OF  THE  ESSENTIAL  OIL  OF  RUE. 
203 
The  quantity  in  my  possession  was  too  small  to  permit  of  an  examination  of  its  deri- 
vatives. I had  hoped  to  obtain  euodic  acid  by  the  action  of  weak  nitric  acid  upon  the 
aldehyde,  but  the  oxidation  proceeds  too  far,  the  carbon  being  attacked  with  formation 
of  capric  acid.  A barium  salt  gave  on  analysis  2 9' 985  per  cent,  of  barium  ; caprate  of 
barium  requires  28'642.  During  the  action  of  the  nitric  acid,  especially  if  it  be  not 
very  weak,  pelargonic  acid  is  formed.  A small  quantity  was  also  obtained  of  another 
substance,  which  was  separated  in  the  following  manner.  The  acid  solution,  and  the 
oily  layer  produced  by  cohobating  euodic  aldehyde  and  ordinary  nitric  acid  diluted  with 
its  own  bulk  of  water,  were  separated  by  means  of  a tap  funnel.  The  oily  liquid,  on 
treatment  with  a strong  solution  of  potash,  partly  dissolved,  but,  on  filtration,  a soft 
yellow  substance  remained  on  the  paper.  It  dissolved  in  boiling  alcohol,  and  separated 
on  cooling  in  brilliant  yellow  spangles,  exactly  resembling  chrysene  as  it  appears  when 
ciystaUized  from  Boghead  naphtha.  On  examination  it  appeared  to  be  the  potassium 
salt  of  the  highly  singular  substance  described  by  Chiozza^,  and  which  he  regards  as  a 
compound  of  pelargonic  acid  Avith  binoxide  of  nitrogen.  He  states  that  great  difficulties 
were  found  in  its  analysis,  owing  to  the  strong  tendency  of  the  nitrogen,  in  the  state  in 
which  it  exists  in  the  acid,  to  form  nitrous  or  nitric  acid,  which,  entering  the  potash 
apparatus,  increases  its  weight,  and  in  consequence  causes  the  carbon  to  come  out  too 
high.  The  entire  quantity  at  my  disposal  being  only  0'2170grm.,  a correct  result  on 
combustion  was  scarcely  hoped  for,  especially  as  0-02  had  been  used  in  a few  almost 
microscopic  preliminary  experiments.  The  following  result  is,  nevertheless,  sufficient 
to  identify  the  substance  with  that  described  by  Chiozza. 
T976  gramme  gave  -3135  carbonic  aoid  and  T282  water. 
Calc.  C'®  H'‘  KN=  0^ 
Carbon  . . . 43-3  42-20 
Hydrogen  . . 7-2  6-64 
By  carefully  treating  the  residues  of  the  distillates,  previously  alluded  to,  a small 
quantity  of  the  lauric  aldehyde  was  obtained.  It  was  not  quite  free  from  euodic  aldehyde. 
Its  boiling-point  is  about  232°  C.  The  following  is  the  result  of  its  analysis : — 
•1986  gramme  gave  -5686  carbonic  acid  and  -2310  water. 
Experiment. 
Calculation. 
^ 
Carbon 
. 78-1 
C24 
144 
78-26 
Hydrogen . 
. 12-9 
H24 
24 
13-04 
Oxygen 
9-0 
0^ 
16 
8-70 
lOO-O 
184 
100-00 
The  density  of  its  vapour  was  found  to  be  6-182,  a number  considerably  below  that 
required  by  theory  (6-366),  but  quite  high  enough,  taken  in  conjunction  with  the 
analysis,  to  show  the  presence  of  lauric  aldehyde  in  oil  of  rue. 
* Compt.  Eend.  xxxv.  797  (1852). 
2 E 2 
