Am.  Jour.  Pharm.  1 
March,  1902.  / 
Solubility  of  Alkaloids. 
135 
estimate  of  the  amount  remaining  in  solution  was  gained,  and  a 
new  series  of  dilutions  made  and  precipitated  as  in  the  foregoing. 
That  solution  which  gives  a  barely  perceptible  precipitate,  using  a 
control  solution  for  comparison,  is  taken  as  the  solubility,  or  this 
dilution  and  the  lowest  giving  no  perceptible  precipitate  are  taken 
and  the  solubility  is  reckoned  as  the  mean  of  the  two.  Applying 
this  method  to  morphine,  it  gave  results  agreeing  with  the  solubility 
given  by  the  Pharmacopoeia. 
I  therefore  suggest  the  following  method  of  finding  the  solu- 
bility of  those  alkaloids  which  do  not  readily  dissolve  in  water: 
Take  o-i  gramme  of  the  substance,  rub  with  water  to  a  smooth 
paste  and  then  with  water  until  a  smooth  mixture  of  about  9  c.c.  is 
obtained,  to  this  add  enough  N  H2S04  from  a  burette  to  convert 
the  alkaloid  into  the  sulphate,  and  then  enough  water  to  make 
10  c.c.  of  solution;  of  this  take  portions  of  1  c.c.  each  and  dilute 
in  several  proportions  ;  to  each  add  a  slight  excess  of  N  NaOH, 
and  from  the  relative  amounts  of  precipitate  estimate  the  solubility; 
again,  take  several  portions  of  1  c.c.  each  and  dilute  to  approxi- 
mately the  point  of  saturation,  in  one  case  using  higher  and  in 
another  lower  dilutions;  again,  precipitate  with  slight  excess  of 
NaOH,  and  more  accurately  estimate  the  solubility.  From  a  third 
series,  using  the  second  estimate  as  a  basis,  the  solubility  may  be 
learned  by  taking  the  mean  of  the  highest  giving  a  precipitate  and 
the  lowest  giving  none  that  is  perceptible. 
I  would  also  suggest  the  application  of  this  method  for  testing 
those  alkaloids,  the  solubility  of  which  is  known.  Thus,  morphine 
is  soluble  in  4350  parts  of  water  ;  and  if  01  gramme  morphine  be 
rubbed  with  water  and  then  with  enough  N  H2S04  to  convert  it 
into  the  sulphate  and  diluted  to  10  c.c,  and  two  portions  of  I  c.c. 
each  of  this  be  further  diluted  to  43  c.c.  and  44  c.c,  including  the 
requisite  amount  of  N  NaOH  to  give  a  very  slight  alkalinity,  a 
slight  turbidity  or  precipitate  should  be  found  in  the  first  and  none 
in  the  second,  from  which  is  taken  the  mean,  or  1  part  in  4350,  as  the 
solubility  of  morphine.  Of  course,  in  the  case  of  expensive  alka- 
loids, o-Oi  gramme  may  be  used  instead  of  01  gramme,  but  more 
accurate  results  will  be  had  by  using  the  larger  quantity. 
