178 LEGUMINOStE. 



it swells, and in the course of some hours disintegrates so that it can be 

 diffused through the liquid. So great is its power of absorbing water 

 that even with 50 times its weight, it forms a thick mucilage. If one 

 part of tragacanth is shaken with 100 parts of water and the liquid 

 filtered, a neutral solution may be obtained which yields an abundant 

 precipitate with acetate of lead, and mixes clearly with a concentrated 

 solution of ferric chloride or of borax, — in these respects differing from 

 a solution of gum arable. On the other hand, it agrees with the latter 

 in that it is thrown down as a transparent jelly by alcohol, and rendered 

 turbid by oxalate of ammonium. The residue on the filter is a slightly 

 turbid, slimy, non-adhesive mucilage, which when dried forms a very 

 coherent mass. It has received the name of Bassorin, Traganthin or 

 Adraganihin, and agrees with the formula C^2JJ2oqio 



Tragacanth is readily soluble in alkaline liquids, even in ammonia 

 water and at the same time assumes a yellow colour; heated with 

 ammonia in a sealed tube at 90° C. it blackens. 



The drug loses by diying about 14 per cent, of water, which it 

 absorbs again on exposure to the air. Pure flake tragacanth incinerated 

 leaves 3 per cent, of ash. 



Commerce — Tragacanth is shipped from Constantinople, Smyrna 

 and the Persian Gulf The annual export of the gum from Smj^rna has 

 been recently stated^ to be 4,500 quintals, value 675,000 Austrian 

 florins (£67,500) ; and the demand to be always increasing. 



Uses — Though tragacanth is devoid of active properties, it is a very 

 useful addition to many medicines. Diffused in water it acts as a 

 demulcent, and is also convenient for the suspension of a heavy powder 

 in a mixture. It is an important ingredient for imparting firmness to 

 lozenges and pill masses. 



Adulteration — The fine quantities consisting of large distinct pieces 

 are not liable to adulteration, but the small and the inferior kinds are 

 often sophisticated. At Smyrna, tragacanth is mixed with gums termed 

 respectively Mosul and Caraniania Gum. The former appears to be 

 simply very inferior tragacanth ; the latter which is sometimes called in 

 the London market Hog Gum Tragacanth or Bassora Giim,^ is said to 

 be the exudation of almond and plum trees. It occurs in nodular 

 masses of a waxy lustre and dull brown hue, which immersed in water 

 gradually swells into a voluminous white mass. To render this gum 

 available for adulteration, the lumps are broken into small angular 

 fragments, the size of which is adjusted to the sort of tragacanth with 

 which they are to be mixed. As the Cararaania Gum is somewhat 

 daik, it is usual to whiten it by luhite lead, previous to mixing it with 

 Small Leaf or Flake, or with the Vei^iicelli gum. 



By careful examination the fraud is easily detected, angular 

 fragments not being proper to any true tragacanth. The presence of 

 lead may be readily proved by shaking suspected fragments for a 

 moment with dilute nitric acid, which will dissolve any carbonate 

 present, and afford a solution which may be tested by the ordinary 

 Teagents. 



^ C. von Scherzer, Smyrna, Wien, 1873. * It is sometimes shipped from Bussorah. 



143. 



