Disinfectants

DISINFECTANTS are intended for the destruction of: 1) pathogenic microorganisms outside the tissues of the human body, 2) insect vectors of infections (disinsection), and 3) rodents (deratization). The action of disinfectants is based on their chemical and physicochemical affinity for the constituent parts of protoplasm: penetrating the organism, these substances react with its colloids or lipoids, acting as poisons. The strength of the bactericidal action of disinfectants depends on the following conditions: 1) physical and chemical properties of the agents used; 2) duration of exposure; 3) concentration of solutions and their temperature (as a rule, the bactericidal action of chemical substances increases in proportion to the increase in concentration and temperature of their solutions); 4) resistance of microorganisms; 5) wettability of the objects being disinfected; 6) their physical properties, e.g., surface properties: disinfected items with a smooth surface are easier to decontaminate than those with recesses, protrusions, etc. Disinfectants are divided into physical and chemical. Physical disinfectants. Light. The bactericidal power of sunlight varies within wide limits depending on the degree of sensitivity of microorganisms, the time of year, month, day, altitude of the locality, etc. Sunlight exhibits an exclusively superficial action, its intensity is very variable and cannot be regulated; therefore, light has only an auxiliary value in disinfection practice and is used as an additional factor after treatment with chemical substances. The opinion of various researchers on the disinfection value of cathode rays and X-rays is not uniform. Radium rays act weaker than sunlight in terms of disinfection. Drying has an energetic effect on microorganisms, but the times of their death vary extremely (from several hours to many months and even years) depending on the degree of resistance and a number of intervening conditions. The temperature effect on the infectious agent, other things being equal, depends on the form of application of heat. Low temperature (frost) is not used for disinfection, since most microorganisms withstand temperatures significantly below 0° for a prolonged period. High temperature kills microorganisms. Dry heat in the form of burning and calcination immediately destroys microorganisms, but its application is naturally limited. Dry heat is more often used for disinsection in the form of: a) a Swedish blowtorch for burning insects, b) a hot iron for ironing the surfaces of linen, clothing, and bedding for the purpose of destroying insects and their eggs, and c) special thermal chambers. Moist heat is used in the form of boiling linen, utensils, etc. for 1/2-1 hour; the items must be under the level of the boiling liquid. The addition of 1-2% alkalis (soap, soda, potash, wood-ash lye) enhances and accelerates the disinfection effect. Water vapor plays a very important role in disinfection practice, used in special chambers. In a number of methods of physical disinfection, one cannot neglect the use of mechanical cleaning by removing dust, cobwebs, debris, cleaning dresses, floors, etc., in particular by using vacuum cleaners. Chemical disinfectants. Of inorganic substances, acids, alkalis, and salts are used in disinfection practice, and of organic ones, mainly benzene derivatives. Chemical disinfectants are subdivided into agents for the wet and gas methods. A. Agents for the wet method. 1. Metals. Disinfectant action is attributed to copper, mercury, and silver. On household items made of copper, despite their contact with human hands, intestinal bacteria are not detected, in contrast to other items; hence it is clear how desirable the use of door handles made of copper is. The disinfectant property to a greater or lesser extent is also inherent in water that has been in contact with the aforementioned metals, nevertheless, metals do not yet have widespread use in disinfection practice.

2. Sublimate (HgCl₂) is used in 2 forms—crystals and tablets; the latter contain 0.5-1 g of sublimate and represent a mixture of this product with sodium chloride in equal weight parts, tinted with fuchsin. In practice, a 1-2‰ sublimate solution is used (12.5-25 g of crystalline sublimate or a corresponding amount of tablets are taken per bucket of water). The sublimate solution is odorless, transparent, colorless (prepared from tablets it is colored pink). The shortcomings of sublimate solutions include their low chemical stability—the ability to decompose under the influence of many inorganic and organic substances (soda, alkaline-earth metal salts in hard water, fatty acid salts of potassium and sodium in soaps, protein and fat products, metals, etc.). The addition of sodium chloride in a fivefold amount or hydrochloric acid in a twofold amount to the sublimate solution increases the stability of sublimate solutions and promotes better solubility of the product. Sublimate solutions are used for a variety of wet manipulations: washing contaminated surfaces (floors, walls, home furnishings), soaking linen, etc.

3. Crystalline carbolic acid (or phenol). It is regarded as benzene in which one of the ring hydrogens is replaced by OH, i.e., C₆H₅OH. Phenol represents thin, needle-like, colorless, very hygroscopic crystals with an aromatic odor, which turn pink under the influence of light and impurities. In practice, it is used either in the form of an aqueous solution, 3-5%, or in the form of a soap-carbolic solution, weak and strong; the former is a combined aqueous solution consisting of 2% phenol and 3% green soap, and the latter consists of 3% phenol and 5% soap. In view of the inconvenience of handling the crystalline product, it is better to use Acidum carbolicum liquefactum for practical purposes, obtained as a result of adding 10% water to phenol. Particular cases of application of carbolic acid solutions are the same as for sublimate. 4. Crude carbolic acid (or black carbolic). A coal tar product, which is a mixture of several aromatic derivatives, among which cresols play a substantial role, regarded as derivatives of benzene in which one of the ring hydrogens is replaced by OH and another by CH₃ (hence the three possible isomers of cresol: ortho-, meta-, and paracresol).

