CHAPTER II 

 THE ANTIRACHITIC VITAMINE VITAMIN E A 



The history of the discovery of vitamine A has already been dis- 

 cussed, so that we may take up the chemistry of this substance at 

 once. We have noted that for a long time, vitamine A was supposed 

 to be free from nitrogen, but we feel that in the interest of future 

 investigation this question should be left open. We must also leave 

 for the future, the question as to whether the designation, vitamine 

 A, includes several substances of the same type, or only a single 

 substance. The chemistry of vitamine A has advanced but little 

 so that we shall only discuss its resistance to physical agents, solu- 

 bility and occurrence. 



CHEMISTRY OF COD LIVER OIL 



Cod liver oil is the only starting material from which attempts 

 have been made to isolate the vitamine. Although Qsborne and 

 Mendel (570) showed in 1914 that this oil contains vitamine A, and 

 although, because of its relationship to the therapy of rickets, it has 

 commanded attention for a long time, we are still in the dark as to 

 the nature of the vitamine contained therein. However, when we 

 consider the known facts about the resistance of vitamine A from 

 various sources, and the technical preparation of cod liver oil (571), 

 it is obvious that because of the stability of the vitamine, cod liver 

 oil is the best material to use for the chemical isolation of vitamine A. 

 Iscovesco (572) believed that almost all of the phosphorus and nitro- 

 gen of cod liver oil occurs as a lecithide or as a lecithalbumen. If 

 acetone is added to cod liver oil, with stirring, a precipitate is formed, 

 which, on reaching a maximum, is redissolved. The oil, freed from 

 some of its lecithin by acetone, was shaken with an equal volume of 

 95 per cent alcohol. To the alcoholic solution, which contains all 

 of the phosphorus of the oil, absolute alcohol was added, giving two 

 separate fractions. The soluble part was concentrated at a low 

 temperature, the residue dissolved in ether and precipitated with 

 acetone. In this way, from 1 kilo of oil, 0.02 gram of the pure 

 lecithide was obtained, which was soluble in benzol and chloroform, 



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