SULPHURIZATION OF CAOUTCHOUC. 
359 
benzine, placed on the object-bearer of the microscope, deposits on 
evaporation transparent octahedra. 
100 parts of hot sulphuret of carbon dissolve 73*46 sulphur. 
100 parts of cold sulphuret of carbon dissolve 38*70 sulphur. 
100 parts of hot ether dissolve - - 0*54 sulphur. 
100 parts of cold ether dissolve - - 0*188 sulphur. 
On cooling, the sulphur crystallizes in large octahedra from 
sulphuret of carbon; from ether, in minute octahedra and some 
prisms. 
Ether and sulphuret of carbon, kept for a long time in contact 
with vulcanized india-rubber, retain from 4 to 5 per cent, in solu- 
tion, which may be isolated by evaporating several times, and 
each time removing by ether the free sulphur, and then treating 
with anhydrous alcohol, which removes from 1 to 1*50 per cent, 
of fatty matter. The caoutchouc thus extracted may be separated 
into two portions, one very ductile, which dissolves in benzine, 
and is deposited on evaporation ; the other more tenacious, less 
extensible and insoluble. Both these portions come from the in- 
terior of the strips at a certain depth, where* the combination is 
less intimate, and contains less sulphur than near the surface. 
The want of homogeneity in the combination of the sulphur with 
the organic substance is greater in the two other methods of vul- 
canization, which I shall describe further on. 
After vulcanization, the caoutchouc still consists of two parts, 
differing in cohesive power and solubility. This may be proved 
by keeping it immersed for two months in a mixture of 10 parts 
sulphuret of carbon and 1 of absolute alcohol. The dissolved por- 
tion consists of the interposed sulphur, which is removed after de- 
siccation by a solution of caustic soda ; the organic substance the 
least aggregated is then left as a translucid, yellowish, slightly- 
resisting mass. The undissolved portion is become more brown 
and less transparent. The following are the proportions obtained 
in the experiment, besides the fatty matter: — 
Insoluble tenacious portion 65 
Soluble soft portion ... 25 
Excess of sulphur 10 
Vulcanized objects, applied on metals, especially upon silver, 
