138 
PIPERIC  ACID. 
alcoholic,  acetic,  and  etherial  solutions,  &c.  The  crude  essential 
oil  does  not  present  this  phenomenon,  probably  on  account  of 
the  presence  of  the  yellow  matter. 
Lastly,  the  oil  deviates  the  plane  of  polarization  to  the  right, 
and  this  power  of  deviation  was  always  found  to  be  —111-5, 
tint  of  passage,  whence  the  rotary  power  corresponding  to  the 
red  ray  would  be  equal  to  85-5.  This  rotary  power  is  greater 
than  that  of  the  essential  oils  of  turpentine,  lemon,  orange,  and 
bergamot,  which  have  all  the  same  composition. 
Thus  this  essential  oil  is  defined  by  the  constancy  of  its  physi- 
cal properties,  density,  boiling-point,  and  rotatory  power,  as  well 
as  by  that  of  its  chemical  properties.  It  is  the  first  known  ex- 
ample of  such  homogeneity  in  a  natural  essential  oil  Chem* 
Graz.,  Jan.,  1858,  from  Oomptes  Hendus,  November  23,  1857. 
ON  PIPERIC  ACID. 
By  Prof,  von  Babo  and  E.  Keller. 
Piperine  is  placed  in  a  flask  with  an  alcoholic  solution  of  pot- 
ash, and  the  flask  connected  with  a  condenser,  so  that  the  products 
of  the  action  flow  back  into  the  flask,  which  is  heated  on  the 
water-bath.  (For  1  part  piperine,  3  parts  of  hydrate  of  potash 
and  12  to  20  absolute  alcohol  are  taken.)  A  decomposition  of 
the  piperine  takes  place,  lustrous  scales  are  formed  in  the  brown 
liquid,  and  at  the  same  time  the  characteristic  odor  of  piperine  is 
observed.  This  treatment  is  continued  until  no  more  crystals 
are  formed  (which  for  30  grms.  piperine  requires  about  12  hours), 
and  the  piperine  is  then  completely  decomposed.  The  crystals 
are  separated  from  the  mother-liquor  by  means  of  a  linen  filter. 
The  mother-liquor  contains  piperidine,  for  by  distilling  it  and 
collecting  the  distillate  in  hydrochloric  acid,  the  hydrochlorate 
of  that  base  was  obtained.  The  residue  in  the  retort  contains 
substances  which  appear  to  be  identical  with  the  products  of  the 
action  of  potash  on  absolute  alcohol. 
The  crystalline  plates  consist  of  the  potash-salt  of  a  new  acid, 
which  the  authors  name 
Piperic  Acid. — The  potash- salt  may  be  purified  by  repeated 
crystallizations  and  the  use  of  animal  charcoal.     Or  if  this 
