Conanga oil is a poorer quality of ylang-ylang oil, obtained from the same plant. Two varieties are distinguished in commerce, viz: the Javanese and Indian. The Java oil is the best, and may be used where ordinary qualities of ylang-ylang oil will do. According to Schimmel & Co.'s report the cheaper Indian oil is very resistant and durable in soaps, especially when combined with licari or linaloë oil.
[CHAPTER V.]
RESINS AND BALSAMS.
The term resins is applied to certain organic substances which are very closely related to volatile oils, in so far as many of them are formed from the latter by oxidation. As previously mentioned, by exposure to the atmospheric air all volatile oils undergo a change, whereby they thicken and are finally converted into substances possessing the character of resins. In nature most resins also occur mixed with volatile oils.
The elementary constituents of resins are carbon, hydrogen, and oxygen; but, generally speaking, they are poor in oxygen and rich in carbon. Chemically they behave like weak acids, their solutions frequently reddening litmus and sometimes expelling, on boiling, the carbonic acid from alkaline carbonates.
Independent of a possible content of volatile oil, every naturally occurring resin consists of several resins which, however, can, as a rule, be separated only with difficulty.
The resins are generally divided into hard resins, soft resins or balsams, and gum-resins. The hard resins are, at the ordinary temperature, solid, hard, and brittle, can be readily pulverized, and contain little or no volatile oil. The soft resins or balsams are kneadable, and sometimes even semi-fluid; they represent solutions of resins in volatile oils, or a mixture of volatile oil and resin. On exposure to the air they are changed by the volatile oil suffering oxidation, they becoming then more or less hard, and may be converted into actual resins. The gum-resins are mixtures of vegetable gum, resin, and volatile oils, and are obtained by inspissation of the milky juice of several plants. When triturated with water they yield a milky, turbid fluid, and dissolve only partially in alcohol.
The resins are widely diffused in the vegetable kingdom, there being scarcely a plant which does not contain resin in one form or another. Some families of plants and organs of plants are, however, distinguished by their special wealth of resins. The resins are, as a rule, secreted simultaneously with volatile oils in special reservoirs, from which they flow out naturally at certain periods, or are obtained by incisions made in the plants. A few bodies of the character of resins also occur in the animal kingdom, and a series of them, the fossil resins, are generally classed in the mineral kingdom, though most of them are very likely derived from plants. Some resins, such as the aldehyde resins, etc., are purely artificial products.