14 CIRCULAR 5 9, U. S. DEPARTMENT OF AGRICULTURE 



machines which applied the hydrochloric acid in solid jets with con- 

 siderable pressure, forcing the acid deeply into the calyx, also caused 

 considerable damage of this nature. 



Frequent renewal of the washing solution to prevent the accumu- 

 lation of toxic concentrations of soluble arsenic is a most important 

 precautionary measure. It is significant that when the tanks were 

 drained after each day's run, fresh washing solutions being provided 

 daily or after washing about 1,000 boxes, no further serious trouble 

 was experienced. The use of a final fresh-water rinse applied as 

 a spray as the apples leave the machine is also desirable in connec- 

 tion with removing traces of soluble arsenic as w T ell as spores of rot 

 fungi. 



A further precautionary procedure was indicated by experiments 

 in which the injury was prevented by using a lime water rinse. In 

 this case the lime reconverts the soluble arsenic found on the apples 

 into a relatively insoluble and noninjurious form. The lime was 

 added to the rinse water in the form of fresh stone lime, slaked and 

 added in the concentration of 2 pounds to 50 gallons of water. If 

 there is a conspicuous lime residue, a final fresh-water rinse may be 

 employed to remove it. There is practically no need for the use of 

 lime in the rinse water when pears are washed, and there is some 

 question as to whether its use on russeted pears may not result in 

 surface injury. 



In some cases baking soda or sodium bicarbonate was added to the 

 rinse water. While baking soda will neutralize the hydrochloric acid 

 carried over on the fruit and thus prevent its further action upon 

 unremoved spray residue, it is not entirely effective in the direct 

 prevention of arsenical injury. Its reaction with arsenic acid pro- 

 duces sodium arsenate, which is almost as soluble and toxic as arsenic 

 acid itself. 



The alkaline solvents used also react with lead arsenate to produce 

 sodium-arsenic compounds, which likewise produce injury when they 

 become sufficiently concentrated. 



In addition to arsenical injury, apples washed with alkaline solvents 

 have shown a superficial brownish deposit in the calyx basin. This 

 has been merely unsightly in most cases and apparently has been due 

 to insufficient rinsing with fresh water. 



HYDROCHLORIC-ACID BURNING 



Hydrochloric-acid injury is distinguished from arsenical injury 

 primarily by its lighter color. The cases observed were due to in- 

 sufficient rinsing, contact of the fruit with box boards soaked with 

 acid solution during the washing process, and deep-submersion 

 methods whereby fruit was held in contact with the acid for extended 

 periods. 



Most of the homemade washing devices have either submerged the 

 apples in boxes or floated the fruit through long tanks with occasional 

 submersion under paddle wheels. The low initial cost of such ma- 

 chinery and its simplicity of operation have made it generally adapt- 

 able to the average small orchard. A number of cases have come 

 to attention, however, in which excessive losses from core rots 

 occurred on apples washed by these methods. Likewise, very serious 

 losses from core rots were experienced as a result of washing apples 



