218 THE VITAMINS 



of similar activity, thus suggesting that a protective substance had 

 been removed during fractionation. 



Decitrated lemon juice submitted to dialysis in a collodion thimble 

 previously soaked in 83 per cent alcohol retained most of its antiscor- 

 butic property and slightly less than half its reducing property, while 

 similar juice dialyzed in a thimble soaked in 92 per cent alcohol retained 

 none of its antiscorbutic or reducing properties. 



Previous dialysis experiments by Zilva and Miura (1921) and 

 Connell and Zilva (1924) had suggested the probability that the di- 

 mensions of the vitamin C molecule were not far different from those of 

 the hexoses, since an 87 per cent membrane was impermeable to both 

 the sugar and the vitamin in decitrated lemon juice, while an 88.5 

 per cent membrane allowed the slow passage of the sugar but not 

 the vitamin. The different rates of diffusion of the reducing and 

 antiscorbutic materials now demonstrated were thought by Zilva to 

 suggest the probability that the vitamin C molecule is larger than 

 hitherto surmised and that its apparent inactivation on dialysis noted 

 in the earlier studies was due to diffusion of the protective reducing 

 agent. 



Zilva (1929) studied the effect of heating at temperatures lower 

 than 100° C. Decitrated lemon juice adjusted to pH 7 was heated in 

 air-exhausted, nitrogen-filled ampoules at temperatures of 55° to 58°, 

 and 80° to 85°, respectively, for 1 hour, adjusted if necessary to pH 7, 

 and kept in the cold for 7 days before being tested for vitamin C. 

 With the exception of one series in which the juice was heated to 

 55° C. there was no more deterioration of vitamin C in the heated 

 than in unheated juices in corresponding periods of storage. The de- 

 struction of the reducing principle was likewise of the same order as 

 that of unheated solutions. 



The stability of the vitamin after autoclaving was not increased 

 by the addition of decitrated lemon juice previously inactivated by 

 aeration at ordinary temperatures, or of the inactive precipitate ob- 

 tained by treating ordinary decitrated lemon juice with alcohol, or of 

 the neutral lead acetate fraction, although it was noted that occasionally 

 considerable antiscorbutic activity could be demonstrated in the neutral 

 lead acetate precipitate. Decitrated lemon, cabbage, tomato, and ruta- 

 baga juices were all found to contain a peroxidase, the activity of 

 which persisted after the vitamin had been partially or entirely de- 

 stroyed. Autoclaving decitrated lemon juice under anaerobic conditions 

 diminished somewhat its capacity for reducing phenolindophenol, but 

 increased its capacity for decolorizing iodine. This increased capacity 



