CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 343 



different solvents. He classified the solvents into three groups as 

 follows according to their relation to the leaf pigments. 



"i. Alcohols (methyl, ethyl, amyl), acetone, acetaldehyde, ether, 

 chloroform: These solvents, acting on freshly cut up or dried leaves 

 dissolve out all pigments equally and completely." 



"2. Petroleum ether or petroleum benzin: This solvent, acting 

 on fresh leaves finely ground with sand or emery, takes on a 

 more less yellow appearance, which is especially due to carotin, 

 but contains also other pigments. Dried leaves (at a low temperature) 

 likewise give up their carotin to this solvent, and in somewhat purer 

 condition." 



"3. Benzol, xylol, toluol, and carbon bisulphide: These solv- 

 ents set intermediately between the first two groups." 



Willstatter and Mieg J a little later approached the same problem 

 from another standpoint and showed that the methods used by Kraus 2 

 and Sorby 3 for demonstrating the presence of more than one pigment 

 in green plants, when properly applied could be made characteristic 

 properties of carotin and xanthophylls. Kraus shook his alcoholic 

 extracts of green leaves with petroleum ether and found that the 

 green pigment went into the petroleum ether leaving the alcoholic 

 solution yellow. Sorby shook his alcoholic extracts with carbon 

 bisulphide and found that the latter solvent contained the green pig- 

 ment while the alcohol was left yellow. Wilstatter and Mieg, apply- 

 ing these tests to the isolated carotin and xanthophyll pigments obtained 

 the following results: 



"i. If methyl alcohol is added to a petroleum ether solution 

 of carotin so that the liquids do not mix, the carotin will remain for 

 the greatest part in the petroleum ether layer, the alcohol layer being 

 only slightly colored. If a trace of water is added, the methyl alcohol 

 layer will become colorless. The same phenomenon occurs with ethyl 

 alcohol, and one can start with an alcohol or benzol solution and 

 show the same thing." 



"2. If carbon bisulphide is added to an alcoholic carotin solu- 

 tion and a little water added, the carbon bisulphide will separate and 

 will quantitatively contain the carotin." 



"3. If an alcoholic solution of the xanthophylls is mixed with 

 petroleum ether and the liquids separated with a little water, by far the 

 greatest portion of the xanthophylls will be found in the alcohol layer." 



1. Ann. der. Chemie 355 p. 8 (1907). 



2. Flora, p. 155 (1875). 



3. Proc. Roy. Soc. 21, p. 456 (1875). 



