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brown, more or less opaque, but translucent and glassy when frac- 

 tured. The powder is of a whitish or grayish-white color. The gum 

 is further distinguished by not giving precipitates with solutions of 

 lead sub-acetate, ferric chloride and sodium borate. Mesquite forms 

 a somewhat adhesive mucilage and can be used as an emulsifying 

 agent. 



Ghatti gum or Indian gum is an exudation from the wood of Ano- 

 geissus latifolia (Fam. Combretacese), a tree indigenous to India and 

 Ceylon. It occurs in yellowish-white tears with a dull rough surface 

 and a vitreous fracture. It is entirely soluble in cold water, forming 

 a very viscous mucilage. 



Adulterants. An artificial gum has been prepared by heating 

 starch with sulphuric acid in an autoclave, the resulting product 

 being neutralized, washed and then dried. It is said to resemble 

 acacia in appearance and adhesiveness. 



The powder, while sometimes adulterated with dextrin and 

 rice starch, is more frequently mixed with inferior gums, especially 

 the Mesquite gum. 



TRAGACANTHA. Tragacanth. A gummy exudation from the 

 stem of Astragalus gummifer and other species of Astragalus (Fam. 

 Leguminosse, sub-fam. Papilionacea), small shrubs indigenous to 

 southeastern Europe and western Asia. Some of the walls of the 

 pith and medullary rays are transformed into mucilage, which exudes 

 spontaneously, but is obtained in commercial quantities by making 

 incisions in the bark, the gum being collected after it dries. The 

 principal points of export are Smyrna and various ports along the 

 the Persian Gulf; that obtained from the latter is known as Persian 

 or Syrian Tragacanth and is preferred. 



Persian or Syrian Tragacanth. In flattened, lamellated, ribbon- 

 like pieces, 0.5 to 2.5 cm. in length, about 1 cm. in width and from 1 

 to 3 mm. in thickness, irregularly oblong, more or less curved; 

 externally nearly colorless or pale yellowish, with numerous con- 

 centric ridges or lamella; translucent; fracture short, tough, horny, 

 rendered more easily pulverizable by a heat of 50 C.; inodorous; 

 taste insipid. 



Inner Structure. Pieces of the gum softened in water and 

 mounted in glycerin show numerous lamella and a few starch grains, 

 the latter being mostly spheroidal and single, occasionally 2- to 4- 

 compound, the individual grains from 0.003 to 0.015 mm. in diameter 

 and colored blue with iodin. 



Powder. Whitish; slowly affected by water; starch grains 

 mostlv single, occasionally 2- to 4-compound, the individual grains 



