118  Gymene  from  Oil  of  Turpentine,  etc.  [A "ifi^ES* 
"  treating  the  mixture  with  sulphuric  acid  so  as  to  polymerise  the 
terpene  present,  and  then  diluting  with  water,  and  distilling  in  a 
current  of  steam." 
Shortly  after  (April  3,  1873),  the  writer  read  a  second  paper  de- 
scribing the  properties  of  the  cymene  thus  obtained,  and  contrasting 
them  with  those  of  cymene  from  other  sources  {Chemical  News,  vol. 
xxvii.,  p.  180 :  Journ.  Chem.  Soc.  [2],  xi.,  686). 
On  Feb.  21,  1873,  M.  Ribau  communicated  to  the  Paris  Chemical 
Society  the  results  of  his  experiments  on  the  action  of  sulphuric  acid 
on  terebenthene  (Bui.  Soc.  Chem.  Paris,  xix.,  242),  and  on  July  4, 
1873,  he  also  read  another  paper  on  the  same  subject  (Ibid.,  xx.,  97 
and  100),  the  result  arrived  at  being  that  cymene  is  formed  from  the 
terpene  by  the  reaction  C10H16+H2SO4^2H2O+SO2+C10H14.  In  a 
postscript  to  the  second  of  the  above  mentioned  papers,  written  before 
the  appearance  of  M.  Ribau's  second  communication,  the  writer  sug- 
gested that  the  cymene  obtained  by  M.  Ribau  was  not  formed  thus> 
but  was  that  pre-contained  as  such,  the  main  reason  given  being  that 
by  cautiously  acting  on  oil  of  turpentine  with  sulphuric  acid,  "  the 
writer  had  succeeded  in  isolating  cymene  from  oil  of  turpentine,  without 
the  evolution  of  more  than  inconsiderable  quantities  of  sulphurous 
acid.*'  The  method  employed  was  as  follows  : — Oil  of  turpentine 
freed  from  oxidized  substances  by  distillation  over  sodium  was  very 
gradually  mixed  with  about  its  own  weight  of  sulphuric  acid,  the 
mixture  being  carefully  cooled  ;  after  a  few  minutes  the  whole  was 
poured  into  a  large  bulk  of  water,  the  oily  layer  decanted  and  dis- 
tilled with  water,  and  the  oily  layer  of  distillate  treated  repeatedly  in 
the  same  way.  Only  once  or  twice  was  a  very  faint  odor  of  sulphurous 
acid  observed ;  and,  as  about  3  per  cent,  of  nearly  pure  cymene  was 
ultimately  obtained  (irrespective  of  losses  and  waste  in  distillation), 
it  was  inferred  that  this  was  pre-contained  as  such. 
It  being  in  no  way  improbable  that  some  specimens  of  oil  of  tur- 
pentine might  contain  more  cymene  than  others,  the  pre-existence  of 
M.  Ribau's  cymene  thus  appeared  exceedingly  probable,  even  though 
the  amount  obtained  by  this  chemist  was  considerably  above  3  per  cent. 
Between  August  20  and  September  1,  1873,  Herr  Orlewski  read 
before  the  Meeting  of  Russian  Naturalists,  at  Kasan,  a  paper,  in 
which  he  states  (as  reported  by  Richter,  Ber.  Deut.  Chem.  Gres,  vi., 
1257),  that  considerable  quantities  of  cymene  are  produced  by  the 
action  of  sulphuric  acid  on  turpentine  oil  in  the  ordinary  process  for 
