Elements of Chemistry

Matricaria parthenium exerts a left-handed rotatory action upon a ray of polarized light (Chautard); whilst, according to Biot, the camphor deposited by oil of lavender is destitute of any such rotatory effect upon a polarized ray.

In the ordinary process of extracting camphor, the wood and branches of the camphor laurel are chopped up, and placed with water in a rude kind of still, the head of which is filled with rice straw. On the application of heat the camphor rises in vapour with the water, and is condensed in the straw. It is then submitted to a second sublimation, by which means it is obtained in the form of the crude, granular camphor of commerce. This article is subsequently refined in this country, by placing charges of 10 lb. or 12 lb. of the crude camphor in large globular glass flasks, furnished with a short wide neck: heat is applied to the bottom of these flasks by means of a sand bath; and as soon as the camphor is melted, a portion of lime is added to each flask, after which the heat is steadily maintained for forty-eight hours: during this period the camphor is slowly sublimed into the upper part of the flasks. When the operation is finished the flasks are cooled, and at the same time broken, by sprinkling them with cold water: the pure camphor can then be removed with facility. The produce of this operation assumes the form of white, tough, translucent masses. Camphor has a peculiar odour and an aromatic taste, at first hot, and afterwards cooling. It floats in water, and is sparingly soluble in this liquid; but is dissolved freely by alcohol, ether, acetic acid, and the essential oils. Although pure camphor is tough and difficult to pulverize, yet if moistened with a few drops of alcohol, it may be reduced to powder with facility. When particles of powdered camphor are thrown on the surface of water, free from grease, each fragment begins to be dissolved with a remarkable and rapid gyratory motion, which is instantly checked by allowing a drop of any essential oil to fall upon the surface of the water. Camphor is very inflammable, and burns with a white smoky flame. It becomes slowly volatilized at common temperatures; if kept in glass bottles it becomes gradually sublimed, and condensed in octohedral crystals on the side of the vessel which is coolest. If a coil of red-hot platinum wire be suspended just over a lump of camphor, the metal continues to glow, and produces a slow combustion of the camphor, which may be maintained so long as any portion remains unconsumed.

If camphor be heated under pressure with caustic potash, it combines with the alkali, a salt termed potassic campholate being formed :—

When camphor is distilled with phosphoric anhydride, or with dry zincic chloride, it undergoes decomposition, and is deprived of the elements of water, whilst cymol is formed :

2 10 14

(1426) Camphoric Acid (H2¤1H104); Fusing pt. 158° (70° C.). -Camphor, when heated with ten times its weight of concentrated nitric acid, is slowly oxidized, and becomes converted into camphoric acid. This substance is sparingly soluble in water, but is freely dissolved by alcohol, as well as by ether and the essential oils. It is deposited from its solutions in the form of prismatic needles, which have a very sour taste: they are destitute of odour. Camphoric acid is dibasic; it may be deprived of its basic water, and obtained in the form of anhydride by sublimation. A solution of camphoric acid produces a precipitate in a solution of normal acetate of lead.

It appears that three isomeric modifications of camphoric acid exist: the compound just described is characterized by its power of producing right-handed rotation of a ray of polarized light; but, according to Chautard, the camphoric acid obtained by treating the camphor of the Matricaria parthenium with nitric acid, exerts a left-handed rotatory action; and if concentrated alcoholic solutions of the right-handed and left-handed camphoric acids be mixed in equivalent proportions, the temperature rises several degrees, and a copious white crystalline deposit of paracamphoric acid is obtained, which like racemic acid, is destitute of any rotatory action upon the plane of polarization : paracamphoric acid differs somewhat in chemical properties from either of its two components, being less soluble in alcohol, ether, and water. A similar acid may be obtained by the oxidation of lavender camphor.

(1427) Borneo Camphor (Є10H18); Fusing pt. 388° (198° C.); Boiling pt. 413° (212° C.).—This substance differs from the preceding variety of camphor in containing 2 atoms more of hydrogen. It is less fusible and volatile than common camphor, but is denser and harder. It exerts a right-handed rotatory action upon polarized light, but its power in this respect is weaker than that of ordinary camphor, from which it can scarcely be distinguished in taste, smell, solubility, and general appearance.

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INDIFFERENT ESSENTIAL OILS CONTAINING OXYGEN.

