126 METHODS OF ANALYSIS. 



Allow to stand a few hours, then draw off the aqueous layer, evaporate to dry- 

 ness, and test with sulphuric acid which in the presence of annatto gives first 

 a blue or violet blue, changing quickly to green and finally to brown. 



Saffron, which would be extracted at the same time, acts differently when 

 treated with sulphuric acid, not giving the green coloration. 



The aqueous solutions, if not clear enough to use, must not be filtered, as 

 the filter paper will take up large amounts of the color, but can be shaken up 

 again with fresh portions of ether. Carbon disulphid may also be used as a 

 solvent Uncolored butters treated in this way give only a very slight trace of 

 coloring matter. 



(2) MASSACHUSETTS BOARD OF HEALTH METHOD FOE ANNATTO. PBO VISIONAL. 



Treat 2 or 3 grams of the melted and filtered fat (freed from salt and water) 

 with warm dilute sodium hydroxid, and after stirring pour the mixture while 

 warm upon a wet filter, using to advantage a hot funnel. If annatto is present 

 the filter will absorb the color so that when the fat is washed off by a gentle 

 stream of water the paper will be dyed straw color. It is well to pass the warm, 

 alkaline filtrate two or three times through the fat on the filter to insure 

 removal of the color. If, after drying the filter, the color turns pink on 

 application of a drop of stannous chlorid solution the presence of annatto is 

 assured. 



(3) GEISLEB'S METHOD FOB AZO COLOBS. PBO VISIONAL. 



Spread a few drops of the clarified fat upon a porcelain surface and add a 

 pinch of fuller's earth. In the presence of various azo dyes a pink to violet 

 red coloration will be produced in a few minutes. Some varieties of the 

 fuller's earth react much more readily than others with azo colors. 



(4) LOW'S METHOD FOB AZO COLOBS. PBOVISIONAL. 



Melt a small amount of the fat in a test tube, add an equal volume of the 

 mixture of one part of concentrated sulphuric acid and four parts of glacial 

 acetic acid and heat nearly to the boiling point, the liquids being thoroughly 

 mixed by shaking. Then set aside and after the acid solution has settled it 

 will be colored wine red in the presence of azo color, while with pure butter 

 fat comparatively no color will be produced. 



(5) ACID AND ALKALI TESTS. PBOVISIONAL. 



Pour into each of two test tubes about 2 grams of the filtered fat dissolved 

 in ether. Into one of the tubes pour 1 or 2 cc of hydrochloric acid and into 

 the other about the same volume of dilute potassium hydroxid solution. Shake , 

 the tubes well and allow to stand. In the presence of azo dye the test tube 

 to which the acid has been added will show a pink to wine-red coloration, j 

 while the potash solution in the other tube will show no color. If, on the other j 

 hand, annatto or other vegetable color has been used the potash solution will 

 be colored yellow, while no color will be apparent in the acid solution. 



CHEESE. 

 1. Selection and Preparation of Sample. Official. 



When the cheese can be cut take a narrow wedge-shaped segment reaching 

 from the outer edge to the center of the cheese. Cut this into strips and pass 

 through a sausage grinding machine three times. When the cheese can not be | 



