358 
SULPHURIZATION OF CAOUTCHOUC. 
The uncombined excess of sulphur is gradually eliminated from 
the caoutchouc by the mechanical effect of the extension and con- 
traction of the pores; this continues for several months. Several 
chemical reagents remove the interposed sulphur more rapidly and 
more completely, as hot solutions of caustic potash and soda (and 
even cold in the course of a month if renewed frequently), sul- 
phuret of carbon, essential oil of turpentine, benzine, and anhydrous 
ether. These liquids cause the organic matter to swell to such 
an extent, that its bulk is soon, increased eight or nine times. 
Ether removes the sulphur in a peculiar manner. A small 
proportion is first dissolved, which is then carried to the exterior ; 
there it separates in crystalline particles ; other particles, succes- 
sively dissolved in the interior, follow the same course, and in- 
crease the size of the crystals, which soon become pretty large, 
and are of the octahedral form. Neither turpentine nor benzine 
transfer the crystalline particles of the sulphur removed from the 
interior of the swollen mass to the exterior. This peculiarity ap- 
peared to me to be owing to the hitherto unobserved greater sol- 
vent power of the turpentine and benzine ,* in order to verify this 
fact, I saturated these two liquids, kept at a constant temperature 
of 167° F., in the water-bath with an excess of flowers of sulphur. 
The yellow solutions were immediately filtered, when they de- 
posited crystals on cooling : — 
In turpentine. In benzine. 
The hot solutions contained O0587 0'0733 sulphur. 
After cooling they contained 0'0135 0-0173 sulphur. 
Moreover, the crystals were not similar; the turpentine, on 
slow cooling, as also on evaporation at 77°, had deposited the 
sulphur in small octahedrons ; on sudden cooling, it deposited it 
in acicular prisms ; in the benzine the crystals were prismatic. It 
is curious to observe this last mode of crystallization in a test-tube ; 
a number of diaphanous rectangular plates are seen to form, ascend 
and descend rapidly in the liquid, and successively agglomerate at 
the bottom of the vessel in laminae, which thus gradually lengthen ; 
if, after cooling to 59°-60°, evaporation is allowed to recom- 
mence, a further crystallizat l on takes place now in diaphanous 
octahedra, which attach themselves to the extremities of the opake 
yellowish lamellar prisms first formed. On evaporation with heat, 
long silky lamina are obtained. A drop of the same solution in 
