228 



REPOnT OF CHEMICAL LABORATORY 



Us*s of gum 



So called 



■• Khartoum' 



and 



■■ Kordofan" 



gums 



Gum funiiiitiun, ijiiiiinioniK, iiuin finr, in plunts has long been held, iit least in some cases, 

 to Ik? the result of a pathological condition. Maiden (I'hiir. .Tour. 8, XX. (1890), 869), who 

 consiilered it to be the general rule, ijuotes an observation of Trecul to the effect that Acacias 

 and Rosacea' yield their gums most abundantly when sickly or in an abnormal state. So far 

 as regards the Su<lan, and, it would appear Senegal as well, it is in sandy, not very rich soils, 

 moist in the rainy, hut iltticiiiit in moisture in tlic drvir season, that the trees seem to yield 

 gum most abmidaiitly. A plentiful supply of moisture at all sea.sons appears to result in a 

 condition of vigour in the plant which enables it to resist infection. This would explain the 

 state of aflairs mentioned by JIuriel (see page 'I'!!}), who found a good growth of " Hashab" 

 trees bearing no trace of gum, and yet, on either side, in dryer soil, there was a good 

 gum producing Creneina. This also appears to be the case in the Blue Nile Province. 



As Dr. Greig Smith {lor. cit.) states, while every susceptible tree does not produce gums 

 it might be made to do so by an artificial infection, either with pure bacterial cultures or with 

 the fresh juice from a selected and infected tree. The case cited above would .seem to 

 indicate that infection would only take place under certain favourable conditions. It seems 

 little likely that the group of trees referred to would have remained uninfected, situated as 

 they were, had they been susceptible ; but it is quite possible that other acacias, differently 

 situated, might have remained uninfected, and inoculation might be practised with profit. In 

 any case, as Dr. Smith further notes, all branches of a tree may not be producing gum, and 

 an artificial infection of these might increase the yield. There is, possibly, a very profitable 

 field for research in this direction. 



Uses of Gum Akabic. — Gum arabic has a very wide application in the arts. The 

 better grades are used in confectionery, in dyeing and finishing silks and other fabrics, in 

 water colours and in pharmaceutical preparations. The lower grades are used in the 

 manufacture of inks, matches, stationery, etc. The t'ommeri'ial value of the gum will depend 

 principally upon its freedom from colour, odour, taste, and foreign matter, and upon its 

 strength, as measured by the viscosity of its solutions. 



GKADrso. — At the present time by far the larger portion of Sudan gum is exported in 

 the crude state. A small amount of it is partially picked, and some of it, already of a light 

 colour, is further bleached by exposure to the sun. The result is an almost perfectly white 

 gum, yielding a nearly colourless solution, odourless and practically tasteless, or of a slight 

 agreeable flavour. This grade is highly prized for use in confectionery. 



Although all the gum from Kordofan is collected from the AcacUi Wrek; the gum 

 presents certain differences in quality. How far these differences are due to soil, to tilt 

 amount of rainfall and to season of collection, to the barking and iige of the trees, etc., etc., 

 has not as yet been worked out ; the last mentioned, the age of the tree, seems to be a most 

 important factor. Generally speaking, the stronger gum is the product of young, and the 

 weaker variety of the more fully matured trees. In Trieste, where much of the gum goes 

 for sorting and cleaning, the giun is divided into two main classes — " Khartoum ' and 

 "Kordofan." "Khartoum" is the hard gum, presenting more the characteristics of the 

 Senegal product. The surface is smooth and shiny and the pieces are hard and tough. This 

 gum yields a solution highly viscous, and, as a rule, of light colour. 



The grade known as " Kordofan " is a softer gum, which in drying quickly becomes 

 covcreil with innumerable cracks and fissures, so that after even a moderate exposure to 

 the Sim the tears lose their transparency and appear whitish and opaipie. As a rule this 

 variety of gum furnishes a very pale, clean solution of good flavour. The viscosity may be, 



