176 
Alkaloids  of  Cinchona  Bark. 
[Am.  Jour.  Pharm, 
\      April,  1910. 
solved  part  and  tested,  the  salt  will  be  found  of  a  much  greater 
solubility,  requiring  even  less  than  200  parts  of  water  for  solution, 
according  to  time  and  quantity  used.  The  remaining  undissolved 
part,  when  dried  and  treated  again  with  water  in  the  same  propor- 
tion and  under  the  same  conditions  as  before,  shows  further 
decomposition,  but  in  a  lesser  degree,  and  the  solution  will  be 
found  to  contain  considerably  less  of  the  salt  than  the  first  solution, 
and  so-  on.  Some  others  of  the  salts  of  cinchona  alkaloids  act  more 
or  less  in  the  same  way.  Therefore  the  figures  in  the  appended  list 
show  in  each  case  that  proportion  of  water  which  is  required  to 
make  a  solution  with  one  part  of  the  pure  and  finely  powdered  salt, 
when  kept  at  25 0  C.  for  several  days,  the  mixture  being  frequently 
shaken.  The  results  from  tests  obtained  from  saturated  solutions 
made  with  a  large  excess  of  the  salts  or  taking  the  difference  between 
the  quantity  of  the  substance  used  and  the  weight  of  the  undissolved 
and  dried  salt,  in  many  instances,  when  testing  salts  of  the  cinchona 
group,  show  too  great  a  solubility  of  the  substances,  the  solutions 
containing  a  more  soluble  compound  than  the  original  salt,  leaving 
undissolved  a  less  soluble  residue.  The  same  salts  also  show  a 
greater  solubility  when  treated  with  hot  water,  the  mixture  allowed 
to  cool  off  to  25 0  C,  and  kept  at  that  temperature  for  hours  to 
crystallize. 
For  the  determination  of  the  solubility  of  the  pure  alkaloids — 
quinine,  cinchonidine,  cinchonine  and  quinidine — I  used  saturated 
solutions,  which  were  shaken  out  with  chloroform  or  ether,  as  the 
nature  of  the  alkaloid  required,  and  determined  by  weight  after 
evaporation  of  the  solvent.  The  solubility  of  these  alkaloids  in  water 
differs  greatly,  according  to  age  and  method  of  manufacturing. 
The  figures  in  the  appended  list  are  obtained  from  products  made  a 
short  time  ago,  but  cannot  be  used  as  fixed  standards.  Other 
specimens  of  these  alkaloids  may  be  found  to  be  more  or  less  soluble, 
though  chemically  perfectly  pure,  the  physical  condition  and  amount 
of  water  of  crystallization  being  responsible  for  the  discrepancies. 
The  same  can  be  said  of  the  tannates.  Other  salts  of  these  alkaloids 
formed  with  volatile  organic  acids  also  become  less  soluble  by  age. 
I  trust  that  this  paper  will  be  of  some  use  and  regret  very  much 
not  to  have  the  time  at  present  to  give  more  complete  figures,  in- 
cluding the  solubility  of  chinehona  salts  and  alkaloids  in  alcohol, 
ether,  etc.,  the  published  figures  being  in  many  cases  incorrect. 
The  following  table  gives  the  amount  of  water  required  to  dis- 
