8 Department Circular 28^, U. S. Dept. of Agriculture 



forming organism similar in nature to Bacillus larvae, suggested 

 its use in the treatment of American foulbrood. Various dilute 

 solutions of iodine were suggested, since iodine is successfully used 

 in the sterilization of drinking water. A solution of formalin in 

 water, with the addition of acetic acid to increase its penetrating 

 power, is often used for fixating histological preparations; for 

 the treatment of American foulbrood a similar solution was ac- 

 cordingly suggested. 



A number of tests were made to compare the germicidal efficiency 

 of the commercial alcohol-formalin solution, now frequently used 

 by beekeepers, with that of the various other solutions tried, and 

 in particular with the 20 per cent solution of formalin in water. 

 Kronig and Paul (17) have shown that increasing quantities of 

 either ethyl or methyl alcohol added to a solution of formalin in 

 water progressively decreases the germicidal efficiency of the solu- 

 tion. Tests were therefore made with various dilutions of dena- 

 tured alcohol as the carrier for the 20 per cent solution of forma- 

 lin. Formula No. 1 {££, p. 100) for specially denatured alcohol was 

 used as a basis for these dilutions. Conamercial alcohol-formalin 

 solution was diluted in a similar manner by the addition of varying 

 quantities of a 20 per cent solution of formalin in water. These 

 tests were made to determine whether the presence of a greater pro^ 

 portion of water mixed with the alcohol changes the germicidal 

 efficiency of the solution. 



In this preliminary work no measurements were made of surface 

 tension and other physical properties, but the bacteriological re- 

 sults were used as a criterion of the relative efficiency of the various 

 disinfectant solutions tested. 



OBSERVATIONS 



SOAP SOLUTIONS 



In the use of soap-formalin solutions it was found immaterial 

 whether soft or hard soap is used. The greatest difficulty with 

 the soap solutions, aside from the fact that they do not seem to 

 penetrate sealed cells imiformly, which will be discussed later, is 

 a rapid change in reaction from alkalinity to marked acidity during 

 the period of immersion of one piece of comb. The acid reaction 

 causes the soap gradually to precipitate, so that the solution is 

 soon little better than ordinary water-formalin solution. Even the 

 addition of sufficient normal sodium-hydroxide solution to bring 

 the reaction back to alkaline after the comb is removed fails to 

 remedy this fault, as the precipitated soap does not return into 

 solution on the addition of the sodium hydroxide. The prolonged 

 action of soap and alkali on the wax of the comb during an im- 

 mersion of 48 hours causes more softening of the cell walls than 

 is desirable, and makes the combs quite fragile. Since some of the 

 sealed cells in practically every series of combs tested failed to be 

 sterilized, as indicated from the cultures made (Table 1), this 

 solution was dropped from consideration for use with combs having 

 sealed brood. 



In the case of the sodium-oleate-formalin solutions, 59 open and 

 59 sealed cells were cultured in 10 series, varying in length (Table 



