SIMPLE PURITY AND ADULTERATION TESTS 241 



Coal Tar Yellow in Butter. The custom of coloring butter is ex- 

 tensively followed in the United States. Vegetable dyes were employed 

 largely in the past, but coal tar products (aniline dyes) are now quite 

 frequently used. Coal tar yellow may be detected by the following 

 experiment : 



Into a weak solution of alcohol put one teaspoonful of butter, a small 

 amount of cream of tartar, and bits of white silk or wool. Boil the mixture. If 

 coal tar coloring is present, the samples will be dyed. 



Canned Goods. Domestic canned goods are very rarely adul- 

 terated with preservatives or coloring matter. A few simple tests, 

 however, can be made to detect imperfect sterilization, defective 

 containers, and the amount of solid matter present. 



Before opening observe the ends or heads of the can. Any internal gas 

 pressure due to bacteria action will cause the can to bulge. A concave appear- 

 ance indicates no internal pressure. Make a very small hole in the can. Note 

 if there is an escape of gas. If there is any indication' of the presence of gas, 

 the contents should be rejected, as the can has not been properly sterilized or 

 has been imperfectly sealed. In either case decomposition has been taking 

 place, and gases have formed through the action of micro-organisms. 



When peas have been imperfectly sterilized, a gas is frequently 

 produced which is soluble in the liquid. In such a case decomposi- 

 tion has taken place, but no escape of gas can be detected when the 

 can is pierced. The liquid, however, is intensely acid, and has a 

 muddy appearance. 



Note the condition of the can. If it is rusty, old, or soiled, it should be 

 looked upon with suspicion. Examine the inner surface. If it is corroded, 

 the contents of the can may have dissolved the metal. 



Compare the expensive and cheap varieties of canned goods by weighing 

 the solid matter and measuring the liquid in each can. 



As a rule, coloring matter is not added to domestic goods. Im- 

 ported varieties, as green peas, having an intense color, usually 

 have had copper compounds added in small amounts. It may be 

 detected by: 



adding a few drops of hydrochloric acid to a portion of the material and dropping 

 on a bright steel nail or the blade of a knife. If copper salts are present, a 

 reddish color will appear on the steel. 



