ii BUTTER 177 



with water, straining off the liquid and the dye-stuff floating 

 in it and boiling them together. 



Annatto is a solution of the dye-stuff in sesame oil or in fine 

 olive oil. The dye is brownish-yellow, but when diluted has a 

 beautiful bright yellow colour. Other substances which are 

 used for colouring butter are safflowers, marigolds, saffron, and 

 curcuma. 



As the vegetable colouring substances are sensitive to light 

 that is, they are bleached when exposed to light and as the 

 B'ixa orellana is becoming more and more rare, the practice of 

 using artificial dye-stuffs such as aniline yellow dimethyl- 

 amidoazobenzol (butter yellow), Martins yellow dinitro-, 

 naphthol, Victoria yellow potassium dinitrocresolate, &c., 

 has commenced in the last few years. The question whether 

 such aniline colours should be allowed is still under discussion, 

 although the colours which come into question are not 

 poisonous. A certain test for aniline dyes in butter colouring 

 is simply to shake the melted butter with hydrochloric acid, 

 sp. gr. T125, and the presence of such dyes is shown by the 

 acid becoming red. 



A complete scheme for investigating butter colouring has 

 been worked out by A. R. Leeds, 1 who advises the following 

 procedure : 100 g. of the butter-^natural or artificial are 

 dissolved in 300 g. of pure petroleum ether (sp. gr. 0*638) and 

 then separated from the water and salts in solution by means of 

 a separating funnel. The petroleum ether containing the fat 

 is washed several times with water, 100 c.c. in all, and then 

 allowed to stand for fifteen to twenty hours in ice water in 

 summer, or in a cold place in winter, whereby a considerable 

 quantity of stearin crystallises out. The clear solution is 

 decanted from the stearin and shaken with 50 c.c. of JVyiO 

 standard alkali, which withdraws the colouring matter from 

 the petroleum ether. The aqueous solution containing the 

 colouring matter is separated from the fat solution and care- 

 fully acidified with dilute hydrochloric acid until the liquid has 

 a distinct acid reaction to litmus paper. Thereupon the 

 colouring matter (along with some fatty acid) separates out, 

 and it is then filtered through a tared filter and washed with 

 cold water. It must not be forgotten that the petroleum ether 

 1 The Analyst, 1887 ; Chem. Zeitung Repert., 1887, p. 188. 



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