Collodium

COLLODIUM (FUN), Collodium (from Greek kolla-glue), a solution of collodixin. Collodixin represents a mixture of nitric acid esters of cellulose (the term "nitrocellulose" is an inexact name), with an approximate formula: C₁₂H₁₀(OH)_n(ONO₂)₁₀-n, where n varies between 5 and 8. When n is less than 5 (nitration carried too far), pyroxylin is obtained, which is insoluble in alcohol and ether but only swells (gun cotton). To obtain collodixin, degreased cotton or other pure cellulose is placed in a mixture of strong sulfuric and nitric acids or strong sulfuric acid and saltpeter, and the cellulose is pressed until a sample taken out dissolves completely in a mixture of 1 part alcohol with 3 parts ether (according to VII-1 part alcohol and 7 parts ether). The relationships between the strength of the acids, their quantities, temperature, and duration of action on the cotton have been established empirically. After treatment, the collodixin must be immediately washed with water to a neutral reaction and dried in the dark. Collodixin is soluble in acetone, in amyl acetate, and in glacial acetic acid, insoluble in water; a 4% solution of collodixin in a mixture of alcohol (1 part) and ether (7 parts) is called K. Collodion is a colorless or only slightly yellowish liquid, viscous, easily evaporating, after which collodixin remains in the form of a transparent, strong film. It ignites very easily from fire. K. (as well as collodixin and gun cotton) was first prepared by Schonbein in Basel in 1846 and was recommended by him for medical purposes. The application of K. consists in obtaining a durable coating (film) that is impermeable to moisture and dust on wounds, tumors, inflamed areas, etc. Collodion must be completely neutral on litmus; acidic K. exhibits an irritating action and is subject to spoilage. Because the film of K. shrinks strongly and contracts the skin, elastic K. (Collodium elasticum, C. flexile) was introduced, obtained by adding 3% castor oil (VII) or 2% glycerin to collodion. Medicinal substances (iodoform, tannin, antiseptic substances, etc.) soluble in ether or alcohol-ether can be added to collodion; various prescriptions for blistering collodion (Collodium vesicans) with the addition of strongly irritating substances have been introduced in the pharmacopoeias of different countries. VII uses ether extract of Spanish fly (Collodium cantharidatum) for this purpose. Such a solution of medicinal substances in K. is also the callus liquid. Its composition: 10% salicylic and 10% lactic acids (or only one of them) in simple or elastic K. The practice of adding extract of Indian hemp is as futile as the ordinary coloring of the liquid green. Solutions of collodixin in acetone (Acetoncollodium) or in acetic ether are used as nail varnishes. Similar solutions are also used as varnish (filling) for covering bottle corks instead of caps or tin caps. Alloys of collodixin with camphor are known as celluloid and are used for various handicrafts (combs, billiard balls, tool handles, etc.). Celluloid is soluble in most organic solvents except hydrocarbons (gasoline, kerosene) and absolute ether. It dissolves in an alcohol-ether mixture; such a solution can be used as K. Collodion-impregnated silk (loops) was used by Speransky to delimitate areas of the cerebral cortex. In place of the easily flammable K., collodion based on cellulite was proposed, in which nitrocellulose is replaced by acetyl(hydro)-cellulose obtained by the action of acetic anhydride on cellulose (cotton). For dissolution, acetone, chloroform, or a mixture of alcohol with benzene is used in this case. Collodixin and acetylcellulose serve as intermediate products in the production of artificial silk.

I. Obergard. Collodion bags represent films of K. (collodion membranes) prepared in the form of bags. As a semipermeable partition, collodion bags serve in physical chemistry for the dialysis and filtration of colloidal solutions, and in bacteriology for the growth of microbes in the animal organism (Roux; 1896). The advantages of such growth depend on the fact that collodion bags are impermeable to all microorganisms and ultramicroscopic viruses and at the same time freely pass nutrient juices of a living organism. To prepare collodion bags, a 10% solution of K. diluted with a mixture of absolute ethyl alcohol and ether is used: 400 cm³ of K., 200 cm³ of ether, 500 cm³ of alcohol (Naumov). Bechhold recommends taking a solution of collodixin in glacial acetic acid (10% solution of colloidal cotton in acetic acid + 2.5% potassium carbonate). The technique of preparing bags: a thoroughly washed and dried test tube or other cylindrical vessel is filled with a solution of K. and, by means of constant horizontal rotation of the test tube, one tries to distribute K. so that its layer uniformly covers the walls of the vessel. Then K. is poured out, and the test tube is dried, leaving it in the air (upside down) until the ether smell disappears completely. This procedure is repeated three times. To extract the finished bag from the test tube, it is filled with water and left for 15-30 minutes. After this, the bag is removed, for which the water is poured out and, grabbing the threads of K. or inserting a finger slightly inside, it is carefully pulled upward without rotating. The finished collodion bag is put on or on a glass tube or on a rubber stopper, through which a glass tube passes. In bacteriological technique, gelatin capsules are used as a form for collodion bags, with a rubber ring corresponding to the diameter of the capsule being introduced into the upper part of the capsule. The ring allows the capsule to be grabbed with tweezers or fixed on a wooden rod; with the help of these devices the capsule is immersed in a solution of K. (3 times, each time drying). To remove the gelatin, collodion bags are immersed in hot water and thoroughly washed. A collodion bag is considered suitable if it is transparent and does not pass coarse-molecular solutions, e.g., Congo red and others. If a collodion bag is subject to sterilization, it must be preliminarily subjected to special treatment, otherwise it becomes almost impermeable. The treatment consists in a half-hour washing of the bag in a 20% aqueous solution of ammonium polysulfide, warmed to 40°, followed by washing with ammonia and distilled water. A collodion bag prepared in this way can even be sterilized in an autoclave. Finished collodion bags can be closed with a rubber stopper or by careful layering of collodion.

A. Kompaneets. Collodion is used in histological technique 1) for embedding pieces, 2) for gluing sections (for this 3-4 parts of K. are mixed with 1 part of clove oil, or 2 parts of K. with 3 parts of clove oil, or 2 parts of K. with 3 parts of ether and 1 part of castor oil), and 3) for enclosing cells isolated by maceration (the "collodion-nage" of French authors). For this purpose, 5-6 cm³ of absolute alcohol is poured onto the sediment containing cells, it is replaced by the same amount of ether, and finally 1-2 cm³ of K. Then the centrifuge is used, and a drop of K. containing the sediment is placed on a slide, allowed to spread, and, without allowing it to dry, the slide is immersed in 80° alcohol. The film formed on the slide can be subjected to any staining. The method is quite suitable for processing blood elements, spermatozoa, etc., which for this purpose are dropped by drops into one or another fixing liquid, and the resulting sediment is processed by the indicated method.