448 GUMS 



by dilute mineral acids ; it is strongly dextrorotatory, most gums 

 being slightly Isevorotatory. 



ACACIA GUM 



(Gum Arabic, Acaciae Gummi) 



Source, &c. Acacia gum is a dried exudation from the stem and 

 branches of various species of Acacia (N.O. Leguminosce) , especially 

 of Acacia Senegal, Willdenow, a small tree attaining a height 

 of 5 or 6 metres, and growing freely both in Western Africa (Sene- 

 gambia) and in Eastern Africa (the upper Nile districts), possibly 

 also in Central Africa, forming forests of considerable extent. The 

 first formation of gum appears to take place in the cambium 

 or the young bast tissue produced from the cambium and to be in- 

 duced by a wound inflicted on the stem. Such wounds may be 

 produced by animals (ants, beetles, &c.), or by the cracking of the 

 bark during the process of growth, or intentionally with the object 

 of producing gum. Bacteria, moulds and other organisms may thus 

 gain admittance to the gum-forming tissues, but whether these take 

 an initial part in the formation of the gum is more than doubtful. 



The best gum is produced near Kordofan from trees specially cul- 

 tivated and worked for gum. Strips of bark 0'5 to 1 metre long and 

 from to 2 to 8 cm. wide are removed from the trunks and large 

 branches, care being taken not to injure the cambium. About two 

 or three weeks afterwards the gum is collected, and the orchard is 

 then picked over about every four days until the rain sets in, when 

 the exudation of gum ceases. Gum is also spontaneously exuded 

 from wild trees, but this is usually rather darker in colour and not so 

 valuable. The trees begin to yield gum when they are about three 

 years old and continue to yield for about fifteen years. 



The gum as collected is in translucent tears which, ' ripened ' 

 by exposure to the sun, develop cracks and become friable. 

 Native girls clean it by picking out pieces of bark and sifting 

 out the sand. It is then packed into sacks and sent from the nearest 

 rail-head (El Obeid) to Port Sudan for shipment. Large quantities 

 are sorted and packed in Omdurman. 



In some districts another acacia yielding smaller quantities of gum 

 (A. Seyal, Delile) occurs. The gum, which is called talk or talka gum, 

 is collected by the natives with that of A. Senegal (hachab gum). 

 As talka gum is of inferior quality it has to be separated by picking. 



Description. Kordofan (hachab) gum, which is the best variety, 

 occurs in rounded or ovoid tears, varying in size from a pea to a 

 hazel nut or even larger. They are often quite white, but sometimes 

 show a yellowish tinge, and are opaque from the presence in the outer 



