482 LEGUMINOS 2. 
parts of water a thick, jelly-like mucilage. When diffased in 
a much larger quantity of water it forms a ropy liquid which 
may be passed through a filter, leaving behind an insoluble 
residue, which in centact with iodine acquires a blue colour from 
the presence of starch. The mucilage acquires a yellow colour 
on the addition of caustic soda, and the solution of tragacanth | 
yields clear mixtures with borax, ferric chloride, and sodium 
silicate, is precipitated by alcohol, thickened by cold lead 
acetate and subacetate, and precipitated by these salts on heat- 
ing. (Flickiger.) 
Chemical composition.—Tragacanth has a specific gravity of 
1:38, and contains two gums, one insoluble and the other 3 
soluble in water, about 14 per cent. of moisture and 8 per — 
cent., or less, of ash. A reaction for starch is obtained in 
most samples, and a peculiar red-colouring matter has been 
observed in some specimens from Persia. The insoluble gum 2 
has been named Bassorin, C'? H2®9 01°, an isomer of starch, 
which forms a sugar when boiled with diluted acid, and mucic 
acid when heated with nitric acid. The soluble gum affords 
no precipitate or jelly with alkaline borates, silicates or stannates 4 
or ferric chloride, and its solution is rendered turbid by plumbiec 4 
acetate, and throws up a transparent jelly with alcohol, all of ~ 
which reactions point to the gum being different to arabin. 3 
Giraud considers the insoluble portion of tragacanth to bea — 
pectic compound, andthe soluble portion to be a mixture of 3 
different bodies, not a definite principle like arabin. Bassorin — 
isan unsaturated compound, whereas arabin and the soluble 4 
gums are usually associated with lime or potash. The propor- 4 
tion of solable gum has been variously estimated at from 56 to 
50 per cent., but these results are attendant upon the employ- 
ment of small or large quantities of water, and the period of P 
immersion. — ; : 
In Northern India the seeds of Astragalus multiceps, _ 
Wall., and A. tribuloides, Delite, are used on account of © 
_ their demulcent properties, 4 
