Chapter XXXVIII: Part 38

=Chemical Composition=—Larch bark has been examined by Stenhouse,[2289] who finds it to contain a considerable amount of a peculiar tannin, yielding olive-green precipitates with salts of iron. The same chemist also discovered[2290] in larch bark an interesting crystallizable substance called _Larixin_ or _Larixinic Acid_, which has the composition C₁₀H₁₀O₅. It may be obtained by digesting the bark in water in 80° C. and evaporating the infusion to a syrupy consistence. From this, by still further cautious heating in a retort, the larixin may be distilled, during which operation some of it crystallizes on the inner surface of the receiver, the remainder being dissolved in the distilled liquor. From the latter it may be obtained in crystals by evaporation. The substance forms colourless crystals, sometimes as much as an inch long; it volatilizes even at 93° C., and melts at 153°. It requires about 88 parts of water for solution at 15° C., but more freely dissolves in boiling water or in alcohol. From ether, in which it is but sparingly soluble, it separates in brilliant crystals. The solutions have a bitterish astringent taste and a slightly acid reaction, and assume a purple hue on addition of ferric chloride. When a solution of baryta is added to a concentrated solution of larixin, the latter being in excess, a bulky gelatinous precipitate falls; it is readily soluble in boiling water and is deposited again on cooling. Stenhouse failed to obtain it either from the bark of _Pinus Abies_ L., or from that of _P. silvestris_ L.

[2288] _Herball, enlarged by Johnson_, Lond. 1636. 1366.

[2289] _Proceedings of the Royal Society_, xi. (1862) 404.

[2290] _Phil. Trans._, vol. 152 (1862) 53.—We write the name _Larixin_ instead of _Larixine_, with the concurrence of Dr. Stenhouse.

=Uses=—Larch bark, chiefly in the form of tincture, has been prescribed to check profuse expectoration in cases of chronic bronchitis; it has also been found useful in arresting internal hæmorrhage.

TEREBINTHINA CANADENSIS.

_Balsamum Canadense_; _Canada Balsam_, _Canadian Turpentine_; F. _Térébenthine ou Baume de Canada_; G. _Canada Balsam_.

=Botanical Origin=—_Pinus balsamea_ L. (_Abies balsamea_ Marshall), the Balsam Fir or Balm of Gilead Fir, a handsome tree, 20 to 40 feet high, with a trunk 6 to 12 inches in diameter, sometimes attaining still larger dimensions, growing in profusion in the Northern and Western United States of America, Nova Scotia and Canada, but not observed beyond 62° N. lat. It resembles the Silver Fir of Europe (_Pinus Picea_ L.), but has the bracts short-pointed and the cones more acute at each end.

Canada balsam is also furnished by _Pinus Fraseri_ Pursh, the Small-fruited or Double Balsam Fir, a tree found on the mountains of Pennsylvania, Virginia, and southward on the highest of the Alleghanies.[2291]

_Pinus canadensis_ L. (_Abies canadensis_ Michx.), the Hemlock Spruce or Pérusse, a large tree abundant in the same countries as _P. balsamea_, and extending throughout British America to Alaska, is said to yield a similar turpentine, which however has not yet been sufficiently examined. The Hemlock Spruce is of considerable importance on account of the resin collected from its trunk, and the essential oil distilled from its foliage, the latter operation being performed on a large scale in Madison County, New York. The inner bark of the tree is a valuable material for tanning.

=History=—The French, in whose possession Canada remained until the year 1763, were probably acquainted with Canada balsam long before this period. Yet no mention of it is found in Pomet’s work, but in 1759 it was at Strassburg a current article of the pharmacy.[2292] As to England, Lewis, in his _History of the Materia Medica_ published in 1761, says that “_an elegant balsam_,” obtained from the Canada Fir, is sometimes brought into Europe under the name of _Balsamum Canadense_. Canada balsam was first introduced into the London Pharmacopœia in 1788. From the books of a London druggist, J. Gurney Bevan, we find that its wholesale price in 1776 was 4_s._, in 1788, 5_s._ per lb.

=Description=—Canada balsam is a transparent resin of honey-like consistence, and of a light straw-colour with a greenish tint. By keeping, it slowly becomes thicker and of a somewhat darker hue, but always retains its transparency. When carefully examined in direct sunlight, it exhibits a slight greenish fluorescence in the same degree as other turpentines or as copaiba; this optical power appears to increase if the balsam is exposed to a heat of about 200° C.

[2291] Asa Gray, _Botany of the Northern United States_, New York, 1866. 422.

[2292] Flückiger, _Pharm. Journ._ vi. (1876), 1021.

Canada balsam has a pleasant aromatic odour and bitterish, feebly acrid, not disagreeable taste. On account of its flavour it is sometimes called _Balm of Gilead_, but erroneously, as this latter is derived from a tree of the genus _Balsamodendron_ growing in Arabia. We found a good commercial balsam to have a sp. gr. of 0·998 at 14·5° C., water at the same temperature being 1·000. Four parts, mixed with one of benzol and examined in a column of 50 mm. in length, deviated a ray of polarized light 2° to the right. The balsam is perfectly soluble in any proportion in chloroform, benzol, ether, or warm amylic alcohol; and the solution in each case reddens litmus. With sulphate of carbon it mixes readily, but the mixture is somewhat turbid. Glacial acetic acid, acetone or absolute alcohol dissolve the balsam partially, leaving, after ebullition and cooling, a considerable amount of amorphous residue. Colophony and Venice turpentine are completely dissolved by the liquids in question, as well as by spirit of wine containing 70 to 75 per cent. of alcohol.

=Chemical Composition=—Like all analogous exudations of the _Coniferæ_, Canada turpentine is a mixture of resins with an essential oil. If the latter is allowed to evaporate, the former are left as a transparent, somewhat tough and elastic mass. The proportion of the components is within certain limits, variable in different samples. The specimen before mentioned lost after an exposure in a steam-bath during several days, no less than 20 per cent. of volatile oil, or even 24 per cent. if the experiment was made on a very small scale, as with 20 grammes or less in a thin layer.

By distillation with water, it is not easy to obtain more than 17 to 18 per cent. of essential oil. The resin in this case is a tough, elastic, non-transparent mass, retaining obstinately a large proportion of water, which can only be removed by keeping it for some time at a temperature of 100°-176° C.

