20 MISC. PUBLICATIOIT 16 8, U.S. DEPT. OF AGEICULTUEE 



jurious strength through evaporation, the outline of the affected 

 area is usually circular (pi. 12, A, B), but where acid accumulates 

 between an apple and some other object in contact with it the out- 

 line may be quite irregular. This injury bears a close resemblance 

 to that sometimes found on apples when sulphur dioxide escapes 

 from refrigerating systems. In the latter case, however, the apples 

 are usually more generally speckled at lenticels and the margins of 

 the bleached areas become black with age, while the spot itself may 

 become faintly zoned in appearance. 



Acid injury can be prevented by careful attention to instructions 

 given in Farmers' Bulletin 1687 {SI) and Technical Bulletin 215 

 {70) for the use of hydrochloric acid solutions for washing apples. 

 Of especial importance in preventing acid injury is thorough rinsing 

 of the fruit after it passes through the washing solution. {60^ 68, 

 69, 70,) 



INJURY BY ALKALINE SOLVENTS 



Although hydrochloric acid is the solvent commonly used for the 

 removal of arsenical spray residue, a number of alkaline materials, 

 including solutions or mixtures of sodium hydroxide, sodium car- 

 bonate, trisodium phosphate, borax, sodium silicate, and other sub- 

 stances are also employed. These solvents are sometimes used at a 

 temperature of 100° F. or higher. 



Arsenical injur}^ occurs somewhat more commonly on apples 

 washed in alkaline solvents than on those washed in hydrochloric 

 acid. Because the alkaline solvents are much more difficult to rinse 

 off than is the hydrochloric-acid solution, apples washed in the for- 

 mer often retain some of the solvent in the calyx cavity, where it 

 continues to react with residual lead arsenate, forming the injurious 

 soluble arsenic. 



Occasionally the alkaline solution itself causes chemical injury. 

 Such injury is usually localized around the stem or calyx but is 

 sometimes found at the lenticels as well (pi. 12, E). It is shown 

 by the effect on the skin, which becomes dry and papery, tightly 

 stretched, but seldom cracked, as in the case of hydrochloric-acid 

 injury, and is often torn loose from the underlying fleshy tissues. 

 The color is yellowish or brownish yellow, except when a consider- 

 able quantity of arsenic is present, in which case the color becomes 

 dark brown or black. {68, 69, 70.) 



INJURY BY SOLUBLE ARSENIC 



The injury that has sometimes been called calyx scald or water 

 scald should be designated as arsenical injury. It occurs as de- 

 pressed black or brownish spots in the calyx cavity, often encircling 

 the calyx, or occasionally it is found in the stem basin. Sometimes 

 the flesh is killed to a depth of half an inch or more. When the skin 

 is killed the apple is readily attacked by decay fungi (pi. 12, C, D). 



Arsenical injury on harvested fruit may be produced in several 

 ways: (1) By allowing heavily sprayed fruit to become or remain 

 wet for a period of several hours before the spray residue is removed. 

 In this case it is due to soluble arsenic in the spray residue and may 

 occur on the trees before picking. (2) By the prolonged use of 



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