136 
Solubility  of  Cinchonine. 
/  Am.  lour.  Pharm. 
I      March,  1902. 
THE  SOLUBILITY  OF  CINCHONINE. 
By  Robert  A.  Hatcher,  M.D. 
Being  requested  to  examine  a  specimen  of  cinchonine  from  a  repu- 
table manufacturer  (Schuchardt),  which  was  sold  as  pure,  the  phar- 
macopoeial  tests  were  applied,  including  those  for  the  detection  of 
other  cinchona  alkaloids,  melting  point,  solubility  in  alcohol,  ether 
and  water.  It  conformed  to  every  requirement  save  that  of  solu- 
bility in  water. 
The  Pharmacopoeia  states  that  cinchonine  is  soluble  in  3,760  parts 
of  water.  Roscoe  and  Schorlemmer  quote  Hesse,  giving  the  solubility 
as  1  to  3,670  at  20°,  1  to  2,500  at  the  boiling  point.  I  regret  that. 
I  have  not  access  to  the  original  paper,  as  there  is  evidently  a  typo- 
graphical error  in  one  of  these,  transposing  the  6  and  7. 
The  difficulty  experienced  in  effecting  solution  led  to  the  device 
which  is  the  subject  of  the  preceding  article.  Prolonged  boiling  in 
15,000  parts  of  water  proved  ineffectual,  none  seeming  to  have  dis- 
solved. Having  added  an  alcoholic  solution  to  water,  the  amounts 
precipitated  from  dilutions  of  i-io.OOO  and  1-20,000,  while  none 
precipitated  from  the  1-25,000,  furnished  an  approximate  idea  of 
the  solubility. 
The  method  just  described  was  used,  o*i  gramme  being  dissolved 
N 
in  90  c.c.  of  water  with  the  aid  of       H2S04,  and  enough  water 
10 
added  to  make  the  volume  up  to  100  c.c.  Several  portions  of 
10  c.c.  each  of  this  solution  were  diluted  to  150  c.c,  200  c.c.  and 
250  c.c,  respectively,  making  dilutions  of  1-15,000,  1-20,000  and 
N 
1-25,000.   To  each  of  these  was  added  a  slight  excess  of  —  NaOH  ; 
10 
the  weakest  solution  showed  no  precipitate,  the  next  showed  some, 
and  the  strongest  considerable.  The  solubility  evidently  lay  between 
1-20,000  and  1-25,000.  The  process  was  now  repeated,  using  10 
c.c.  and  diluting  to  1-20,000,  1-22,000  and  1-24,000.  Upon  adding 
N 
a  slight  excess  of  NaOH  to  each,  and  cooling  to  21 0  C.  for  about 
10 
12  hours,  a  slight  precipitate  was  observable  in  the  dilution  of 
1-22,000,  but  none  in  that  of  1-24,000.  The  mean  was  taken  as 
the  approximate  solubility  of  cinchonine — 1-23,000 — and  this  is  as 
near  the  exact  figure  as  can  be  attained  by  ordinary  procedures, 
