502 
Cantharides. 
f  A  »r.  Joue.  Phasic 
X     Nov.  1,  1872. 
and  still  retain  its  activity  ;  whilst  a  cerate  made  from  perfectly  dry 
prepared  cantharides  by  prolonged  heat  with  the  fatty  matter  was 
unsusceptible  of  generating  mould,  but  was  equally  ineffective  as  a 
vesicant. 
A  method  much  in  vogue  for  regenerating  inactive  cantharides  con- 
sists in  dampening  the  powder  with  a  small  proportion  of  oil  of  tur- 
pentine and  macerating  it  for  several  days  previous  to  preparing  the 
cerate.  The  oil  dissolves  a  portion  of  the  cantharidin  and  renders 
the  rest  more  soluble  in  the  fatty  matters. 
Another  invariably  successful  method,  much  employed  for  reviving 
the  activity  of  inefficient  plaster,  consists  in  the  addition  of  a  small 
quantity  of  chloroform,  which  abundantly  dissolves  uncombined  can- 
tharidin. The  writer  has  found  this  procedure  especially  adaptable 
for  the  cerate  made  from  prepared  cantharides,  with  which  it  infalli- 
bly produces  a  powerfully  vesicating  plaster. 
The  writer,  finding  that  the  use  of  aqueous  potash  was  very  im- 
practicable, then  resorted  to  the  application  of  alcoholic  potash.  This 
was  attended  by  greatly  superior  advantages  so  far  as  the  manipula- 
tion was  concerned,  since  a  comparatively  less  volume  was  required 
to  moisten  the  powder,  and  as  it  was  afterward  far  more  easily  ex- 
pelled, but  to  produce  a  vesicating  product  it  was  equally  powerless 
with  the  aqueous  solution. 
In  the  application  of  an  aqueous  solution  of  potassium  hydrate,  the 
writer  noticed  that  even  with  a  very  small  proportion  of  the  dilute 
solution  a  very  distinct  evolution  of  ammonia  occurred,  which  was 
rendered  more  perceptible  by  the  proximity  of  a  glass  rod  moistened 
with  acetic  acid.  A  similar  result  was  obtained  with  the  alcoholic 
solution. 
Now,  since  cantharidin  is  insoluble  in  ammonia,*  then  the  canthari- 
date  of  ammonia  is  evidently  insoluble  in  water ;  perhaps,  also,  in  al- 
cohol, ether,  etc.  If,  therefore,  a  portion  of  the  cantharidin  is  origt 
inally  combined  as  ammonium  cantharidate,  it  is  highly  probable  that 
this  will  remain  unextracted  by  the  ordinary  solvents,  but  decomposed 
and  dissolved  by  means  of  potassium  or  sodium  hydrate.  It  will  then 
also  be  decomposable  by  chlorhydric  acid,  and  consequently  the  cir- 
cumstantial treatment  with  fixed  alkali  can  be  dispensed  with  and  a 
small  amount  of  chlorhydric  acid  employed  instead. 
*That  cantharidin  is  not  insoluble  in  ammonia  has  been  shown  by  Professor 
Procter,  and  recently  again  by  Dr.  E.  Masing. — Ed.  Am.  Jour.  Pharm. 
