1826.] On pure Caoutchouc. 181 



'': Thinking it probable that whilst in its natural state of divi- 

 sion the caoutchouc would combine more intimately or readily 

 with fixed and volatile oils than when aggregated, as it gene- 

 rally is in commerce, an experiment or two were made in con- 

 sequence. A portion of well-washed milky caoutchouc being 

 added to olive oil, and the two beaten well together, a singu- 

 larly adhesive stringy substance was produced, which holding 

 the water diffused through it, assumed a very pearly aspect, 

 stiffened, and was almost solid ; upon being heated so as to 

 drive off the water, it became oily, fluid and clear, and was 

 then a solution of caoutchouc in the fixed oil. On adding water 

 and stirring considerably, it again became adhesive as before. 

 Thus introduced, caoutchouc would probably be a useful ele- 

 ment in varnishes. 



Oil of turpentine being added to a mixture of one volume of 

 sap and one volume of water, and well agitated with it, was 

 found to be only imperfectly miscible ; after standing twenty- 

 four hours, three portions were formed : the lower, the usual 

 aqueous solution ; the upper, oil of turpentine, holding a little 

 caoutchouc in solution ; the intervening part a clot or tenacious 

 mass, soft and adhesive, like bird-lime, consisting of caoutchouc, 

 with some oil of turpentine. It was very difficult to dry, and 

 always remained adhesive at the surface ; but experiments of 

 this kind were not pursued, for want, at that time, of further 

 quantities of the original sap. 



Such is a general view of the nature of the sap from which 

 the substance is obtained, and of the substance itself. I have 

 not endeavoured to give an accurate account of the properties 

 or quantities of the other substances present, because there is 

 reason to believe that both vary in different specimens, pro- 

 bably according to the age of the tree, the time of the year, 

 or the manner in which the sap is drawn ; nor have I dwelt 

 upon the inaccuracies of former accounts, inasmuch as they 

 are evidently referable to the impurity of the substance ex- 

 amined. 



Those who wish to look to former accounts of the chemical 

 or physical qualities of this remarkable substance, will perhaps 

 find the following references useful : 



1751. De la Condamine on an Elastic Resin, newly discovered at Cayenne, 

 by M. Fresneau ; and on the Use of various Milky Saps from Trees of 



