270 DISEASES OF ECONOMIC PLANTS 



the use of formaldehyde gas ^ hberated by mixing the com- 

 mercial solution with potassium permanganate. This 

 method is adapted to the disinfection of large quantities of 

 potatoes in a short time. To use it, an air-tight shed should 

 be constructed of sufficient size to hold whatever quantity 

 it may be desired to treat at one time. This may be made of 

 rough lumber fined with building paper and provided with 

 a tight door. The potatoes may be treated in sacks, but 

 these sacks should be so piled as to permit free circulation 

 of air all around them. It is suggested that they be piled 

 in tiers with two 2-by-4-inch scantlings between each layer 

 of sacks. Space should be left in the center of the building 

 for placing the charge of formaldehyde, which should be 

 set off in shallow vessels, such as galvanized washtubs. For 

 each 1000 cubic feet 23 ounces of potassium permanganate 

 and 3 pints of formaldehyde should be allowed. After the 

 potatoes are properly stacked and everything is made ready, 

 the permanganate should be spread in a thin layer on the 

 bottom of the pan, the required quantity of formaldehyde 

 poured in, stirred quickly, and the building vacated. The 

 building should then be kept tightly closed for twenty-four 

 hours, when it may be opened and the potatoes taken out. 

 The precaution should be taken not to pile any potatoes 

 directly over the pans or within three feet laterally, since 

 the gas there might be strong enough to injure the potatoes 

 and destroy their germinating power. The formaldehyde 

 works best in a humid atmosphere. It is therefore advised 

 that the floor of the shed be dampened before the treatment 

 is made. The potatoes, however, should not be moist, 



1 Jones, L. R., and Edson, A. W., Vt. Agr. Exp. Sta. Rpt. 14, 1900-1901, 

 and Morse, W. J., Me. Agr. Exp. Sta. Bui. 141, p. 89, March, 1907. 



