REPORT OF CHEMICAL LABORATORY 229 



and usually is, lower than that of " Khartoum " gum, but whether because this is 

 overbalanced by its other qualities, or because of different methods of working, this gum 

 fetches in Trieste a higher price for use in confectionery than the harder and so-called 

 " stronger " gum. 



Senegal gum is picked to a great number of grades.* In the following tables of Grading 

 results of examinations, the Sudan gum was in some cases picked to the same grades 

 in order to afford a better comparison. The latter was possible only with Kordofan 

 Hashab, this season's gum from Gedaref and Ghezireh not yet being available. 



The proportion of moisture was noted to be closely dependant upon the size of the 

 tears, the smaller ones offering more evaporating surface and containing less water. 



The amount of acidity varied but little. The sourish taste which some samples 

 possess is not always associated with higher actual acidity. The determination of ash has 

 little significance. In gums from the same variety of tree and the same immediate 

 neighbourhood the darker tears have as a rule a very slightly higher ash. These darker 

 gums are, as a rule, stronger, but not invariably so. 



The colour of the Sudan hard gum picked as large white tears {grouse blanche, Senegal) 

 was a shade darker than the corresponding grade of Senegal gum ; the colour of the 

 mucilage of equal strength was, however, almost identical. All the other grades of the 

 Sudan gum and of the mixed (crude) gum were very considerably lighter than the same 

 grade of Senegal gum — a point which tells strongly in favour of the Sudan product. 

 The average strengthf of the picked grades of hard Sudan gum is appreciably higher 

 than that of the same grades of Senegal gum. All the crude (unpicked) Kordofan gums, 

 that is, both the hard ami the soft gums, show a higher strength than the unpicked 

 Senegal gum. Thus the soft variety, unpicked, was found to possess a strength of 92"5, 

 as against an average of 83 for the three samples of " Bas du Fleuve " tested. 



• Crude Senegal gum is divided into three main classes : — 



1. Hard gum. Gomme du, bas du ftcuve. This consists of largish round, vermiform or irregular shaped tears, 

 varying from almost colourless to dark yellow. 



2. Gomme du haul du fleuve. This, the second grade, is obtained from Upper Senegal. The tears are smaller 

 than those of " Bas du fleuve " and, on the whole, darker. 



Both the above are derived in the main from the A. Senegal {Acacia verck), but they are often mixed with 

 pieces of reddish colour, glassy, of bitter taste, due to the gum of the A. arabica and its varieties. 



3. Gomme friable. This is the product largely of the A. albieda (White tree. Cedra beida or by corruption 

 Sadra-beida and Salabreda). 



The gum resembles coarse salt. It is very friable, and its solution has less viscosity than that of the gums 

 already mentioned. It is usually in small fragments or vermiform tears. The latter are often almost colourless, 

 but the fragments are usually dark coloured. The variety corresponds in quality to the Talh gum of the Sudan. 



Senegal gum is picked into a great number of classes of which the principal are : — 



(a) La gomme grosse blanche, in rather large tears, unbroken, colourless or slightly yellowish. 



(6) La gomme petite blanche, which d iff ers from the above only in that the tears are smaller. 



(c) La gomme grosse blonde, in tears about the same size as those of gomme grosse blanche, but yellowish or 

 reddish yellow. 



(d) La gomme petite blonde, like the above but smaller. 



(e) La gomme d^usciemc blonde, of a reddish colour. 



(/) La gomme vermicelle, vermiform or branched tears, usually of light colour. 



(g) La gomme fabrique, of which the pieces, of larger or smaller size {fabrique and petite J'abrique) are not 

 suitable for classification with any of the above. 



(A) La gomme marron, dark coloured, very impure, containing much foreign matter — bark and other 

 impurities. 



(i) La gomme friable — already described above. 



Broken gum is also sorted by sieves into Gomme gros grabeaux, Gomtne mm/ens grabeaux, Gomme menus 

 grabeauT, and Gomme poussiere grabeaux. 



t This is measured by the viscosity of a solution of given strength, as compared with the viscosity of an 

 average hard gum of the best quality. The method of determining the viscosity is detailed on pp. 232 and 233. 



