To test the value of oil of cloves, introduce, according to Stohman, into a graduated glass cylinder 10 volumes ether, 10 oil of cloves, and 30 of a 10-per cent. soda solution. After vigorous shaking, the eugenol dissolves; the increase in volume of the aqueous fluid is then proportional to the quantity of eugenol present. For more exact determinations, dissolve a weighed quantity of oil, repeatedly shake the aqueous fluid with ether to remove the terpene, then decompose the eugenol-sodium with dilute sulphuric acid, dissolve the separated eugenol in ether and weigh after evaporating the ethereal fluid. Good oil of cloves does not contain less than 80 per cent. of eugenol, and frequently 90 per cent. or more. Oil of cloves is chiefly adulterated with copaiba oil and cedar oil. Such adulteration is recognized by the oil not forming a clear solution in every proportion with alcohol, as is the case with pure oil of cloves. Oil of cloves is much used for perfuming purposes. _Eucalyptus oil_ (_oleum eucalypti_) is obtained from the leaves of various trees of the eucalyptus family. According to Merk two kinds of oil must be strictly kept apart: _oleum eucalypti_ from the leaves of _eucalyptus globulus_ and _oleum eucalypti australe_, the former being used in medicine, and the latter, which is considerably cheaper, chiefly for perfuming purposes. However, Piesse's opinion that eucalyptus oil, as far as its odor is concerned, does not deserve to be classed among perfumes is undoubtedly correct. It has an odor between that of oil of turpentine and cajeput oil, and as long as perfumery is the art of sweet odors, such oil cannot be designated a perfume. When not rectified, eucalyptus oil is mostly yellowish or bluish. In a rectified state it is colorless, clear, limpid, lighter than water, of a strong odor, and acrid taste. The oil from _eucalyptus globulus_ has a specific gravity of 0.900 to 0.925, and dissolves in every proportion in 90 per cent. alcohol. It is optically inactive or turns the plane of polarization slightly to the right. On standing with sodium it acquires a yellowish coloration, and does not detonate with iodine. The oil from _eucalyptus australe_ has a specific gravity of 0.86 to 0.87, and is but sparingly soluble in 90 per cent. alcohol, so that even a solution prepared in the proportion of 1:15 is turbid. It turns the plane of polarization strongly to the left; acquires, on standing with sodium, a red coloration, and detonates with iodine. Eucalyptus oil consists of eucalyptol and eucalyptene, and perhaps other hydrocarbons. The content of the first, on which depends the medicinal value of the oil, varies very much in the oils from the different species of eucalyptus, the oil from some species, it is said, containing no eucalyptol whatever.