250 STERILIZATION, ANTISEPSIS AND DISINFECTION 



of sufficient heat to boil the liquid takes place. Formaldehyde gas and 

 heated water vapor are evolved. The entire process requires but a 

 few minutes, and when two parts of formalin to one part of perman- 

 ganate are used the residue is small in amount and practically dry 

 and free from reactive substances. 



Ten ounces of formalin and five ounces of permanganate of potash 

 crystals are required for each thousand cubic feet of space to be disin- 

 fected. The temperature must be not less than 60 F., and the 

 humidity must be at least 60 per cent, for successful results. It is 

 convenient to place the permanganate in a three-gallon, galvanized- 

 iron pail with flaring sides, because the reaction between permanganate 

 and formalin is attended with considerable spattering. It is also 

 advisable to place two or three layers of heavy paper under the pail, 

 of sufficient size to project two feet at least in all directions, or better, 

 to place a galvanized-iron plate of similar dimensions under the pail 

 to catch all the liquid which is ejected from the pail during the process 

 of evolution of the gas. For successful disinfection, all closets, drawers 

 and alcoves should be opened as freely as possible; doors, windows 

 and fireplaces leading to the exterior should be tightly closed. The 

 room should be left closed and undisturbed for at least four hours. 



The Sheet Volatilization Method. This method requires no appara- 

 tus except sheets, and some mechanical device for spraying formalin 

 upon the sheets. The conditions of moisture and humidity and the 

 same general preparation of the room as for the potassium perman- 

 ganate formalin method must prevail. 



Sheets are hung upon tightly stretched cords or other similar sup- 

 port, in such a manner that they rest at an angle of about 45 with 

 the perpendicular. They are wet with warm water, are "wrung out" 

 to remove the excess, and sprayed with formalin in the proportion of 

 ten ounces to each thirty square feet of surface. One sheet (thirty 

 feet square) is sufficient for each thousand cubic feet of room space. 



The evolution of formaldehyde is slower with the sheet method than 

 with the permanganate method, but equally efficient disinfection is 

 obtained if the room is kept closed eight hours. 



2. Paraform. Paraform is a polymer of formaldehyde; it is a white 

 solid which is readily ignited, and burns with a bluish flame. It offers 

 no advantages over formaldehyde, except that it occupies much less 

 space. Special lamps have been devised to liberate formaldehyde 

 from it in the gaseous state, but the efficiency of the method is not 

 greater than the permanganate method, and the apparatus is some- 