The oil as obtained by distillation with water is colourless, and has the odour of common oil of turpentine rather than the agreeable smell of the balsam; it consists of an oil, C₁₀H₁₆, mixed with an insignificant proportion of an oxygenated oil, the presence of which may be proved by the slight evolution of hydrogen on addition of metallic sodium, after the oil has been freed from water by contact with fused chloride of calcium. After this treatment, a small proportion begins to distil at about 160°, but by far the larger part boils at 167° C., a small portion only distilling at last at 170° and above. The oil obtained at 167°, examined under the conditions already mentioned, has a sp. gr. of 0·863, and the power of rotating a ray of polarized light 5·6° to the left. The portion distilling at 160° does not differ in this respect; but that passing over at 170°, deviates the ray 7·2° to the left. The oil readily dissolves a large proportion of glacial acetic acid; an equal weight of each mixes perfectly at about 54° C., but some acetic acid separates on cooling.

The essential oil of Canada balsam, saturated with dry hydrochloric acid, does not yield a solid crystallizable compound; but this is easily obtained on addition of fuming nitric acid and gently heating, when the inside of the retort becomes covered by sublimed crystals of C₁₀H₁₆ + HCl.

Thus this oil in its general characters bears a close resemblance to the essential oils of the cones of _Pinus Picea_ L., and of the leaves of _P. Pumilio_ Hänke, and to most of the French varieties of oil of turpentine, rather than to the American turpentine oils, which rotate to the right, and combine immediately with HCl to form a solid crystalline compound.

On the other hand, the resin of Canada balsam is dextrogyre: two parts of it, entirely deprived of essential oil and dissolved in one of benzol, deviating the ray 8·5° to the right. The optical powers of the two components (oil and resin) are therefore antagonistic.

The resin of Canada balsam consists however of two different bodies, 78·7 per cent. of it being soluble in boiling absolute alcohol, and 21·3 (in our specimen) remaining as an amorphous mass, readily soluble in ether. Neither the alcoholic nor the ethereal solution yields a crystalline residue if allowed to evaporate. They redden litmus, but we did not succeed in obtaining any crystallized resinous acid, crystals of which are formed if common turpentine or colophony is digested with dilute alcohol. Glacial acetic acid acts upon the resins like absolute alcohol. Caustic alkalis do not dissolve either the balsam or the resin; the former however is considerably thickened by incorporation with ⅕ of its weight of recently calcined magnesia. If the mixture, moistened with dilute alcohol, is kept at 93° C. for some days and frequently stirred, a mass of hard consistence, finally translucent, results. Caustic ammonia heated with the balsam in a closed bottle, forms a thick milky jelly, which does not afterwards separate.

Hence, according to our investigations, 100 parts of Canada turpentine consist of

Essential oil, C₁₀H₁₆}, with a very small proportion of
an oxygenated oil 24
Resin soluble in boiling alcohol 60
Resin soluble only in ether 16

The result of Wirzen’s examination of Canada balsam[2293] are not in complete accordance with those here stated. He found 16 per cent. of oil and three different amorphous resins, one of which had the composition of abietic acid.

[2293] _De balsamis et præsertim de Balsamo Canadense_, Helsingforsiæ, 1849,—abstracted in the _Jahresbericht_ of Wiggers for 1849. 38.

=Production and Commerce=—Canada balsam is obtained either by puncturing the vesicles which form under the suberous envelope of the trunk and branches, and collecting their fluid contents in a bottle, or by making incisions. It is obtained principally in Lower Canada, and is shipped from Montreal and Quebec, in kegs or large barrels. In the neighbourhood of Quebec, about 2000 gallons (20,000 lb.) used to be collected annually; but in 1868, owing to distress among the farmers, the quantity obtained was unusually large, and it was estimated that nearly 7000 gallons would be exported to England and the United States.[2294] During a recent scarcity (1872-73) a sort of balsam from Oregon has been substituted in the American market for true Canada balsam.[2295]

=Uses=—The medicinal properties of Canada balsam resemble those of copaiba and other terebinthinous oleo-resins, yet it is now rarely employed as a remedy. The balsam is much valued for mounting objects for the microscope, as it remains constantly transparent and uncrystalline. It is also used for making varnish.

TEREBINTHINA ARGENTORATENSIS.

_Strassburg Turpentine_; F. _Térébenthine d’Alsace ou de Strasbourg_, _Térébenthine du sapin_; G. _Strassburger Terpenthin_.

=Botanical Origin=—_Pinus Picea_ L. (_Abies pectinata_ DC.), the Silver Fir,[2296] a large handsome tree, growing in the mountainous parts of Middle and Southern Europe from the Pyrenees to the Caucasus, and extending under a slightly different form (var. β. _cephalonica_) into continental Greece and the islands of Eubœa and Cephalonia.

=History=—Belon in his treatise _De Arboribus coniferis_ (1553) described this turpentine, which is also briefly yet accurately noticed by Samuel Dale,[2297] a learned apothecary of London and the friend of Sloane and Ray. It had a place in the London Pharmacopœia until 1788, when it was omitted from the materia medica.

=Extraction=—The oleo-resin of _P. Picea_, like that of _P. balsamea_, is contained in little swellings of the bark[2298] of young stems, and is extracted by the tedious process of puncturing them and receiving in a suitable vessel the one or two drops which exude from each. It is still collected near Mutzig and Barr, in the Vosges (1878), though only to a very small extent.

=Description=—An authentic sample collected for one of us by the Surveyor of Forests in the Bernese Jura, Switzerland, resembles very closely Canada balsam, but is devoid of any distinct fluorescence. It has a light yellow colour, a very fragrant odour,[2299] more agreeable than that of Canada balsam, and is devoid of the acrid bitterish taste of the latter.

We found our specimen to have sp. gr. of distilled water. It deviates a ray of polarized light 3° to the left, if examined either pure or diluted with a fourth of its weight of benzol, in the manner described at p. 610. Our drug is soluble in the same liquids as the Canadian, yet is miscible with glacial acetic acid, absolute alcohol and acetone, without leaving any considerable flocculent residue. It is even soluble in spirit of wine, the solution being but very little turbid. The solutions have an acid reaction.

[2294] From information obligingly communicated by Mr. N. Mercer of Montreal and Mr. H. Sugden Evans of London.—See also _Proc. Am. Pharm. Assoc._, 1877, page 337, abstracted in _Ph. Jour._ viii. (1878) 813.

