CONIFEE^ 21
and a small quantity of paraffinoid hydrocarbons. It never exceeds
4 to 5 per cent, of the volume of the original sample, and with care is
as low as 3* per cent. If the volume notably exceeds 5 per cent., it is
advisable as a precaution to repeat the treatment with the (4 to 1) acid.
When treated in this manner, petroleum naphtha is not appreciably
affected; hence the proportion may be fairly estimated by making an
allowance of 4 to 5 per cent, from the volume of volatile oil which has
survived the repeated treatment with sulphuric acid. A further puri-
fication may be effected by violently agitating the surviving oil with
several times its volume of concentrated sulphuric acid heated to 50° or
60 °. This treatment can be repeated if necessary, after which the
residual hydrocarbon is separated, steam distilled and again measured,
when the surviving oil from pure turpentine oil will not exceed from
•J- to 1 per cent, of the original sample. Any excess over this will be
the minimum quantity of petroleum naphtha present. Shale naphtha
cannot be at all estimated in this way. The behaviour of the oil on
distillation is the best indication of the presence of rosin spirit, as the
temperature rises gradually, and no considerable fraction is obtained at
158° to 160° if much rosin spirit be present.
Allen (Commercial Organic Analysis) gives the table on page 22 as
indicating some of the properties of some substances which have been
used as adulterants for turpentine oil.
More empirical methods for detecting adulteration in turpentine have
been published than is the case for any other essential oil. These are
principally based on colour reactions, and are, in very many cases, quite
useless, especially when the adulterant is carefully purified. Many modi-
fications of processes described above have been published, but do not
appear to possess any advantages over those which have been described.
It is, therefore, considered unnecessary to reproduce so large a bulk of
published work, which has so little bearing on the practical examination
of this oil; but readers who wish for information on these or other little-
used processes or tests, or for details of methods which for any other
reason are not dealt with here, are referred to the following papers :—
J. M. McCandless (J. Amer. Chem. Soc., 1904 (26), 981).
Marcusson and Winterfeld (Chem. Zeit., 1909, 987).
W. Burton (/. Amer. Chem. Soc., 1890 (12), 102).
P. H. Conradson (J. Soc. Chem. Lid., 1897 (16), 519).
H. Wolff (Farbenzeit., 1912 (17), 1553).
Grimaldi (Chem. Zeit., 1908 (32), 8, and 1910 (34), 721).
Dunwody (Amer. Jour. Pharm., 1892 (33) 131).
H. Herzfeld (Chem. Zentralblatt, 1903 (1), 258).
P. van der Wielen (Pharm. Weekblad., 1911 (8), 35).
Nicolardot and Clement (Bull. Soc. Chim., iv. (1910), 7, 173).
V6zes (Bull. Soc. Chim., iii. (1903), 29, 896).
C. Piest (Chem. Zeit., 1912 (36), 198).
Utz (Chem. Zentralblatt, 1905 (1), 1673).
A. W. Schorger l has examined the oils from a number of pine-trees
(^1) U.S. Department of Agriculture, Bulletin 119.