232 ANNUAL OF SCIENTIFIC DISCOVERY. 



the weight of the chloroform, and mix perfectly. Preserve in well- 

 stopped bottles. 



The ' chloric ether ' must not redden litmus paper, or give rise to 

 a precipitate when mixed with a solution of nitrate of silver." 



ON THE VULCANIZATION OF INDIA RUBBER. 



AN elaborate memoir on the sulphuration of caoutchouc has been 

 communicated to the French Academy by M. Payen, of which the 

 following is an abstract. The principal conditions of success, says 

 M. Payen, in the practical operation of sulphuration have been care- 

 fully determined in England, America and France, but it has not 

 been known in what the chemical action consisted ; there was no ac- 

 curate idea concerning what has been called the desulphuration ; 

 finally, certain alterations, especially the rigidity and fragility of 

 several objects after sometimes a very short duration of the use for 

 which they were destined, could not be comprehended, nor, conse- 

 quently, prevented. The researches I have undertaken, will, I think, 

 clear up this point of applied science ; I will first describe what occurs 

 in one of the first processes of vulcanization, still employed by several 

 manufacturers. If a sheet of caoutchouc, two or three millimetres 

 in thickness, be kept for two or three hours immersed in sulphur, 

 liquified at the temperature of 201 to 208 Fahr., the liquid will pene- 

 trate into the pores as water or alcohol would do, and the weight of 

 the sheet will be increased 10 or 15 per cent. No considerable mod- 

 ification, however, will have been made in the properties of the 

 organic matter ; it may be fashioned, and its recent sections joined the 

 same as in the normal state. Solvents will attack it with the same 

 energy. It is, however, less porous. If, then, we raise in any 

 medium whatever, inert of itself, the temperature to 275, 302, or 

 320 Fahr., the conversion will be effected in a few minutes. The mark 

 would be overshot by prolonging the action of the heat ; the product 

 would become gradually less supple and less elastic, and would very 

 soon be hard and brittle. This last alteration would be more com- 

 plete if the caoutchouc were maintained at the same temperature, 

 (275 to 320 Fahr.,) in fused sulphur ; the proportion of the latter body 

 absorbed would gradually increase, until it became, in 24 hours, 

 almost equal to the weight of the organic matter, or would constitute 

 48 per cent, of the compound. From the commencement of the 

 action of the sulphur at this temperature, a slight but continuous 

 disengagement of sulphuretted hydrogen occurs. At the same time 

 an equivalent quantity of organic matter, containing more carbon 

 than caoutchouc does, is separated, and may be extracted with a hot 

 solution of caustic potassa or soda, which do not perceptibly attack 

 the mass of caoutchouc combined with the sulphur. Liquid sulphur, 

 at the temperature of 302 absorbs, and may retain, a volume of 

 sulphuretted hydrogen almost equal to its own. A curious phenome- 

 non results from the foregoing facts. At the moment when the 

 abatement of temperature allows the sulphur to crystalize, every 



