Am.  Jour.  Pharm. 
June,  1887. 
Oil  of  Erigeron  and  Fireweed. 
309 
the  17th  fraction  is  rapidly  augmented  the  same  as  in  the  erigeron,  but 
in  a  still  more  marked  degree,  rising  from  —  9°  to  —  53°.  In  the 
18th  fraction  a  remarkable  polarization  of  —  85°  takes  place,  being 
the  highest  yet  noticed  in  an  essential  oil. 
Boiling  Points. — In  making  this  test,  20  cc.  of  each  oil  were  placed 
in  a  test  tube,  immersed  in  an  oil  bath  of  ordinary  temperature  and 
slowly  heated1.  When  the  bath  had  attained  a  temperature  of  340° 
the  boiling  began  slightly  in  the  fireweed  at  331°  ;  the  bulb  of  the 
thermometer  being  immersed  in  the  liquid,  as  there  was  not  sufficient 
vapor  to  give  a  good  indication.  Within  the  space  of  a  minute  the 
temperature  of  the  oil  rose  to  360°,  boiling  violently.  The  tempera- 
ture of  the  vapor  was  found  to  be  358°.  By  applying  more  heat  and 
raising  the  bath  to  a  temperature  of  410°,  the  oil  attained  a  tempera- 
ture of  370°  with  the  vapor  at  365°.  On  continuing  the  boiling  for 
some  time,  it  was  found  quite  difficult  to  increase  the  temperature 
more  than  3°.  It  was  not  found  that  the  oil  had  evaporated  to  the 
extent  of  5  per  cent.,  so  that  the  boiling  point  of  the  vapor  of  fireweed 
during  the  progress  of  the  distillation  of  the  first  5  per  cent,  is  mostly 
between  358°  and  365°.  The  oil  used  in  the  above  test  was  the  na- 
tural oil  of  fireweed  used  for  the  rectification  mentioned. 
In  oil  of  erigeron  at  340°  slight  ebullition  Avas  shown,  the  ther- 
mometer immersed  in  the  oil.  At  347°  boiling  progressed  vigor- 
ously with  the  vapor  at  342°.  Continuing  the  boiling  four  minutes, 
the  temperature  of  the  vapor  had  risen  to  347°,  at  which  it  was  prac- 
tically constant. 
From  this  it  will  be  observed  that  the  boiling  point  of  the  fire- 
weed-oil  under  the  same  circumstances  is  about  18c  to  20°  higher  than 
that  of  the  oil  of  erigeron. 
Chemical  Reactions. — This  branch  of  investigation  was  unfortun- 
ately quite  unfruitful,  both  oils  fulminating  vigorously  with  iodine, 
yet  with  less  violence  than  spirit  of  turpentine.  Upon  adding  to  50 
drops  of  each  oil  from  one  to  three  drops  of  nitric  acid  alternately, 
(sp.  gr.,  1*2),  there  were  no  special  colors  produced,  the  only  effect 
being  that  in  eight  hours  the  erigeron  had  changed  to  a  dark  straw 
color,  the  fireweed  being  of  a  medium  brown.  (In  the  case  of  pep- 
permint a  beautiful  spectral  effect  is  produced.) 
1  This  precaution  of  immersing  the  oil  under  analysis  in  a  bath  at  a  tem- 
perature below  its  boiling  point  is  important,  as  more  exact  and  uniform  re- 
sults can  be  obtained  in  the  earlier  stages. 
