88 MAINE AGRICULTURAL EXPERIMENT STATION. I907. 



DISINFECTING AGENTS. 



Corrosive sublimate and formaldehyde (usually sold under 

 the name of formalin) are so far the only agents found to be 

 satisfactory for tuber disinfection. These chemicals' as well as 

 the potassium permanganate which is used with formalin to 

 generate formaldehyde^ gas can be supplied by any druggist. 



Corrosive sublimate is a white crystalline powder. It is a 

 deadly poison if taken internally, but is safe to handle provided 

 care is taken to keep the treated tubers and solution away from 

 stock and children. It is a good disinfectant, but on account of 

 its poisonous nature it is doubtful if it would have come into 

 so general use if the value of formaldehyde had been demon- 

 strated earlier. Corrosive sublimate costs about 15 cents per 

 ounce and should be purchased for $1.50 or less per pound. 



Formalin is a liquid having a sharp, pungent odor. It is a 

 solution of formaldehyde gas, the best grades containing about 

 40 per Cent. The ordinary commercial goods should show at 

 least 35 per cent, and should not be accepted unless the dealer 

 will guarantee that percentage of formaldehyde, subject to 

 analysis. Compared with corrosive sublimate formalin is 

 equally effective as a disinfectant for scab and possesses the 

 advantage of being absolutely safe to handle. Good formalin 

 should be obtained at from 40 to 50 cents per pint, or even less 

 if bought in any quantity. 



Commercial potassium permanganate comes in the form of 

 small, glistening, purple-brown crystals. It is sold for about 30 

 cents per pound. 



METHODS OF DISINFECTION OF SEED POTATOES. 



I. Soaking seed in a disinfecting solution. Applicable where 

 the acreage is small but impracticable for the large 

 grower or dealer. 



(a) Formalin solution. Add one-half pint of com- 

 mercial formalin to 15 gallons of water, stir thoroughly, 

 and soak uncut tubers 2 hours in this solution. 



(b) Corrosive sublimate solution. In a wooden or 

 earthern vessel (metal vessels cannot be used on 

 account of the corrosive action of the chemical) dis- 

 solve 2 ounces of corrosive sublimate in 2 gallons of 

 hot water, and then dilute to 15 gallons with cold water. 

 Place uncut tubers in a sack and soak iy 2 hours in this 

 solution. 



