ESSENTIAL OIL OF TURPENTINE

OIL OF TURPENTINE

Numerous members of the family of the Conifera contain large quantities of resin, and an oil consisting almost entirely of terpenes, in well-characterised resin ducts in the wood. This is especially the case with the various species of pine. The exudation from the wood, an oleo-resin, is often known as crude turpentine. Oil of turpentine, or as it is generally called, turpentine or " turps," is the oil obtained by distilling this, leaving the crude resin or " rosin " behind.

At the present time American turpentine is the chief commercial variety, although a considerable amount is produced in France, Eussia, and many other countries, and India produces a fair quantity which, although at present consumed in the East, may before long find its way to Western markets.

In the United States the turpentine (i.e. the oleo-resin) is obtained either by what is known as the "box system" or by the "cup and gutter " system. The box system, briefly, is carried out as follows: As spring approaches, a groove is cut diagonally across the trunk of the tree, and inclined inwards, ending in a hollow excavation about 12 to 18 ins. above the ground level. This wound in the sapwood induces the flow of the oleo-resin, and as the warmer weather approaches, the bark above and on both sides of the excavation or "box" is peeled off and shortly afterwards the flow of oleo-resin commences. Every two or three weeks fresh cuts are made so as to open up fresh passages for the exudation. The oleo-resin collects in the box" and is baled out into barrels and transferred to the distillery. Trees are not considered worth tapping after four to six years. The cup and gutter system is a combination of the older box system and of the usual method employed in France. The cutting of a large hollow in the trunk is obviated, and its place is taken by a receptacle which is suspended from a nail in the trunk. As in the "box" system, here also the first work is cutting strips in the bark, and as the work proceeds, the space above the receptacle is gradually cleared of bark. In order to let the exuding resin collect in the earthen ware pots or vessels placed below, two strips or gutters of galvanised sheet-iron about 2 ins. wide by 6 ins. to 12 ins. long are employed. These are placed in grooves cut into the trunk with a broad axe in such manner, that each of the two cuts forms an angle of 60° with the longitudinal axis of the itree, and the two together therefore form an angle of 120° open at the top. The two gutters, however, are not placed at the same height, hut one about 1 in or 2 ins. above the other, so that the resin flowing along the upper gutter only passes the other one when flow ing down, and then passing through the lower gutter reaches the vessel placed below the latter. When the cuts in the trunk and the peeling of the bark are continued in an upward direction, the gutters and the vessel are also moved upwards. In older trees containing more oleo-resin, several such vessels can of course be placed around the tree.

The French turpentine industry is practically confined to the Lander district, where the following method of collection is followed :

This crude materialt he "gemme," to give it the name under which it is known in the Landes exudes during the warm season (from March to October) from an incision made by the axe of the resin collector in the stem of the maritime pine. Kept open by the removal of a thin slice every week, this incision the "carre " rises gradually up the trunk of the tree until it reaches, after five years' working, a height of nearly 4 metres. The tree is then left alone for two or three years, after which time a fresh " carre " is made at another point of the base. The same tree is tapped in this manner for about forty years, after which it is "bled to death " (that is, it is worked by means of several "carres" simultaneously), before being felled and delivered to the timber merchants.

The forest is, moreover, rapidly reconstituted, by means of sowings made at the proper time, so that the resin production of the Landes district is not diminished by the work of the wood-cutters and the operations of the mechanical saw-mills. So far, this principle has not been followed in the United States, where every tree was "tapped to death " from the beginning, and every plot which was subjected to tapping was thereby practically destroyed after four years' working, without any steps being taken for its reconstitution. For some years, however, a serious movement has been set on foot in America to save what remains of the pine forests by a more rational and less destructive system of exploitation ; and this appears to be producing good results. From the top of the "carre," the drops of "gemme " as they exude from the resin ducts of the tree, run down into the receiver placed to collect them; this was in former times in the Landes (and was until three or four years ago in America) a hole the "crot " hollowed out of the stem of the tree itself, at the base of the " carre " ; at the present day it is, both in America and in the Landes, an earthenware or metal pot, suspended at the base of the " carre " and raised every year so as to bring it near the upper part of the incision and reduce the distance over which the drops of the exudation have to run. The importance of this change and why it is advantageous that the path of the "gemme" down the "carre" should be as short as possible, is obvious when one remembers how easily the turpentine is oxidised.

