POTATOES 349 



the potatoes may be soaked in formaldehyde or a solution of 

 bichloride of mercury ; or, better still, where conditions will per- 

 mit, they may be fumigated with formaldehyde gas while in the 

 car or warehouse. 



The corrosive sublimate (bichloride of mercury) treatment is as 

 follows : soak the uncut seed one and one half to two hours in a 

 solution made by dissolving 2 ounces of corrosive sublimate in 16 

 gallons of water. The solution is exceedingly poisonous and must 

 be guarded to prevent stock from gaining access to it. 



The most economical and effective method of disinfecting seed 

 potatoes on a large scale is by the use of formaldehyde gas liberated 

 by mixing the commercial solution with potassium permanganate. 

 The following is a description of this method of disinfection : 



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, lined with building paper, and provided with a tight door. 

 The potatoes may be treated in sacks, but these sacks must be piled so as to 

 allow a free circulation of air all around them. It is suggested that they be 

 piled in tiers, with two 2x4 inch scantlings between the layers of sacks. Space 

 should be left in the center of the building for placing the charge of formalde- 

 hyde, which should be set off in shallow pans, 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 and stirred quickly, and the building vacated. The building should then 

 be kept closed tight for twenty-four hours, when it may be opened and the 

 potatoes taken out. 



Formaldehyde is a nonpoisonous but highly irritant fluid which can be pur- 

 chased in small lots at about 50 cents a pound, in carboy lots at 20 cents, or 

 in barrel lots at about 12 cents. Potassium permanganate is a reddish-brown 

 crystalline substance, purchasable at from 13 to 25 cents a pound. 



The precaution should be taken not to pile any potatoes directly over the 

 pans or within 3 feet laterally, as 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 wet down before the treatment is made. The potatoes, however, 

 should not be wet, as the disinfection is more thorough if the surfaces are dry. 



.Small quantities of potatoes may be disinfected by soaking in a solution of 

 i pint of formaldehyde to 30 gallons of water for two hours. Either the gas or 

 the solution treatment may be applied some time previous to planting, pro- 

 vided the potatoes are not exposed to reinfection by being put into receptacles 



