Am.  Jour.  Pharm. 
June,  1880, 
Cantharides, 
This  loss  has  been  determined  by  DragendorfF  to  be  for  100  cc.  petro- 
leum ether  o*oio8  gram  cantharidin. 
The  flies,  freed  from  oil,  are  now  thoroughly  moistened  with  solu- 
lution  of  soda,  and  the  mass  thus  produced  dried  in  a  porcelain  dish 
on  the  water  bath.  By  this  treatment,  during  which  quantities  of 
ammonia  gas  are  evolved,  a  soluble  cantharidate  of  soda  is  formed, 
which  is  subsequently  decomposed  by  hydrochloric  acid.  It  must  be 
borne  in  mind  that  not  all  the  cantharidin  in  the  flies  is  present  in  the 
free  state.  Dragendorff  has  already  shown  ^  that  cantharides  contain- 
ing about  0*3  per  cent,  cantharidin  yielded  only  half  that  quantity  to 
boiling  water,  the  remainder  being  extracted  by  solution  of  potash. 
Among  the  combinations  of  cantharidin  insoluble  in  water  occur  pro- 
bably salts  of  lime  and  magnesia  j  among  the  soluble,  cantharidic  acid, 
possibly  cantharidate  of  ammonia,  etc.  (the  ammonia  being  derived 
from  the  albuminous  substances  by  their  decomposition  during  the  dry- 
ing of  the  flies). 
The  dried  mass  (containing  now  cantharidate  of  soda)  is  removeo 
from  the  dish  and  finely  powdered.  It  is  then  transferred  to  a  flask, 
25  to  30  grams  of  chloroform  added,  and  the  whole  rendered  strongly 
acid  by  the  addition  of  dilute  hydrochloric  acid.  This  is  then  well 
shaken  with  from  25  to  30  grams  of  pure  ether,  the  ether-chloroform 
solution  separated  and  shaken  with  distilled  water.  The  shaking  with 
■ether  is  repeated  until  cantharidin  ceases  to  pass  into  solution.  The 
major  part  of  the  ether  can  be  recovered  by  distillation,  the  residue 
being  allowed  to  evaporate  to  dryness  in  a  flat-bottomed  glass  dish. 
This  residue  is  then  transferred  with  the  aid  of  a  small  quantity  of 
absolute  alcohol  to  a  tared  filter,  and  washed  first  with  alcohol  and 
then  with  two  or  three  cubic  centimeters  of  water.  Should  traces  of 
oil  still  adhere  to  the  cantharidin  they  may  be  removed  by  washing 
with  petroleum  ether.  The  quantities  of  these  liquids  used  must  be 
noted,  since  a  slight  correction  has  to  be  made,  viz.:  for  10  cc.  alco- 
hol 0*0077  gram;  ^  water  0*0005  gram.  'I"he  washed  can 
tharidin  is  dried  at  ioo°C.,  weighed  and  the  corrections  for  petroleum 
ether,  alcohol  and  water  added  to  the  figure  so  found. 
Proceeding  in  this  way  31*1405  grams  of  the  flies  in  question  yielded 
me  0  2022  gram  of  nearly  white  cantharidin.     The  corrections  for 
petroleum  ether,  alcohol  and  water  amounted  to  o  0303  gram,  totai 
cantharidin  0*2325   gram,  equivalent   to   0*746   per  cent.     This  is 
^  '*  Pharmacist,"  v.  78  j  "  Pharm.  Jour."  [3],  ii.  1029, 
