VITAMIN C 213 



Eh^= -\- 0.248 volts for cabbage juice. Thus the work of Kenny clarifies 

 the earlier work of Delf as well as that of La Mer, Campbell and 

 Sherman. 



Kohman (1923) called attention to the fact that fruits and vege- 

 tables, as well as the water in which they are cooked, may contain suffi- 

 cient dissolved oxygen to become an important factor in the destruc- 

 tion of vitamin C. Interested in the practical problem of the preserva- 

 tion of vitamin C in canning processes he suggested various methods of 

 removing oxygen from liquid and solid foods without the application 

 of heat, including vacuum exhaust and for certain fruits and vegetables 

 preliminary respiration. These suggestions were put into efifect in the 

 later studies of Kohman, Eddy, and associates as noted elsewhere. 



Concentration Experiments 



Zilva (1921, 1922) in the first of his series of studies on the sta- 

 bility and chemical nature of vitamin C, used, as his source of vitamin 

 C, lemon juice from which the organic acids had been removed by 

 precipitation with powdered chalk. The "minimum protective dose" of 

 this decitrated lemon juice was from 1.5 to 2 cubic centimeters daily. 

 After air had been aspirated through the solution for 12 hours at 

 laboratory temperature, daily doses of 3 and 5 cubic centimeters proved 

 insufficient to prevent, but delayed slightly, the onset of scurvy and 7 

 cubic centimeters was inadequate for promoting growth. After the 

 decitrated juice had been boiled for an hour with constant aeration, a 

 daily dose of 7 cubic centimeters were inadequate to prevent or delay 

 the onset of scurvy, while 1.5 cubic centimeters of the juice boiled 

 for 2 hours in an atmosphere of carbon dioxide provided ample pro- 

 tection. Hydrolysis with hydrochloric acid for 5 hours impaired but 

 did not entirely destroy the vitamin C value of the juice. 



In an attempt to correlate the effects of the reaction of the medium 

 and of oxidation on the stability of vitamin C, Zilva (1923) adjusted 

 portions of decitrated lemon juice to pH 6.6 to 6.8, 12.12, and 2.2 to 

 2.4. Portions of the alkaline solution (pH 12.12) were allowed to 

 stand for 24 hours under aerobic and strongly anaerobic conditions, 

 while the strongly acid solution (pH 2.2 to 2.4) was aerated for 1 or 

 2 hours and the nearly neutral solution for 1 hour at 100° C. The 

 alkaline solution was acidified with citric acid immediately before being 

 tested and all the preparations were tested on guinea pigs which had 

 been for about 14 days on a ration of oats and bran supplemented by 

 not more than 40 cubic centimeters of autoclaved milk daily. As thus 

 tested, the alkaline solution was found to have lost about 80 per cent 



