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See also:RESIN (through O.Fr. resine, See also:modern reline, from See also:Lat. resina, prcbably Latinized from See also:Greek Pirivrt, resin) , a secretion formed in See also:special See also:resin canals or passages of See also:plants, from many of which, such as, for example, coniferous trees, it exudes in soft tears, hardening into solid masses in the See also:air . Otherwise it may be obtained by making incisions in the bark or See also:wood of the secreting plant . It can also be extracted from almost all plants by treatment of the See also:tissue with See also:alcohol . Certain resins are obtained in a fossilized See also:condition, See also:amber being the most notable instance of this class; See also:African See also:copal and the kauri See also:gum of New See also:Zealand are also procured in a semi-fossil condition . The resins which are obtained as natural exudations are in See also:general mixtures of different, See also:peculiar acids, named the resin acids, which dissolve in alkalis to See also:form resin soaps, from which the resin acids are regenerated by treatment with acids . They are closely related to the See also:terpenes, with which they occur in plants and of which they are oxidation products . Examples of resin acids are abietic (sylvic) See also:acid, C,8H28O2, occurring incolophony, and pimaric acid, C2OH3002, a constituent of gallipot resin . Abietic acid can be extracted from colophony by means of hot alcohol; it crystallizes in leaflets, and on oxidation yields trimellitic, isophthalic and terebic acid . Pimaric acid closely resembles abietic acid into which it passes when distilled in a vacuum; it has been supposed to consist of three isomers . Resins when soft are known as oleo-resins, and when containing benzoic or cinnamic acid they are called balsams . Other resinous products are in their natural condition mixed with gum or mucilaginous substances and known as gum-resins . The general conception of a resin is a noncrystalline See also:body, insoluble in See also:water, mostly soluble in alcohol, essential See also:oils, See also:ether and hot fatty oils, softening and melting under the See also:influence of See also:heat, not capable of sublimation, and burning with a See also:bright but smoky See also:flame .
A typical resin is a transparent or translucent See also:mass, with a vitreous fracture and a faintly yellow or See also: |
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