[2295] _Proceedings of the American Pharmaceutical Association_, Philadelphia, 1873. 119—also 1874. 433.

[2296] _Sapin_ in French; _Weisstanne_ or _Edeltanne_ in German.

[2297] _Pharmacologia_, Lond. 1693. 395.

[2298] See Morel, _Ph. Jour._ viii. (1877) 21.

[2299] Hence it is sometimes called in French _Térébenthine au citron_.

=Chemical Composition=—After the complete desiccation of a small quantity, there remained 72·4 per cent. of a brittle, transparent resin, soluble in glacial acetic acid, but not entirely in absolute alcohol or in acetone. By submitting half a pound of the turpentine to distillation with water, we obtained 24 per cent. of essential oil, the remaining resin being when cold perfectly friable. The fresh oil, purified by sodium, deviates the ray of polarized light to the left, whereas the remaining resin, dissolved in half its weight of benzol, shows a weak dextrogyre rotation. The oil boils at 163° C. After having kept it for two years and a half in a well-stopped bottle, we find that it has become considerably thicker and now deviates to the right. If saturated with dry hydrochloric acid, the oil does not yield a solid compound.

This oil has nearly the same agreeable odour as the crude oleo-resin, yet the essential oil of the _cones_ of the same tree is still more fragrant. The latter is one of the most powerfully deviating oils, the rotation being 51° to the left, and it is consequently extremely different from the oil obtained from the turpentine of the stem, though its composition is represented by the same formula, C₁₀H₁₆.

A peculiar sugar called _Abietite_, nearly related to mannite but having the composition C₁₂H₁₆O₆, has been detected by Rochleder[2300] in the leaves of the Silver Fir.

=Uses=—Strassburg turpentine possesses the properties of common turpentine, with the advantage of a very agreeable odour. It was formerly held in great esteem, but has now become nearly forgotten.

PIX BURGUNDICA.

_Pix abietina_; _Burgundy Pitch_; F. _Poix de Bourgogne ou des Vosges_, _Poix jaune_; G. _Fichtenharz_, _Tannenharz_.

=Botanical Origin=—_Pinus Abies_ L. (_Abies excelsa_ DC.), the Norway Spruce Fir,[2301] a noble tree attaining an elevation of 100-160 feet, widely distributed throughout Northern and the mountainous parts of Central Europe, but not indigenous to Great Britain, though extensively planted. In Russian Lapland it reaches at 68° N. lat. almost the extreme limit of tree-vegetation, while southward it extends to the Spanish Pyrenees. In the Alps it ascends to 6,000 feet above the level of the sea.

=History=—In accordance with the definition of the London Pharmacopœias and the custom of English druggists the name _Burgundy Pitch_ is restricted to the product of the above-named species. The pharmacologists of France use an equivalent term with the same limitations; but in other parts of the Continent _Pix Burgundica_ has a wider meaning, and is allowed to include the turpentines of other _Coniferæ_. We here employ it in the English sense.

Parkinson, an apothecary of London and herbarist to King Charles I., speaks of “_Burgony Pitch_” as a thing well known in his time.[2302] Dale in his _Pharmacologia_ (1693) mentions _Pix Burgundica_ as being imported into England from Germany, and it is also noticed by Salmon (1693), who says “it is brought to us out of Burgundy, Germany and other places near Strasburgh.”[2303]

[2300] Wiggers and Husemann, _Jahresbericht_, 1868. 53.

[2301] _Pesse_ or _Epicéa_ of the French; _Fichte_ or _Rothtanne_ of the Germans.

[2302] _Theater of Plants_, 1640. 1542.

[2303] _Compleat English Physician_, 1693. 1031.

Pomet, writing in Paris about the same period, discards the prefix _Burgundy_ as a fiction, remarking that the best _Poix grasse_ comes from Holland and Strassburg.[2304]

Whether this resin ever was collected in Burgundy we are unable to determine. It may probably have acquired the name through having been brought into commerce from Switzerland and Alsace by way of Franche Comté, otherwise called Comté de Bourgogne or Haute Bourgogne.[2305]

Burgundy pitch is enumerated among the materia medica of the London Pharmacopœia of 1677, and in every subsequent edition. In that of 1809 it was defined under the name of _Pix arida_, as the _prepared resin of Pinus Abies_.

=Production=—Burgundy pitch is produced in Finland, in the Black Forest in the Grand Duchy of Baden, Austria and Switzerland. On the estate of Baron Linder at Svarta near Helsingfors, it is obtained by melting the crude resin in contact with the vapour of water, and straining. The quantity annually produced there was stated in 1867 to be 35,000 kilogr. (689 cwt.);[2306] that afforded by an establishment at Ilm in the same country amounted to 80,000 kilogr. (1,575 cwt.).[2307]

In the neighbourhood of Oppenau and on the Kniebis mountain in the Grand Duchy of Baden the stems of the firs are wounded at equal distances by making perpendicular channels, 1½ inches wide and the same in depth. The resin which exudes from these channels is scraped off with an iron instrument made for the purpose, and purified by being melted in hot water and strained. This is performed in three or four small establishments at Oppenau and the neighbouring village of Löcherberg. In this state the resin, which is opaque and contains much moisture, is called _Wasserharz_. By further straining and evaporating a portion of the water its quality is improved.

The manufacture in that part of Germany is on the decline, partly in consequence of the timber being injured by the wounding of the trees, so that the collecting of resin is not permitted in the large forests belonging to the governments of Baden and Württemberg. We have had the opportunity of observing[2308] that in the establishments in question French turpentine or _galipot_, imported from Bordeaux, as well as American rosin or colophony, are used in quantities certainly exceeding that of the resin grown on the spot.

In the middle of the last century some Burgundy pitch was produced, according to Duhamel,[2309] in the present canton of Neuchâtel, but no such branch of industry is now pursued there, at least on a large scale. On the other hand, in the districts of Moutier and Delémont in the Bernese Jura this resin is still collected, though it is not known as _Burgundy Pitch_, but is termed simply _Poix blanche_ (White Pitch). The surveyor of the forests of this district, which is one of the richest in _Pinus Abies_, has informed one of us that from 790 to 850 quintals are collected and exported to Basle, Zürich, Aarau and Vaud. The pitch is worth _in loco_ (1868) 100 to 110 francs (£4 to £4 8_s._) the _bosse_ of 6 quintals. The quantities collected in other parts of Switzerland are even less considerable.

