520 POWDERED VEGETABLE DRUGS 



199. (Fig. 191). TRAGACANTH. Gum Tragacanth. U. S. 



The dried gummy exudation of Astragalus gummifer Lab., Leguminosse. 



Snow white to light brownish. 



Odorless. 



Highly mucilaginous. 



In water mounts the particles immediately swell and become trans- 

 lucent, showing lamellate lines and markings, with here and there 

 groups of simple, nearly spherical starch granules, measuring from 4 

 to SA* in diameter. Tincture of iodine reveals yellowish striae and 

 groups of organic particles marking the interstices and lines of separa- 

 tion of the lamellate particles. The quality of tragacanth is inversely 

 proportional to the amount of starch present. In the crude drug (not 

 powdered) the quality is also indicated by the color, the lighter and 

 more translucent the article (as in the gibbon or vermicelli variety) 

 the purer and better it is. The brown article (sorts) will show abun- 

 dant starch. 



Ash should not exceed 3 per cent. 



The powdered article is likely to be made from the inferior sorts 

 and refuse. It may be adulterated with India gum, cherry gum and 

 other spurious vegetable gums. Gum tragacanth is much employed 

 for adulterating purposes; as ice cream and sausage meat fillers, as 

 thickening agents, in egg substitutes, etc. 