From the pots the " gemme" is transferred, about once a month, into casks and carried from the forest to the factory; this harvest,

"I'amasse," takes place in the Landes from five to eight times a year. In India, the chir, as the Pinus longifolia is termed, is treated by a method based on the French method. An initial blaze about 6 ins. long, 4 ins. broad and not more than 1 in. deep is cut near the base of the tree, and the blaze is freshened every six or seven days throughout the summer, until it is about 18 ins. long by the end of the year : if the freshening is carefully done the use of a ladder is thus as a rule unnecessary till the fifth year. The resin collects in a cup fixed at the base of the current years' blaze, and the contents are emptied periodically. A curved channel, in place of the former rectangular channel, is now universally adopted in the United

Provinces, as it works easily, does not injure the tree so much, gives a cleaner cut, and so far shows promise of giving a higher out-turn. There are two classes of tapping : (1) light tapping and (2) heavy tapping, sometimes termed tapping to death. The latter is carried out in the case of trees due to be felled within five years, and consists in making; as many blazes as the tree will hold the former consists in making a moderate number of blazes, and is carried out in the case of trees not due to be felled within the next few years. In the Naini Tal Division light tapping under the present system' is commenced when the trees reach a girth of 3 1/2 ft., and the following number of blazes are cut:

(1) Trees over 6 ft. in girth . . . . . . ................... 3 blazes

(2)       „ „       4 1/2 to 6 ft. in girth.......... .........2 blazes

(3)       „ „       3 1/2 to 4 1/2 ft. in girth.......... . 1 blaze

In the maritime pine forests of Bordeaux no tree is tapped lightly till it reaches a girth of 1,10 metres (3 ft. 7 ins.), when one blaze is made: the tree is then about fifty years old. A second blaze is added when the tre reaches a girth of 1,30 metres (4 ft. 3 ins.). In the Chakrata Division tapping is confined to fire-protected forests of the first and second periodic blocks in Jaunsar-Bawar; no tapping is at present done in the Tehri-Garhwal forests owing to the cost of carriage. At present no heavy tapping is done in this Division : light tapping commences when the trees reach 4J ft. in girth. In periodic block I. trees 4 1/2 to 6 ft. in girth have two blazes, and those over 6 ft. in girth have four blazes. In periodic block II. trees 4 1/2 to 6 ft. in girth have one blaze, and those over 6 ft. in girth have two blazes.

The object of heavy tapping is to obtain the largest possible out-turn of resin before felling the tree, and for this purpose as many blazes are made as there is room for. Experiments carried out so far show that only a comparatively small proportion of trees tapped in this way die: recent experiments in the Kangra Division showed a mortality of 6 per cent, in two years. In the maritime pine forests of Bordeaux trees to be removed in thinnings are heavily tapped as soon as they are large enough to hold a cup : this ordinarily commences when they are fifteen years old.

In the United Provinces the season's tapping commences in March and continues till November, after which the flow of resin practically ceases. In order to promote the free outflow of resin, the blazes require to be freshened with an adze at intervals. Eecent experiments carried out by Mr. E. A. Smythies in the Naini Tal Division showed that the out-turn increased steadily up to at least ten freshenings per month: this is borne out by similar experiments made in the Punjab. In Naini Tal, however, it was found that the yield did not increase in proportion to the extra labour required beyond five freshenings per month, and this number (i.e. once in about six days) is now universally adopted in that Division in place of the four freshenings per month formerly in vogue. As regards labour, in the Naini Tal Division the most economical working is found to be attained by an allotment of about 600 trees per man, that is, 100 trees a day per man.

In the case of light tapping, it is customary in India to tap for a certain number of years and then to allow a period of rest before tapping is recommenced. In the Naini Tal Division, and in Kumaon generally, the rule hitherto has been to tap for five years and then to give a rest for ten years before recommencing tapping: this complete period of fifteen years may be termed the tapping-cycle. In the Chakrata Division a similar procedure was in force till 1914, when a nine years' tapping-cycle was introduced, with tapping for three years followed by a rest for six years. The cycle was shortened in order to avoid the use of a ladder, which was found necessary in the fifth year. The highest yield of resin is obtained in the third and fourth years of tapping, and thus by reducing the tapping period to three years considerable loss is involved, which is avoidable considering that a ladder is not required in the fourth season if reasonable care is taken in freshening the blazes.

