extract the color from the residue with strong alcohol ; or the sugar 

 may be wholly or in part removed by diluting and fermenting with 

 yeast. In cereal products and in other cases, possibly, it is a good 

 plan to make a preliminary extraction with ether. This removes 

 interfering fat or oil and indicates the presence or absence of oil- 

 soluble color. 



The color is dyed on a piece of white zephyr yarn or nun's veiling, 

 freed from dirt and grease by boiling with very dilute sodium 

 hydroxid (0.1 per cent), in a solution slightly acid with hydrochloric 

 acid. The wool is removed, well washed, and the color extracted 

 therefrom by warming in very dilute ammonia. In most cases 

 fifteen minutes' gentle boiling is sufficient. The wool is then removed, 

 its color noted, and the solution made slightly acid with hydrochloric 

 acid and the dyeing and extraction process repeated on a new piece 

 of wool. 



If the second piece of wool, after extracting the coal-tar color a 

 second time with ammonium hydroxid as far as possible, is clean 

 and shows no indication of the presence of vegetable color on the 

 fiber, the alkaline solution of coal-tar color is sufficiently pure. 

 Otherwise the process of dyeing and extraction must be repeated on a 

 new piece of wool till the absence of vegetable color is indicated. 



The color solution is then evaporated to dryness on the water bath, 

 when there is obtained a residue of the dry color, on part of which 

 the reaction with concentrated sulphuric acid may be tried and from 

 which a neutral aqueous solution may be prepared for extraction and 

 color tests. 



This procedure applies only to acid coal-tar dyes; similarly, by 

 reversing the process that is, dyeing in neutral or slightly alkaline 

 solution, and extracting the color from the fiber by a solution weakly 

 acid with hydrochloric acid basic coal-tar dyes can be isolated in a 

 state of reasonable purity for identification. The solution of color 

 may also be investigated by the spectroscope. 



EXAMINATION OF OILS AND FATS. 



(1) Carry out the process for determination of unsaponifiable 

 organic matter, and test for colors in the unsaponifiable matter. 



(2) In case the oil or melted fat shows positive reaction by Geisler's 

 fuller's earth test, 6 continue by treating 50 grams or more of the oil 

 with 25 grams of fuller's earth, and after standing one hour, with 

 frequent shaking, filter, wash earth free from oil with gasoline, and 



Formanek, Untersuchung und Nachweis organischer Farbstoffe auf spektrosco- 

 pischem Wege. 



& Zts. Nahr. Genussm., 1899. 2 : 150. 

 [Cir. 63] 



