400 
Botany  and  Chemistry  of  Essential  Oils.  { 
Am.  Jour.  Pharm. 
Aug.,  1893.- 
To  summarize — the  oils  are  found  in  vessels  or  cavities  of  proto- 
genetic  or  hysterogenetic  origin,  and  are  produced  by  the  proto- 
plasm, probably  as  bye-products  in  the  elaboration  of  the  food 
material  of  the  plant. 
Chemistry. — The  constitution  of  the  oils  is  so  varied  that  it  is 
difficult  to  divide  them  into  any  well-defined  groups,  but  for  the 
sake  of  convenience  we  may  study  them  in  the  following  classes : 
(«)  Oils  which  are  single  chemical  compounds,  and  whose  con- 
stitution is  known,  as  oil  of  bitter  almonds,  wintergreen,  etc. 
(/?)  Terpenes  or  the  constituents  present  in  most  essential  oils, 
belonging  to  the  hydrocarbons,  as  pinene,  limonene,  etc. 
(j)  Other  constituents  in  the  oil,  and  to  which  often  the  peculiar 
odor  is  due.  These  may  be  further  subdivided  into  aldehydes, 
ketones,  alkyl  salts,  alcohols,  phenol  derivatives,  etc. 
[a)  There  are  not  many  essential  oils  consisting  of  one  body,  but 
there  are  a  few,  the  chief  of  which  are — oil  of  wintergreen  obtained 
from  Ganltheria,  Procumbens  and  Betula  lenta,  essential  oil  of  mus- 
tard, oils  of  rue,  meadow-sweet  {Spircea  Ulmarid)  and  bitter 
almonds.  Of  these  the  oil  of  wintergreen  is  an  alkyl  salt,  and  is 
1-2  methyl  salicylate,  C6H4OHCOOMe.  Oil  of  meadow-sweet 
belongs  to  the  same  series  of  bodies,  but  is  the  aldehyde  of  the 
acid  of  which  oil  of  wintergreen  is  the  methyl  ester.  It  is  salicyl 
aldehyde,  I  2C6H4  OH-CHO\  Both  may  be  made  by  generic 
methods. 
Oil  of  bitter  almonds  is,  of  course,  benzaldehyde,  and  rapidly 
oxidizes  into  the  acid. 
These  all  belong  to  the  aromatic  group,  but  the  other  oils  belong 
to  the  aliphatic  series.  Essential  oil  of  mustard  is  allyl-isothio- 
cyanate,  and  bears  the  same  relation  to  the  thiocyanate  that  carba- 
mide does  to  a  nitrile.  It  is  prepared  by  a  method  which  one  would 
expect  to  yield  thiocyanate,  which  is  probably  the  case.  By  treat- 
ing allylamine  with  CS2  we  get  first  the  thiocyanate,  which,  on  dis- 
tillation, undergoes  molecular  rearrangement,  forming  the  iso-mus- 
tard  oil 
CS2  +  NH2-C3H5 
CS:N-C3H5  +  H2S 
Though  really 
CS2  +  NH2C3H5 
C3H5S-CN  -j-  H2S 
and 
C3H5S-C:N 
CS:NC3H5 
