fi 4 CAOUTCHOUC, 



separation of the caoutchouc. The composition and density of the natural 

 sap is by no means constant, possessing a variable amount of caoutchouc, 

 which may be stated to average from 30 to 45 per cent. : the specific 

 gravity also varies from 1-012 to 1-04125 ; and its composition may be 

 represented by the following formula : — 



Water containing free Acid - 57-00 



Caoutchouc - - - - - - 33 - 10 



Albumen - - - - - 1-00 



Nitrogenised bodies soluble in water, variable - 6-10 



Substances insoluble in water, variable - - 2-80 



100-00 

 Albumen, although existing in the sample from which this analysis has 

 been made, is not at all times found in the juice, and the amount of 

 caoutchouc is greatly influenced by the age of the plant from which it has 

 been collected. After solidification and separation from the various sub- 

 stances associated with it, caoutchouc exists essentially as a pure carbide 

 of hydrogen — 



C. 87-20 

 H. 12-80 



100-00 

 and when freshly prepared and moulded into the various shapes and forms 

 known in commerce, it is perfectly white and opaque. In this state it is 

 surcharged with an acid moisture, and seldom presents a fresh cut surface 

 or mass homogeneous, or free from minute air cavities or cells, almost 

 imperceptible to the eye, and through which a gradual transudation of air 

 and moisture readily takes place. 



By age and exposure, caoutchouc loses this appearance, and becomes 

 perfectly clear and transparent, resembling tortoiseshell both in colour 

 and appearance. The moisture evaporates slowly, and this gradual loss 

 causes the caoutchouc to shrink and contract. The air cells and cavities 

 which were observable in its fresh state disappear, and it cannot again be 

 made, under any condition, to take up an ecpial amount of water. Its 

 specific gravity in this form also varies from - 9190 to 0-9430 ; the produce 

 of Java, Singapore, and Assam (Ficus elastica) being represented by the 

 former, that of South America (Siphonia elastica) by the latter. 



Caoutchouc in its solid state is a substance sui generis, possessing many 

 specific properties, and approaching in its composition nearer to the 

 essential oils than any similar substance. Microscopically examined, it 

 presents neither definite form nor structure, resembling a mass or substance 

 which may be likened to clear, transparent jelly. It is unaffected by water, 

 alcohol, and most of the strong acids. Hydrochloric acid in the cold 

 exerts no action upon it ; neither does the same acid when aided by heat 

 affect it to any sensible extent. 



Concentrated sulphuric acid acts slightly upon the surface of caout- 



