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



The pipettes may be obtained from any dealer in chemical appara- 

 tus. The standard sodium bicarbonate solution should be made up 

 by dissolving the bicarbonate in 1 liter (1.000 c. c.) of water, to which 

 has been added enough methyl orange indicator to produce a good 

 yellow color. The total equipment described should not cost much 

 more than $1 and if not available otherwise may be obtained from '■ 

 druggists. 



In order to determine the strength of the acid proceed as follows : 

 Fill the bulb pipette with acid from the acid tank, drawing it into the 

 pipette by suction ; let the excess acid flow out until even with the 

 mark on the upper part of the pipette, and then allow the measured 

 acid to drain into the 2-ounce bottle. Next fill the measuring pipette 

 from the standard sodium bicarbonate solution. Adjust the level of 

 the liquid with the c. c. mark, and let it flow slowly into the bottle 

 containing the measured acid, shaking the bottle meanwhile. At the 

 point where the color of the acid changes from red to yellowish note 

 the number of cubic centimeters (c. c.) of soda that has been used. 

 This will indicate the percentage of acid strength directly. For ex- 

 ample, if 5.3 c. c. of the standard sodium bicarbonate were used to 

 neutralize 10 c. c. of the acid, the strength of the acid would be 0.53 

 per cent. 



Always use the bulb pipette for measuring the acid and the other 

 pipette for the soda. Rinse out the bulb pipette with the acid to be 

 tested. 



EFFECT OF CLEANING METHODS ON KEEPING QUALITY 



In considering the capacity of any cleaning method to remove spray 

 residue the question arises immediately as to the effect such a treat- 

 ment may have on the keeping quality of the fruit and upon storage 

 diseases. Perhaps no other factor has militated so strongly against 

 the universal adoption of fruit-cleaning programs as has the uncer- 

 tainty on these points, and the following suggestions summarize the 

 best information now available. 



The dry cleaning of apples can be done on a commercial scale in 

 such a manner that there will be no exceptional loss from decay or 

 deterioration in storage. This statement assumes that the proper 

 sanitation precautions are taken, that the dry-cleaning equipment is 

 properly adjusted and not overloaded, and that the cleaning agents 

 are kept reasonably clean. 



The dry cleaning of pears is less satisfactory mainly from a 

 handling standpoint. Especially with the tender-skinned varieties 

 such as Cornice and Anjou, dry cleaning often results in skin 

 scratches, abrasions, and stem punctures. Equipment employing 

 rope-wound rolls for conveying the fruit as well as the oscillating-^ 

 brush cleaners were found to give the most trouble. The smaller sized 

 pears were generally most seriously affected, the character of the 

 injury being a dark discoloration of the skin accompanied by 

 excessive wilting. 



The prevalence of rot was mainly dependent upon skin punctures, 

 which in turn were determined by the character of the handling 

 which the fruit received. 



Mature apples and pears can be washed satisfactorily with dilute 

 hydrochloric acid under commercial conditions without serious 



