CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 355 



STANDARDIZATION OF ABSORPTION BANDS OF CAROTIN AND 



XANTHOPHYLLS. 



Before proceeding further it may be well to make a few state- 

 ments in regard to the spectroscopic properties of the various pig- 

 ments which have been under consideration and which are still to 

 be considered. It will be obvious that measurements of absorption 

 bands could not be made in this work with the accuracy attained 

 by Willstatter and his collaborators who used solutions of standard 

 strength and a spectroscope of great exactness. Small differences 

 in measurement among xanthophylls or between carotins should ac- 

 cordingly be disregarded. It was merely attempted in every case 

 to secure solutions of such concentration that the bands were of as 

 nearly the same intensity as could be detected with the eye before 

 making measurements. It was not always possible to use the same 

 thickness of cell to secure the required intensity of the bands, small 

 amounts of pigment naturally requiring a greater depth of solution 

 than large amounts. 



In order to have standard spectroscopic properties for future 

 comparison, carotin and xanthophylls were extracted from the car- 

 rot, and a careful study made of the spectroscopic properties of each 

 pigment. 



A grated carrot was boiled in water for about two hours, the 

 water squeezed out of the pulp and the pulp dried on the steam 

 bath. It was pulverized and extracted with ether in a Soxhlet extrac- 

 tor until colorless. The ether was evaporated into ninety-five per 

 cent alcohol at a low temperature. The resulting solution was diluted 

 with a little water to eighty per cent and the pigment carefully 

 separated between petroleum ether (b. p. 30-50 C) and the eighty 

 per cent alcohol. Both portions of the pigment were carefully trans- 

 ferred to pure carbon bisulphide and the solutions adjusted for the 

 10 m. m. cell until all bands were distinct and as nearly as possible 

 of equal intensity. With the spectrometer set at the sodium line stand- 

 ard the positions of the absorption bands were standardized. The 

 color of the solutions was measured also, by means of the Lovibond 

 tintometer. (See Figure V.) 



