AKTIFH'IAL COLORS. 45 



of alum in a pint of water. >haken vigorously, and tillered t li rough 

 filter paper. Here sixain a dear or only slightly turbid li(|uid passes 

 through the paper. 



About a teaspoouful of the liquid obtained by any one of the method^ 

 mentioned above is placed in any dish, not metal, and :> drops of hydro- 

 chloric (muriatic) acid added. A strip of turmeric pa pel- is now dipped 

 into the liquid and then held in a warm place near a stove or lamp 

 till dry. If boric acid or borax was present in the sample the turmeric 

 paper becomes bright cherry red when dry. A drop of household 

 ammonia changes the red color to dark green or greenish black. If 

 too much hydrochloric acid is used the turmeric paper may take on a 

 brownish red color even in the absence of boric acid. In this case, 

 however, ammonia changes the color to brown just as it does turmeric 

 paper which has not been dipped into the acid solution. 



DETECTION OF FORMALDEHYDE. 



Formaldehyde is rarely used with other foods than milk. The 

 method for its detection in milk is given on page 5^. For its detec- 

 tion in other foods it is usually necessary to first separate it by distil- 

 lation, a process which is scarcely available for the average peison 

 without laboratory training and special apparatus. For this reason 

 no method is suggested here for the detection of formaldehyde in 

 other foods than milk. 



DETECTION OF SACCHARIN. 



Saccharin has a certain preservative power, but it is used not so 

 much for this effect as because of the very sweet taste whix'h it imparts. 

 It is extracted by means of chloroform, as described under the detec- 

 tion of salicylic acid (p. 43). In the case of solid and semisolid foods, 

 the sample must, of course, be prepared by extraction with water, as 

 described under salicylic acid. The residue left after the evaporation 

 of the chloroform, if a considerable amount of saccharin is present, 

 has a distinctly sweet taste. 



The only other substance having a sweet taste which may be present 

 in foods, i. e., sugar, is not soluble in chloroform, and therefore does 

 not interfere with this reaction. Certain other bodies (tannins) which 

 have an astringent taste are present, and as they are soluble in chloro- 

 form ma} T sometimes mask the test for saccharin, but with practice 

 this difficulty is obviated. 



DETERMINATION OF ARTIFICIAL COLORS. 

 DETECTION OF COAL-TAR DYI->. 



As has been stated, coloring matters used with foods are usually 

 soluble in water. If the food under examination be a liquid, it may 

 therefore be treated directly by the method given below. If it be a 



