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ASTRAGALUS VERUS. 
to the taste. This gum differs from all other known gums, in giving 
a thick consistence to a much larger quantity of water, and at the 
same time being much more difficult of solution, or rather, dissolving 
only imperfectly, unless triturated after digestion with a larger 
portion of water ; for although the liquor looks turbid, on standing 
the mucilage subsides, the water on the surface retaining little or 
none of the gum. If the water be acidulated with any of the 
mineral acids, a small portion of the gum becomes dissolved. 
Tragacanth is reduced to powder with much difficulty, unless 
thoroughly dried. According to Neumann it gives nothing over in 
distillation, either to water or alcohol ; it is also insoluble in alcohol 
or ether. The mucilage is precipitated by the sulphate of copper, 
superacetate of lead, and oxymuriate of tin ; but not by silicated 
potass, or the oxysulphate of iron : in these circumstances tiie 
mucilage of tragacanth differs from that of gum arabic. 
Medical Properties and Uses. Gum tragacanth is de- 
mulcent, hence it is very useful for allaying tickling coughs, and 
sheathing the fauces in catarrhal affections ; * and for these purposes 
(from its great viscidity) it is preferable to gum arabic : it is seldom 
given alone, being generally combined with more powerful medicines, 
more especially in the form of troches, for which purpose it is very 
well adapted. Tragacanth may be taken in powder, from ten grains 
to one drachm or more, in any suitable vehicle. 
Off. The Gum. 
Off. Pp. Mucilago Astragali Tragacanthae, E. D. 
Pulvis Tragacanthae Compositum, L. 
* Bergius says, virtus demulcens, obtnndens, incrassans, usus dysenteria, diarrLoea, 
stranguria. 
