236 LEGUMINOStE. 



Arabia called the Hejaz, the gum thence brought receives the name of 

 Samagh Hejazi ; it is also called Jiddah or Gedda Gum. The gums of 

 Zeila, Berbera and the Somali country about Gardafui, are shipped to 

 Aden, or direct to Bombay. A little gum is collected in Southern 

 Arabia, but the quantity is said to be insignificant/ 



In the French colony of Senegal, gum, which is one of its principal 

 productions, is collected chiefly in the country lying north of the river, 

 by the Moors who exchange it for European commodities. The gather- 

 ing commences after the rainy season in November when the wind 

 begins to set from the desert, and continues till the month of July. 

 The gum is shipped for the most part to Bordeaux. The quantity 

 annually imported into France since 1828 from Senegal is varying from 

 between IJ to 5 millions of kilogrammes. 



Description — Gum arable does not exhibit any very characteristic 

 forms like those observable in gum tragacanth. The finest white gum 

 of Kordofan, which is that most suitable for medicinal use, occurs in 

 lumps of various sizes from that of a walnut downwards. They are 

 mostly of ovoid or spherical form, rarely vermicular, with the surface in 

 the unbroken masses, rounded, — in the fragments, angular. They are 

 traversed by numerous fissures, and break easily and with a vitreous 

 fracture. The interior is often less fissured than the outer portion. At 

 100° C. the cracks increase, and the gum becomes extremely friable. 

 In moist air, it slowly absorbs about 6 per cent of water. 



The finest gum arable is perfectly clear and colourless ; inferior 

 kinds have a brownish, reddish or yellowish tint of greater or less 

 intensity, and are more or less contaminated with accidental impurities 

 such as bark. The finest white gum turns black and assumes an 

 empjT-reuraatic taste, when it is kept for months at a temperature of 

 about 98° C, either in an open vessel, or enclosed in a glass tube, after 

 having been previously dried over sulphuric acid or not. 



An aqueous solution of gum deviates the plane of polarization 5° 

 to the left in a column 50 mm. long ; but after being long kept, it 

 becomes strongly acid, the gum having been partly converted into 

 sugar, and its optical properties are altered. An alkaline solution of 

 cupric tartrate is not reduced by solution of gum even at a boiling heat, 

 unless it contains a somewhat considerable proportion of sugar, extrac- 

 table by alcohol, or a fraudulent admixture of dextrin. 



We found the sp. gr. of the purest pieces of colourless gum dried in 

 the air at 15° C, to be 1'487 ; but it increases to 1'525, if the gum is 

 dried at 100°. 



The foregoing remarks apply chiefly to the fine white gum of 

 Kordofan, the Picked Turkey Gum or White Sennaar Gum of druggists. 

 The other sorts which are met with in the London market are the 

 following : — 



1. Senegal Ghmi — As stated above, this gum is an important item 

 of the French trade with Africa, but is not much used in England. 

 Its colour is usually ydlowish or somewhat reddish, and the lumps, 

 which are of large size, are often elongated or vermicular. Moreover 

 Senegal gum never exhibits the numerous fissures seen in Kordofan 

 gum, so that the masses are much firmer and less easily broken. In 



^Vaughan, f.c. 



