452  Olefinic  Constituents  of  Ethereal  Oils.  {AnlsepZ'i89*rm" 
paper,  any  fixed  oil  present  will  not  volatilize,  but  leave  a  perma- 
nent stain. 
A  sophistication  more  difficult  to  recognize  consists  in  the  admix- 
ture of  essential  oil  of  cedar  or  copaiba,  either  made  after  distilla- 
tion, or,  as  is  sometimes  practised,  by  distilling  the  cedar  and  sandal 
woods  together.  In  this  case  it  is  not  easy  to  detect  the  fraud, 
especially  upon  a  brief  examination.  It  can,  however,  be  discovered 
with  the  aid  of  the  polarimeter,  as  the  addition  of  either  cedar  or 
copaiba  oil  to  oil  of  sandal  wood  diminishes  its  rotatory  power. 
OLEFINIC  CONSTITUENTS  OF  ETHEREAL  OILS.1 
By  F.  W.  Semmler. 
Geranaldehyde,  C10H1GO,  boils  at  224-2280,  under  a  pressure  of 
760  mm.,  and  at  no-1200  under  a  pressure  of  12  mm.;  the  sp.  gr. 
is  0-1972  at  I5°/I5°.  The  compound  is  optically  inactive;  the 
refractive  index  indicates  the  presence  of  two  ethylene  bonds,  and 
this  view  is  supported  by  the  formation  of  a  tetrabromo-addiuve 
compound  which  has  not  yet  been  obtained  in  crystals.  Hydroxyl 
may  be  substituted  for  the  bromine  atoms,  and  the  products  thus 
obtained  are  being  further  investigated. 
Orange  oil  appears  to  contain  from  0-5  to  0-75  per  cent,  of  oxygen; 
its  sp.  gr.  is  0.8435  at  20°/20°  ;  on  treatment  with  hydrogen  sodium 
sulphite,  a  crystalline  compound  is  formed ;  on  decomposing  this 
and  distilling  the  oily  product,  geranaldehyde  is  obtained  together 
with  a  very  small  quantity  of  a  lower  boiling  aldehyde.  "  Citral " 
is  the  technical  term  applied  to  an  ethereal  oil  which  is  contained 
to  the  extent  of  6-8  per  cent,  in  lemon  oil ;  this  substance  proves 
to  be  identical  with  geranaldehyde,  which  is  also  found  in  a  number 
of  other  ethereal  oils. 
On  heating  geranaldehyde  with  hydrogen  potassium  sulphate  for 
20  minutes  at  1700,  and  distilling  the  product  in  a  current  of  steam, 
cymene,  C10HU,  is  obtained,  and  is  regarded  as  being  formed  by 
elimination  of  water  from  the  aldehyde. 
Coriander  oil  consists  of  terpenes  and  about  90  per  cent,  of 
another  substance  which  is  termed  coriandrol,  and  may  be  readily 
separated  by  distillation  under  reduced  pressure.  Coriandrol, 
C10H18O,  boils  at  194-1980  under  a  pressure  of  760  mm.,  and  at 
85-900  under  a  pressure  of  20  mm.,  the  sp.  gr.  is  0  8679  at  20°/20°, 
1  Berichte,  24,  201-211  ;  reprinted  from  Jour.  Chem.  Soc,  1891,  p.  539. 
