Am.  Jour.  Pharm. 
Dec,  1887. 
Terpenes. 
621 
terpinolene,  the  hydrochloride,  hydrobromide,  etc.,  of  dipentene  are 
formed.  Pure  sylvestrene  hydrochloride  is  obtained  by  saturating 
Swedish  oil  of  turpentine  (b.  p.  174-178°)  diluted  with  ether  with 
dry  hydrogen  chloride.  After  an  interval  of  two  days,  the  ether  is 
distilled  olf,  and  the  residue  is  poured  into  shallow  dishes,  when  the 
hydrochloride  slowly  crystallizes  out.  The  operation  should  be  carried 
out  in  winter.  After  recrystallization  from  warm  alcohol,  the  hydro- 
chloride melts  at  72°.  It  is  less  soluble  in  ether  and  in  light  petroleum 
than  dipentene  hydrochloride.  The  ethereal  solution  is  powerfully 
dextrogyrate.  Sylvestrene  boils  at  175-178°;  an  intense  blue  colora- 
tion is  produced  by  adding  a  drop  of  strong  sulphuric  or  nitric  acid 
to  a  solution  of  the  hydrocarbon  in  acetic  anhydride.  Sylvestrene  re- 
generated from  the  hydrochloride  is  identical  with  the  hydrocarbon 
present  in  Swedish  oil  of  turpentine.    It  is  dextrogyrate. 
The  hydrochloride,  hydrobromide,  and  tetrabromide  crystallize  in 
the  monoclinic  system. 
The  hydrochloride  forms  plates,  a  :  b  :  o  =  2*0199  :  1  :  2-7641  ; 
p  =  76°  321', 
The  hydrobromide  also  forms  plates,  a:b  :  c  =  1*8887  :1  :  2*6937  ; 
p  =  73°  14', 
For  the  tetrabromide,  a  :  b  :  c  =  1*2166  :  1  :  1*6581  ;  p  =  46°  9'. 
Terpinene  is  obtained  by  gradually  adding  70  cc.  of  strong  sulphuric 
acid  to  two  litres  of  oil  of  turpentine.  The  mixture  is  kept  cool  and 
is  well  shaken.  After  an  interval  of  two  days  the  acid  is  neutralized 
with  soda,  and  the  terpinene  distilled  over  in  a  current  of  steam. 
Dipentene,  phellandrene,  and  cineol  also  yield  the  same  hydrocarbon. 
Terpinene  nitrite,  C10H16*N2O3,  is  obtained  in  crystals  by  adding  sodi- 
um nitrite  in  small  quantities  to  a  mixture  of  terpinene,  acetic  acid, 
and  water.  The  compound  is  deposited  in  the  course  of  two  days  at 
the  ordinary  temperature,  or  immediately  in  working  on  the  small 
scale  if  the  vessel  containing  the  mixture  is  dipped  for  an  instant  into 
hot  water.  . 
The  nitrite  melts  at  155°.  It  is  insoluble  in  water  and  light  petro- 
leum, but  dissolves  freely  in  alcohol,  ether  and  ethyl  acetate. 
The  solutions  are  optically  inactive.  The  nitrite  dissolves  in  strong 
hydrochloric,  sulphuric  and  acetic  acids,  and  is  reprecipitated  unal- 
tered on  diluting  the  acid  solutions.  On  reduction  with  stannous 
chloride,  the  nitrite  is  converted  into  a  base  which  has  not  yet  been 
properly  investigated.    Terpinin  is  not  converted  into  camphene  or 
