aflets concentrically grouped, and in the alcoholic solution fine
irregular leaflets. Zaloziecki has recently developed these
microscopic investigations to a much greater extent. According to this
observer, the principal part of paraffine, as seen under the
microscope, consists of shining stratified leaflets with a darker
edge. The most characteristic and well developed crystals are formed
by dissolving paraffine in a mixture of ethyl and amyl alcohols and
chilling. The crystals are rhombic or hexagonal tablets or leaves, and
are quite regularly formed. They are unequally developed in different
varieties of paraffine. The best developed are those obtained from
ceresine. Their relative size and appearance give an indication as to
the purity of the paraffine, and, as they are always present, they are
to be counted among the characteristic tests for paraffine.
Reichenbach observed that mere traces of empyreumatic oil prevented
their formation.

The old method of determining the amount of paraffine in petroleum was
to carry out the refining process on a small scale; that is, to
distill the residue from the kerosene oils to coking, chill out the
paraffine, press it thoroughly between filter paper, and weigh the
residue. The sources of error in this procedure are manifold; the
principal one is the solubility of paraffine in oils, which depends
upon the character of both the paraffine and the oil, and also upon
the temperature. The next greatest source of error is variation in the
process of distillation and the difference between working on the
small scale and on the large scale.

In most cases, where a paraffine determination is to be carried out,
one has to deal with a mixture of paraffine with liquid oils. Now,
paraffine is not a substance defined by characteristic physical
properties which distinguish it from the liquid portions of petroleum.
It consists of a mixture of homologous hydrocarbons, which form a
solid under ordinary conditions. The hydrocarbons of this mixture show
a gradation in their properties, and gradually approximate to those
which are liquid at ordinary temperatures. It is a well known fact
that a separation of these homologues is entirely impossible by
distillation. It has also been ascertained that the liquid
constituents of petroleum do not always possess boiling points that
are lower than those of the solid constituents. This shows that we
have to deal not merely with hydrocarbons of one, but of s