RUBBERS AND GUMS 211 



water. In Ceylon the cost of producing camphor is about 27 

 cents a pound. 



The bulk of the world's camphor is used in the manufacture 

 of celluloid and in connection with nitro-cellulose compounds. 

 In addition to this chief use of camphor, it is also employed 

 to a less extent in the preparation of various medicines. 



OTHER GUMS AND RESINS 



All of the products which have been discussed in this chap- 

 ter would be generally included under the head of gums and 

 resins. Most of them, however, are of so great importance for 

 specific uses that it was thought best to discuss them separately. 

 A few brief notes seemed desirable in connection with certain 

 other gums and resins which have some importance in the 

 world's commerce. The chemical composition of gums and 

 resins is not well understood. Ordinarily, gums are defined 

 as amorphous CHO compounds which dissolve in water or 

 take up enough water to become mucilaginous and are insolu- 

 ble in alcohol. Resins, on the other hand, are CHO com- 

 pounds which are insoluble in water, but soluble in alcohol, 

 ether, and volatile oils. Balsams are a group of resins or 

 oleoresins with a fragrant aroma or agreeable flavor. A well 

 known example of this group of products is Canada balsam. 



Copal resin is obtained either directly from living trees or 

 as a semi-fossil product. It occurs in the East Indies, South 

 America, New Zealand, Africa, Sumatra, Java, Philippines, 

 and Australia. Macassar, or Singapore copal, is obtained from 

 Agathis loranthifolia. South American copal comes from liv- 

 ing trees of Hymencza courbaril. Kauri copal is a fossil resin 

 from the Kauri pine {Dammara australis) . The dammar resin 

 of the Federated Malay States comes chiefly from species of 

 Balanocarpus. The copal resins are widely used in varnishes. 



Gum arable is a gummy exudation which occurs on the 

 trunks of Acacia Senegal and other species of wattle trees. 



