BLACKLEG. 325 



as near air-tight as possible, when closed. Spread the potas- 

 sium permanganate evenly over the bottom of a large, rather 

 deep pan or pail. If the quantity is large a small wash tub, 

 or half of a barrel may be used. Pour in the formaldehyde and 

 give the dish one rapid tilt to ensure thorough mixing; leave the 

 room at once and tightly close from without. Keep closed for 

 about 24 hours, or at least over night. 



The dish used for a generator should be placed in the middle 

 of the room. To avoid injury from the strong gas as it is 

 liberated no potatoes should be placed directly above the genera- 

 tor. It is also better to leave a clear space of at least three 

 feet on all sides of the generator, and the slat-work bins or 

 crates should be so arranged that the gas can circulate on all 

 sides of them and mix with the air of the room before it comes 

 in contant with the potatoes. Formaldehyde gas possesses 

 about the same specific gravity as air, but when generated in 

 this way the strong gas is driven off very rapidly mixed with 

 hot, watery vapor and probably the most of it goes first to the 

 top of the room, but it quickly diffuses and mixes with the air 

 contained therein. 



Temperature is an important factor in disinfecting with 

 formaldehyde. It is more effective above 80 degrees F. and 

 disinfection with this gas should never be attempted wdiere the 

 temperature of the chamber used is below 50 degrees F. A 

 certain amount of moisture in the air is also very essential, 

 therefore just before placing the formaldehyde in the generator- 

 the floor of the disinfecting chamber should be thoroughly wet 

 down with boiling water. However, no water should be placed 

 on the tubers to be treated. 



The exposure of the tubers to the gas should not be made 

 in sacks. It takes a large volume of gas and a long cx])osure 

 to penetrate the sacks. Large quantites of the formaldehyde 

 are lost bv uniting chemicallv with the organic matter of the 

 fabric, and the meshes tend to convert the gas into a solid sul>- 

 stance known as paraform. 



Upon completion of the time required to disiiifect, the door 

 of the room is opened and in a very short time the gas will 

 have diffused outward sufficiently to allow the treated tubers 

 to be taken out. There is absolutely no danger to human beings 

 in working with the gas as here recommended. When first 



