58  Resins  and  Relations  to  Ter penes.  m™' 
are  interesting,  but  needless  to  say  they  are  not  based  on  experi- 
mental data. 
In  the  starch  explanations  of  the  formation  of  the  resins  in 
plants,  it  must  be  assumed  that  the  resins  are  formed  by  first 
building  up  the  complex  starch  molecules  from  the  simpler  alde- 
hydes, and  then  breaking  them  down  again  into  the  resins  and 
terpenes.  So  far  as  can  be  ascertained  there  are  no  experimental 
data  in  favor  of  this  theory.  If,  on  the  contrary,  we  assume  that 
the  resins  are  built  up  from  the  simple  aldehydes,  the  process  is 
more  logical,  as  it  only  requires  two  steps,  namely,  polymerization 
and  reduction,  instead  of  three  distinct  steps  as  indicated  in  the 
following  simple  diagram : 
Starch  v 
Aldehydes  >Resin-  ^Terpenes 
(Formaldehyde) 
While  the  above  theories  have  many  points  in  their  favor, 
there  is  another  which,  while  it  may  have  some  objections,  has 
at  the  same  time  decided  advantages  over  the  starch  or  reduction 
theory. 
It  is  common  knowledge  that  the  terpenes,  when  exposed  to 
air,  slowly  change  to  complex  polymers  and  resins  of  unknown 
composition.  The  principle  involved  is  doubtless  condensation  fol- 
lowed by  oxidation.  Wohler  was  the  first  to  suggest  that  the 
resins  may  be  built  from  the  terpenes  by  the  above-mentioned 
condensation  and  oxidation  process.  He  based  his  assumption  on 
the  well-known  fact  that  turpentine  absorbs  oxygen,  forming  a 
resin.  This  oxidation  process  may  be  represented  by  the  following 
equation : 
2C10H1,  +  30  =  GoH?002  -f  H20. 
Wohler,  unfortunately,  presented  no  experimental  data.  Later, 
Cailliots  obtained  a  resin  by  the  oxidation  of  turpentine  with  nitric 
acid.  It  was  not  well  defined,  however,  and  not  identical  with 
any  of  the  common  resins,  although  it  bore  some  semblance  of 
common  pine  resin. 
Barth 4  obtained,  by  oxidizing  oil  of  lavender,  a  terpene,  an 
*  Ann.,  143-313. 
