3l6 PLANTS PRODUCING GUMS AND RESINS 



It has been observed that when gum tragacanth is plunged into 

 cold water it swells up to a considerable extent, though slowly, and 

 eventually forms a very thick, whitish mucilage. 



In acidulated water (a i per cent, solution) this gum becomes com- 

 pletely soluble after two or three hours in the water-bath. Experiments 

 have shown that 25 grm. of this gum mixed with a litre of water give 

 it the consistency of a thick starch, whereas 160 grm. of starch or a 

 kilo of soluble gum would be recjuired to give a similar result. 



Butea frondosa. — This is a small tree with compound pinnate 

 leaves having opposite leaflets, whilst the inflorescences are in simple, 

 multiflorous clusters of orange-yellow colour. 



According to Watt and Atkinson the gum produced by this plant 

 is known as kamarkas. 



Roxburgh, in 1874, gave a similar descrii)tion to that published by 

 J. Lepine in 1859 in his nomenclature of the products of Pondicherry 

 at the Madras Exhibition. This ran as follows : " There flows from 

 the bark when cut a transparent gum of a fine red, ruby colour. It 

 is in small fragile pieces with smooth or wrinkled surface, and is 

 partially soluble in water. If allowed to dry on the tree it turns 

 brown and decomposes. In commerce pieces of bark are found mixed 

 with it and adhering to it. In bulk it is of a dark red colour. It 

 is very astringent and is capable of utilization for medicinal and 

 commercial purposes." 



Professor Solly has devoted considerable time to its study, and 

 gives its composition as follows : — 



Water ... ... ... ... ... ... 1323 



Tannin ... ... ... ... ... ... 5o'7o 



Divers impurities ... ... ... ... ... i7"oo 



Matters only dissolving with difficulty, precipitated during 



evaporation and concentration ... ... ... 3'5o 



Gum, gallic acid, extractives, salts and earthy matter ... i5'oo 



(Gum kino) 



In the course of further research Professor Solly states that when 

 a weight of 10 gr. (o'65 grm.) of this kino of the necessary purity 

 is heated in a closed platinum vessel till it is red-hot the whole of 

 the matters are burnt ; there remains a residue of o"45 of the original 

 weight, consisting of white ash, a small portion of which dissolves in 

 acids with effervescence. In cold water this kino swells and gives its 

 fine red colour to the liquid. 



Experiments by the same writer show that dilute acids and acid 

 salts colour the solutions orange-yellow and cause an abundant pre- 

 cipitate of the same shade. A small quantity of a concentrated solu- 

 tion of caustic potash colours the gum solution a magnificent crimson; 

 with an excess of potash this coloration rapidly becomes grey and an 

 abundant precipitate is formed. Caustic soda and aminonia act like 

 potash. Generally speaking, alkaline solutions give a rose-coloured 

 or grey precipitate, or a shade between these. Lead acetate, like 

 several other metallic solutions, causes the whole of the colouring 

 matter to be precipitated. This precipitate takes various tints, but 