If a tapping-cycle at all is to be decided on, twelve years (i.e. four years' tapping and eight years' rest) appears to be preferable to either nine or fifteen years. The objection to the former has been mentioned, while in the case of the latter it cannot be made to fit in with a suitable scheme of thinnings.

In the maritime pine forests of Bordeaux light tapping, once begun, continues without interruption, no rest being given unless a tapped tree shows signs of becoming sickly, when a rest of five years is given: such cases are rare. Now in the case of the chir pine, experiments have shown that the tree possesses remarkable vitality even under the strain of heavy tapping. There seems to be no reason, therefore, why the continuous light tapping system of France should not be employed in the chir forests. Not only would it increase largely the out-turn of resin, but it would avoid the complication in the general scheme of management which is inevitable if a tapping-cycle is adopted. Much has been written in reference to the adulteration of oil of turpentine, most of which is of little more than historical interest to-day. The chief difficulty the expert has to contend with at the present time is the detection of the so-called wood or stump turpentine oil. This oil is clearly entitled to the description "turpentine oil," on account of its origin and character, which are exceedingly close to those of normal or "gum " turpentine ; but it is generally conceded that it properly requires the qualification " wood "or " stump," so that users may know exactly what they are dealing with.

Wood turpentine, "stump turpentine" or "wood spirits of turpentine" as the product is variously known, is turpentine oil made from cut pine, fir, or spruce, by distilling the wood in closed retorts. When properly refined it closely resembles gum spirits of turpentine, obtained by distilling the oleo-resin exuding from the cut surface of the living tree.

The turpentine made by distilling the wood with steam below a temperature of 150° C. more closely resembles gum spirits than that obtained by destructively distilling the wood. The latter is always contaminated with other oils derived from the breaking down of the wood and the resins which it contains.

As a result of the reckless devastation of the pine forests which has been practised for many years, in the United States, the tree-stumps which have been left standing, and which are known as "light wood" are now often distilled. The stumps which are being used up in America at present have remained in the ground many years after the trunk had been removed, and yield a pine wood which is very rich in resin. It would appear that a chemical process is taking place in these stumps by which oil is formed subsequent to the removal of the trunk, for the oil yield from new stumps is very low. This fact would also explain why the oil thus obtained is somewhat different from ordinary oil of turpentine, and why the percentage is so high.

The stumps which are mostly employed for distilling purposes are those of Pinuspalustris (long leaf pine), whence the oil is called "long leaf pine oil". Similar products are brought to market under the names of "light wood oil" and " oil of fir";. while the designations "white” and "yellow pine oil " appear to apply to separate fractions of the oil.

According to Teeplel ordinary commercial long leaf pine oil in its crude state has a specific gravity 0,935 to 0,944, optical rotation -11°, and refractive index T4830. These values, however, are often exceeded, and genuine samples may have a specific gravity 0*954 and may be dextro-rotatory up to + 8°. A sample was examined by Schimmel & Co.² which had the following characters :

Specific gravity ...................0,9536

Optical rotation ................. - 3°26'

Refractive index ................. . 1,48537

Ester n u m b e r .................... 14,2

Total alcohols (by acetylation)... 58 per cent.

The bulk of the oil boiled between 190° and 220°. The following terpenes were identified in the oil: α-pinene, β-pinene, L-limonene, dipentene, and g-terpinene. A considerable amount of α-terpinene was found (this had previously been identified by Teeple), as well as borneol and methyl-chavicol. Fenchyl alcohol was also found as a constituent of the oil, and traces of camphor and cineol. The presence of fenchyl alcohol is of particular interest as it occurs in the inactive variety. It is well known that this body results from the reduction of fenchone, but it has never before been discovered as a natural constituent of an essential oil.

The table below shows the character of the fenchyl alcohol occurring in this oil and of those prepared by the reduction of active and inactive fenchone.