38 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



are hung up in the compartment containing the infected materials. 

 The gas is liberated by simple evaporation, this liberation being 

 favored by the wide surface which is exposed. The gas is liberated 

 much more slowly by this method than by either of those already 

 described, and the diffusion is also relatively much slower. For 

 these reasons the compartment to be disinfected should not be very 

 large, and should remain closed for at least twenty-four hours. Not 

 less than 10 ounces of formalin should be used for each 1,000 cubic 

 feet of space. 



Liberation of the Gas by Chemical Means. Several methods 

 of liberating formaldehyde from formalin solutions without the use 

 of artificial heat have been proposed in recent years. The most im- 

 portant of these is known as the "permanganate method." Formalin 

 is poured upon crystallized or powdered potassium permanganate. 

 A violent chemical reaction takes place immediately, heat is gene- 

 rated, and a rapid liberation of formaldehyde gas takes place. As 

 will be understood, the heat is caused by the reaction between the 

 formaldehyde in solution and the permanganate, a large portion of 

 the formaldehyde being consumed by the reaction. The amount 

 of gas evolved depends in great measure upon the relative weights 

 of permanganate and formalin employed. Experiments have shown 

 that when the formalin and permanganate are mixed in the pro- 

 portion of 6 parts of formalin to 5 parts of chemically pure perman- 

 ganate, by weight, 50 per cent of the formaldehyde employed is lib- 

 erated in the form of gas. If 10 ounces of formalin are required for 

 disinfection of 1,000 cubic feet of space by the first three methods 

 described, twice that amount is necessary when the permanganate 

 method is employed, as half of the formaldehyde is destroyed by the 

 reaction. For disinfecting 1,000 cubic feet, therefore, use 20 ounces 

 of formalin and 16 2-3 ounces of permanganate. The needle-shaped 

 crystals of potassium permanganate should be employed. Place the 

 required amount of permanganate in a wide-bottomed vessel (an 

 ordinary dish pan is excellent) and pour the formalin on quickly, 

 then close the compartment for from six to twelve hours, depending 

 upon the character of the materials to be disinfected. 



GAS FROM PARAFORM AND WOOD ALCOHOL. 



Lamps provided with a pan for holding the paraform are ob- 

 tainable on the market. The paraform is placed in the pan and 

 heat applied by means of an alcohol lamp. The evolution of gas in 

 this manner is slow. Two ounces of paraform is required for the 

 disinfection of 1,000 cubic feet of space, and the compartment 

 should remain closed for at least twelve hours. This method is best 

 suited to the disinfection of small spaces. 



Generation of Formaldehyde from Wood Alcohol. Formal- 

 dehyde is readily produced by the oxidation of wood alcohol (me- 

 thyl alcohol). This fact has been taken advantage of for use in 

 practical disinfection. Lamps have been designed by means of 

 which the vapor of wood alcohol is passed over hot, finely divided 

 platinum. This causes the oxidation of the alcohol to formalde- 

 hyde, which is given off in the room to be disinfected. There is 



