198 
CHROMIC  ACID  AND  THE  VOLATILE  OILS, 
-was  not  strychnia  but  alcohol,  or  one  of  its  constituents,  which 
passed  over  from  the  drop  to  the  acid  mixture.  In  order  to  de- 
termine this  point,  I  placed  two  shallow  concave  glasses  side  bj 
side,  but  half  an  inch  distant  from  each  other ;  and  into  one  I 
put  some  newly  prepared  mixture  of  the  acid  and  chromate,  and 
into  the  other  alcohol.  The  alcohol  maintained  a  quiet,  well  de- 
fined margin,,  but  the  edge  of  the  acid  liquid  immediately  began 
to  flap,  and  commencing  at  the  point  nearest  the  alcohol,  the 
whole  mass  of  acid  mixture  gradually  became  green.  The  flap- 
ping of  the  margin  of  the  acid  is  best  seen  under  a  magnifier. 
My  next  object  was  to  ascertain  whether  other  volatile  liquids 
would  act  in  like  manner  as  alcohol.  Oil  of  peppermint  was  first 
substituted  for  the  spirits.  A  violent  effervescence  began  direct- 
ly in  the  whole  circumference  of  the  oil,  (but,  on  subsequent  ex- 
amination, I  found  the  same  thing  took  place  independent  of  the 
acid  mixture,)  and  the  same  discoloration  followed  as  with  the 
alcohol,  until,  as  before,  the  whole  body  of  the  acid  mixture  be- 
came green.  The  surface  of  the  acid  liquid  was  one  inch  in 
diameter.  While  the  change  of  color  was  going  on  in  this  case, 
motes  could  be  seen,,  under  the  microscope,  rapidly  approaching 
the  edge  nearest  the  oil ;  and  in  an  instant  wheel  about  and  re- 
treat, as  if  shot  back]  by  electrical  repulsion.  This  motion  was 
perceived  even  at  the  most  remote  part  of  the  acid  mixture,  as 
the  discoloration  proceeded  backward  from  the  oil.  The  oil  be- 
came thicker  and  opaque  while  under  the  influence  of  the  acid,, 
but  when  the  glass  was  removed  from  the  vicinity  of  the  acids, 
the  oil  recovered  its  transparency  but  not  its  proper  fluidity  *  and 
finally  a  watery  liquid  separated  from  it,  tasting  like  water  im- 
pregnated with  the  oil. 
The  oils  of  lavender  and  sassafras  behaved  like  alcohol  as  to 
the  quietude  of  their  margins  ;  and,  unlike  the  oil  of  peppermint, 
caused  no  flapping  motion  in  the  acid  mixture,  but  they  all  pro- 
duced discoloration. 
From  the  results  of  a  limited  number  of  experiments,  I  was  at 
first  tempted  to  think  that  my  acid  mixture  had  distinguished 
the  terebenes  of  Lowig  from  the  oxygenous  volatile  oils,  long 
before  this  author  had  classified  the  fifth  group  of  his  hydro- 
polycarbyls  into  the  terebene  and  non-terebene  oils,  but  an  ex- 
tension of  the  experiments  to  the  oils  of  lemon,  orange  and  cu- 
