_Terebinthina Laricina_; _Venice Turpentine_,
_Larch Turpentine_; F. _Térébenthine de
Venise ou de Briançon_, _Térébenthine du
mélèze_; G. _Venetianischer Terpenthin_,
_Lärchen-Terpenthin_.
=Botanical Origin=—_Pinus Larix_ L. (_Larix europæa_ DC.), a tall
forest tree of the mountains of Southern Central Europe, from Dauphiny
through the Alps to Styria and the Carpathians, ascending to an
elevation of 3000 to 5500 feet above the sea-level. It is largely grown
in plantations in England and also, since 1738, in Scotland.
=History=—The turpentine of the larch was known to Dioscorides as
imported from the Alpine regions of Gaul.[2281] Pliny also was
acquainted with it, for he correctly remarks that it does not harden.
Galen in the 2nd century also mentions it, admitting that it may well
be substituted for Chian turpentine (see p. 165), the true, legitimate
_Terebinthina_. Yet even in the beginning of the 17th century many
pharmacologists complained of such a substitution. Mattioli[2282] gave
an account of the method of collecting it about Trent in the Tirol,
by boring the trees to the centre, which is true to the present day.
It used formerly to be exported from Venice, then the great emporium
for drugs of all kinds; the turpentine may even at times have been
collected in the territories of the Venetian republic. We find it
expressly called _Terebinthina Veneta_ by Guintherus of Andernach.[2283]
The name _larch_ seems to belong to the turpentine rather than to the
tree. Dioscorides says the resin is called by the natives λάρικα, and
a similar name is mentioned by Galen. In Pasi’s _Tariffa de pesi e
misure_, 1521 (see Appendix), we find “_Termentina sive Larga_,”—and
_larga_ is still an Italian name for larch turpentine. The peasants of
the Southern Tirol call it _Lerget_, and in Switzerland the common name
in German is _Lörtsch_.
=Extraction=—Larch turpentine is collected in the Tirol, chiefly
about Mals, Meran, Botzen and Trent. A very small amount is obtained
occasionally in the Valais in Switzerland, and in localities in
Piedmont and France where the larch is found. The resin is obtained
from the heartwood, by making in the spring a narrow cavity reaching to
the centre of the stem at about a foot from the ground. This is then
stopped up until the autumn of the same or of the following year, when
it is opened and the resin taken out with an iron spoon. If only one
hole is thus made, the tree yields about half a pound yearly without
appreciable detriment. But if on the other hand a number of wide holes
are made, and especially if they are left open, as was formerly the
practice in the Piedmontese and French Alps, a larger product amounting
to as much as 8 lb. is obtained annually, but the tree ceases to yield
after some years, and its wood is much impaired in value.
[2281] Lib. i. cap. 92.
[2282] _Comment. in libr. i. Dioscoridis_, Venetiis, 1565. 106.
[2283] _De medicina veteri et nova etc._, Basileæ, 1571. 183.
Mohl, who witnessed the collection of this turpentine in the Southern
Tirol,[2284] observed that when a growing larch stem was sawn through,
the resin flowed most abundantly from the heartwood, and in smaller
quantity, though somewhat more quickly, from the sapwood, and that
the bark contained but few resin-ducts. The practice of closing the
cavities is adopted, not only for the sake of preserving the wood
and for the greater convenience of removing the turpentine, but also
because it tends to maintain the transparency and purity of the latter.
=Description=—Venice turpentine is a thick, honey-like fluid, slightly
turbid, yet not granular and crystalline; it has a pale yellowish
colour and exhibits a slight fluorescence. Its odour resembles that
of common turpentine, but is less powerful; its taste is bitter and
aromatic. When exposed to the air, it thickens but slowly to a clear
varnish, and hardens but very slowly when mixed with magnesia. Larch
turpentine, though common on the Continent, is seldom imported into
England,[2285] and the article sold for it is almost always spurious.
=Chemical Composition=—Larch turpentine dissolves in spirit of wine,
forming a clear liquid which reddens litmus; hot water agitated with it
also acquires a faint acid reaction, due to formic and probably also
to succinic acid. Glacial acetic acid, amylic alcohol, and acetone
mix with it perfectly. By distillation it yields on an average 15 per
cent. of essential oil of the composition, C₁₀H₁₆, which boils at 157°
C., and when saturated with dry hydrochloric acid gas, easily produces
crystals of the compound C₁₀H₁₆ + HCl. The residual resin is soluble
in two parts of warm alcohol of 75 per cent., and more copiously in
concentrated alcohol.
Two parts of the turpentine diluted with one of benzol or acetone
deviate the ray of polarized light 9·5° to the _right_. The essential
oil deviates 6·4° to the _left_; the resin perfectly freed from
volatile oil and dissolved in half its weight of acetone, deviates
12·6° to the _right_ in a column 50 mm. long.
We have not succeeded in preparing a crystallized acid from the resin
of Venice turpentine, although its composition according to _Maly_
(1864) is the same as that of American colophony, which is easily
transformed into crystallized abietic acid.
=Uses=—Venice turpentine appears to possess no medicinal properties
that are not equally found in other substances of the same class, and
as a medicine it has fallen into disuse. But in name at least it is in
frequent requisition for horse and cattle medicines.
=Adulteration=—Alston (1740-60) said of Venice turpentine[2286] that
it is seldom found in the shops,—a remark equally true at the present
day, for but few druggists trouble themselves to procure it genuine.
The Venice turpentine usually sold is an artificial mixture of common
resin and oil of turpentine, which may be easily distinguished from the
product of the larch by the facility with which it dries when spread on
a piece of paper,[2287] and by its stronger turpentine smell.
[2284] _Botanische Zeitung_, xvii. (1859) 329, abstracted in the
_Jahresbericht_ of Wiggers, 1859. 18.
[2285] On one occasion I observed Venice Turpentine in a public drug
sale in London, 21 barrels imported from Trieste being offered, 14
July, 1864.—D. H.
[2286] _Lectures on the Materia Medica_, Lond. ii. (1770) 398.
[2287] Thus if a thin layer of true Venice turpentine and another of
common turpentine be spread on two sheets of paper it will be found
after the lapse of some weeks that the former cannot be touched without
adhering to the fingers, while the latter will have become a dry, hard
varnish.