234 THE VITAMINES 



Later, Harden and Robison (625) showed that vitamine C is not 

 volatile on distillation, that the dry residue has almost the same 

 activity as the original juice, and that it may be kept in a dry con- 

 tainer for six months. Apple juices were found to be much poorer 

 in vitamine C. This applies to juices concentrated in the labo- 

 ratory; when prepared in large amounts, these preparations lose 63 

 per cent of their activity, according to Harden and Robison (626). 

 Vedder (626a) prepared active extracts by successive extractions 

 with absolute alcohol acetone and ethyl acetate. Vitamine C was 

 destroyed by phosphotungstic .acid and the last extract exhibited 

 about one-seventh of the initial activity and contained only traces 

 of nitrogen. This led Vedder to the somewhat premature conclusion 

 that vitamine C is nitrogen-free. Without going further, we see 

 that active preparations of vitamine C may be obtained also in the 

 absence of citric acid, and we are therefore not yet certain whether 

 these acids possess protective qualities. 



Givens and McClugage (627) dried orange juice in two different 

 ways. First, in shallow dishes at 55 to 60C. for 50 hours; second, 

 according to a method used in drying milk (Just-Hatmaker process), 

 in which a quick drying at 75 to 80C. is obtained. Whereas the 

 second preparation was almost as active as the original juice, the 

 first lost a great part of its effectiveness. The active products were 

 kept for 3^ months without loss of activity. Stable preparations 

 of vitamine C were made by Dubin and Lewi (628) and also by 

 Bassett-Smith (629). As regards the stability of vitamine C to 

 alkalis, a number of papers have been published. Harden and Zilva 

 (630) made orange juice alkaline with a /<r sodium hydroxide and 

 kept this for 24 hours, resulting in a loss of activity. Hess and 

 linger (631) carried out similar experiments and believed that, for 

 the most part, storage in alkaline medium exerted an unfavorable 

 influence on the activity. Accordingly, if the juice is boiled up in a 

 slightly alkaline solution and immediately neutralized, the activity 

 is only slightly diminished. McClendon and Sharp (632) investi- 

 gated the reaction of natural juices to determine if they are not some- 

 what alkaline, which would explain the destruction of vitamine C 

 on boiling; however, most of the juices were found slightly acid. 



Sommer and Hart (633) stated that the destructive action of boiling 

 on vitamine C was not due to the precipitation of citrates, while 

 Faber (634) found that an addition of sodium citrate (even in a con- 

 centration of 0.25 per cent) has a destructive action on this vitamine. 



