450  Active  Principle  of  Digitalis.        { Member 
'  {      THE  ACTIVE  PRINCIPLE  OF  DIGITALIS.1 
By  C.  C.  Keller.2 
The  unsatisfactory  results  obtained  with  the  digitalin  prepared 
according  to  the  method  described  by  Kiliani3  have  again  directed 
attention  to  digitoxin,  which  is,  according  to  Schmiedeberg,  the 
most  potent  constituent  of  digitalis  leaves,  and  forms  the  chief  part 
of  Nativelle's  digitalin.  On  that  account  C.  C.  Kellei  has  devised 
a  method  of  determining  the  efficacy  of  digitalis  preparations  by 
ascertaining  the  amount  of  digitoxin  present  in  them. 
The  chief  characters  of  digitoxin,  which  are  of  importance  in 
this  connection,  are  its  free  solubility  in  alcohol  and  chloroform, 
slight  solubility  in  ether,  and  its  insolubility  in  petroleum  spirit.  It 
is  precipitated  from  solutions  in  water  or  dilute  alcohol  by  tannin 
but  not  by  basic  lead  acetate.  From  acid  or  alkaline  water  solu- 
tions it  can  be  extracted  by  shaking  with  chloroform.  Although 
pure  digitoxin  is  almost  insoluble  in  water,  it  is  dissolved  to  some 
extent  in  the  presence  of  extractive  materials,  and  the  other  gluco- 
sides  of  digitalis.  Digitonin  and  digitalin  are  almost  insoluble  in 
chloroform. 
To  ascertain  the  amount  of  digitoxin  in  digitalis  leaves  they  must 
first  be  extracted  with  70  per  cent,  alcohol,  preferably  by  percola- 
tion, which  must  be  continued  until  the  residue  from  3  or  4  cubic 
centimetres,  redissolved  in  water  with  2  drops  of  dilute  hydro- 
chloric acid,  gives,  after  filtration,  no  appreciable  turbidity  on  the 
addition  of  tannin. 
The  residue  of  the  extract,  from  which  alcohol  has  been  removed 
by  evaporation,  is  mixed  with  water,  washed  into  a  beaker  of  about 
250  c.c.  capacity,  diluted  to  the  volume  of  222  c.c,  and  mixed  with 
basic  lead  acetate.  The  very  voluminous  precipitate  is  separated 
by  filtration,  and  excess  of  lead  removed  from  the  filtrate  by  adding 
sodium  sulphate.  The  clear  liquid  is  then  mixed  with  2  c.c.  am- 
monia solution  (10  per  cent.)  and  shaken  four  or  five  times  with 
about  30  c.c.  of  chloroform.  The  clear  chloroform  solution  evapo- 
rated gives  the  digitoxin  mixed  with  some  fat  and  other  substances. 
For  purification  the  residue  is  dissolved  in  3  c.c.  chloroform,  7  c.c. 
1  Pharmaceutical  Journal,  July  24,  1897. 
2 Berichte  deutsch.  pharm.  Gesellsch.,  VII,  1^5. 
3  See  Phar.  Jour.,  LV,  29. 