[2304] _Hist. des Drogues_, Paris, 1694. part i. 287.

[2305] Chabræus in his _Stirpium Sciagraphia_ (1666) remarks that he had seen the _Pesse_ (_P. Abies_ L.) in great plenty “_in Burgundicis montibus_,” yet makes no particular allusion to its yielding resin.

[2306] _Pharm. Journ._ ix. (1876) 164; also in Hanbury’s _Science Papers_, pp. 46 to 53.

[2307] _Oesterreichischer Ausstellungs-Bericht_, x. (Wien, 1868) 471.

[2308] I spent several days in the localities in 1873.—F. A. F.

[2309] _Traité des Arbres_, etc. i. (1775) 12.

=Description=—Pure Burgundy pitch, of which we have numerous authentic specimens, is a rather opaque, yellowish-brown substance, hard and brittle when cold, yet gradually taking the form of the vessel in which it is kept. It is strongly adhesive, breaks with a clear conchoidal fracture, and has a very agreeable, aromatic odour, especially when heated. It does not exhibit a crystalline structure, although, as we have frequently observed, the resin on the stem of the tree is distinctly crystalline.

Burgundy pitch is readily soluble in glacial acetic acid, acetone, absolute alcohol, and even in alcohol of 75 per cent. (sp. gr. 0·860), yet its solubility in these liquids is considerably altered by the presence of water or essential oil; and still more by the formation of abietic acid in the resin itself. The same influences also affect the melting point.

The crude resin of _Pinus Abies_,[2310] deprived of essential oil and dissolved in one part of absolute alcohol, was found to deviate a ray of polarized light 3° to the left, in a column of 50 mm.; the essential oil deviated 8·5° to the same direction. The oil contains a small amount of an oxygenated oil. After treatment with sodium the oil which remains does not form a solid compound if saturated with hydrochloric acid.

[2310] Collected by myself.—F. A. F.

=Chemical Composition=—The investigations of Maly mentioned at p. 607 afford a satisfactory elucidation of the chemical properties of the pinic resinous exudations. They all, according to that chemist, are mixtures of the same amorphous resin, C₄₄H₆₂O₄, with essential oils of the composition C₁₀H₁₆. These terebinthinous juices are collected and sold either in their natural state as _turpentine_, or deprived more or less completely of their volatile oil, in which condition they are represented by _Burgundy Pitch_, and finally by _rosin_ or _colophony_.

The turpentines flowing down the stems of the trees gradually lose their transparency if allowed to dry slowly in the air, becoming at the same time harder and somewhat granular. This alteration is due to the incorporation of water, which at last is not only mixed with the components of the resinous juice, but to some extent combines chemically with the resin so as to transform it into a crystalline body having the characters of an acid. The fact is easily observed if clear drops of the turpentine of _Pinus silvestris_, _P. Abies_ or _P. Picea_ are collected in vials and kept perfectly dry. Thus treated these turpentines remain transparent, but the addition of water causes after a short time the formation of microscopic crystals of abietic acid, rendering them more or less opaque.

If turpentines are collected before they lose their essential oil by evaporation and oxidation, and before they have become crystalline, they can be retained perfectly transparent by distilling off the volatile oil without water. The distillation being most commonly carried on _with water_, the remaining resin is opaque.

Maly is of opinion that the same amorphous resin occurs in all the _Coniferæ_, and that it yields by hydration the same acid, namely _Abietic_, which has been described by former chemists as _Pinic_, _Silvic_, and _Pimaric_ acids, all of which indeed are admitted to have the same composition. We must however remember that several sorts of turpentine, as Canada Balsam, appear incapable, according to our experiments, of yielding any crystalline resinoid compound whatever; and that their amorphous resin being but partially soluble is certainly not a homogeneous substance.

The crystals as formed naturally in the common turpentines do not exhibit precisely the same forms as those obtained artificially when the resins are agitated with warm diluted alcohol, as in the preparation of abietic acid. As to _Pimaric Acid_, we have prepared it in quantity from _galipot_, the resin of _Pinus Pinaster_, but have always found its crystalline character entirely different from that of abietic acid.[2311]

[2311] _Jahresbericht_ of Wiggers and Husemann for 1867. 37.

We are inclined, therefore, to think that the composition of the resins of _Coniferæ_ is not so uniform as Maly suggests. The remarkable variety of their essential oils is a fact which seems in favour of our view.

=Uses=—Burgundy pitch is prescribed as an ingredient of plasters, and thus employed is useful as a mild stimulant. In Germany it has some economic applications, one of which is the lining of beer casks, for which purpose a composition is used called _Brauerpech_ (brewers’ pitch), made by mixing it with colophony or _galipot_.

=Adulteration=—No drug is the subject of more adulteration than Burgundy pitch, so much so that the very name is understood by some pharmacologists to be that of a manufactured compound. The substance commonly sold in England is made by melting together colophony with palm oil or some other fat, water being stirred in to render the mixture opaque. In appearance it is very variable, different samples presenting different shades of bright or dull yellow or yellowish-brown. Many when broken exhibit numerous cavities containing air or water; all are more or less opaque, becoming in time transparent on the surface by the loss of water. Artificial Burgundy pitch is offered for sale in bladders; it has a weak terebinthinous odour, and is devoid of the peculiar fragrance of the genuine. The presence of a fatty oil is easily discovered by treatment with double its weight of glacial acetic acid, which forms a turbid mixture, separating by repose into two layers, the upper being oily.

PIX LIQUIDA.

_Wood-Tar_; F. _Goudron végétal_, _Poix liquide_; G. _Holztheer_, _Fichtentheer_.

=Botanical Origin=—Tar is obtained by submitting the wood of the stems and roots of coniferous trees to dry or destructive distillation. That found in commerce is produced in Northern Europe, chiefly from two species, namely _Pinus silvestris_ L. and _P. Ledebourii_ Endl. (_Larix sibirica_ Ledeb.). These trees constitute the vast forests of Arctic Europe and Asia.

=History=—Theophrastus gives a circumstantial description of the preparation of tar, which applies with considerable accuracy to the processes still practised in those districts where no improved methods of manufacture have yet been introduced.

=Production=—The great bulk of the vegetable tar used in Europe, and known in commerce as _Archangel_ or _Stockholm Tar_, is prepared in Finland, Central and Northern Russia, and Sweden.

