342 MISSOURI AGRICULTURAL EXPERIMENT STATION, BULLETIN NO. IO 



In addition to the above properties it was found that all fat-free, 

 but not necessarily cholesterol-free solutions of the pigment showed 

 spectroscopic absorption bands. In alcohol two sharp bands were 

 exhibited in the blue part of the spectrum; and in carbon bisulphide 

 these bands were nearly always accompanied by a third faint band 

 in the violet, which was now visible on account of the general shifting 

 of the bands toward the red end of the spectrum. The unstable char- 

 acter of the butterfat pigment required that the isolation be carried 

 out as rapidly as possible in order to preserve all the characteristic 

 properties of the pigment. This was especially true for the study of 

 the absorption spectra. Fifteen to thirty grams of fat were found 

 to yield sufficient pigment for a spectroscopic study. The use of 

 large quantities of fat (300 to 1,000 grams) always led to unsatis- 

 factory results. 



The general properties of the butter fat pigment show that it is 

 to be classed as a true lipochrome. The chemical relation of the pig- 

 ment to the carotin and xanthophylls of green plants remains to 

 be shown. 



METHODS OF IDENTIFICATION. 



The nature of the substances with which the butter fat pigment 

 is associated at once precluded its isolation in sufficient quantity to 

 establish its chemical composition and molecular weight. It was 

 therefore necessary to adopt other methods of identification which 

 would be sufficiently accurate and characteristic that the final results 

 could not be mistaken. 



The methods that were adopted were, (i) a study of the spec- 

 troscopic absorption properties, (2) a study of the relative solubility 

 properties, (3) a study of the adsorption properties with respect to 

 calcium carbonate; (4) an attempt was also made to study the crys- 

 talline form. 



Before giving the results of our studies, some discussion will be 

 given of the relative solubility and adsorption properties of carotin 

 and the xanthophylls. 



RELATIVE SOLUBILITY OF CAROTIN AND XANTHOPHYLLS. 



M. Tswett * was the first one to publish a comprehensive state- 

 ment in regard to the relative solubility of the plant pigments in 



1. Ber. der. Deut. Botan. Gessel. 24, pp. 316, 384 (1906). 



