Cotton Wool

COTTON WOOL, cotton obtained from the cotton plant Gossypium barbadense L., Gossyp. hirsut. L., Gossyp. herbac. L. (fam. Malvaceae), cleaned on scutching machines of ordinary design and combed on a special machine. According to its quality, cotton wool is divided into several grades. Ordinary cotton wool has diverse applications. It is used for various fabrics, yarn, for the preparation of artificial silk, leather, and other artificial materials; for the preparation of nitrocellulose, celluloid, and smokeless powder. Absorbent cotton wool, Gossypium depuratum (Pharmacopoeia VII), is used in medicine for dressings; it is prepared from the best quality of ordinary cotton wool, previously degreased by prolonged and repeated boiling in 0.5–1% and up to 4% sodium lye or soda with soap and bleached with the help of solutions of bleaching lime and hydrochloric acid, followed by washing in water, wringing, drying, and combing on machines. Cotton wool used in eye operations is sometimes washed additionally with alcohol and ether and dried. Good absorbent cotton wool must be of a pure white color, without any odor. Under a microscope, it has the appearance of long, ribbon-like, very often twisted single-celled hairs (up to 3 cm in length and from 0.015 to 0.04 mm in width). The hair has its greatest width not at the very base, but slightly higher, and it gradually narrows and ends in a point, although the latter turns out to be torn off in the majority of hairs. Often the hairs are twisted into a spiral in places, which is considered a sign of good merchandise; then a large cavity and a comparatively thin-walled shell are clearly visible in them, covered by an even thinner cuticle, speckled with the smallest reticulated lines and dashes. The shell of the cotton wool consists almost of pure cellulose (C₆H₁₀O₅)_n and gives all the reactions of the latter; only the inner layer, representing the remains of the protoplasmic contents of the cell, consists of protein substances and yellow pigment. Cotton wool hairs are stained blue or violet by chlor-zinc-iodine; in an ammoniacal solution of copper, they first swell and then dissolve. When thrown into water, compressed, or rolled into a ball, cotton wool must sink immediately. Absorbent cotton wool must have a neutral reaction and may contain only negligible traces of chloride and sulfate salts, as well as traces of calcium salts. The fat content should be no more than 0.5%. Cotton wool must not contain reducing substances; it may be stained by alcohol only to a slightly yellowish color, and after burning, it must yield no more than 0.3% ash. Cotton wool is used in medicine almost exclusively as a dressing material. If cotton wool is impregnated with substances that kill microorganisms (carbolic acid, thymol, iodoform, ferric chloride, salicylic acid, boric acid, etc.), then cotton wool called antiseptic is obtained. Such cotton wool often irritates wounds and sometimes, due to the absorption of the medicinal substances contained in it, even becomes a cause of poisoning. Sterilized cotton wool, obtained by treating cotton wool at a high temperature, does not have these disadvantages. Such cotton wool is called aseptic and fully satisfies the requirements of the best dressing material. Aseptic cotton wool must possess the highest absorbency, which allows wounds to be kept as dry as possible, and dryness best guarantees against the development of microorganisms. Purified cotton wool finds wide medical application. Simple cotton wool is used for warming compresses over oilcloth and in the surgical care of patients (fractures, bandages). Gauze, muslin, bandages, etc., are prepared from purified cotton. Colloxylin is prepared from purified cotton wool, from which collodion is made, which has quite a large application in medical practice.