356 
SULPHURIZATION OF CAOUTCHOUC. 
tenacity which renders it so useful for certain purposes, for in- 
stance, for transmitting steam and the mechanical force by flexi- 
ble tubes. 
The principal conditions of success in this manufacturing ope- 
ration had been carefully determined ; in England, America and 
France, several methods had been successively imagined, which 
realized more or less perfectly the curious and important modi- 
fications of the sulphated substance ; but it was not known in 
what the chemical reaction consisted ; no one had an accurate 
idea of what is termed desulphuration. Lastly, it was impossible 
to understand, and consequently to prevent, certain altera- 
tions, especially the rigidity and fragility of several objects, after 
having served often but a short time the purposes for which they 
were made. 
The investigations which I have the honor to bring before the 
Academy have had for their object to throw some light on these 
points of applied science. I shall first describe what takes 
place in one of the processes of vulcanization still employed by 
several manufacturers ; it will then be more easy for me to point 
out the effects of other processes. If a strip of caoutchouc 
from two to three millims. thick is kept immersed for two or 
three hours in melted sulphur, at the temperature of 234- 
240°, the liquid will penetrate into the pores like water or alco- 
hol, as we have already shown, but still more quickly, and the 
weight of the strip will have increased by 10- to 15-hundredths. 
The organic matter will have experienced no considerable modi- 
fication in its properties ; it can be shaped, and its recent sec- 
tions joined, just as in the normal state ; solvents will act upon 
it with the same force ; but its porosity will be diminished. If 
* the temperature be now raised to 275°, 302<> or 320°, in any 
medium whatever, inert of itself, a few minutes suffice to effect 
the change. By prolonging the action of the temperature, the 
object in view would be exceeded, the product, gradually less sup- 
ple and less elastic, would soon become hard and fragile. This 
last alteration would be still more marked if the caoutchouc 
were kept at the above temperatures, 275°-320°, in melted sul- 
phur. The amount absorbed would gradually increase until it* 
became in twenty-four hours, for instance, nearly equal to the 
