20 Mr. Faraday on 



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202.4 grains of the liquid dried in a Wedgewood basin, at 100 

 Fah., became, in a few days, 944 grains, and the solid piece formed 

 being then removed from the capsule, and exposed on all sides to 

 the air until quite dry, became 91 grains : hence 100 parts of sap 

 left nearly 45 of solid matter. Heat caused immediate coagula- 

 tion of the sap, the caoutchouc separating in the solid form, and 

 leaving an aqueous solution of the other substances existing with 

 it in its first state. 



Alcohol poured into the sap in sufficient quantity, caused a 

 coagulum and a precipitate, both of which were caoutchouc of 

 considerable,purity. The alcohol retained in solution the extra- 

 neous matters, which, possessing peculiar properties, will be here- 

 after described. 



Solution of alkali added to the sap evolved a very fetid odour, 

 but did not appear to exert any particular action on the caoutchouc. 



The sap, left to itself JFor several days, gradually separated into 

 two parts, the opaque portion contracted upwards, leaving beneath 

 a deep-brown, but transparent, solution, evidently containing 

 suhstances very different in their nature from caoutchouc itself, 

 and which, considering the specific gravity of the sap and of pure 

 caoutchouc (the latter being lighter than water), were probably 

 present in considerable quantity. 



It was found that, by mixing the sap with water, no other 

 change took place than mere dilution. The mixture was uni- 

 form, and had all the properties of a weak or thin sap. Heat, 

 evaporation, acids, and alkali, produced the same effects, gene- 

 rally, as before, 



When the diluted sap was suffered to remain at rest, a sepa- 

 ration soon took place, similar to that which occurred with the 

 native juice, but to a greater extent ; a creamy portion rose to 

 the top, whilst a clear aqueous solution remained beneath. Hence 

 it was found easy to wash the caoutchouc, and remove from it 

 other principles which had' been generally involved in it to a 

 greater or smaller extent during its coagulation. For this purpose 

 a portion of the sap was mixed with about four volumes of water, 







and the mixture put into a funnel, stopped below by a cork ; in 



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