234 THE VITAMINS 



neutralize the sodium hydroxide that had previously been introduced. 

 Two cubic centimeters daily of the juice heated at pH 4.2 were fed to 

 rats and a comparison of the growth resulting was made with the growth 

 of litter mates receiving an exactly equivalent amount (correction being 

 made for increase in volume due to acid and alkali added in adjusting 

 the pH) of the juice heated at pH 9.2. The total average weight gain 

 for the 8-week period was 47 grams for test animals fed the juice which 

 had been heated at pH 4.2 and 45 grams for those receiving the juice 

 which had been heated at pH 9.2. Thus the change of hydrogen-ion 

 activity from pH 4.2 to pH 9.2 did not appreciably influence the rate of 

 destruction of vitamin A, 



Since results of the first series of experiments had shown vitamin A 

 in a plant material to be relatively stable, it seemed desirable to compare 

 the stability of the vitamin from animal and plant sources when heated 

 under conditions as nearly identical as possible, including the use of the 

 same solvent. It was found that an extract fairly rich in vitamin A could 

 be prepared by shaking dry powdered spinach leaves with olive oil. 

 Since a solution of butterfat in olive oil could readily be obtained, these 

 two olive oil preparations were used as materials for the study. 



These olive oil solutions containing the vitamin A of spinach leaves 

 and of butterfat, respectively, were heated for 4 hours at 97° C. ± 2° 

 under anaerobic conditions, essentially as described above. Frequently 

 repeated quantitative determinations of the vitamin A values by the 

 feeding method already described, showed that of the vitamin A of the 

 spinach about 20 per cent, and of that of the butter about 33 per cent, 

 were destroyed during the 4 hours heating. 



Cady and Luck (1930) have also noted greater stability of the vita- 

 min A in plant than in animal materials. On bubbling purified sulfur 

 dioxide through cod-liver oil at temperatures of from 20° to 100° C. 

 for periods of 15 minutes to 2 hours, the vitamin A activity was com- 

 pletely destroyed, while similar treatment of a concentrated alcoholic 

 extract of alfalfa was without appreciable effect. Butter occupied an 

 intermediate position, the destruction of vitamin A being reported very 

 slight. In a further study of the stability of vitamin A in cod-liver oil 

 toward various reagents, complete destruction was demonstrated with 

 phosphorus pentachloride, chlorine, acetyl chloride, nitrous acid fumes, 

 Benedict's alkaline copper reagent, and after prolonged treatment with 

 sodium bisulfite. Hydrogen sulfide, ethylene, ammonia, and Benedict's 

 reagent after neutralization had no, and formaldehyde very slight, 

 destructive effect, while hydrogen peroxide brought about a partial loss 

 of vitamin A activity. Attempts to regenerate the vitamin A potency of 



