MARKET DISEASES OF FRUITS AND VEGETABLES 25 



retain some of the solvent in the calyx cavity, where it continues 

 to react with residual lead arsenate and forms the injurious 

 soluble arsenic. Occasionally the alkaline solution itself causes 

 chemical injury. Such injury is usually localized around the stem 

 or calyx, but it is sometimes found also at the lenticels (pi. 5, B). 

 The skin becomes dry, papery, and tightly stretched — but seldom 

 cracked as in the case of hydrochloric acid injury — and is often 

 torn loose from the underlying fleshy tissues. The skin color is 

 yellowish or brownish yellow, except when a considerable quan- 

 tity of arsenic is present; in that case it becomes dark brown 

 or black. 



(See 46, 136.) 



INJURY BY SOLUBLE ARSENIC 



The injury that has sometimes been called calyx scald, or water 

 scald, should be designated as arsenical injury. It usually occurs 

 as depressed black or brownish spots in the calyx cavity, often 

 encircling the calyx ; but occasionally it is found in the stem basin. 

 Sometimes the flesh is killed to a depth V2 inch or more. When 

 the skin is killed the apple is readily attacked by decay fungi. 



Arsenical injury on harvested fruit may be produced in several 

 ways: (1) By allowing heavily sprayed fruit to remain wet for 

 several hours before the spray residue is removed (in this case 

 the injury is due to the soluble arsenic in the spray residue and 

 may occur on the trees before picking) ; (2) by prolonged use 

 of washing solutions in which dissolved arsenic has accumulated 

 in toxic amounts; and (3) by use of faulty rinsing facilities, 

 which permit some of the solvent to remain in the calyx region, 

 where it continues its solvent action on arsenical-spray residue 

 not removed in the washing treatment. 



Arsenical injury may appear within a week or two after wash- 

 ing, but it usually requires several weeks to develop on all the 

 apples that may be affected in any lot. It seldom if ever occurs 

 on the cheek of the fruit. Chemical injuries appearing on the 

 cheek of washed apples are usually due to the solvents employed 

 for spray removal. Dissolved arsenic present in washing solutions 

 often causes such injured areas to turn black; but the primary 

 cause of damage in those areas is not arsenic but the solvents 

 used for spray removal. 



(See U6 y 57, 90.) 



INJURY BY SULFUR DIOXIDE 



Apples are sometimes injured by accidental exposure to sulfur 

 dioxide escaping from a refrigerating system in which this gas 

 is used as the refrigerant. Small quantities of sulfur dioxide 

 (50 to 100 parts per million) present in a chamber containing 

 apples have been found to produce injury. Such injury usually 

 consists in decolorized, whitish papery spots at the lenticels. If 

 the concentration of the gas is high and remains so for several 

 days, all the skin of fruits exposed to it becomes decolorized if 

 the apple was yellow or it bleaches to a uniform pink if the apple 

 was originally red ; the flesh becomes soft and rubbery and usually 

 has a strong, nauseating sulfurous flavor. 



