620 
Vulcanization  of  India-rubber. 
Am  Jour.  Pharm. 
Dec,  1890. 
canizing  because  it  does  not  act  too  strongly  upon  the  rubber, 
whilst  the  dark  colored  chloride  of  sulphur,  containing,  as  it  does,  a 
large  quantity  of  the  higher  chlorides  of  sulphur,  is  liable  to  render 
the  rubber  quite  hard  by  vulcanizing  it  too  much.  The  theory 
generally  adopted  to  explain  this  is,  that  these  higher  chlorides 
break  up  easily,  liberating  their  sulphur,  which  thus  combines  in 
greater  quantity  with  the  rubber  ;  but  my  experiments  and  analyses 
prove  that  it  is  chiefly  the  chlorine  and  not  the  sulphur  of  the 
chloride  of  sulphur  which  produces  the  vulcanization. 
A  rubber  substitute  much  used  at  present  is  produced  by  acting 
on  vegetable  oils,  such  as  rape,  linseed,  etc.,  with  a  mixture  of 
chloride  of  sulphur  and  bisulphide  of  carbon.  The  oil  becomes  con- 
verted into  a  solid  substance  resembling  india-rubber  to  some  ex- 
tent, but  being  much  more  brittle.  This  body  is  now  used  in  large 
quantity  for  mixing  with  india-rubber  for  the  purpose  of  cheapening 
its  production.  On  analysis  of  some  samples  of  this  material  I  have 
invariably  found  that  it  contained  a  much  greater  proportion  of 
chlorine  than  of  sulphur,  and  this  process,  therefore,  is  a  vulcaniza- 
tion by  chlorine  rather  than  by  sulphur. 
Recently  I  analyzed  three  samples  of  rubber  substitute,  the  one 
termed  "  special,"  another  "  spongy  "  india-rubber  substitute,  the 
third  being  similar  to  the  first  in  appearance.  The  first  contained 
of  sulphur  3-4  and  of  chlorine  76  per  cent. ;  the  second  contained 
of  sulphur  4-56  and  of  chlorine  8  22,  and  the  third  2-67  of  sulphur 
and  7  90  of  chlorine  per  cent. 
These  rubber  substitutes  contain  considerable  quantities  of  oily 
matters  soluble  in  ether,  which  I  have  also  found  to  be  chlorine  and. 
sulphur  compounds  of  the  oils.  The  first  yielded  20-0  per  cent., 
the  second  14-3,  and  the  third  11-5  per  cent,  of  these  thick  oily  mat- 
ters soluble  in  ether.  This  oily  substance  from  the  first  sample  con- 
tained 2-6  per  cent,  of  sulphur  and  6-1  per  cent,  of  chlorine,  whilst 
that  from  the  second  contained  2-97  and  6-87  per  cent,  of  sulphur 
and  chlorine  respectively. 
Some  rubber  manufacturers  regard  this  oily  matter  as  injurious  to 
the  rubber  and  reject  any  substitute  which  contains  any  consider- 
able proportion  of  it.  I  have  found,  however,  by  experiment  that 
this  oily  compound  instead  of  acting  injuriously  on  india-rubber, 
actually  acts  as  a  preservative  of  it ;  some  rubber  threads  were 
smeared  with  this  oily  extract,  some  with  ordinary  (unvulcanized) 
