622  Extraction  of  Alkaloids  from  Cinchona.  {^"'DeT'iSr'"" 
ON  THE  EXTRACTION  OF  THE  ALKALOIDS  FROM 
CINCHONA  BARK  BY  DILUTE  ACIDS. 
By  Dr.  J.  E.  De  Vrij,  CLE. 
Heprint  from  the  "  Chemist  and  Drugc/isi,''^  August  15,  1885,  communicated 
bu  the  Author. 
Many  years'  experience  has  taught  me  that  all  the  alkaloids  contained 
in  cinchona  bark  can  be  completely  extracted  by  treating  the  bark 
in  fine  powder  with  hydrochloric,  nitric,  or  phosphoric  acid,  but  that 
extraction  cannot  be  completely  effected  by  sulphuric  acid.  This  has 
been  disputed  by  some  chemistSj  and  by  no  one  more  strongly  than  by 
Dr.  B.  Paul,  wlio  stated  at  the  evening  meeting  of  the  Pharmaceutical 
Society,  lield  on  December  3,  1884,  as  the  result  of  recent  investiga- 
tions on  various  succirubra  barks,  that  they  retained  nearly  50  per 
cent,  of  their  alkaloids  after  extraction  by  hydrochloric  acid.^  But 
since,  as  I  showed  some  years  ago,^  40  per  cent,  of  the  alkaloids 
present  in  cinchona  bark  may  be  extracted  by  cold  water  alone.  Dr. 
Paul's  statement  will  appear  on  the  face  of  it  extremely  improbable. 
I  have,  nevertheless,  been  induced  to  make  a  new  and  accurate  investi- 
gation of  this  matter,  thus  late  in  my  career,  by  the  fact  that  other 
chemists  have  also  obtained  unsatisfactory  results  in  attempting  to 
extract  the  alkaloids  of  cinchona  bark  by  dilute  hydrochloric  acid. 
When  I  published,  some  years  ago,^  my  process  for  the  preparation 
of  ext.  cinchonse  liq.,  in  which  two  molecules  of  HCl  are  used  for 
each  molecule  of  total  alkaloids,  I  pointed  out  that  a  material  quantity 
of  alkaloid,  amounting  to  about  20  per  cent,  of  the  whole  was  left 
behind  in  the  bark.  It  follows,  therefore,  that  if — as  I  hope  to  show 
— tlie  extraction  of  the  whole  of  the  alkaloids  by  dilute  HCl  is  possi- 
ble, more  than  two  molecules  of  the  acid  must  be  used.  The  explana- 
tion of  this  is  that  the  alkaloids  do  not  exist  in  the  bark  in  the  free 
state,  but  m  combination  with  quinic,  quinovic,  and  more  largely  with 
cinchotannic  acid.  When  also  it  is  remembered  that  the  amount  of 
the  latter  (cinchotannic  acid)  is  often  very  considerable,  reaching,  as  I 
have  recently  observed  in  a  bark  of  cinchona  officinalis,  to  more  than 
12  per  cent.,  as  against  6-72  per  cent,  of  alkaloids,  and  when  we 
^  "Pharmaceutical  Journal,"  December  6,  1884. 
2  "Haaxman's  Tydschrift  der  Pharmacie,"'  1879,  p.  258. 
^''Haaxman's  Tydschrift  der  Pharmacie,"  1880,  p. 5. 
