2i6  Contributions  from  H.  M.  Gordin.    { AmMIa°yuri9^' >arrr- 
quires  to  be  proved  is  that  emetine,  like  most  other  alkaloids,  can 
be  exactly  estimated  by  my  alkalimetric  method.1  Though  this 
could  be  admitted  a  priori,  for  the  reason  that  emetine  is  precipi- 
tated by  Mayer's  and  Wagner's  reagents  from  extremely  dilute 
slightly  acid  solutions,  it  was  thought  best  to  bring  experimental 
proof  of  the  exactness  of  the  alkalimetric  estimation  of  this  alka- 
loid. For  the  establishment  of  this  fact  also  it  is  immaterial  what 
the  real  formula  of  emetine  is.  All  that  we  need  to  prove  is  that 
if  we  standardize  our  acid  and  alkali  with  definite  amounts  of  this 
alkaloid,  and  in  this  way  deduce  a  factor  for  our  standard  liquids, 
this  factor  will  give  exact  results  with  other  quantities  of  the  same 
alkaloid. 
N  \ 
A  dilute  (about  —  )  solution  of  sulphuric  acid  was  standardized 
40  / 
against  a  dilute  solution  of  KOH,  using  phenolphtalein  as  indi- 
cator, so  that  the  acid  and  alkali  corresponded  exactly  cubic  centi- 
metre per  cubic  centimetre..  0-0926  gramme  of  emetine  (Merck's) 
was  now  dissolved  in  50  c.c.  of  this  dilute  acid  contained  in  a  IOO  c.c. 
measuring  flask.  An  excess  of  Mayer's  reagent  was  added,  and  the 
flask  filled  up  to  100  c.c.  After  a  few  shakings  the  precipitate  sep- 
arated out  completely  and  the  supernatant  liquid  became  perfectly 
transparent.  The  liquid  was  now  filtered,  and  in  50  c.c.  of  the  fil- 
trate the  excess  of  acid  determined  by  means  of  the  alkali.  It  was 
found  that  the  0-0926  gramme  emetine  consumed  14  c.c.  of  our 
acid.  Hence  1  c.c.  of  our  acid  was  equivalent  to  0*0066  gramme 
of  our  emetine. 
Two  samples  of  the  alkaloid  were  now  weighed  out  and  the 
amounts  estimated  exactly  as  above,  using  the  factor  0-0066  for 
each  cubic  centimetre  of  acid. 
Our  Acid  Our  Acid  Emetine  by 
Emetine  Taken.  Taken.  Consumed.         Factor  0  0066. 
(1)  ....       0*1829  75  c.c.         27*6  c.c.  0*1822 
(2)  ....       0*1071  30  c.c.  16*4  c.c.  0*1082 
We  see  that  the  alkalimetric  method  gives  as  good  results  with 
emetine  as  with  quinine,2  cinchonidine,2  morphine,  atropine,  cocaine, 
strychnine,  hydrastine,  caffeine  and  acid  salts  of  berberine.3 
1  The  application  of  the  method  to  the  cinchona  alkaloids  I  shall  show  in 
my  next  paper. 
2  Will  be  shown  later. 
3  This  will  be  shown  in  another  paper. 