The process is conducted in the following manner:—vast stacks of pine wood consisting chiefly of the roots and lower portions of the trunks (the more valuable parts of the trees being used as timber), and containing as much as 30,000 to 70,000 cubic feet, are carefully packed together, and then covered with a thick layer of turf, moss, and earth, beaten down with heavy stampers. The whole stack of billets is constructed over a conical or funnel-like cavity made in the ground, if possible on the side of a hill, this arrangement being adopted for the purpose of carrying on a downward distillation. Fire being applied the combustion of the mass of wood has to be carried on very slowly and without flame in order to obtain the due amount of tar and a charcoal of good quality. During its progress the products, chiefly tar, collect in the funnel-like cavity, from which they are discharged by a tube into a cast-iron pan placed beneath the stack, or simply into hollow tree trunks. The time required for combustion varies from one to four weeks, according to the size of the stack.

During the last few years this rude process has been improved and accelerated by the introduction of rationally constructed wrought-iron stills, furnished with refrigerating condensers, as proposed in Russia by Hessel in 1861. By this mode of manufacture the yield in tar of pine wood is about 14 per cent. from stems, dried by exposure to the open air; and 16 to 20 per cent. from roots. Large quantities of pyroligneous acid and oil of turpentine are at the same time secured. The wood of the beech and of other non-coniferous trees appears not to afford more than 10 per cent. of tar, while turf yields only from 3 to 9 per cent.

=Description=—The numerous empyreumatic products which result from the destructive distillation of pine wood, and which we call tar, constitute a dark brown or blackish semi-liquid substance, of peculiar odour and sharp taste. When deprived of water and seen in thin layers, tar is perfectly transparent. The magnifying glass shows some of the varieties to contain colourless crystals of _Pyrocatechin_, scattered throughout the dark viscid substance, and to these tar owes its occasionally granular, honey-like consistence.[2312] A gentle heat causes them to melt and mix with the other constituents.

[2312] _Jahresbericht_ of Wiggers and Husemann for 1867. 37.

True vegetable tar has always a decidedly acid reaction. It is readily miscible with alcohol, glacial acetic acid, ether, fixed and volatile oils, chloroform, benzol, amylic alcohol or acetone. It is soluble in caustic alkaline solutions, but not in pure water or watery liquids. The sp. gr. of tar from the roots of conifers is about 1·06 (Hessel) yet at a somewhat elevated temperature, it becomes lighter than warm water.

Water agitated with tar acquires a light yellowish tint, and the taste and odour of tar, as well as an acid reaction. On evaporation the solution becomes brown, and at last microscopic crystals are obtained with a brown residue like tar itself, which is no longer soluble in water. A microscopical examination of tar which has been exhausted with water, shows that all crystals have disappeared.

=Chemical Composition=—Dry wood may be heated to about 150° C. without decomposition; but at a more elevated temperature, it commences to undergo a change, yielding a large number of products, the nature and comparative quantity of which depend upon circumstances. If the process is carried on in a closed vessel, a residue will be got which has more or less resemblance to coal. By heating fir-wood enclosed with some water to 400° C., Daubrée (1857) obtained a coal-like substance, which yielded by a subsequent increase of temperature scarcely any volatile products.

The results are widely different if a process is followed which permits the formation of volatile bodies; and these substances are formed in largest proportion, if the heat acts quickly and intensely. At lower degrees of heat, more charcoal results and more water is evolved.

Among the volatile products of destructive distillation, those alone which are condensed at the ordinary temperature of the air are of pharmaceutical interest; and of these, chiefly the portion not soluble in water, or that which is called _Tar_ or _Liquid Pitch_. The aqueous portion of the products consist principally of empyreumatic acetic acid, to which tar owes its acid reaction.

The tissue of wood is chiefly formed of cellulose, intimately combined with a saccharine substance, which may be separated if the wood is boiled with dilute acids. The remaining cellulose is however not yet pure, but is still united to a substance which, as shown by Erdmann,[2313] is capable of yielding pyrocatechin.

[2313] Liebig, _Annalen der Chemie u. Pharmacie_, Suppl. v. (1867) 229.

It is well known that sugar subjected to an elevated temperature, yields a series of pyrogenous products; and the same fact is observed if purified cellulose is heated in similar manner. But for tar-making, wood is preferred which is impregnated with resins and essential oils, and these latter furnish another series of empyreumatic products. From these circumstances, the components of wood-tar are of an extremely complicated character, which is still more the case when other woods than those of conifers form part of the material submitted to distillation. In the case of beech-wood, _Creasote_ is formed, which is obtained only in very small quantity from the _Coniferæ_. Volatile alkaloids and carbolic acid, which are largely produced in the destructive distillation of coal, appear not to be present in wood-tar.

The components of the latter may be considered under two heads:—first, the _lighter aqueous portion_, which separates from the other products of distillation, forming what is called _Impure Pyroligneous Acid_. This contains chiefly acetic acid and _Methyl Alcohol_ or _Wood Naphtha_, CH₄O; _Acetone_, C₃H₆O; besides other liquid products abundantly soluble in water and acetic acid. In this portion, some pyrocatechin also occurs.

The second class of pyrogenous products of wood consists of a homologous series of liquid hydrocarbons, sparingly soluble in water, and which therefore are chiefly retained in the heavy layer below the pyroligneous acid, forming the proper wood-tar. The liquid in question furnishes _Toluol_ or _Toluene_, C₇H₈ (boiling point 114° C.), _Xylole_ C₈H₁₀, and several other analogous substances.

If tar is redistilled, an elevated temperature being used towards the end of the process, some crystallizable solid bodies are obtained, the most important of which is that called _Paraffin_, having the formula CₙH₍₂ₙ₊₂₎, _n_ varying from 20 to 24.

The crystals already mentioned as occurring in tar are _Pyrocatechin_. They are easily sublimed at some degrees above their fusing point (104° C.), or removed by acetic acid, in which as well as in water they are readily soluble. Hence in some sorts of tar this substance does not occur, it having probably been removed by water.

