DECOLORIZING  PROPERTY  OF  THE  ESSENTIAL  OILS.  399 
of  nitric  acid  on  some  other  substances,  and  still  retaining  acid 
enough  to  affect  the  cork. 
On  boiling  some  of  the  whitened  portion  of  the  cork  in  distilled 
water,  and  adding  solution  of  sulphindigotic  acid,  the  blue  color 
was  quickly  discharged.  I  tested  for  chlorine,  but  no  indications 
of  its  presence  appeared. 
Although  there  seemed  to  be  sufficient  evidence  of  the  existence 
of  N05  in  the  boiled  liquid,  I  could  not  but  hesitate  before  I  adopt- 
ed this  conclusion,  especially  as  I  observed,  while  cutting  the  cork, 
that  it  retained  nearly  its  original  elasticity  or  toughness.  1  found 
also  that  the  oil  readily  bleached  the  blue  solution,  and  at  the 
same  time  exhibited  no  acid  reaction  with  blue  litmus  paper.  The 
conclusion  appeared  unavoidable,  that  the  essential  oil  discharged 
the  color  from  both  the  cork  and  the  indigo  solution. 
Here  a  new  inquiry  wras  opened  to  me.  Was  this  bleaching 
property  possessed  by  essential  oils  generally  ?  I  subjected  the 
sulphindigotic  acid  solution  to  the  action  of  twenty-two  volatile 
oils.  With  the  exception  of  two,  they  all  completely  discharged 
the  color  of  the  indigo.  The  oils  tried  were : 
01.  Limonis,  01.  Tanaceti,  01.  Bergamii,  01.  Sabinae, 
Fceniculi,  Piperitae.,         Cari,  Hedeomae, 
Juniperi,  Rorismarini,      Lavendulae,  Gaultheriae, 
Terebinthinae,    Chenopodii,       Caryophylli,  Sassafras, 
Anisi,  Cinnamomi,  Origani, 
and  that  of  fir  and  of  hemlock. 
Of  these  the  oils  of  winter-green  and  sassafras  produced  the  least 
impression  on  the  An02  S03>*  but  even  they  ultimately  discharged 
the  color ;  all  the  rest  speedily  dissipated  the  blue,  so  as  to  leave 
the  liquid  limpid  and  colorless  as  water.  The  oils  of  tansy  tur- 
pentine, juniper,  lemons,  fir,  hemlock,  and  peppermint,  were  among 
the  most  active.  Two  or  three  drops  of  the  oil  of  tansy,  quickly 
bleached  a  test-tube  full  of  the  blue  reagent.  This,  like  most  of 
the  oils,  discharged  the  color  without  the  aid  of  heat,  simple  agi- 
tation for  less  than  quarter  of  a  minute  being  sufficient.  Some  of 
the  more  obstinate  would  bleach  little  more  than  equal  parts  of  the 
colored  liquid,  and  then  only  by  the  assistance  of  heat.  The  oils 
in  some  cases  became  somewhat  milky  after  agitation  with  the 
[*  This  formula  for  sulph  indigotic  acid  represents  it  as  sulphate  of  the 
deutoxide  of  Anyle;  Anyle=An=C16H6N. — Editor.] 
