Gossypium Purificatum (U. S. P.)—Purified Cotton.
"The hairs of the seed of Gossypium herbaceum, Linné, and of other species of Gossypium (Nat. Ord.—Malvaceae), freed from adhering impurities and deprived of tatty matter"—(U. S. P.).
SYNONYMS: Gossypium (Pharm., 1880), Absorbent cotton, Bombyx, Lana gossypii, Lanugo gossypii, Pili gossypii, Cotton wool.
Source and Preparation.—Purified cotton is now made on an enormous scale by manufacturers whose processes, being private and of great personal value, should not be published in justice to the owners. All the absorbent cotton of commerce is purchased by pharmacists and other consumers, none being made on a small scale. It may be prepared from raw cotton by "mercerizing" the latter, that is, by boiling with weak solutions of alkalies. By union with the fatty material of the cotton a soap is formed which is removed by repeatedly washing the cotton with water. F. L. Slocum's process (Amer. Jour. Pharm., 1881, p. 53), is as follows: Carded cotton is boiled for one-half hour in diluted solution (5 per cent) of caustic potash (or caustic soda). The soap formed is thoroughly washed out, the cotton expressed and placed for 15 or 20 minutes in a diluted solution (5 per cent) of chlorinated lime. It is then washed with water, dipped into water made slightly acid with hydrochloric acid, and again thoroughly washed with water. The cotton is then expressed and again boiled for 15 or 20 minutes with the diluted (5 per cent) alkali (hydroxide of potassium or sodium), washed again with water, next with acidulated water, and lastly with water. The cotton is then expressed and dried rapidly. It requires two boilings with alkalies to completely remove the fats. Mr. Slocum defines absorbent cotton to be cotton entirely freed from all matter (grease), that will obstruct capillary attraction. It is on record that in order to meet a popular demand for pure whiteness and a peculiar "feel" in purified cotton, the latter, after being freed from fatty and resinous matter, has been covered again with a trace of free fatty acid by passing it through a (diluted) soap solution, and an acid solution afterward (Amer. Jour. Pharm., 1891, p. 189).
Description.—Cotton is tasteless, odorless, highly combustible, and according to Thompson, is not soluble in alcohol, water, ether, oils, or vegetable acids; weak alkaline liquids have no perceptible action on it but when very strong they dissolve it by the aid of heat. Tannic acid forms a brown or yellow compound with it; nitric acid decomposes it when assisted with heat, oxalic acid being formed; sulphuric acid dissolves it. The strong mineral acids generally decompose it. Gun-cotton (Pyroxylin) a nitro-compound of an explosive character, is prepared from it by means of nitric acid (see Collodium and Pyroxylinum).
Purified cotton is almost pure cellulose. It is officially described as follows: "White, soft, fine filaments, appearing under the microscope as hollow, flattened and twisted bands, spirally striate, and slightly thickened at the edges; inodorous and tasteless; insoluble in ordinary solvents, but soluble in copper ammonium sulphate solution. Purified cotton should be perfectly free from all visible impurities, and, on combustion, should not leave more than 0.8 per cent of ash. When purified cotton, previously compressed in the band, is thrown on the surface of cold water, it should readily absorb the latter and sink, and the water should not acquire either an acid or an alkaline reaction (evidence of proper purification)"—(U. S. P.).
Action and Medical and Surgical Uses.—Externally, cotton is used as a local application in erysipelas, erythema, fresh burns, wounds, severe bruises or contusions, in rheumatic pains, and has been successfully employed in dressing blisters. In burns and blisters, it quickly allays pain, but care must be taken that the cotton does not harden and adhere firmly to the part over which it is applied, as it will then cause irritation the same as any other foreign body; this may usually be avoided by first applying some simple oleaginous substance over the surface which is to come in contact with the turn or ulcer. Cotton is supposed to prove efficient by excluding the air from the parts over which it is applied, and also by imbibing the secretions. As an application after surgical operations it is unsurpassed, and by taking up the discharges prevents purulent absorption. It is often medicated with boracic acid, carbolic acid, etc., for this purpose. Pessaries and tampons are often prepared with cotton, but should be frequently removed lest they become foul from absorption of the discharges. Surgeons make extensive use of absorbent cotton to clean surfaces and cavities, and it is specially applicable for use in the nasal and aural passages, both for cleansing purposes and for the introduction of medicaments. For packing wounds and cavities and similar surgical uses some of the forms of gauze are preferred.
Cotton Preparations.—GOSSYPIUM STYPTICUM (N. F.), Styptic cotton. Formulary number, 190: "Purified cotton (U. S. P.), solution of chloride of iron (U. S. P.), glycerin, water, of each a sufficient quantity. Mix the liquids in the proportion of five (5) parts of the iron solution, one (1) part of glycerin, and four (4) parts of water, in such quantities that the purified cotton shall be completely immersed in the liquid when gently pressed. Allow the cotton to remain in the liquid 1 hour, then remove it, press it until it has been brought to twice its original weight, spread it out in thin layers, in a warm place, protected from dust and light, and when it is sufficiently dry, transfer it to well-closed receptacles"—(Nat. Form.).
HEMOSTATIC COTTON is prepared by impregnating absorbent cotton with solution of subsulphate of iron or mixture of alum and chloride of iron.
SALICYLIC COTTON or Salicylated cotton, contains from 5 to 10 per cent of the. salicylic acid. Cotton is also impregnated with other substances, as benzoic acid (benzoic cotton), iodoform (iodoform cotton), chlorine (chlorinated cotton), boracic acid (borated cotton), etc.