28 FOODS AND FOOD ADULTERANTS. 



hours, at most, the greater part of the aqueous solution, now colored more or less 

 yellow by the annotto, can, be drawn from beneath the ether with a pipette or by a 

 stopcock below, in a sufficiently clear state to be evaporated to dryuess and tested in 

 the usual way with a drop of concentrated sulphuric acid. 



Sometimes it is well to further purify the aqueous solution by shaking it with some 

 fresh ether before evaporating it, and any fat globules that may lloat on its surface 

 during evaporation should be removed by touching them with a slip of filter-paper ; 

 but the solution should not bo filtered, because the filter-paper may retain much of 

 the coloring matter. 



The dry-yellow or slightly orange residue turns blue or violet blue with sulphuric 

 acid, then quickly green, and finally brownish or somewhat violet (this final change 

 being variable, according to the purity of the extract). 



Saffron can be extracted in the same way ; it differs from aunotto very decidedly 

 the most important difference being in the absence of the green coloration. 



Genuine butter, free from foreign coloring matter, imparts at most a very pale yel- 

 low color to the alkaline solution ; but it is important to note that a mere green col- 

 oration of the dry residue on addition of sulphuric acid is not a certain indication of 

 aunotto (as some books state) because the writer has thus obtained from genuine 

 butter, free from foreign coloring matter, a dirty green coloration, but not preceded 

 by any blue or violet blue tint. 



Blank tests should be made with the ether ; it is easy to obtain ether that leaves 

 nothing to be desired as to purity. 



Turmeric is easily identified by the brownish to reddish stratum that forms between 

 the ethereal fat solution and the alkaline solution before they are intimately mixed. 

 It may be even better recognized by carefully bringing a feebly alkaline solution of 

 ammonia in alcohol beneath the ethereal fat solution with a pipette, and gently agitat- 

 ing the two, so as to mix them partially. 



Martin 1 gives a method of separating and determining artificial color- 

 ing matters in butter. To 5 grams of fat, dry, are added 25cc. OS 2 and 

 the mixture well shaken with water made slightly alkaline with NaOH 

 or KOH and the mixture gently shaken. The alkaline water will dis 

 solve all the coloring matter. This is now determined qualitatively by 

 the spectroscope or quantitatively by making up a comparative mixture 

 with the coloring matter found. Butters act better when treated as 

 above than oleomargarine. 



The relative amount of color in butters is thus estimated by Babcock : 2 



The relative amount of color in butters maybe determined with accuracy as follows : 

 One gram of the fresh butter is digested with 15cc. of refined kerosene till the fats 

 are completely dissolved and the solutions filtered. The filtrate will be colored in 

 proportion to the coloring matter of the butter, and may bo compared to that 

 from another butter or preferably to a standard solution by means of a Dubcsque 

 colorimeter. A standard color for comparison may be prepared by adding a small 

 quantity of any of the commercial butter colors to kerosene oil. This standard will 

 keep for a long time without changing, if kept from the light. 



The scale of the colorimeter on the side which the butter solution occupies is always 

 set at the same degree, while the scale for the other standard is made variable. The 

 reading of this side will, therefore, vary with the amount of color in the sample. 



If some of the kerosene oil in which the butters are dissolved be substituted for 

 the solution of butter, a small reading will be obtained which should bo deducted 



1 Analyst, 1885, p. 1G3. 



'Fifth An. Rep't B'd Control, N. Y. Exp. Sta., p. 335-336. 



