9 



which may be solitary or in clusters, and a four-sided capsular fruit, 

 which is closely enveloped in a hard woody calyx-tube. Oq young 

 plants the leaves are opposite, ovate, cordate at the base, sessile, and 

 their surfaces are parallel with the ground ; but in the case of older 

 plants, and especially at the upper parts of the trees, the leaves are 

 longer, stalked, and scimitar-shaped, whilst a twist in the petiole causes 

 the surfaces to be at right angles to the ground. Both forms are used 

 in distilling the oil, but the dried leaves are of the second form only ; 

 they are thick, glabrous, leathery, with an entire, somewhat thickened 

 margin. The presence of numerous oil glands, situated in the mesD- 

 phyll and easily seen on examining a leaf with a lens whilst held up to 

 a strong light, gives the leaves a distinctly punctate appearance ; the 

 surfaces are also frequently marked with a number of minute, warty, 

 brown spots, which consist of groups of cork cells. The leaves contain 

 when fresh, from 3 to 5 per cent, of volatile oil, together with tannin 

 and a bitter principle. The oil is obtained from the fresh leaves by 

 distillation and possesses powerful antiseptic, deodorising and anti- 

 pyretic properties, the official dose is from 0*5 to 3 minims, and the 

 oil is used in the preparation of Unguentum Eucalypti. 



Characters and Jests — Oil of Eucalyptus (s.g. 0*910 to 0*930) should 

 be col mrless or pale yellow, with an aromatic camphoraceous odour, 

 and a pungent taste which is followed by a sensation of coldness in the 

 mouth ; the characteristic taste and odour are due to the cineol (eucalyptol) 

 present, and a high percentage of that body is insured by the limita- 

 tion of the specific gravity of the oil, as also by the optical activity of the 

 oil beinglimited to 10 degrees in either direction. Tne presence of a due 

 proportion of cineol is further provided by the requirement that the oil 

 should become semi-solid on being stirred, when cold, with one-third 

 or one-half its volume of phosphoric acid (s.g. 1*750) ; the cineol com- 

 bines with the acid to form a crystalline compound from which it is 

 liberated in the pure state on adding hot warer. The nitric reaction 

 serves to guard against the presence of more than small quantities of 

 phellandrene, which constitutes the chief constituent of certain Euca- 

 lyptus oils ; thus, if to 1 c.c. of an oil containing but little phellan- 

 drene, 2 c.c. of glacial acetic acid, and 2 c.c. of a saturated aqueous 

 solution of sodium nitrate be added, the mixture will remain liquid 

 when gently stirred, but the presence of mac i phellandrene will cause 

 the formation of a crystalline mass. The oil is soluble in all propor- 

 tions of absolute alcohol, in one third its volume of 9 J p^r cent, alcohol 

 and in 38 parts of 60 per cent, alcohol. 



Notes. — The distinctive characters of oil of Eucalyptus are its odour, 

 taste and specific gravity. It contains about 50 per cent, of cineol 

 v(eucalyptol), a body which also occurs in the oils of cajaput, worm seed, 

 spike lavender etc., and can be produced by treating terpin hydrate 

 with dilute acids. Cineol is an optically inactive, nearly colourless 

 liquid (s.g. 0*930) with a strong, aromatic, camphoraceous odour, and 

 a pungent, spicy, aud cooling taste; it has a refractive index of 1*4559, 

 solidifies at low temperatures, melts at — 1°, boils at 176° and forms a 

 crystalline phosphate when treated with phosphoric acid. Other consti- 

 tuents of oil of Eucalyptus are pinene and various aldehydes and alco- 

 hols. Phellandrene should not be present in any appreciable quantity, 

 .the oil of E. amyydalina and other species being thus excluded. 



