SULPHURTZATION OF CAOUTCHOUC. 
357 
weight of the organic matter, or forming 48 per cent, of the 
stable compound. 
From the commencement of the reaction of the sulphur at 
this temperature, and during the whole of the time it is con- 
tinued, a slight hut constant disengagement of sulphuretted hy- 
drogen takes place.* Even the liquid sulphur at 302° absorbs, 
and is capable of retaining a volume of this gas nearly equal 
to its own. A curious phenomenon results from this fact ; at the 
moment when the sulphur crystallizes, from the decrease of tem- 
perature, each crystalline particle liberates a bubble of gas; 
sometimes this is disengaged ; sometimes, meeting with the crys- 
tals, it raises them and remains interposed, so that gradually 
the whole mass rises, and increases from 15 to 20 per cent, of 
its primitive bulk, instead of diminishing, as would happen in a. 
normal crystallization of pure sulphur. 
Instead of causing the liquid sulphur to penetrate at a tempera- ' 
ture near its melting-point, the caoutchouc may be mixed by a 
mechanical roller with from 12 to 20 per cent, of its weight of 
sulphur in a state of fine powder ; the properties of the organic 
matter are not altered, but can be modelled and joined together as 
in the normal state. But if the temperature is now raised to the 
point at which the vulcanization is effected, it takes place as in 
the first case ; the suitable term would be equally exceeded under 
the same circumstances, and the alterations above mentioned 
would be likewise manifested. 
Composition and Properties of the Caoutchouc vulcanized by 
the Methods above described. — When the suitable term has not 
been exceeded, the organic substance contains sulphur in two dif- 
ferent states ; from 1 to 2 per cent, is held in intimate combina- 
tion ;f the remainder is simply interposed in its pores. 
*At the same time an equivalent quantity of an organic substance sepa 
rates, which contains more carbon than the caoutchouc, and which can 
be extracted with a hot solution of caustic potash or soda, which does 
not act perceptibly upon the mass of the caoutchouc combined with the 
sulphur. 
t This compound has not altered the relations between the elements of 
the organic substance which is represented by the formula C 8 H T , as I have 
proved by several analyses made upon normal caoutchouc, or one of its two 
unequally soluble parts, and also on the compounds containing from 0-015 
to 485 sulphur. 
31* 
