212 CAROTINOIDS AND RELATED PIGMENTS 



which have been macerated with emery in the presence of CaC0 3 or 

 MgO (to neutralize plant acids) are allowed to stand in contact with 

 pure carbon disulfide in a stoppered flask for 24-48 hours. The 

 solvent is filtered off and evaporated to dryness in vacuum. The 

 residue is boiled for thirty minutes with 50 cc. of 20 per cent methyl 

 or ethyl alcoholic potash (using only solutions which alone give no 

 coloration whatever on boiling). After cooling, 150 cc. of distilled 

 water are added and the mixture shaken with 200 cc. of pure ether 

 in a separatory funnel. After the two layers have separated the lower 

 greenish layer is drawn off and shaken with 100 cc. of fresh ether. 

 A third extraction with fresh ether should not be necessary, but can 

 be tried to insure the complete extraction of the carotinoids. The 

 combined golden yellow ether extracts, which may have a slight green 

 tinge, are washed with successive equal portions of distilled water 

 until the washings no longer react alkaline to phenolphthalein. The 

 ether may now be filtered through a layer of powdered anhydrous 

 Na 2 S0 4 , to remove the water. The filtrate is evaporated to dryness 

 in vacuum and the residue taken up at once in 100 cc. of hot petro- 

 leum ether (b. p. 30-50 C.). After cooling, the solution is shaken 

 with successive 100 cc. portions of 80 per cent methyl alcohol until 

 no more color is extracted. The combined methyl alcohol solutions 

 contain the xanthophylls. On dilution with water to form a 25-30 

 per cent alcohol solution ether will now extract these pigments. After 

 washing the ether free from alcohol with water and drying with 

 Na 2 S0 4 , the ether can be evaporated off in vacuum and the pig- 

 mented residue used for an examination of any of the usual xantho- 

 phyll properties. 



Egg yolk. The large amount of protein, fat, lecithin and other 

 lipoids in egg yolk presents certain rather difficult problems in the 

 isolation of the xanthophyll pigment present. The isolation was ac- 

 complished, however, by Willstatter and Escher (1912) in the fol- 

 lowing manner, but not without loss of a great deal of pigment, as can 

 be readily seen. Egg yolk weighing 100 kgs., representing 6,000 

 eggs, was beaten up and 6 kg. portions placed in stone jars with 7 

 liters of methyl alcohol to coagulate the protein. The coagulum was 

 separated by means of the centrifuge, the alcohol, it is stated, being 

 almost free from color. Each portion of coagulum, amounting to a 

 little over 5 kgs., was thoroughly mixed with 3 liters of acetone, and 

 the golden yellow extract sucked off through a sand filter. After 

 the coagulum from each 6 kg. portion of egg yolk had been extracted 



