^Mar!UM874tRM}  Cymene  from  Oil  of  Turpentine,  etc.  119 
preparing  terebene  ;  and  that  terebene  itself  is  altered  by  this  reagent, 
cymene  being  formed,  sulphurous  acid  being  simultaneously  generated. 
At  the  same  time  Herr  Orlewski  stated,  that  by  long  continued  frac- 
tional distillation  of  an  old  yellowish  sample  of  turpentine  oil,  he  suc- 
ceeded in  isolating  a  small  per  centage  of  cymene  (10  grammes  from 
1J  litres),  and  ascribed  the  presence  of  this  substance  to  the  action  of 
atmospheric  oxygen  on  the  original  oil,  whereby  hydrogen  is  removed 
from  the  terpene. 
As  regards  this  explanation,  the  writer  has  shown  (loc.  cit.)  that  by 
the  action  of  oxidizing  agents,  certain  terpenes  undergo  the  reaction, 
2C10H16-|-O2=2C10H16O,  the  resulting  bodies  presenting  great  simi- 
larity to  certain  isomerides  of  camphor  which  readily  break  up  by 
treatment  with  dehydrating  agents  into  cymene  and  water,  C10H16O= 
H2O+C10H16.  M.  Ribau  has  very  recently  published  in  the  Bulletin 
of  the  Paris  Chemical  Society  (January  5,  1874,  pp.  3,  4)  two  notes, 
the  one  a  reclamation  for  priority  over  Herr  Orlewski,  the  other  a 
discussion  of  the  reasons  assigned  by  the  writer  for  supposing  that 
the  cymene  obtained  by  M.  Ribau  was  pre-contained  as  such. 
As  regards  the  first  question,  a  comparison  of  the  above  dates  will 
show  that,  whilst  M.  Ribau  undoubtedly  preceded  Herr  Orlewski  in 
this  matter  by  several  months,  the  results  of  the  writer  were  made 
public  in  London  more  than  a  fortnight  before  those  of  M.  Ribau 
were  first  brought  before  the  notice  of  Parisian  chemists  ;  it  is  there- 
fore evident  that,  whilst  the  experiments  of  M.  Ribau  and  the  writer 
must  have  been  carried  on  almost  simultaneously,  the  actual  claim  to 
priority  rests  with  England  rather  than  with  France  or  Russia. 
As  regards  the  second  point,  the  writer  has  great  pleasure  in  con- 
firming the  exactitude  of  M.  Ribau's  results  ;  whilst  he  has  no  doubt 
from  his  own  results  (and  those  of  Herr  Orlewski)  that  cymene  is 
actually  pre- contained  in,  at  any  rate,  some  specimens  of  oil  of  tur- 
pentine ;  and  in  other  terpenes  he  has  yet  found  that  when  the  action 
of  the  sulphuric  acid  is  prolonged  for  some  hours  at  the  ordinary  tem- 
perature (and  especially  if  the  mixtures  be  made  quickly  so  as  to  heat 
rapidly),  sulphurous  acid  is  copiously  given  off,  and  a  much  larger 
■quantity  of  cymene  is  obtainable  than  can  be  if  all  possible  care  and 
precautions  are  taken  to  avoid  the  formation  of  sulphurous  acid;  this 
additional  quantity  must  necessarily  be  found,  as  M.  Ribau  first  sug- 
gested, by  the  reaction  C10H16+H2SO4=2H2O+SO2+C10Hu. 
Chemical  Laboratory,  St.  Mary's  Hospital,  Jan.  11,  1874. 
Chemical  News,  London,  January  23,  1874. 