Pyrocatechin, C₆H₄(OH)₂, can be obtained by the destructive distillation of many other substances, as catechu, kino, the extracts of rhatany and bearberry leaves, and other extracts rich in that form of tannin which produces _greenish_ (not _blue-black_) precipitates in salts of iron. It is extracted from the granular sorts of wood-tar, by exposing them at a proper temperature to a current of heated dry air, or by exhausting them with water. Ether when shaken with the concentrated aqueous solution and left to evaporate, leaves colourless crystals of pyrocatechin which after purification are devoid of acid reaction. They have a peculiar burning persistent taste, and are very pungent and irritating when allowed to evaporate. A solution of pyrocatechin yields with perchloride of iron a dark green coloration changing to black after a few moments, and becoming red on the addition of potash. This mixture finally acquires a magnificent violet hue, like a solution of alkaline permanganate. No alteration is produced in a solution of pyrocatechin by protosalts of iron.

Among the few medicinal preparations of tar, is _Tar Water_, called _Aqua vel Liquor Picis_, made by agitating wood-tar with water. The presence in it of pyrocatechin is easily proved by the above-mentioned reactions, or by a few drops of red chromate of potassium, which produces a brownish black colouration. It may hence be inferred that pyrocatechin is perhaps the active ingredient in tar-water, and that for making this liquid the granular, crystalline sorts of tar should be preferred.[2314]

=Commerce=—Tar as well as pitch is manufactured in Finland, and shipped from various ports in the Gulf of Bothnia, as Uleaborg, Gamla Carleby, Jacobstad, Ny Carleby and Christinestad; also from Archangel and Onega on the White Sea. Some tar is also produced in Volhynia, and finds its way by the Dnieper to the Black Sea.

The North of Sweden likewise produces tar, chiefly about Umea and Lulea, the distillation being now performed in well-constructed apparatus of iron.

The pine forests of North America afford tar and pitch. Wilmington in North Carolina exported in 1871, 25,260 barrels of tar, and 3788 barrels of pitch.[2315]

[2314] We may suppose that the authors of the French _Codex_ were not of this opinion, inasmuch as in making _Eau de Goudron_, they order that the liquid obtained by the first maceration of the tar, shall be thrown away.

[2315] Consul Walker, _Report on the Trade of North and South Carolina—Consular Reports_ presented to Parliament, May, 1872.

The imports of tar into the United Kingdom in 1872, were 189,291 barrels, valued at £218,339. Of this quantity 145,483 barrels were shipped from the northern ports of Russia.

The barrels in which tar arrives hold about 30 gallons. Smaller sized vessels termed _half-barrels_ are also used, though less frequently.

=Uses=—In medicine of no great importance: an ointment of tar is a common remedy in cutaneous diseases, and tar water is sometimes taken internally. The consumption of tar in shipbuilding and for the preservation of fences, sufficiently explains the large importations.

Other Varieties of Tar.

_Juniper Tar_, _Pyroleum Oxycedri_, _Oleum Juniperi empyreumaticum_, _Oleum Cadinum_, _Huile de Cade_.—This is a tar originally obtained by the destructive distillation of the wood of the _Cade_, _Juniperus Oxycedrus_ L., a shrub or small tree, native of the countries bordering the Mediterranean. It was for centuries used in the South of France as an external remedy, chiefly for domestic animals, but had fallen into complete oblivion until ten years ago, when it began to be prescribed in skin complaints.

The _Huile de Cade_ now in use, is transparent and devoid of crystals. It is somewhat thinner than Swedish tar, but closely agrees with it in other respects. It is imported from the Continent, but where made and from what wood we know not. _Huile de Cade_ is mentioned by Olivier de Serres,[2316] a celebrated French writer on agriculture of the 16th century; it is named by Parkinson[2317] in 1640; also by Pomet,[2318] in whose time (1694) it was rarely genuine, common tar being sold in its place.

[2316] _Théâtre d’Agriculture_, Paris, 1600. 941.

[2317] _Theatrum Botanicum_, 1033.

[2318] _Hist. des Drogues_, Paris, 1694. part i. chap. xii. xiv.

_Beech Tar_—Tar is also manufactured from the wood of the beech, _Fagus silvatica_ L., and has a place in some pharmacopœias as the best source of creasote.

_Birch Tar_—is made to a small extent in Russia, where it is called _Dagget_, from the wood of _Betula alba_ L. It contains an abundance of pyrocatechin, and is esteemed on account of its peculiar odour well known in the Russia leather. A purified oil of birch tar is sold by the Leipzig distillers.

PIX NIGRA.

_Pix sicca vel solida vel navalis_; _Pitch_, _Black Pitch_; F. _Poix noire_; G. _Schiffspech_, _Schusterpech_, _Schwarzes Pech_.

=Botanical Origin=—see _Pix liquida_.

=Production=—When the crude products of the dry distillation of pine wood, as described in the previous article, are submitted to re-distillation, the following results are obtained. The first 10 to 15 per cent. of volatile matter consists chiefly of methylic alcohol and acetone. A higher temperature causes the vaporization of the acetic acid, while the still retains the tar. This last, subjected to a further distillation, may be separated into a liquid portion called _Oil of Tar_ (_Oleum Picis liquidæ_), and a residuum which, on cooling, hardens and forms the product under notice, namely _Black Pitch_. Again heated to a very elevated temperature, it is capable of yielding paraffin, anthracene and naphthalene.

=Description=—Pitch is an opaque-looking, black substance, breaking with a shining conchoidal fracture, the fragments showing at the thin translucent edges a brownish colour. No trace of distinct crystallization is observable when very thin fragments are examined, even by polarized light. Pitch has a peculiar disagreeable odour, rather different from that of tar. Its alcoholic solution has a feeble taste somewhat like that of tar, but pitch itself when masticated is almost tasteless. It softens by the warmth of the hand, and may then be kneaded. It readily dissolves in those liquids which are solvents of tar. Alcohol of 75 per cent. acts freely on it, leaving behind in small proportion a dark viscid residue. The brown solution reddens litmus paper, and yields a dingy brownish precipitate with perchloride of iron, and whitish precipitates with alcoholic solution of neutral acetate of lead, or with pure water. Pitch dissolves in solution of caustic potash, evolving an offensive odour.

=Chemical Composition=—From the method in which pitch is prepared, we may infer that it contains some of the less volatile and less crystallizable compounds found in tar. Ekstrand (1875) extracted from it _Retene_, C₁₈H₁₈, a colourless, inodorous crystalline substance, melting at 90° C.

The pitch of beech-wood boiled with a caustic alkali, yields a fœtid volatile oil; when this solution is acidulated, fatty volatile acids are evolved. These principles however have not yet been isolated either from the pitch of pine or beech. The whitish compound formed by acetate of lead in an alcoholic solution of pitch deserves investigation, and perhaps might be the starting point for acquiring a better knowledge of the chemistry of this substance.

