46 FOOD ADULTERATION AND METHODS FOR DETECTION. 



solid or a pasty substance, soluble in water either in the cold or after 

 heating, it may be dissolved in sufficient water to form a thin liquid. 

 If it contains some insoluble material, it may be treated with sufficient 

 water to dissolve the soluble portion with the formation of a thin 

 liquid and filtered, and then strained through a clean white cotton 

 cloth to separate the insoluble portion. About a half teacupful of 

 the liquid thus described is heated to boiling, after adding a few drops 

 of hydrochloric acid and a small piece of white woolen cloth or a few 

 strands of white woolen yarn. (Before using, the wool should be boiled 

 with water containing a little soda, to remove any fat it may contain, 

 and then washed with water.) The wool is again washed, first with 

 hot and then with cold water, the water pressed out as completely as 

 possible, and the color of the fabric noted. If no marked color is pro- 

 duced, the test may be discontinued and the product considered free 

 from artificial colors. If the fabric is colored, it may have taken up 

 coal-tar colors, some foreign vegetable colors, and if a fruit product 

 is being examined, some of the natural coloring matter of the fruit. 

 Rinse the fabric in hot water, and then boil for two or three minutes 

 in about one- third of a teacupful of water and two or three teaspoon- 

 fuls of household ammonia. Remove and free from as much of the 

 liquid as possible by squeezing or wringing. Usually the fabric will 

 retain the greater part of the natural fruit color, while the coal-tar 

 color dissolves in dilute ammonia. The liquid is then stirred with a 

 splinter of wood and hydrochloric acid added, a drop or two at a time, 

 until there is no longer any odor of ammonia. (The atmosphere of the 

 vessel is sometimes charged with the ammonia for several minutes after 

 it has all been driven out of the liquid; therefore one should blow into 

 the dish to remove this air before deciding whether the ammonia odor 

 has been removed or not.) When enough acid has been added the 

 liquid has a sour taste, as may be determined by touching the splinter, 

 used in stirring, to the tongue. 



A fresh piece of white woolen cloth is boiled in this liquid and 

 thoroughly washed. If this piece of cloth has a distinct color the food 

 under examination is artificially colored. The color used may have 

 been a coal-tar derivative, commonly called an anilin dye, or an arti- 

 ficial color chemically prepared from some vegetable color. If of the 

 first class the dyed fabric is usually turned purple or blue by ammonia. 

 In either case if the second fabric has ;i distinct color it is evident that 

 the product under examination is artificially colored. Of course a 

 dull, faint tint must be disregarded. 



DETECTION OF COPPER. 



The presence of copper, often used to deepen the green tint of 



imported canned peas, beans, spinach, etc., may be detected as follows: 



Mash some of the sample in a dish with a stiff kitchen spoon, Place 



