236 LEGUMINOS.E. 



Arabia called the Hejaz, the gum thence brouglit 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 tlie French colony of Senegal, gum, which is one of its principal 

 productions, is collected chiefly in the country lying north of tlie 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 1| to 5 millions of kilogrammes. 



Description — Gum arable does not exhibit any very characteristic 

 f(3rms like those observable in p'um traii'acanth. The finest white gum 

 of Kordofan, which is that most suitable for medicinal tise, occurs m 

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

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

 the unbroken masses, rounded, — in the fragments, angukr. 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 G per cent of water. _ . 



The finest gum arable is perfectly clear and colourless; mfenor 

 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 

 empyreumatic taste, when it is kept for months at a temperature o 

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

 having been previously dried over sulphuric acid or not. _ , 



An aqueous solution of gum deviates the plane of polarization a 



-he left in a column 50 mm. long ; but after being long kept- 



to the 



becomes strongly acid, the gum having been partly converted m 

 sugar, and its optical properties are altered. An alkaline sow<^ion 

 cupric tartrate is not reduced by solution of gum even at a ^^^^^^S^^^ 

 unless it contains a somewhat considerable proportion of sugar, ex 

 table by alcohol, or a fraudulent admixture of dextrin. . , -^^ 



We found the sp. gr. of the purest pieces of colourless gum arie ,^ 

 the air at 15° U, to be 1-487 ; but it increases to 1-525, if the guu^ 

 dried at 100^ • ^ m of 



The foregoing remarks apply chiefly to the fine white gu^.^^ 

 Kordofan, the Picked Tiirhey Gum or Wliite Sennaar Gum oiJJ^'J^^ ^he 



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

 following : 



1. Senegal Gmn—As stated above, this gum is an iniportaut i ej^ 

 of the French trade with Africa, but is not much used in ^"° 

 Its colour is usually yellowish or somewhat reddish, and t'f. ^er 

 which are of large size, are often elongated or vermicular. ^ 0^^ 

 benegal gum never exhibits the numerous fissures seen in ^ j^^ 

 gum, 80 that the masses are much firmer and less easily broKt; • 



^Vaughan, I.e. 