=Commerce=—The same countries that produce tar produce also pitch. The quantity of the latter imported into the United Kingdom during 1872 was 35,482 cwt., four-fifths of which were supplied by Russia. Pitch is also manufactured from tar in Great Britain.

=Uses=—Pitch is occasionally administered in the form of pills, or externally as an ointment; but its medicinal properties are, to say the least, very questionable.

FRUCTUS JUNIPERI.

_Baccæ Galbuli Juniperi_; _Juniper Berries_; F. _Baies de Genièvre_; G. _Wacholderbeeren_, _Kaddigbeeren_.

=Botanical Origin=—_Juniperis communis_ L., a diœcious evergreen, occurring in Europe from the Mediterranean to the Arctic regions, throughout Russian Asia as far as Sachalin, and in the north-western Himalaya, where it is ascending in Kashmir at 5400 feet, in Lahoul to 12,500, on the upper Biās and in Gurhwal to 14,000 feet. It abounds in the islands of Newfoundland, Saint Pierre, and Miquelon, and is also found in Continental North America. Dispersed over this vast area the Common Juniper presents several varieties. In England and in the greater part of Europe it forms a bushy shrub from 2 to 6 feet high, but in the interior of Norway and Sweden it becomes a small forest tree of 30 to 36 feet, often attaining an age of hundreds of years.[2319] In high mountain regions of temperate Europe and in Arctic countries it assumes a decumbent habit (_Juniperus nana_ Willd.), rising only a few inches above the soil.

=History=—The fruits of Juniper, though by no means exclusively those of _J. communis_, were commonly used in medicine by the Greek and Roman as well as by the Arabian physicians; they had a place among the drugs of the Welsh “physicians of Myddvai” (see Appendix), and are mentioned in some of the earliest printed herbals. The oil was distilled by Schnellenberg[2320] as early as 1546.

Popular uses were formerly assigned in various parts of Europe to Juniper berries. They were employed as a spice to food;[2321] and a spirit, of which wormwood was an ingredient, was obtained from them by fermentation and distillation. The spirit called in French _Genièvre_ became known in English as _Geneva_, a name subsequently contracted into _Gin_.[2322]

[2319] Schübeler, _Culturpflanzen Norwegens_, Christiania, 1873-1875. 140, with fig.

[2320] _Artsneybuch_, Königsberg, 1556. 35.

[2321] Valmont de Bomare, _Dict. d’Hist. nat._ ii. (1775) 45.

[2322] The gin distilled in Holland is flavoured with Juniper berries, yet, as we are told, but very slightly, only 2 lb. being used to 100 gallons.

=Description=—The flowers form minute axillary catkins; those of the female plant consist of 3 to 5 whorls of imbricated bracts. Of these the uppermost three soon become fleshy and scale-like, and alternate with three upright ovules having an open pore at the apex. After the flowers have faded these three fleshy bracts grow together to form a berry-like fruit termed a _galbulus_, which encloses three seeds. The three points and sutures of the fruit-scales are conspicuous in the upper part of the young fruit; but after maturity the sutures alone are visible, forming a depressed mark at its summit. A small point, surrounded by two or three trios of minute bracts, indicates the base of the fruit.

This fruit or pseudo-berry remains ovate and green during its first year, and it is not until the second autumn that it becomes ripe. It is then spherical, ³/₁₀ to ⁴/₁₀ of an inch in diameter, of a deep purplish colour, with a blue-grey bloom. Its internal structure may be thus described:—beneath the thin epicarp there is a loose yellowish-brown sarcocarp, enclosing large cavities, the oil-ducts; the three hard seeds lying close together, triangular and sharp-edged at the top, are attached to the sarcocarp at their outer sides, and only as far as the lower half. The upper half, which is free, is covered by a thin membrane. In the longitudinal furrows of the hard testa towards the lower half of the seed are small prominent sacs growing out into the sarcocarp. Each seed bears on its inner side 1 or 2, and on its convex outer surface 4 to 8 of these sacs, which in old fruits contain the resinified oil in an amorphous colourless state.

Juniper berries when crushed have an aromatic odour, and a spicy, sweetish, terebinthinous taste.

=Microscopic Structure=—The outer layer of the fruit consists of a colourless transparent cuticle, which covers a few rows of large cubic or tabular cells having thick, brown, porous walls. These cells contain a dark granular substance and masses of resin. The sarcocarp, which in the ripe state consists of large, elliptic, thin-walled, loosely coherent cells, contains chlorophyll, drops of essential oil, and a crystalline substance soluble in alcohol,—no doubt a stearoptene. Before maturity it likewise contains starch granules and large oil-cells. This tissue is traversed by very small vascular bundles containing annulated and dotted vessels.

=Chemical Composition=—The most important constituent of juniper berries is the volatile oil, obtainable to the extent of 0·4 to 1·2 per cent. The latter amount is obtained from Hungarian, 0·7 per cent. from German fruits.[2323] It is a mixture of levogyre oils, the one of which having the composition C₁₀H₁₆ boils at 155° C.; the prevailing portion of the oil, boiling at about 200°, consists of hydrocarbons, which are polymeric with terpene, C₁₀H₁₆. The crude oil as distilled by us deviated 3°·5 to the left in a column of 50 mm.

[2323] According to Messrs. Schimmel & Co. (see p. 306, note 2.)

By passing nitrosyl chloride gas, NOCl, into it, Tilden (1877) obtained from the portion boiling below 160° the crystallized compound C₁₀H₁₆(NOCl), which is yielded by all the terpenes.

Another important constituent of juniper berries is the glucose, of which Trommsdorff (1822) obtained 33 per cent., while Donath (1873) found 41·9, and Ritthausen (1877) not more than 16 per cent. in the berries deprived of water. Of albuminoid substances about 5 per cent. are present, of inorganic matters 3 to 4 per cent. The fruit, moreover, contains also according to Donath small amounts of formic, acetic, and malic acids, besides resin.

=Collection and Commerce=—Juniper berries are largely collected in Savoy, and in the departments of the Doubs and Jura in France, whence they find their way to the hands of the Geneva druggists. They are also gathered in Austria, the South of France and Italy. In Hamburg price-currents they are quoted as _German_ and _Italian_. The largest supplies are apparently furnished by Hungaria.

