90 maine; agricultural experiment station. 1907. 



gas as described by Messrs. Evans and Russell of the Maine 

 Laboratory of Hygeine.* 



By this method all danger from fire is eliminated as the heat 

 required for the liberation of the gas is generated by the chemi- 

 cal action of the potassium permanganate upon the formaldehyde 

 in the solution. It is true that some of the formaldehyde is 

 used up in the reaction but this is more than offset by the fact 

 that within 5 minutes 80 to 85 per cent of the available gas is 

 liberated, and in this manner the maximum strength of for- 

 maldehyde is acting upon the fungus almost at once. Where 

 the gas is liberated by boiling it comes off more slowly, there is 

 constant loss by leakage from the room and at no time is the 

 maximum amount of available gas present in the disinfecting 

 chamber. The results of hundreds of tests with various patho- 

 genic bacteria by Evans and Russell and of one test with potato 

 scab by the writer indicate that gas generated by the perman- 

 ganate method is equally if not more effective than that gener- 

 ated in other ways. 



The disinfection of seed potatoes with formaldehyde gas has 

 not been tried on a commercial basis but the results of repeated 

 trials on a small experimental scale with the gas generated by 

 various means are such that it is believed worthy of recom- 

 mendation, especially where a convenient and rapid method of 

 treating large quantities of seed at one time is desired. 



The room in which the work is to be done should be made as 

 tight as possible and be provided with a tightly fitting door. 

 The conditions which obtain in a good potato house intended 

 for winter storage would doubtless meet the requirements. On 

 account of the large amount of space in the open house it woula 

 probably be more economical to partition off an end or a corner 

 for the disinfecting room. This partition need not be of expen- 

 sive material provided care is taken to make it tight by the use 

 of weather strips and pasting builders' or other heavy paper 

 over the cracks and openings. 



While it is known that formaldehyde gas has considerable 

 penetrating powerf there is no experimental evidence as to how 



* Me. State Bd. Health Rep. 13,p. 234, (1904). 



t Me. State Bd. Health Rep. 14, (1906). (Evans' experiments here recorded 

 indicate that the gas can penetrate from one to lour thicknesses of silk, cotton 

 flannel and ticking and stilll he perfectly effective upon pathogenic hacteria.) 





