cid, yields its
mixture of phenols in the form of a dark oil from which carbolic acid is
separated by a laborious series of fractional distillations. The
undissolved hydrocarbon is similarly purified by fractional distillation,
and furnishes the solid crystalline naphthalene. The tar from one ton of
Lancashire coal yields about 1-1/2 lbs. of carbolic acid, equal to about 1
per cent. by weight of the tar, and about 6-1/4lbs. of naphthalene, so
that this last hydrocarbon is one of the chief constituents of the tar, of
which it forms from 8 to 10 per cent. by weight.

The crude carbolic acid as separated from the alkaline solution is a
mixture of several phenolic compounds, and all of these but the carbolic
acid itself are gradually removed during the process of purification.
Among the compounds associated with the carbolic acid are certain phenols
of higher boiling-point, which bear the same relationship to carbolic acid
that toluene bears to benzene. That is to say, that while phenol itself
is hydroxybenzene, these other compounds, which are called "cresols," are
hydroxytoluenes. The cresols form an oily liquid largely used for
disinfecting purposes under the designation of "liquid carbolic acid," or
"cresylic acid." Carbolic acid is a white crystalline solid possessing
strongly antiseptic properties, and is therefore of immense value in all
cases where putrefaction or decay has to be arrested. It was discovered in
coal-tar by Runge in 1834, and was obtained pure by Laurent in 1840.

The gradual establishment of the germ-theory of disease, chiefly due to
the labours of Pasteur, has led to a most important application of
carbolic acid. Once again we find the coal-tar industry brought into
contact with another department of science. Arguing from the view that
putrefactive change is brought about by the presence of the germs of
micro-organisms ever present in the atmosphere, Sir Joseph Lister proposed
that during surgical operations the incised part should be kept under a
spray of the germicidal carbolic acid to prevent subsequent mortification.
No operation upon portions of the body exposed to the air is at present
conducted without this precaution, and many a human life must have been
saved by Lister's treatment. To this result the chemist and technologist
have contributed, not only by the discovery of the carbolic acid in the
tar, but also by the development of the necessary processes for its
purification. It should be a