Am.  Jour.  Pharm. ) 
December,  1899.  J 
Analysis  of  Essential  Oils. 
567 
hitherto  unobserved  compounds.  It  is  even  safe  to  say  that  not  a 
single  oil  has  yet  been  analyzed  so  thoroughly  that,  by  further 
work,  no  new  facts  regarding  the  same  could  be  detected,  even  if, 
as  in  the  case  of  oil  of  peppermint,  the  sum  of  known  constituents 
runs  up  to  seventeen.  There  are  still  a  great  number  of  unsettled 
problems  about  essential  oils  towards  the  solution  of  which  scarcely 
the  first  steps  have  been  made,  as,  for  instance  :  how  far  does  the 
composition  of  the  essential  oil  vary  in  the  different  parts  of  the 
same  plant  ?  How  is  it  influenced  by  the  conditions  of  soil,  climate 
and  cultivation  ?  What  is  the  variation  in  oils  from  the  successive 
stages  of  vegetation  of  the  plant  ?  and  at  length,  in  what  way,  by 
what  chemical  processes  does  the  plant  produce  all  these  so  mani- 
fold compounds  ?  Is  each  single  one  formed  in  a  separate  process, 
or  do  several  or  all  constituents  of  an  oil  stand  in  genetic  connec- 
tion, being  formed  successively  in  one  process  ?  There  are  many 
indications  for  such  a  connection.  Perhaps  nobody  will  doubt  that 
it  exists  between  terpenes  and  terpene  alcohols  so  often  associated 
in  essential  oils ;  but  the  question  is,  are  the  terpenes  formed  from 
terpene  alcohols  by  splitting  off  water,  or  the  latter  from  the  former 
by  hydratation  ?  The  frequent  occurrence  of  small  quantities  of 
the  lower  aldehydes,  like  acetic  and  iso-valerianic  aldehyde,  and 
ketones  in  the  oils  seems  to  indicate  that  these  bodies,  which  are  so 
susceptible  to  condense  with  formation  of  unsaturated  compounds  of 
considerable  complication,  play  an  important  role  in  the  building  up 
of  various  constituents  of  the  oils;  so,  for  instance,  it  seems  possible 
that  i-valeraldehyde  might  form  terpenes  : 
CH3  CH3  CH3  CE 
</    '  \/ 
CH  CH 
C 
HC  CH 
II 
H  \  HC  CH,  +  2H20. 
H    /  rO 
oc  Vh 
H*C  CH 
CH 
CH, 
CH 
CH3 
But  so  far  it  has  been  impossible  to  effect  any  such  or  similar  con- 
