CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 365 



quart bottles. The butter thus obtained was rendered at a tempera- 

 ture of 50 to 60 C. and the rendered fat filtered. The pure filtered 

 fat was analyzed colorimetrically by means of the Lovibond tintometer 

 and its standard color glasses. The color of the fat was always com- 

 pared in one-inch layer. The Lovibond tintometer is shown in Fig- 

 ure V. 



FIGURE V. 



The solution (in the present case melted butter fat) whose color 

 is to be measured is placed in a cell with glass ends (one inch apart 

 in all this work), and the color matched by standard color glasses 

 of various units of yellow, red or blue, and the color of the solution 

 read by adding together the various glasses of color used to match 

 the unknown color. Melted butter fat having an orange tint requires 

 only yellow and red to match its color. All readings are made with 

 the instrument pointing towards the daylight (not sunlight). The 

 instrument is quite sensitive towards the yellow glasses below 25 units 

 of yellow but the sensitiveness decreases considerably above 40 units 

 of yellow. In other words, it is possible to match the exact color of 

 an "unknown" much more closely when its color is below 30 to 35 

 units of yellow than when its color is above this value. In a great 

 many cases, and this nearly always applies to butter fat, it is possible 

 to match the tint of the fat but the color of the fat is more brilliant 

 than that of the combined standard glasses. In this case an exact 

 match can be obtained by "damping down" the butter fat color by 

 inserting in front of it equal units of the three colors, yellow, red 

 and blue, and recording this as "light." 



Before reporting the data dealing with the variation in the color 

 of the butter fat it may be possible to convey some idea of what the 

 various colors mean when applied to butter fat by stating that ren- 

 dered "June" butter in the one-inch cell will give a color of from 80 

 to 60 units of yellow. Color readings between 45 and 25 units of 



