472  Chemical  Assay  of  Foxglove.       { ^j1^/*^™- 
with  chloroform  were  not  sufficient  to  remove  all  the  physiologically 
active  substances;  for  this  eight  shakings  were  necessary.  The 
physiological  activity  of  the  digitoxin  obtained  was,  however,  not 
proportionate  to  that  of  the  aqueous  solution  before  its  removal, 
and  the  authors  conclude  from  this  and  other  experiments  that  the 
original  solution  contains  the  active  and  inactive  substances  in  some 
form  of  combination  which  is  broken  up  by  the  shaking  with 
chloroform.  By  means  of  color  reactions  it  was  shown  that  various 
menstrua  did  not  effect  any  separation  of  the  glucosides  contained  in 
the  leaves  that  might  have  been  expected  from  their  varying  solu- 
bility when  isolated ;  they  appear,  therefore,  to  influence  one 
another's  solubility.  Leaves  were  then  extracted  with  various  sol- 
vents to  determine  which  exhausts  them  best.  Ether  and  carbon 
tetrachloride  extract  no  active  substances ;  chloroform,  acetic  ether, 
and  benzene  exhaust  them  partially ;  absolute  alcohol,  acetone,  and 
amy  lie  alcohol  exhaust  them  completely,  but  the  high  temperature 
necessary  for  the  evaporation  of  the  amylic  alcohol  solution  appears 
to  produce  partial  decomposition.  An  objection  to  the  use  of  ace- 
tone as  also  of  alcohol  is  its  miscibility  with  water ;  this,  however, 
can  be  overcome  by  using  a  saline  solution  instead  of  water.  Ace- 
tone is  preferable  to  absolute  alcohol,  as  the  solution  obtained  is 
colorless.  The  authors  finally  propose  the  following  method  for 
the  chemical  assay  of  foxglove  leaves :  The  leaves  are  first  ex- 
hausted with  ether,  by  which  chlorophyll,  fat  and  resin  are  removed. 
They  are  then  treated  according  to  Keller's  method,  but  after  pre- 
cipitating with  lead  the  glucosides  are  shaken  out  with  acetone,  the 
acetone  solution  being  made  to  separate  by  adding  sodium  chloride. 
In  this  way  a  mixture  of  all  the  active  constituents  of  the  leaves  is 
obtained,  for  which  the  authors  propose  the  name  of  pandigiton. 
The  physiological  activity  of  the  pandigiton  obtained  is,  however, 
less  than  that  of  the  corresponding  quantity  of  the  solution  before 
its  removal,  although  the  solution  left  after  its  removal  is  quite 
inactive.  Two  explanations  of  this  are  possible,  viz.,  either  the 
separation  has  involved  some  change  or  the  inactive  substances  in 
the  liquid  exert  some  favorable  influence.  Moreover,  the  weight  of 
pandigiton  obtained  is  not  proportionate  to  the  physiological  activity 
of  the  leaves.  Nevertheless,  the  authors  claim  that  the  acetone 
method  is  a  chemical  method  of  assay  inasmuch  as  by  it  all  the  ac- 
tive constituents,  and  not  the  digitoxin  alone,  are  separated  and 
weighed. 
