324 PLANTS PRODUCING GUMS AND RESINS 



his experiments that Courbaril resin is made up of three distinct 

 resins : one soluble in chloroform, another in ether, and, finally, a 

 third which dissolves in absolute alcohol. This latter also dissolves 

 the two resins first named and is, in fact, the best solvent of this 

 product. 



These results contradict those obtained by Laurent and Paoli, who 

 were no doubt deceived by a sample from an unauthenticated source. 



According to de Cordemoy, semi-hard copal gives varnishes of paler 

 colour than those manufactured from the hard copal, but they are less 

 resistant ; they may be used to advantage for interior varnishing work. 

 They may also be used dissolved in Xylol instead of Canada balsam 

 for mounting preparations for the microscope. 



Hymenssa stHbocarpa — In Brazil this plant is called Jatoha, and 

 produces a copal apparently differing very little from that produced 

 by the Courbaril species. 



Tamarindus indica. — In Madagascar this plant yields a gum called 

 Madiro. It occurs in somewhat bulky pieces formed by an agglomera- 

 tion of tears. When examined separately these latter are clear and 

 semi-transparent, and have a brilliant fracture. 



This gum is absolutely insoluble in water. It swells up enormously 

 in this liquid and forms a compact jelly (de Cordemoy). 



Sebipira major. — In Brazil a gum withdrawn from this tree is used 

 chiefly in medicine. 



MIMOSE/E. 



Acacia arabica. — This plant supplies the gum arable which has 

 been familiar from the very remotest times. It is a small tree, 2 to 

 6 metres high, with very many branches and a brownish bark covering 

 a reddish-brown wood. 



This gum was once gathered in the lower valle> of the Nile; under 

 the Roman dominion large quantities were produced in Arabia and 

 exported to Europe, hence the designation of gum arable. The Arabs 

 no longer pay much attention to their gum ; what is exported to-day 

 comes chiefly from Somaliland. 



In commerce this gum, the true gum arable, is divided into three 

 classes, called first white, second white, and third white. It has a 

 density of r355 ; a solution turns litmus paper red through the presence 

 of a small quantity of bi-malate of lime; it also contains traces of 

 potassium and calcium chloride and potassium acetate. 



De Cordemoy gives the following composition : — 



Arabia ... ... ... ... ... 79'40 



Water ... ... ... ... ... ... 17-60 



Saline matters and organic debris ... ... ... 3'oo 



loo-oo 



The Indian gum arable also comes from this plant. This gum, 

 which is either exuded naturally by the tree or through properly made 

 incisions, appears in the form of irregular broken tears, cohering in 



