24 CIRCULAR 3 7 3, U. S. DEPARTMENT OF AGRICULTURE 



COMPARISONS OF THE USE OF CALCIUM CYANIDE AND LIQUID 

 HYDROCYANIC ACID 



During one treating season (1932) liquid hydrocyanic acid was 

 used to fumigate a total of 111 cars at a cost of $6.37 per car (6 

 ounces of hydrocyanic acid at $1 per pound). The calcium cyanide 

 costs $3.45 per car (3 pounds of calcium cyanide at $1.15 per pound) . 

 In this way a saving Avas made of approximately $340 on materials 

 for treating the 111 cars with the hydrocyanic acid. In addition, 

 no fruit injury due to the treatment was reported at any time dur- 

 ing the treating season. 



The introduction of the hydrocyanic acid from the top of the cars 

 is much simpler than the introduction of calcium cyanide through 

 the side doors. In the former method the cups and pans can be 

 placed in the ice compartments while the interiors of the cars are 

 being loaded with fruit. As soon as the cars have been loaded the 

 side doors may be closed and sealed. The operator can then go 

 along the tops of the cars, applying the fumigant, followed by an 

 assistant to lower the covers of the ice compartment. At the con- 

 clusion of the treatment the operator can remove the apparatus 

 from the ice compartments. This eliminates the necessity of open- 

 ing and closing the heavy side doors of the car, as is the case both 

 when introducing the trays containing the calcium cyanide and when 

 removing the residues. 



Certain local conditions may, of course, govern the choice of 

 chemical. It is obvious, for example, that although the use of hydro- 

 cyanic acid would probably be more satisfactory for the dealer with 

 a large number of cars to fumigate, the dealer with only a few cars 

 to fumigate would be more inclined to purchase a few cans of cal- 

 cium cyanide. 



ABSORPTION OF HYDROCYANIC ACID BY BANANAS 



In connection with this work there naturally arose the question of 

 whether or not the bananas would absorb any appreciable quantity 

 of fumigant. Griffin and others (3) had found that ripe bananas 

 absorbed as much as 440 parts per million when fumigated at the 

 rate of 40 ounces of sodium cyanide per 1.000 cubic feet. The theo- 

 retical production of hydrocyanic acid from this quantity of ma- 

 terial is approximately 22 ounces, which is much greater than the 

 quantity needed in refrigerator-car fumigation. 



In order to determine the amount of hydrocyanic acid absorbed by 

 green bananas, analyses 8 were made in 1927 of green fruit treated 

 for 2 hours with 3 pounds of calcium cyanide per car. The hydro- 

 cyanic acid in the fruit was determined by the method of Viehoever 

 and Johns (8). Only very small quantities were found. In 1931 

 many analyses 9 were made of green fruit which had been subjected to 

 a fumigation of 1 hour with lp 2 pounds of hydrocyanic acid absorbed 

 in disks of wood-paper pulp per car. The method of analysis men- 

 tioned above was used. Separate analyses were made of skin and 

 pulp, samples having been taken from the same bunches both 2 

 hours after fumigation and after thev had remained in a cold 



s This work was done by K. B. Rogers and II. W. Coward, former members of the 

 laboratory staff. 



D 'This work was done by C. W. Mell, a former member of the laboratory staff. 



