Page:Popular Science Monthly Volume 30.djvu/800

776 expose them to great heat, our task would be accomplished. Such isolation is of course impossible, but we make use of heat in the destruction of germs which have found a resting-place in clothes and bedding. The articles are placed in ovens or hot-air chambers, the temperature of which can be raised many degrees above the boiling-point of water. A high temperature, however, has less effect upon the spores than upon the mature organisms, but successive heatings are found to effect the desired result. During their development the spores rapidly pass through several stages, in which they become softened and far more amenable to the action of heat. Exposure to a current of steam at a temperature of 212° is a still more satisfactory method than the use of dry heat. It involves less injury to the articles to be disinfected (a very important point when blankets and other woolen goods have to be dealt with), and it is more simple, more rapid, and more certain in its action. When the necessary appliances are not available, washing the clothes with soap and hot water, and then boiling them for several hours, form an effective substitute. Exposure to sun and air will serve to complete the purification.

For the disinfection of the air of rooms many substances are recommended and employed, but the way in which they are generally used causes them to act merely as deodorants. Even at the present day, the fact is very incompletely realized that ventilation—that is, the continual admission of fresh air—is the only safe method of purifying the atmosphere of rooms containing sources of infection. It is simply useless to place saucers containing chloride of lime, carbolic acid, or Condy's fluid in a contaminated atmosphere with the hope that the germs floating about therein will be caught and killed, like mice in a trap. The chlorine, doubtless, will remove some offensive odors and readily diffuse itself throughout a room, but to act as a true disinfectant it must be so much concentrated that the air in the space containing it would be quite irrespirable by human beings. It is, however, when used scientifically, the best disinfectant we possess for purifying the walls, etc., of an empty room. All the openings should be rendered as nearly air-tight as possible, and the evaporation of a large quantity of water in the room aids the action of the chlorine. It is easily generated by adding hydrochloric acid to bleaching-powder. For deodorizing purposes in sick-rooms and passages, a gas called "euchlorine" will be found very serviceable. It is produced when a few crystals of chlorate of potassium are dropped into a little hydrochloric acid. The mixture can be conveniently made in a small widemouthed bottle, which should be placed as near the ceiling as possible, so that the gas may descend into the room. Chlorine and its compounds are much heavier than atmospheric air. Bromide is even more powerful as a disinfectant than chlorine, and both are far superior to sulphurous acid.

Carbolic acid has been much overrated as a disinfectant. The