ACACIA. GUM ARABIC. 33 



old from natural ruptures in the bark, and is gathered 

 during or after the time of blossoming, January to April. 

 The richness of the exudation depends in large part on 

 the climatic conditions. 



The gum coming from Kordovan from A. Senegal (-A, 

 Verek, Guill. et Perott.) is held to be the best in quality, 

 and is collected in round nut-like pieces, or irregular 

 angular ones, which are transparent and white, or have 

 the slightest tinge of brown. It is easily broken with a 

 glassy fracture and shows numerous cracks, most of which 

 are superficial. Khartoum gum resembles this closely. 



The West African gum from Senegal, mainly derived 

 from A. Semgal {A. Verek, of French writers), comes in 

 pieces egg-shaped, elongated oval or worm-shaped, about 

 two inches long and perhaps one-third of an inch in 

 thickness. There is, however, a great variation in the 

 matter of size and shape. The color is more yellowish, 

 or even more reddish, than that of the East African 

 sorts, and the gum is more regular in surface, showing 

 fewer cracks. Smaller pieces are similar to those from 

 East Africa. 



Cape gum occurs in still smaller fragments, resembling 

 mastiche or sandarac. It is clear brown in color and is 

 often mixed with impurities. Australian and Brazilian 

 gums are of recent introduction. 



The powder of gum arable is odorless, taste sweetish 

 and mucilaginous. 



In commerce the pieces are sorted, often irrespective 

 of origin, and made into different grades with corre- 

 sponding prices, first, second, third, and fourth sifted 

 sorts. 



Chemistry. — The general chemistry of gum acacia has 

 been considered. The specific gravity varies from 1.50 

 to 1.60. They are completely soluble in water and give 

 a thick mucilage, slightly acid in reaction. 



Microscopical. — Little can be made of gum arable under 

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