Bichloride of Mercury (corrosive sublimate) is a potent poison and a powerful germicide; in solutions of 1:15,000 it stops decomposition; in solutions of 1:2,000 it kills bacteria in two hours; and in a strength of 1:500 it acts very quickly as a germicide for all bacteria, and even for spores. Corrosive sublimate dissolves in sixteen parts of cold and three parts of boiling water, but for disinfecting purposes it should be colored so that it may not be inadvertently used for other purposes, as the normal solutions are colorless and may accidentally be used internally. The action of the bichloride is increased by heat.
Formalin is a forty per cent solution of formaldehyde gas, and its uses and methods of employment have already been considered.
Potassium Permanganate is a good germicide, and weak solutions of it are sufficient to kill some bacteria, but the objections against its use are that solutions of potassium permanganate become inert and decompose on coming in contact with any organic matter. Furthermore, the chemical would be too expensive for disinfecting purposes.
Ferrous Sulphate (copperas) was formerly very extensively used for disinfecting purposes, but is not so used at present, owing to the fact that it has been learned that the germicidal power of this material is very slight, and that its value depends mostly upon its deodorizing power, for which reason it is used on excreta in privy vaults, etc.
Lime.—When carbonate of lime is calcined the product is common lime, which, upon being mixed with water, produces slaked lime; when to the latter considerable water is added, the product is milk of lime, and also whitewash. Whitewash is often used to disinfect walls and ceilings of cellars as well as of rooms; milk of lime is used to disinfect excreta in privy vaults, school sinks, etc. Whenever lime is used for disinfecting excreta it should be used generously, and be thoroughly mixed with the material to be disinfected.
Disinfection of Rooms
Practical disinfection is not a routine, uniform, and thoughtless process, but demands the detailed, conscientious application of scientific data gained by research and laboratory experiments. Disinfection to be thorough and successful cannot be applied to all objects, material, and diseases in like manner, but must be adjusted to the needs of every case, and must be performed conscientiously. Placing a sulphur candle in a room, spilling a quart of carbolic acid or a couple of pounds of chlorinated lime upon the floors or objects, may be regarded as disinfection by laymen, but in municipal disinfection the disinfector must be thoroughly versed in the science of disinfection and be prepared to apply its dictates to practice.
Rooms.—In the disinfection of rooms the disinfectant used varies with the part of the room as well as with the character of the room. When a gaseous disinfectant is to be used sulphur dioxide or formaldehyde is employed, with the tendency lately to replace the former by the latter. Wherever there are delicate furnishings, tapestries, etc., sulphur cannot be used on account of its destructive character; when sulphur is employed it is, as a rule, in the poorer class of tenement houses where there is very little of value to be injured by the gas, and where the sulphur is of additional value as an insecticide. Whenever gaseous disinfectants are used the principal work of the disinfector is in the closing up of the cracks, apertures, holes, and all openings from the room to the outer air, as otherwise the gaseous disinfectant will escape. The closing up of the open spaces is accomplished usually by means of gummed-paper strips, which are obtainable in rolls and need only to be moistened and applied to the cracks, etc. Openings into chimneys, ventilators, transoms, and the like must not be overlooked by the disinfector. After the openings have already been closed up the disinfectant is applied and the disinfector quickly leaves the room, being careful to close the door behind him and to paste gummed paper over the door cracks. The room must be left closed for at least twelve, or better, for twenty-four hours, when it should be opened and well aired.
Walls and Ceilings of rooms should be disinfected by scrubbing with a solution of corrosive sublimate or carbolic acid; and in cases of tuberculosis and wherever there is fear of infection adhering to the walls and ceilings, all paper, kalsomine, or paint should be scraped off and new paper, kalsomine, or paint applied.
Metal Furniture should first be scrubbed and washed with hot soapsuds, and then a solution of formalin, carbolic acid, or bichloride applied to the surfaces and cracks.