Unphenolized carbolic acid is a dark brown liquid with an unpleasant odor and staining properties. Black carbolic acid is poorly soluble in water, so it is necessary to prepare soluble products from it—soap-carbolic solution and sulfur-carbolic mixture; the first is an aqueous solution of 5% green soap and 3% unphenolized carbolic acid, while the second is prepared by mixing 3 parts of carbolic acid with 1 part of unphenolized sulfuric acid; the mixture is considered ready for use three days after preparation and is applied as an 8-10% aqueous solution. Products of black carbolic acid have high bactericidal properties, but due to their unpleasant odor, staining properties, and ability to damage objects, they are used mainly for rough disinfection: for latrines, cesspools, animal quarters, etc. 5. Lysol, creolin, saprol, solutol, solveol, deodorol, bacilol, cresolic alkalis, chloromethylcresol, alkalisol and other similar products are used for ordinary wet manipulations and are cresols converted into a soluble state by treatment with soap or some other alkali. Among the soluble cresols, the following deserve attention: a) Lysol, which is the product of treating tricresol with oleic acid. It is a reddish-brown liquid soluble in water in all proportions; solutions foam, slightly opalesce, are transparent, and non-staining; they are used in concentrations from 1% to 10%. Weak solutions are used for washings and atomizations, strong ones—for disinfecting secretions and departments. b) Creolin. Obtained by treating cresols with resin soaps. Aqueous solutions have the appearance of an emulsion due to the precipitation of resin acids. The same concentrations of creolin solutions are used as for lysol, but their use is more limited due to the staining properties of the product. c) Cresolic alkalis are obtained by mixing black carbolic acid with a 16% solution of caustic soda in equal proportions. d) Alkalisol. Contains 67% cresols, 4-5% caustic alkali, and an admixture of emulsifying substances. e) Chloromethylcresol is used in the form of preparations Photogen and Parmetol. 6. Tar. The composition of tar varies and is not rich in active substances. Pine tar is preferable. It is used in alkaline solutions, mainly in disinsection practice (for repelling flies). 7. Unslaked lime (burnt lime, calcium oxide). Obtained by burning limestone, it appears as lumps of yellowish-white color. It is used in practice mainly for disinfection in intestinal infections, in the form of 10-20% lime milk. Milk is prepared ex tempore and consists of freshly slaked lime mixed with the corresponding amount of water. Under the influence of prolonged and irrational storage, unslaked lime undergoes a series of changes, as a result of which calcium carbonate is formed, which is completely indifferent in disinfection. In the process of this transformation, lumps of calcium oxide turn into a powdery state, which is an external sign of product spoilage. 8. Alcohols—methyl, ethyl, and propyl—show strong disinfecting action both in themselves and in the form of preparations: soap alcohol, tincture of iodine, etc. 9. Hydrogen peroxide, potassium permanganate act as oxidizers; due to their high cost, they are not used on a large scale in practice. 10. Chlorine, bromine, iodine. Among the halogens, chlorine holds the leading role in disinfection practice. Of chlorine preparations, the following are most often used: a) Chlorine, or bleaching lime (see.) Ca(OCl)2. It should contain not less than 25% active chlorine. It is used as a 10-20% aqueous mixture for disinfection in intestinal infections. b) Antiformin. It is chlorine water mixed in excess with potassium hydrate. In a 5% solution, it shows energetic disinfecting action, which does not extend to spore-forming forms and the tubercle bacillus. c) Chloramine (para-toluene-sulfamide sodium) CH3C6H4SO2NClNa + 3H2O and similar products (Mi-anin, Activin, Sputamin, etc.) are organic hypochlorites; they are used in a 5% solution for disinfection of tuberculous sputum. 11. Volatile disinfectants: thymol, toluene, chloroform, turpentine, essential oils, menthol, camphor. Some of the listed substances (e.g., thymol) are powerful bactericidal agents, but are rarely used due to their high cost and inconvenience of application forms (low solubility in water). ^. Acids and alkalis. Acids are rarely used directly in disinfection practice due to their caustic properties; weak alkalis—soap, soda, potash, ash—have no direct disinfecting value, but greatly increase the disinfecting action of hot water. Acids and alkalis are most often used in combination with other disinfectants. B. Means for the gas method. 1. Formaldehyde CH2O. It is used as formaldehyde itself, in the form of a 40% solution in water—formalin, as well as its polymerization products—paraformaldehyde and trioxymethylene—mainly in the form of formalin cakes. In formalinization practice, it is necessary to take into account the ability of formaldehyde to polymerize, turning into inactive powdery modifications—paraformaldehyde (trioxymethylene). To prevent the formation of polymers, formalin must be diluted with one and a half times its amount of water before boiling in apparatuses, and the rooms to be fumigated must be kept warm at least to 17-18°. Formaldehyde shows surface action on the objects being disinfected, which necessitates careful hanging and placement of items, as well as the application, along with formalinization, of other disinfection methods—wet, chamber (soaking linen in disinfecting liquids, washing floors, sending massive items—mattresses, pillows, etc.—to the disinfection chamber). After formalin disinfection, rooms are deodorized by the evaporation of ammonia. 2. Sulfur anhydride, phosgene, carbon disulfide, hydrogen cyanide, chloropicrin and other gaseous products are used mainly in disinsection practice. Lit.—see lit. to art. Disinfection. G. Chistyakov.