500 
Estimation  of  Nicotine. 
Am.  Jour.  r-harm. 
Oct.,  1884. 
plus  washings,  was  heated  on  the  water-bath  until  H2S  was  driven  off, 
then  pure  Na2C03  added,  evaporated  to  dryness,  and  strongly  heated. 
Dissolved  in  water,  it  was  slightly  acidulated  with  H2S04,  and  the 
amount  of  I  ascertained  volumetrically  with  ^  normal  solution  of 
HgCl2.  The  addition  of  Na2C03  to  the  acid  solution  is  necessary  to 
drive  off  the  nicotine  in  the  solution. 
In  trying  to  estimate  the  I  in  this  solution  with  HgCl2  before  use  of 
carbonate  of  sodium  was  made,  at  first  a  resinous  yellow  precipitate 
was  obtained  similar  to  the  resinous  precipitate  in  the  original  tests. 
Other  experiments  convinced  me  that  nicotine  was  present,  particularly 
the  strong  odor  after  addition  of  carbonate  of  sodium  and  the  alkali- 
nity of  the  vapors. 
On  making  the  tests  with  M.  S.  it  is  of  importance  to  avoid  and 
prevent  the  precipitate  from  becoming  resinous ;  the  precipitate  is  not 
uniform  in  its  composition  unless  certain  precautions  are  observed ; 
when  a  resinous  precipitate  is  formed,  a  larger  quantity  of  M.  S.  is 
necessary  to  finish  the  test. 
As  the  object  is  to  obtain  a  precipitate  of  definite  composition — 
HgI2,C10HuN2(HI)2 — the  formation  of  any  resinous  precipitate  must 
be  avoided.  To  prevent  this,  at  the  beginning  a  large  quantity  of 
M.  S.  is  added  at  once,  and  the  resulting  mixture  is  briskly  stirred 
until  a  crystalline  precipitate  begins  forming. 
The  quantity  of  acid  added  to  the  nicotine  solution  seems  also  to 
have  influence ;  if  it  is  small  a  resinous  precipitate  is  more  apt  to  be 
formed.  One  drop  of  strong  hydrochloric  acid  for  each  10  cc.  of 
nicotine  solution  acts  very  well ;  more  acid  (2  or  3  drops  for  10  cc.) 
did  not  seem  to  influence  the  quantity  of  M.  S.  required. 
According  to  Dragendorff — 
19'3  cc.  of  M.  S.  in  A.  would  indicate  0*07816  nicotine, 
22-5  cc.      "       in  B.  a.  &  b.    «       0*091125  " 
17-4  cc.      "       in  B.  c.  "       0*07047  " 
and  the  precipitate  in  A.  should  amount  to  0*4207 
in  B.  a.  &  b.      "  0*490 
"  in  B.  c.  "  0*380 
while  there  was  obtained,  respectively,  0*724,  0*866  and  0*645,  or  on 
an  average  73  per  cent  more  than  Dragendorff  accounts  for. 
