Gun Cotton

PYROXYLIN. Explosive compound, formed by immersing pure dry cotton in a mixture of strong nitric and sulphuric acids: discovered by Schonbein 1845; it is a substitution product the group (NO2) replacing hydrogen in cellulose. CHO+3HNO, C,H,(NO2),O,+3H,O. The product here is tri nitrocellulose, but the degree of nitration admits of variation. Lower nitration affords a product soluble in a mixture of alcohol, forming COLLODION (q.v.) used in photography and surgery. It is insoluble in water, but soluble in acetone, and in a mixture of ether and ammonia. Its density, when in flocks or fiber, varies from 0.1 to 0.3; when compre ed 1.1 to 1.5. Wet gun cotton can be compre ed beyond 13,000 lbs. per sq. inch without causing explosion. When dry and loose, it burns with a flash without explosion. Its point of explosion is ab. 182° C. It is the safest explosive known, if attention be paid to directions for handling and storing: 829 volumes of gun cotton of density 1. expand to 12,064 volumes of gas, when the temperature of the gas is 3,700° C., giving a pre ure of 81 tons per sq. inch. The value of gun cotton as a military explosive was much enhanced by the discovery made 1868 by E. O. Brown of Woolwich, that it could be detonated even when unconfined, by means of a small charge of mercury fulminate, and even when wet, if a small initial charge of dry gun cotton be detonated in contact with it. This is the method now used. It is estimated that gun cotton of 1.1 density when in contact exerts a pre ure upon explosion of ab. 160 tons per sq. in., or ab. half that of mercury fulminate. Its combustion rate of propagation is said to be between 5,000 and 6,000 meters per second. See NITRO-CELLULOSE.