Am'ju°ne,!,i!9hrm'}         Salts  °f  Cantharidinic  Acid.  2g$ 
exposed  to  sunlight  for  some  days  and  a  second  to  the  heat  of  a 
water  bath  in  an  open  porcelain  dish  for  twelve  hours  without  any 
change  whatever  in  color  taking  place.  A  third  portion  of  the  oil 
was  treated  on  a  water  bath  for  a  few  minutes  in  presence  of  a  very 
small  piece  of  copper  foil,  when  the  oil  rapidly  assumed  its  original 
green  color,  thus  showing  conclusively  that  the  green  coloration  of 
the  oil  is  due  to  the  presence  of  a  trace  of  copper,  and  that  its 
removal  causes  the  oil  to  assume  its  natural  color,  namely,  yellow. 
The  green  coloration  of  the  oil  was  destroyed  on  heating  to 
500  C,  and  at  a  higher  temperature  an  acid  distillate  was  obtained 
which  was  proved  after  neutralization  to  consist  principally  of  acetic 
acid.  It  seems  possible,  therefore,  that  the  metal  exists  in  combi- 
nation with  this  acid,  the  change  in  color  on  exposure  to  light  either 
depending  on  oxidation  of  an  aldehyde  present  to  acetic  acid,  or  on 
the  partial  decomposition  of  an  ester  of  acetic  acid  contained  in  the 
oil.  Varying  statements  exist  as  to  the  specific  gravity  of  pure 
citronella  oil,  for  whilst  Messrs.  Schimmel  state  that  it  should  not 
fall  below  -895  at  150  C.  (Pharm.  Journ.  [3],  xx,  264),  Dodge 
{Pharm.  Journ.  [3],  xx,  855)  assigns  to  it  a  gravity  of  -877  at 
160  C.  It  will  be  noticed  that  sample  H,  which  contained  no  copper, 
was  of  lower  specific  gravity  than  the  others,  and  fell  considerably 
below  the  limit  proposed  by  Messrs.  Schimmel.  This  sample 
proved,  on  examination  of  its  solubility  in  80  per  cent,  spirit,  to  be 
adulterated  with  petroleum,  as  was  readily  proved  by  fractionation, 
and  the  absence  of  copper  is  probably  due  to  its  distillation  in 
the  earthen  or  iron  stills,  "how  only  used  by  the  poorer  native  dis- 
tillers. The  quantity  of  copper  present,  without  doubt,  derived 
from  distillation  in  stills  of  that  metal,  is,  of  course,  very  minute, 
but  it  seems  desirable  to  call  attention  to  it,  as  pointing  out  that 
pale  yellow,  and  not  green,  is  the  natural  color  of  citronella  oil. 
ON  THE  ACTION  OF  SALTS  OF  CANTHARIDINIC  ACID.1 
By  O.  Liebreich. 
This  important  communication  of  Professor  Liebreich  was  read 
before  the  Berlin  Medical  Society  on  the  25th  of  February,  and  in 
the  discussion  which  followed  several  well-known  physicians  recorded 
their  experience  of  the  effects  produced  by  the  treatment  introduced 
by  the  Berlin  professor. 
1  Abstract  from  Therap.  Monat.,  March,  1891  ;  reprinted  from  The  Jlfedical 
Chronicle,  April. 
