76 REPORTS ON THE STATE OF SOTENCE.—1917. 
and less araban than gum arabics. If the viscosity of these gums could be 
improved there would be a great demand for them ; they are very plentiful, 
and exude freely in large tears or masses, often very fine. 
A very large number of trees of other species and genera yield soluble 
gums, but none of these have ever come into extended use. 
Tragacanth. 
Tragacanth is employed in calico-printing, for painting on linen (A. H. 
Church, ‘ Chemistry of Paints and Paintings,’ p. 70), in the preparation 
ot lozenges, for cosmetic purposes, and in the manufacture of oil emulsions. 
This gum is the product of various species of Astragalus (Imperial Insti- 
tute, “ Report on Gums and Resins,’ p. 161), and it differs from gum arabic 
in that it is almost always the product of incisions. It shows distinct evi- 
dence of metamorphosed or swollen vegetable tissue, the cells containing 
a few granules which have the character of starch, which, however, appear 
to resist hot water to a considerable extent. The content of water varies 
according to the state of the atmosphere ; normally this is about 17 per 
cent., but in moist air it may be as much as 26 per cent. (H. B. Stocks and 
H. G. White, ‘ Jour. Soc. Chem. Ind.’ 1903, 4); it contains 3 to 5 per 
cent. of mineral matter, which is largely composed of carbonates (Rideal 
and Youle, ‘Jour Soc. Chem. Ind.’ 1891, 610), that produced by incision 
containing the larger quantity (Hilger and Dreyfus, * Ber.’ 1891, 33, 610). 
The amount of acetic acid formed on heating with potash is much higher 
than gum arabic, corresponding to 15 to 26-61 per cent. of alkali neutra- 
lised (Rideal and Youle, Stocks), showing a different constitution. The 
carbon and hydrogen in this gum approximate to the formula 0,;H,,0;, 
but both galactan and araban are present, even more of the iatter than 
in gum arabic; there is also a methylpentosan present, as fucose is found 
in the products of hydrolysis (A. Widtsoe and B. Tollens, ‘ Ber.’ 1900, 
133, 132-143). 
On heating tragacanth with water it swells very considerably, forming 
a stiff paste, even at 5 per cent. concentration, which by straining can 
be separated into a white translucent sol and an opaque insoluble gel, 
known as tragacanthine or bassorin. O’Sullivan (‘ Proc. Chem. Soc.’ 
1901, 17, 156-157) states that the gum contains a series of gum acids 
similar to geddic acid, which he termed polyarabin-galactan geddic acids, 
and bassorin, which yields tragacanthan-xylan-bassoric acid by action 
of alkalies and xylan-bassoric acids on partial hydrolysis with acids. 
Xylan-bassoric acid is nearly insoluble in water, and bassoric acid insoluble, 
but the alkali salts are soluble. 
According to Hilger and Dreyfus, on treating bassorin with 35 per cent. 
caustic potash and acidifying with acetic acid, oxybassorin (C, ;Hs901o).0 
is formed. If the alkaline solution is neutralised with acetic acid 
and precipitated by alcohol, the potassium derivative of oxybassorin is 
produced ; this is soluble in water and yields insoluble calcium and silver 
derivatives by double decomposition. These salts do not respond to 
the usual tests for the metals, and therefore do not appear to be true 
salts. These are probably adsorption compounds of the bases. Traga- 
canth is not precipitated by ferric chloride, it is precipitated by alcohol 
and also by basic lead acetate. Dilute solutions of bassoric acid are 
precipitated by alcohol and also by electrolytes ; it can be titrated, using 
