Resins

either accompany terpenes crude e ential oils, or occur as exudations from hardening on exposure to the air. They are i orphous, mostly vitreous bodies, insoluble in water. 1 ey melt at a low heat, are non-volatile, and bum with a smoky flame. They are largely used in t preparation of varnishes, and several are employed Resins are divided into (i) true resins, Jmedicine. gum-resins, and oleo-resins or balsams. The made up chiefly of what are termed " resin acids," which, admixed with fatty acids, are capable of saponifying with alkalies, and yield " resin soaps; '' the gum-resins differ from the true resins only in containing some gum capable of softening in water; and the oleo-resins include the mixtures of e ential oils and resin of whatever consistency, and the mixtures of benzoic and cinnamic acid, and salts of these acids. This last cla is much the largest of the three. To the first cla belong the hard resins, which serve for the manufacture of varnishes, such as copal, dammar, mastic, sandarach, dragons'.blood, gum-lac, and amber; to the second cla , olibanum or frankincense, ammoniacum, asafetida, galbanum, and tragacanth; and to the third cla , crude turpentine, benzoin, storax, copaiba, Peru and Tolu balsams. The following table (Sadller's Industrial Organic Chemistry) gives the bromin absorption, the saponification equivalent, and the proportions of potash neutralized by the various resins. A cla ified table of the resins is also appended. R.-cell, a cell that secretes resin. R., Cera turn, Basilicon Ointment, resin 35, yellow wax 15, lard 50 parts. R., Common, Colophony, Rosin, the residue after the distillation of the volatile oil from turpentine. R.-duct. Same as R. -pa age. R., Emplastrum, Resin Plaster, Adhesive Plaster, resin 14, lead plaster 80, yellow wax 6 parts. R.-flux, a disease caused by the fungus Agaric us melleus, which attacks conifers, giving rise first to an exce ive flow of resin, and ultimately to the death of the tree. R.gland, a large cell, or a group of smaller cells, secreting resin. R. -pa age, an intercellular cavity formed by ma es of ti ue becoming separated from each other, and whose function it is to secrete resin. R.tube. Same as R. -pa age. R., Ung. (B. P.), used for the same purpose as the plaster or cerate. OF RESINS. I. Cop a line or Varnish Resins. African Copal. Black Dammar. Brazilian Copal. Dammar. East Indian Dammar. Gum Anime. Kaurie, or Coudie Resin. Lac. Mastic.