PRACTICAL DISINFECTION AND STK,;U.I'/..\ TION 123 



The solution of bromine must be prepared with great care, as the 

 pure bromine from which it is made is dangerous. It is very caustic 

 when brought in contact with the skin; it is volatile and its fumes are 

 very irritating when inhaled. To prepare the solution an ounce bottle 

 of liquid bromine is dropped into three gallons of water, and broken 

 under the water and thoroughly stirred. 



The Practical Employment of Formaldehyde and Sulphur Dioxide Gases 

 in the Surface Disinfection of Rooms and the Disinfection of Goods 

 which would be Injured by Heat. Formaldehyde gas has come into 

 such general use, and is for many purposes so valuable, that the 

 description of methods employed to generate and use it will be given in 

 detail. 



If we consider now the practical application of formaldehyde gas 

 for purposes of disinfection we find that its destructive action on micro- 

 organisms depends upon a number of factors, the chief of which are its 

 concentration in the surrounding atmosphere, the length of the con- 

 tact, the existing temperature, the accompanying moisture, and the 

 nature of the organism. 



The necessary concentration of the gas in the surrounding atmos- 

 phere to kill the micro-organisms varies with each species, for some 

 resist chemical agents much more than others, and also with the freedom 

 of access of the gas to the bacteria, for if they are under cover or within 

 fabrics a greater amount of gas must be generated than if they are freely 

 exposed. 



For purely surface disinfection, when the less resistant bacteria or 

 other micro-organisms are to be destroyed, there will be required, 

 according to the method used, six to ten ounces of formalin of full 

 strength, or its equivalent, to 1000 cubic feet. 



For the destruction of the more resistant but non-spore bearing 

 forms, such as typhoid fever or tubercle bacilli, at least twelve ounces 

 of formalin should be used. The gas penetrates through fabrics with 

 difficulty, and to pass through heavy goods the concentration of the gas 

 must be doubled and moderate heat added (45 C. or above). 



Value of Moisture. At first it was thought that formaldehyde gas 

 acted more effectually in a dry atmosphere, but further investigation 

 has proved that, although it does destroy bacteria with the amount of 

 moisture usually present in the air, and contained in their own sub- 

 stance, it acts much more powerfully and certainly when additional 

 moisture is present, and best when present up to the point of saturation. 

 The actual spraying of walls and goods to be disinfected with water is 

 even more efficacious. 



A fairly high temperature but one still below that which would 

 injure delicate fabrics increases not only the activity of formaldehyde 

 gas but also its penetrative power, and for heavy goods it is essential. 

 The production of a partial vacuum in the chambers before the intro- 

 duction of the folmaldehyde gas still further assists its penetration. 



The length of exposure necessary for complete disinfection depends 

 upon the nature of the disease for which it is carried out the penetra- 



or THF 

 I iMi\/r DO i T\J 



