COLLODION (Neo-Lat.. from Gk. sconuMns, kallodER, glue-like. from KoXXa, kolla, glue + eloos, (-Nos, form). A solution of pyroxylin in a mixture of alcohol and ether. For its man ufacture a convenient form of cellulose, such as cotton wool, is immersed in a mixture of nitric and sulphuric acid with a little water, or in a mixture of potassium nitrate with sulphuric acid. The resulting product is washed in water and dried. The pyroxylin thus obtained is then treated with ether, to which alcohol is added until the substance is completely dissolved. The solution is a clear, colorless liquid that does not mix with water or alcohol, but readily mixes with ether: when exposed to the air it dries up, leaving a transparent film, which becomes elec tric by friction and may be exploded by heat, pressure, or percussion. Mixed with substances sensitive to light, collodion is extensively used in photography; the mixture is spread over a glass plate, on which it forms, when dried, a sensitive film. Collodion is also used in surgery, the tenacious and transparent film left by its evaporation preventing the access of air to the injured surface and protecting it from infection.
Pills and other medicinal preparations may be coated with it so as to render them tasteless. Among the medicinal collodions that are official is blisteriny or cesicating collodion, which con sists of cautharides dissolved in collodion: the solution is applied to the skin when it is desired to raise a blister. Wood, paper, and fabrics may be rendered waterproof by being covered with collodion. Small balloons are made from it by pouring a solution into a flask of the desired dimensions, which is then turned about so as to spread the liquid uniformly over the surface. and then inverted to allow the excess to run out. The solvent is then allowed to evaporate, and the edges of the remaining film are loosened from the glass by attaching a glass tube to the neck of the flask and withdrawing the air. whereupon the eollodion balloon detaches itself, contracts, and is easily withdrawn. See also CELLULOSE.