Tragacanth »Tragacanth is the dried gummy exudation from Astragalus gummiferLabillardière,or other Asiatic species of Astragalus(Fam.Leguminosae). Packaging and storage— Preserve in well-closed containers. Botanic characteristics— Tragacanth— Flattened,lamellated,frequently curved fragments or straight or spirally twisted linear pieces from 0.5mm to 2.5mm in thickness.Is white to weak yellow in color,translucent,and horny in texture.Its fracture is short.Is rendered more easily pulverizable by heating to 50.Is odorless. Histology— Pieces of Tragacanth softened in water and mounted in water or glycerin show numerous lamellae and a few starch grains. Powdered Tragacanth— White to yellowish white.When examined in water mounts,it shows numerous angular fragments of mucilage with circular or irregular lamellae,and occasional starch grains up to 25µm in diameter,mostly simple,spherical to elliptical,with occasional 2-to 4-compound grains,a few of the grains being swollen and more or less altered.The powder shows few or no fragments of lignified vegetable tissue (Indian gum). Identification— Add 1g to 50mLof water:it swells and forms a smooth,nearly uniform,stiff,opalescent mucilage free from cellular fragments. Microbial limits á61ñ It meets the requirements of the tests for absence of Salmonellaspecies and Escherichia coli. Lead á251ñ: 0.001%. Heavy metals,Method IIá231ñ: 20µg per g. Karaya gum— Boil 1g with 20mLof water until a mucilage is formed,add 5mLof hydrochloric acid,and again boil the mixture for 5minutes:no pink or red color develops. Organic volatile impurities,Method IVá467ñ: meets the requirements.[NOTE—A G16column has been shown to be an appropriate secondary column.] Auxiliary Information— Staff Liaison:Catherine Sheehan,B.Sc.,Scientist Expert Committee:(EMC)Excipients:Monograph Content USP28–NF23Page 3099 Phone Number:1-301-816-8262