340 
ON  THE  USE  OF  BENZOLE. 
and  kept  in  a  warm  stove  for  about  twelve  hours.  The  first  ben- 
zole was  poured  off,  and  a  second,  but  a  smaller  quantity,  was 
added,  and  left  to  digest  in  like  manner  with  the  extract,  and 
afterwards  the  mixed  benzoles  distilled — the  residuum,  treated 
with  acetic  acid,  filtered,  and  precipitated  with  caustic  soda; 
the  precipitate  was  white,  and  consisted  of  strychnia  and  bru- 
cine.  These  were  dissolved  in  sulphuric  acid  and  separated  in 
the  usual  manner.  The  quantity  of  strychnine  yielded  by  this 
process  is  large ;  and,  when  it  is  dissolved  in  a  little  weak 
alcohol  and  allowed  to  crystallize,  the  base  is  yielded  of  great 
beauty  and  perfect  purity. 
The  next  process  I  have  to  describe  is  one  for  preparing  can- 
tharadine.  This  substance,  though  of  great  use  to  the  medical 
man,  has  hitherto,  from  the  great  expense  of  manufacturing  it, 
been  comparatively  little  used  in  its  pure  form.  Powdered  cantha- 
rides  are  to  he  heated  to  about  150°,  with  rather  more  than  an 
equal  bulk  of  benzole  ;  after  about  an  hour's  digestion  the  mag- 
ma is  to  be  transferred  to  a  percolator ;  and,  when  the  first  por- 
tion of  benzole  has  gone  through,  fresh  warm  benzole  is  passed 
through  it.  A  pound  of  cantharides  requires  about  from  six 
pints  to  a  gallon  of  benzole  to  be  thoroughly  exhausted.  The 
benzole  is  now  to  be  distilled.  A  rather  dark  colored  oily  liquid 
is  the  result,  which  is  to  be  poured  into  an  evaporating-basin, 
and  left  for,  say  twelve  hours  ;  at  the  end  of  which  time  the  li- 
quid will  be  found  studded  with  magnificent  crystals  of  cantha- 
ridine  sometimes  a  quarter  of  an  inch  long. 
I  found  some  difficulty  in  purifying  these  crystals  from  the 
mother-liquid,  but  at  length  succeeded  by  washing  the  whole 
mass  in  a  beaker-glass  with  a  little  cold  ether,  which  dissolved 
the  dark  oily  liquid  freely,  but  scarcely  affected  the  canthari- 
dine  ;  the  crystals  subsided  to  the  bottom,  and  the  supernatant 
liquid  being  poured  off,  the  crystals  were  washed  once  or  twice 
more  with  very  small  quantities  of  ether,  and  then  turned  out 
on  bibulous  paper ;  they  speedily  dried  but  were  not  quite 
white ;  by  dissolving  them  in  a  flask  of  fresh  benzole,  heating, 
adding  a  little  charcoal,  filtering,  and  allowing  the  liquid  to  cool, 
they  were  obtained  of  perfect  whiteness,  but  not  so  large  as  at 
first.  From  a  pound  of  cantharides  about  thirty  grains  of  can- 
tharidine  may  thus  be  readily  obtained. 
