The various so-called disinfectants which are often recommended to purify the air of the sick-room are, at the most, simply deodorisers of greater or less value, and are entirely unreliable for the destruction of disease germs under the conditions existing in an occupied apartment.

Disinfection of the vacated room consists in the destruction of all infectious particles which remain attached to surfaces, or lodged in crevices, in interstices of textile fabrics, etc. The object in view may be accomplished by thorough washing with a reliable disinfecting solution, but many sanitarians think it advisable to "disinfect the room" with a gaseous disinfectant, such as formaldehyd or sulphur dioxid. If "fumigation" with sulphur dioxid is resorted to, the directions given by the Committee on Disinfectants of the American Public Health Association should be followed that is, three pounds of sulphur should be burned for every thousand cubic feet of air-space. At the end of from twelve to twenty-four hours, doors and windows should be opened, and the room freely ventilated. After this fumigation, all surfaces should be washed with a disinfecting solution (chloride of lime 2 per cent., carbolic acid 2 per cent., or mercuric chloride 1:1000), and afterwards thoroughly scrubbed with soap and hot water. Plastered walls should be whitewashed.

Experiments made during the past twenty years have shown that fumigation by burning sulphur is not by any means so reliable a method of disinfection as was formerly supposed. It has very little value unless the articles to be disinfected are in a moist condition. This may be effected by introducing steam into the room together with the sulphur fumes. There is a class of diseases, however, in which sulphur fumigation is a most valuable method of disinfection: I refer to yellow fever and the malarial fevers, in which diseases the infectious agent is transmitted by mosquitoes. Such mosquitoes, after filling themselves with blood from the sick person, hang about the room, attached to the ceiling, to window-curtains, etc., for the purpose of digesting their meal and supplying themselves with another when occasion offers. The room is infected because of the presence of these infected mosquitoes, which with the blood of the patient have taken in the disease germs present in such blood. Disinfection in such a case consists in the destruction of the infected mosquitoes, and this is very readily accomplished by means of sulphur fumigation. Owing to the superior germicidal power of formaldehyd and its non-toxic properties, this gas has to a considerable extent taken the place of sulphur fumigation for disinfecting purposes.

Formaldehyd is generated either by the application

of heat to an aqueous solution of the gas (formalin) or by the oxidation of wood alcohol.

In making practical use of this agent a suitable apparatus will be required. For the disinfection of a room with its contents, freely exposed for surface disinfection, one pound of formalin should be volatilised for each thousand cubic feet of air-space-the time of exposure to the disinfecting action of the gas being not less than twelve hours. In the absence of any apparatus satisfactory results have been obtained by the Department of Health of the city of Chicago, as follows:

66

Ordinary bed sheets were employed to secure an adequate evaporatory surface, and these, suspended in the room, were simply sprayed with a forty per cent. solution of formalin through a common watering-pot rose-head. A sheet of the usual size and quality will carry from one hundred and fifty to one hundred and eighty cc. of the solution without dripping, and this quantity has been found sufficient for the disinfection of one thousand

cubic feet of space. Of course, the sheets may be modified to any necessary number. . . . Surface disinfection was thorough, while a much greater degree of penetration was shown than that secured by any other method."

Formalin may also be used in the disinfection of rooms and their contents by spraying all exposed surfaces.

Experiments made by Kinyoun and others show that formaldehyd gas does not injure the colour or textile strength of fabrics of wool, silk, cotton or linen

and that it has no injurious action upon furs, leather, copper, brass, nickel, zinc, polished steel or gilt work. Iron and unpolished steel are attacked by the gas.

As is the case with sulphur dioxid the germicidal power of formaldehyd is increased by the presence of moisture.

Other volatile and gaseous disinfectants have been used, but from a practical point of view those mentioned are the best. Chlorin is a powerful germicide in the presence of moisture, but its irritant and corrosive properties interfere with its usefulness as a disinfecting agent.

CHAPTER X

VARIOUS CHEMICAL DISINFECTANTS

T is my intention in the present chapter to refer briefly to some of the most useful chemical disinfectants. The most potent germicide is not always the best disinfectant for practical use. Questions of cost, poisonous properties, injurious effects upon textile fabrics, etc., must be considered in selecting an agent for any special purpose.

The mineral acids are all active germicides when used in solutions of proper strength, and a one-percent. solution of sulphuric, nitric, or hydrochloric acid will quickly destroy pathogenic bacteria in the absence of spores. Such a solution could be safely used to disinfect the excreta of patients suffering from cholera or typhoid fever. Among the vegetable acids it is only necessary to mention citric acid, which has been recently recommended, in the form of lemon juice, for destroying typhoid bacilli in drinking-water. The idea that the addition of a spoonful of lemon-juice to