ACACIA 331 



the production of gum. The more or less hardened pieces are col- 

 lected and then sorted into different grades, the market supplies 

 being obtained from Egypt by way of Alexandria (Kordofan gum), 

 from the Soudan by way of Suakin (" Turkey sorts " and " Trieste 

 picked "), and from Senegambia by way of the port of St. Louis. 

 The Kordofan gum is considered to be the best. The best grade of 

 gum Arabic (gum Senegal) is obtained from Acacia Senegal and A. 

 glaucophylla, both of tropical Africa. 



Description. In roundish tears of variable size, or broken into 

 angular fragments; externally whitish or yellowish-white, with 

 numerous minute fissures; translucent; very brittle, with a glass- 

 like, sometimes iridescent fracture; nearly inodorous; taste mucil- 

 aginous. 



Acacia is not soluble in alcohol, but is completely soluble in cold 

 water; the solution is adhesive, gives an acid reaction with litmus 

 paper. 10 c.c. of a 10 per cent solution does not yield a gelatinous 

 precipitate with 0.2 c.c. of normal lead acetate test solution, but is 

 precipitated with 0.1 c.c. of a test solution of ferric chloride (Mesquite 

 gum is not precipitated); a cold solution does not give a bluish or 

 reddish color with iodin (absence of artificial gums containing starch 

 or dextrin), or a brownish-black precipitate with solutions of ferric 

 chloride (absence of gum of Australian species). A 10 per cent aque- 

 ous solution of acacia when examined by the polariscope should 

 show but a slight laevbrotation. The U. S. Bureau of Standards 

 proposed a method for the quantitative estimation of Gum Arabic 

 using an alcoholic-copper acetate-ammonia solution. 



Powder. Oyster-white; soluble in cold water, forming a sticky 

 paste and containing few or no altered or unaltered starch grains or 

 vegetable tissues. 



Constituents. A crystalline glucoside, which is apparently arabic 

 acid (arabin or gummic acid) in combination with calcium, magne- 

 sium and potassium, and which constitutes the greater part of the 

 gum; water, 12 to 17 per cent; ash 2.7 to 4 per cent. 



Allied Plants. Gums with a brown or red color are obtained 

 from A. arabica, A. Seyal, A. stenocarpa and A. Ehrenbergiana. 

 There are a number of gums which have many of the properties of 

 gum Arabic, as Cape gum, from A. horrida and A. Giraffse; Australian 

 or wattle gum, from the golden wattle (A. pycnantha), .tan wattle 

 A. decurrens) and A. homalophylla. Gums are also obtained from 

 other genera of the Leguminosse, as Mesquite gum, from Prosopis 

 juliflora, of the southern United States and Mexico. The tears of 

 Mesquite gum are nearly smooth, light yellowish-brown to dark 



