452 GUMS 



than the Persian, so that the two, when placed side by side, can easily 

 be distinguished. Moreover, Smyrna tragacanth contains sufficient 

 starch to give a decided reaction with the iodine test, whereas Persian 

 responds only very faintly. 



Constituents. That portion of tragacanth that is soluble in water 

 consists chiefly of a polyarabinan-trigalactan-geddic acid and yields 

 by hydrolysis arabinose, galactose, and geddic acid ; the insoluble 

 part of the gum is termed bassorin ; it is converted by baryta water 

 into isomeric a- and /3-tragacanthan-xylan-bassoric acids which yield 

 by hydrolysis tragacanthose, xylose, and bassoric acid. Tragacanth 

 contains also water, traces of starch, cellulose, and nitrogenous 

 substances, and yields about 3 per cent, of ash. 



Uses. Tragacanth is chiefly employed medicinally as a means of 

 temporarily suspending insoluble powders in mixtures, and to give the 

 requisite firmness to pill-masses. Very large quantities are used as 

 a thickening agent in calico printing. 



Varieties, &c. In addition to the tragacanth described (flake 

 tragacanth), much is imported of a very inferior quality (' hog ' gum, 

 Caramania gum), the botanical origin of which is doubtful ; such gum 

 is usually in tears or irregular vermiform pieces, and darker in colour. 

 Sometimes it is whitened with lead carbonate before being used to 

 adulterate the finer qualities. 



Vermicelli tragacanth is in thin vermiform pieces often of good 

 colour ; tragacanth of this nature is collected in northern Morea from 

 A. cylleneus, Boissier et Heldreich. 



Indian Tragacanth (Sterculia gum, Karaya gum) is obtained from 

 Sterculia urens, Roxburgh (N.O. Sterculiacece) , and possibly other 

 species. It occurs in irregular, striated, often vermiform, whitish, 

 or pale brownish or pinkish brown pieces, here and there with 

 fragments of bark attached. It has a distinctly acid odour, forms 

 a transparent, colourless jelly with water and assumes at most a 

 slight brownish colour when boiled with 5 per cent, solution of potash 

 (tragacanth turns canary-yellow). The powder has been used to 

 adulterate powdered tragacanth. Scoville gives the following test : 

 Shake 2 grammes, moistened with alcohol, with 50 c.c. of water till 

 homogeneous ; add 2 grammes of borax dissolved in 50 c.c. of water, 

 shake vigorously and stand over night. If Indian tragacanth is 

 present the mucilage will be stringy. The presence of scleren- 

 chymatous cells (from adhering bark) in the powder points to the 

 presence of Indian tragacanth. It is largely used in India as a 

 substitute for tragacanth. 



Powdered acacia may be detected in powdered tragacanth by making 

 a mucilage 1/5 in 50, adding guaiacol 0'5 in 50 of water and 1 drop of 

 hydrogen peroxide. Pure tragacanth remains colourless ; if acacia 

 is present a brownish colour is developed (Caesar and Loretz). 



