57 



chick feeds it is very often foiind in particles large enough to be 

 easily picked out. When a piece of charcoal is rubbed along the 

 surface of a white paper it gives a black smear, and this is the 

 quickest way to identify it. Under the microscope the particles 

 of charcoal appear black and are not cleared by ordinary reagents. 

 Charcoal is not bleached by either aqua regia or any other bleach- 

 ing-agent. 



GLAUBERS AND EPSOM SALTS. 



These are often met with in condimentals but no accurate 

 method may be given for their identification microscopically. 

 Slide tests may be made, when their presence is suspected, for 

 sulfates of soditmi or magnesium, but this may be shown better 

 by a chemical examination. The particles of these salts are 

 colorless and have a peculiar cooling taste somewhat character- 

 istic. They are used as purgatives in condiments. 



IRON SULPHATE. 



Copperas (iron sulphate) sometimes occurs in cattle foods, 

 more especially in the condimentals. The particles are usually 

 coarsely ground and are large enough to be picked out. They are 

 pale green or brownish (if oxidized) in color and may be treated 

 on the slide as in the case of calciimi, using barium chloride as a 

 reagent. A white or milky precipitate indicates sulphuric acid; 

 the iron is usually detected in the chemical analysis and is rather 

 hard to identify microscopically. 



IRON OXIDE. 



Iron oxide (Venetian red) is also sometimes found in finely 

 pulverized condition. It is used as a co^pring matter in the foods 

 and is easily recognized by its characteristic red color. 



Iron oxide (Princess metallic) is also occasionally found in 

 foods. Its identification is the same as that for the previously 

 mentioned oxide of iron. Both of these substances are dry paints 

 and have no medicinal value, being used simply as covers for 

 other substances and to give color to the mixture. 



