The New Student's Reference Work/Resins

Res′ins, a class of natural vegetable products, closely allied to the essential oils and in most cases obtained from the plants which yield them mixed with oil. Resins are divided into hard, soft and gum resins. Hard resins are solid and brittle, and contain little or no oil. Such are copal, lac, mastic, jalap etc. Soft resins can be molded by the hand, and some are sticky and semi-fluid. These are called balsams. They are the solutions of hard resins in essential oils, or are admixtures of the two. Turpentine, storax and the balsams of Tolu, Peru and Canada are examples. Gum resins are the milky juices of certain plants made solid by exposure to the air. Resins are widely diffused throughout the vegetable kingdom, and are much used in medicine and in the mechanic arts. They are generally obtained by making incisions in the wood from which they are obtained, although it is sometimes necessary to use boiling alcohol to extract them from the wood. The common resin or rosin of commerce exudes from several species of pine, and is used in the preparation of ointments and plasters and for various other purposes.