Collodion

Collodion (Gr. kollao, 'I stick') is a solution of Gun-cotton (q.v.) or pyroxylin. Cotton itself is not soluble in alcohol or ether, but when treated, either in the form of cotton-wool, rags, or paper, with a mixture of five parts of strong nitric acid, and six of sulphuric acid, it is found that it can now be dissolved in ether, or in a mixture of ether and alcohol. To this modification the name pyroxylin is applied. There are many varieties of collodion divisible into surgical or medicated collodions, and photographic collodions. When one part of pyroxylin is dissolved in thirty-six parts of ether and twelve parts of alcohol, a thickish liquid is obtained, which evaporates rapidly, leaving a thin film of pyroxylin. As an application to wounds, where it is desired to keep the edges close together, this form of collodion is of use, owing to the contractility of the pyroxylin film which it leaves, but for general purposes a flexible or flexible collodion, as it is called, is desirable. This is produced by the addition of a little Canada balsam and castor-oil to the ordinary variety. Flexible collodion is largely used as a covering for abraded surfaces, as a remedy for burns, for sore nipples, &c., and it is also the basis for many medicated collodions, such as styptic collodion, cantharidal or blistering collodion, &c. Salicylated collodion is well known as a popular corn cure, and it is certainly most effectual in removing hard or soft corns with but slight inconvenience. It contains, in addition to salicylic acid, the active principle, a little extract of Indian hemp, which prevents the slight pain, which might otherwise prove troublesome. Collodion plays a very important part in Photography (q.v.).