This shows that we
have to deal not merely with hydrocarbons of one, but of several
series.
When determinations of the amount of paraffine are to be made, then it
becomes necessary to specify with exactness what is to be called
paraffine. The most definite property that can be made use of for this
purpose is the melting point. For several reasons it is convenient to
include under this name hydrocarbons of melting point as low as
35 deg.-40 deg. C.
The method proposed by Zaloziecki for the determination of paraffine
is the following: The most volatile portions of the petroleum are
separated by distillation, until the thermometer shows 200 deg. C. These
portions are separated, as they exert great solvent action upon
paraffine. At the same time he finds that no pyro-paraffine is formed
under this temperature. A weighed portion of the residue is taken and
mixed with ten parts by weight of amyl alcohol and ten parts of
seventy-five per cent. ethyl alcohol: the mixture is then chilled for
twelve hours to 0 deg. C. It is then filtered cold, washed first with a
mixture of amyl and ethyl alcohols, and then with ethyl alcohol alone.
The paraffine is transferred to a small porcelain evaporating dish and
dried at 110 deg. C. It is then heated with concentrated sulphuric acid to
150 deg.-160 deg. C. for fifteen to thirty minutes with constant stirring.
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