=Uses=—The berries and the essential oil obtained from them are reputed diuretic, yet are not often prescribed in English medicine.

HERBA SABINÆ.

_Cacumina vel Summitates Sabinæ_; _Savin or Savine_; F. _Sabine_; G. _Sevenkraut_.

=Botanical Origin=—_Juniperus Sabina_ L., a woody evergreen shrub, usually of small size and low-growing, spreading habit, but in some localities erect and arborescent.

It occurs in the Southern Alps of Austria (Tirol) and Switzerland (Visp or Viège and Stalden in the Valais, also in Grisons and Vaud), and in the adjacent mountains of France and Piedmont, ascending to elevations of 4,000 to 5,000 feet. It is also found in the Pyrenees, Central Spain, Italy and the Crimea; likewise in the Caucasus, where it reaches 12,000 feet above the sea-level. Eastward it extends to the Elburs range, south of the Caspian, and throughout Southern Siberia, where it ascends in the Balkhasch and Alatau mountains to 8,600 feet. In North America it has been gathered on the banks of the river Saskatchewan, at Lake Huron, in Newfoundland, and in Saint Pierre and Miquelon. There are, however, a few very closely allied species which may occasionally have been confounded with savin.

=History=—Savin is mentioned as a veterinary drug by Marcus Porcius Cato,[2324] a Roman writer on husbandry who flourished in the second century B.C.; and it was well known to Dioscorides (under the name of βρἀθυ) and Pliny. The plant, which is frequently named in the early English leech-books written before the Norman Conquest,[2325] may probably have been introduced into Britain by the Romans. Charlemagne, A.D. 812, ordered that it should be cultivated on the imperial farms of Central Europe. Its virtues as a stimulating application to wounds and ulcers are noticed in the verses of Macer Floridus,[2326] composed in the 10th century.

=Description=—The medicinal part of savin is the young and tender green shoots, stripped from the more woody twigs and branches. These are clothed with minute scale-like rhomboid leaves, arranged alternately in opposite pairs. On the younger twigs they are closely adpressed, thick, concave, rounded on the back, in the middle of which is a conspicuous depressed oil gland. As the shoots grow older the leaves become more pointed and divergent from the stem. Savin evolves, when rubbed or bruised, a strong and not disagreeable odour. The blackish fruit or _galbulus_ resembling a small berry, ²/₁₀ of an inch in diameter, grows on a short recurved stalk, and is covered with a blue bloom. It is globular, dry, but abounding in essential oil, and contains 1 to 4 little bony nuts.

To mycologists, _Juniperus Sabina_, at least in the cultivated state, is interesting on account of the parasitic fungus _Podisoma fuscum_ Duby, the mycelium of which produces, on the leaves of the pear-trees, the so-called _Roestelia cancellata_ Rebentisch.

=Chemistry=—The odour of savin is due to an essential oil, of which the fresh tops afford 2 to 4 per cent., and the berries about 10 per cent. Examined in a column 50 millimetres long it was found to deviate the ray of polarized light 27° to the right, the oil used having been distilled by one of us in London from the fresh plant cultivated at Mitcham. The same result was obtained from the oil abstracted ten years previously from savin collected wild on the Alps of the Canton de Vaud, Switzerland. We find that, by the prolonged action of the air, if the oil is kept in a vessel not carefully closed, the rotatory power after the lapse of years is greatly reduced. Savin oil, according to Tilden (1877), yields a small amount of an oil boiling at 160°, which answers to the formula C₁₀H₁₆O. The greater part of the oil was found by that chemist to boil above 200° C. Tilden asserts that no terpene is present in the oil of savin; we have not been able to obtain from it a crystallized hydrochloride. Savin tops contain traces of tannic matter.

[2324] Cap. lxx. (_Bubus medicamentum_).

[2325] Cockayne, _Leechdoms, etc., of Early England_, ii. (1865) xii.

[2326] Choulant, _Macer Floridus de viribus herbarum_, Lipsiæ, 1832. 48.... “Duplum si desunt _cinnama_ poni in medicamentis iubet _Oribasius_ auctor.”

=Uses=—Savin is a powerful uterine stimulant, producing in overdoses very serious effects. It is but rarely administered internally. An ointment of savin, which from the chlorophyll it contains is of a fine green colour, is used as a stimulating dressing for blisters.

=Substitutes=—There are several species of juniper which have a considerable resemblance to savin; and one of them, commonly grown in gardens and shrubberies, is sometimes mistaken for it. This is _Juniperus virginiana_ L., the _Red Cedar_ or _Savin_ of North America. In its native country it is a tree, attaining a height of 50 feet or more, but in Britain it is seldom more than a large shrub, of loose spreading growth, very different from the low, compact habit of savin.[2327] The foliage is of two sorts, consisting either of minute, scale-like, rhomboid leaves like those of savin, more rarely of elongated, sharp, divergent leaves a quarter of an inch in length, resembling those of common Juniper. Both forms often occur on the same branch. The plant is much less rich in essential oil than true savin,[2328] for which it is sometimes substituted in the United States.

The foliage of _Juniperus phœnicea_ L., a Mediterranean species, has some resemblance to savin for which it is said to be sometimes substituted,[2329] but it is quite destitute of the peculiar odour of the latter. The specific name of the former alludes to its _red_ fruit, from ϕοινίκιος, purple.

[2327] We have examined numerous herbarium specimens (wild) of _J. virginiana_ and _J. Sabina_, but except difference of stature and habit, can observe scarcely any characters for separating them as species. The fruit-stalk in _J. virginiana_ is often pendulous as in _J. Sabina_. Each plant has two forms,—arboreous and fruticose.

[2328] This we ascertained by distilling under precisely similar conditions 6 lbs. 6 oz. of the fresh shoots of each of the two plants, _Juniperus Sabina_ and _J. virginiana_: the first gave 9 drachms of essential oil, the second only ½ a drachm. The latter was of a distinct and more feeble odour, and a different dextrogyre power. In America the oil of _J. virginiana_ is known as “_Cedar Oil_,” and used as a taenifuge. It contains a crystallizable oxygenated portion. This oil however is afforded by the wood. Red Cedar wood from Florida is stated by Messrs. Schimmel & Co. (see p. 306) to afford as much as 4 to 5 per cent. of that oil.

[2329] _Bonplandia_, x. (1862) 55.

_Monocotyledons._

CANNACEÆ.

AMYLUM MARANTÆ.

_Arrowroot._