306 
Oil  of  Erigeron  and  Fireweed. 
Am.  Jour.  Pharm. 
June,  1887. 
which  had  formed  in  the  oil  by  oxidation.  This  resin  is  opaque  and 
cannot  of  course  of  itself  produce  an  optical  test,  but  when  added  to 
the  oil  increases  its  optical  activity.  This  discovery  was  verified  by 
the  fact  that  all  rectified  samples,  except  in  the  cases  hereafter  referred 
to,  were  found  to  have  less  rotatory  power  than  the  original  oil  oper- 
ated upon.  This  phenomenon  was  noticed  when  pipmenthol  and 
menthol,  both  of  which  were  found  showing  no  distinct  polarization, 
are  added  to  oil  of  peppermint,  the  rotatory  power  being  increased  the 
same  as  with  the  addition  of  the  opaque  resin. 
By  the  tests  given  above  it  will  be  noticed  that  the  average  of  the 
sp.  gr.  of  the  fireweed  samples  is  *0096  greater  than  the  average  of 
the  erigeron  ;  but  this  is  accounted  for  by  the  fact  that  Nos.  4  and  5 
of  the  fireweed  were  extremely  resinous ;  whereas  quite  the  reverse 
result  is  obtained  when  samples  of  the  oils  are  compared  under  like 
conditions  of  oxidation.  This  should  be  borne  in  mind  as  having  an 
important  bearing  on  the  test.  It  was  found  that  when  samples  of 
the  oil  in  like  conditions  either  of  freshness  or  oxidation,  were  exam- 
ined, that  the  sp.  gr.  of  the  fireweed  was  about  .012  less  than  that 
of  erigeron;  and  upon  submitting  the  oils  to  fractional  distillation 
and  taking  a  like  number  of  fractions  of  both,  the  sp.  gr.  of  the  fire- 
weed was  about  'Oil  less  than  the  erigeron. 
To  find  the  varying  characteristics  of  the  products  obtained  by 
fractional  distillation,  careful  distillations  were  made  by  diffusion  or 
steam,  the  distillate  being  divided  in  each  case  in  20  fractions  by 
-weight,  the  process  being  continued  as  slowly  as  practicable,  that  the 
fractions  should  present  as  distinct  characteristics  as  possible. 
In  the  distillation  of  erigeron,  100  pounds  of  natural  oil  was  used, 
the  polarizing  test  of  which  was,  —  50*5°.  After  18  full  fractions  of  5 
pounds  each  had  been  recovered,  it  was  found  from  the  slowness  with 
Avhich  distillation  progressed,  and  the  high  color  and  sp.  gr.  of  the 
distillate,  that  but  little  more  could  be  obtained  ;  but  the  process  being 
continued  for  a  long  time  with  increased  power,  3  pounds  more  were 
obtained  for  the  1 9th  fraction  [93  pounds  in  all.]  The  remaining  7 
pounds  which  was  not  recovered,  was  drawn  from  the  still  mixed 
with  the  water  which  had  condensed  therein,  and  separated,  when  cooled, 
into  a  solid  resin  of  a  dark  reddish  brown  color. 
In  the  rectification  of  the  fireweed,  divided  in  like  manner,  18  full 
fractions  only  were  obtained,  the  portion  representing  the  last  two 
fractions  forming  also  a  solid  resin ;  but  that  of  the  fireweed  was  of  a 
