Am   Tour.  Pharm. 
Nov.,  1880. 
Papaine. 
57^ 
precipitate,  obtained  by  alcohol,  was  exhausted  by  ether,  then  dried  in 
a  vacuum  at  75°. 
Papaine,  purified  by  dialysis,  deduction  made  for  ash. 
Carbon,  .  .        5077        5i"8o        50*70  52*77 
Hydrogen,  .  7*23  671  7-50  7-47 
Nitrogen,       .  .         ...         ...  ...  i5'i7 
These  analyses  show  that  the  product  purified  by  dialysis  approaches^ 
in  its  composition  that  of  albuminoid  substances,  and  this  analogy  is 
strengthened  by  the  fact  that  papaine  contains  rather  a  large  proportion 
of  sulphur,  in  two  specimens  there  having  been  found  2'6i  and  2'2  per 
cent  respectively.^ 
The  preceding  analyses  presented  too  much  divergence  to  allow  of 
the  conclusion  that  the  product  is  definite  and  homogeneous.  Another 
mode  of  purification  was  therefore  attempted.  Albumen  and  peptones 
being  precipitated  by  subacetate  of  lead  it  was  hoped  to  separate  them 
by  this  reagent,  which  precipitates  crude  papaine  incompletely.  To 
such  a  solution,  therefore,  subacetate  of  lead  was  carefully  added  until 
a  portion,  after  filtration  no  longer  gave  a  precipitate.  The  precipitate 
was  separated  and  a  current  of  sulphuretted  hydrogen  passed  into  the 
filtrate.  This  was  blackened,  but  the  lead  sulphide  was  not  precipitated 
in  flocks.  To  separate  it  the  liquid  was  concentrated  in  a  vacuum,  and 
alcohol  added  to  it  drop  by  drop,  so  as  to  carry  down  the  lead  sulphide 
with  the  first  portions  of  the  papaine  precipitated.  The  deposit  having 
been  separated  by  filtration  the  clear  liquid  yielded  to  alcohol  a  white 
precipitate  of  papaine.  Two  experiments  made  upon  crude  papaine 
from  different  sources  yielded  specimens  of  purified  papaine,  which 
after  exhaustion  with  ether  and  drying  at  75°C.  in  a  vacuum,  gave — 
deduction  being  made  for  ash — 
I. 
ir. 
III. 
Carbon, 
52-36 
52-19 
52-9 
Hydrogen, 
7-37 
7-12 
Nitrogen, 
16-94 
1 6-40 
16-44 
Ash, 
2-6o 
4-22 
3*40 
The  sulphur  was  not  estimated,  sulphuretted  hydrogen  having  been 
used  during  the  operation.  A  third  specimen  contained  i  per  cent, 
less  of  carbon,  when  submitted  to  dialysis  during  twenty-four  hours 
it  gave  the  figures  stated  under  III. 
^  The  experiments  were  made  with  products  that  had  been  submitted  to  lengthened 
dialysis  and  should  not  have  retained  any  more  sulphate,  but  the  figures  obtained 
require  to  be  checked. 
