximate ratio of about six
to one respectively. It is a mixture of paraffin hydrocarbons having the
general formula of C_{n}H_{2n+2} and the individual members of this
series vary from CH_{4} (methane) to C_{15}H_{32} (pentadecane),
although the solid hydrocarbons are still more complex. Petroleum is
found in many countries and the United States is particularly blessed
with great stores of it.

The ordinary lamp consisting of a wick which draws up the mineral oil
and feeds it to a flame is efficient and fairly free from danger. It
requires care and may cause disaster if it is upset, but it has been
blamed unjustly in many accidents. A disadvantage of the kerosene lamp
over electric lighting, for example, is the relatively greater
possibility of accidents through the carelessness of the user. This
point is brought out in statistics of fire-insurance companies, which
show that the fires caused by kerosene lamps are much more numerous than
those from other methods of lighting. If in a modern lamp of proper
construction a close-fitting wick is used and the lamp is extinguished
by turning down and blowing across the chimney, there is little danger
in its use excepting accidental breakage or overturning.

In oil-lamps at the present time mineral oils are used which possess
flashing-points above 75 deg.F. The highly volatile components of petroleum
are dangerous because they form very explosive mixtures with air at
ordinary temperatures. A mineral oil like kerosene, to be used with
safety in lamps, should not be too volatile. It is preferable that an
inflammable vapor should not be given off at temperatures under 120 deg.F.
The oil must be of such physical characteristics as to be drawn up to
the burner by capillarity from the reservoir which is situated below. It
is volatilized by the heat of the flame into a mixture of hydrogen and
hydrocarbon gases and these are consumed under the heat of the process
of consumption by the oxygen in the air. The resulting products of this
combustion, if it is complete, are carbon dioxide and water-