It crystallizes in small, transparent, regular, colourless, six-sided prisms. If gently warmed with nitric acid of moderate strength, it loses 2 atoms of hydrogen, and is converted into ordinary camphor.

Borneo camphor occurs in the Dryobalanops, in combination with an oil (H16) termed borneène, which has the composition of ordinary oil of turpentine: the same hydrocarbon also occurs in the essential oil of valerian. In order to procure the camphor, punctures are made into the wood of the growing tree, and the oil which exudes is submitted to distillation: the borneène is volatilized, and an imperfect separation of the camphor and oil is thus effected. If borneène be repeatedly distilled with a solution of potash, it combines with the elements of an atom of water, and is converted into Borneo camphor. A similar conversion into the same camphor also occurs if the oil be dissolved in an equal bulk of an alcoholic solution of potash, and be left at rest in imperfectly closed vessels for a few days; on dilution with water, the camphor is separated. Borneo camphor, if mixed with phosphoric anhydride and distilled, loses an atom of water, and is reconverted into borneène.

Allusion has already been made to other camphors, such as

and so on. These compounds, however, are of little importance. (1428) (b) Indifferent essential Oils containing Oxygen.-The properties of many of these have been already mentioned when speaking of the hydrocarbons with which they are associated (1416—1423).

1. Oil of Lavender (Sp. gr. o'898).-The exact composition of this fragrant and well-known oil has not been accurately ascertained. It is soluble in concentrated acetic acid: when long kept it deposits a large proportion of laurel camphor.

2. Oil of Wormwood is isomeric with laurel camphor.

Besides these, there are a great variety of essences which contain oxygen, but which have been but imperfectly examined; such, for instance, as the oils of cajeput, dill, marjoram, pennyroyal, sage, sassafras, and many other plants.

(1429) (c) Aromatic Aldehyds.-The oils of bitter almonds, spiræa, cinnamon, and cumin are characterized by forming crystallized compounds with hydro-sodic sulphite, and, like the aldehyds of the series homologous with ordinary alcohol, they

OILS ANALOGOUS TO THE ALDEHYDS.

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exhibit a strong tendency to form acids by the absorption of one atom of oxygen. The oils of this class, however, differ from the ordinary aldehyds in the facility with which they allow the displacement of one atom of the hydrogen which they contain, by an atom of chlorine, of sulphur, of cyanogen, and of various electronegative elements. They have been regarded as hydrides of peculiar oxidized radicles; for example:

Oil of bitter almonds. €, H, O,H=Bz,H (Benzoyl hydride)
Oil of cumin .
€10H,H=Cu,H (Cumyl hydride)

When these aldehyds are heated with an alcoholic solution of potash they are not resinified like the aldehyds of the fatty acids, but yield the alcohol and a potassium salt of the acid of the series (Cannizzaro). Bitter almond oil, for example, furnishes the

alcohol of the benzoic series and benzoic acid :

Ammonia does not combine directly with these aldehyds, but causes a separation of water: three atoms of the oil react upon two of ammonia, furnishing a hydramide; as for example :—

3 €,H ̧→ + 2 H ̧N = (¤‚H ̧)′′ ̧Ñ2 + 3 H ̧Ð.

In describing these oils it will be convenient to consider their most important derivatives, which are very numerous, and embrace compounds many of which present several points of interest.

In this section the following compounds will be examined :

1. Essence of bitter almonds.-Benzoic series.-Hippuric acid.
2. Essence of cumin.-Cuminic series.

3. Essence of cinnamon.-Cinnamic series.-Coumarin.
4. Essence of spiræa.-Salicylic series.-Salicin.-Populin.
5. Essence of aniseed.-Anisic series.

1. Essence of Bitter Almonds.-Benzoic Series.

(1430) The essence of bitter almonds is the most important member of the group of oxidized essential oils. It formed the subject of a remarkable memoir by Liebig and Wöhler (Ann. de Chimie, II. li. 273), in which they first systematically applied the theory of compound radicles to substances of organic origin.

The publication of this paper exercised an immediate and extraordinary influence upon the study of organic chemistry, in which, indeed, it inaugurated a new era, and thus led to a series of brilliant discoveries, which followed in rapid succession.

The following compounds of the benzoic series will be briefly described, or the mode of their formation will be indicated :—