Pyroxylin, cellulose tetranitrate, or dinitro-cellulose, is prepared by immersing to of cotton in a mixture of 50 of sulphuric acid and 50 of nitric acid, stirring it constantly for three minutes, then removing the product, washing with water until free from acid, draining on filter paper, and drying on a water-bath. The product is a white fibrous substance, resembling cotton in appearance. Pyroxylin is also official in the U.S.P. When ignited it burns with great rapidity; it should be carefully stored in a dry place, or immersed in methylated spirit. When pyroxylin is made by immersing the cotton in the mixture of acids at a high temperature the product yields with ether-alcohol a collodion known as "high-temperature collodion," which, on evaporation, leaves a film of a friable character, and the collodion is unsuitable for many purposes. Made at a low temperature, however, the resulting pyroxylin yields a collodion, the film of which is tough and well adapted in every way for surgical use. The solubility of both varieties is the same. Pyroxylin consists of cellulose tetranitrate, C12H16(ONO2)4O6, or dinitro-cellulose, C6H8(NO2)2O5. and is distinguished from guncotton by its solubility in a mixture of equal volumes of ether and alcohol. Unless it has been properly nitrated, collodions prepared with it may be thicker than is desirable. Guncotton is cellulose hexanitrate, C12H14(ONO2)6O4, or trinitro-cellulose, C6H7(NO2)3O5. it is insoluble in a mixture of alcohol and ether. Celloidin consists of pyroxylin which has been purified by solution in alcohol and ether. Filmogen and other similar preparations are prepared by dissolving celloidin in acetone or other Photoxylin is stated to be prepared from nitrated suitable solvent wood pulp.
Readily soluble in twenty-five volumes of a mixture of ether and alcohol in equal proportions. It is also soluble in methylic alcohol, glacial acetic acid, amyl acetate, or acetone.
Uses.—Pyroxylin is employed in the preparation of collodions and similar rapid-drying, protective varnishes.
- Collodium, B.P.—COLLODION. Syn.—Contractile Collodion; Solution of Pyroxylin.
- Pyroxylin, 2; ether, 72: alcohol, 24. Add the pyroxylin to the mixed liquids and set aside for a few days. Should there be a sediment, decant the clear solution, Collodion is highly inflammable: it should therefore be kept in well-closed bottles in a cool place. Methylated collodion is prepared by some makers with methylated ether (specific gravity, 0.720) and industrial methylated spirit, but other makers use pure spirit for the purpose. Collodion is much used to seal surgical wounds, for application to cuts and abrasions, and as a vehicle for the application of drugs to the skin when prolonged local action is required. The film contracts on drying, and tends to crack. Many substitutes for collodion have been suggested, including the following:—1. The use of celloidin (a purified pyroxylin) gives a clearer solution and a firmer film. The hands may be coated with such a solution as a substitute for rubber gloves. 2. A solution of pyroxylin or celloidin in acetone may be prepared up to a 10 per cent. strength (Filmogen or Photoxylin) 3. A solution of pyroxylin, 1, in absolute alcohol, 20 by weight, with camphor, 20 (Camphoid) 4. A solution of celluloid in acetone or amyl acetate. 5. Solution of pyroxylin in methyl alcohol. The contraction of the collodion film is an advantage when pressure is required, as in applications for chilblains and for checking haemorrhage from cut surfaces or leech-bites, but it is often a disadvantage in surgical work, when applied to large surfaces (see under Collodium Flexile).
- Collodium, U.S.P.—COLLODION, U.S.P.
- Pyroxylin, 4; ether (96 per cent.), 75; alcohol (95 per cent.), 23.
- Collodium Acetonum, B.P.C.—ACETONE COLLODION.
- Pyroxylin, 5; oil of cloves, 2; amyl acetate, 25: benzene, 20; acetone, sufficient to produce 100. If the pyroxylin should not dissolve immediately in the acetone, add the other ingredients and set aside till solution is affected. The product may be thicker than is desirable unless the pyroxylin has been properly nitrated, Pyroxylin, B.P., should be used, and not' that prepared for photographic purposes. This preparation is an excellent liquid court plaster, and a useful application for chilblains and for small cuts and abrasions
- Collodium Acetonum Simplex, B.P.C.—SIMPLE ACETONE COLLODION.
- Pyroxylin, 3.43; acetone to 100.
- Collodium Flexile, B.P.—FLEXIBLE COLLODION. Syn.—Collodium Elasticum.
- Collodion, 96; Canada turpentine, 4; castor oil, 2. Mix the Canada turpentine with the collodion, then add the castor oil. Flexible collodion, being highly inflammable, should be kept in well-closed bottles in a cool place. The film formed by this collodion does not contract on drying, nor does it crack, but it does not adhere so well as that formed by Collodium Acetonum.
- Collodium Flexile, U.S.P.—FLEXIBLE COLLODION, U.S.P,
- Collodion, 92: Canada turpentine, 5; castor oil, 3; all by weight.
- Collodium Methylatum, B.P.C.—METHYLATED COLLODION.
- Pyroxylin, 2; methylated ether, 72; methylated spirit, 24.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.