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POTASSIUM NITRATE. 



Potassium nitrate (saltpetre, nitre) is frequently found in 

 condimental foods; it is a white, finely crystalline salt, and is 

 best detected by its characteristic taste. The taste of this salt 

 may best be described as slightly bitter and cooling to the tongue. 

 In medicine it is used to excite the action of the kidneys and to 

 keep down fever. 



ROSIN. 



Rosin occurs occasionally in foods and may be identified by 

 its odor when rubbed between the fingers. The small particles 

 are of an amber brown color, and when ground become light- 

 yellowish in color. On a slide particles of rosin may be identified 

 by the addition of a little 75% alcoholic tincture of alkanna root. 

 After a short time the rosin is stained a beautiful red. It has 

 no medicinal value, but is used in the substance as a filler. 



SALT. 



Common salt is very often found in cattle foods in varying a- 

 mounts from 1 — 30%. It is easily detected by its taste. It 

 occurs as small crystals, colorless or white, and can usually be 

 picked put with the forceps. Micro-chemically it may be iden- 

 tified by placing a few of the suspected crystals in a drop of water 

 on a slide and adding a drop of silver nitrate solution. A white 

 precipitate shows the presence of chlorine, and may be taken as 

 proof that it is there as sodium chloride or salt. 



SULPHUR. 



Sulphur is sometimes present in a few of the condimentals, 

 and may be recognized by its characteristic lemon-yellow color 

 and by the odor of the oxide fumes when a portion of the sample 

 is ignited. It is usually present as a fine powder. 



If the chemical analysis of a food gives an abnormally high 

 fat content, the presence of free sulphur is to be suspected and 

 the sample is examined as directed. Its object in a condimental 

 appears to be that of a mild laxative. 



SAND. 



Sand is used in commercial foods as a filler, and can be easily 

 distinguished from other gritty substances by its color. While 



