214 
ON  TOBACCO. 
by  boiling,  or  distilling  it  with  a  large  excess  of  caustic  am- 
monia. 
As  the  result  of  several  assays  with  two  troyounces  at  each 
time,  I  obtained  as  mean  proportion  of  nicotina  13-25  grains, 
equal  to  1-36  per  cent,  of  the  leaf,  precisely  the  percentage  in 
the  first  assay  as  given  above. 
Tobacco  seed  of  the  same  variety  possesses  scarcely  any  acrid- 
ity, except  what  arises  from  rancidity  of  the  oil.  The  latter  is 
at  times  extracted  as  from  other  seeds,  and  employed  for  house- 
hold use.  Decoction  with  acidulated  water  was  found  to  be  the 
best  mode  for  their  extraction. 
Three  troyounces,  thoroughly  bruised,  were  boiled  for  several 
hours  with  water  and  a  little  sulphuric  acid.  The  filtered  liquor 
indicated,  with  iodohydrargyrate,  646  grains  of  nicotina=  0.45 
per  cent,  of  the  seed. 
The  leafstalks  and  ribs  of  the  commercial  leaf,  and  the  liber 
of  the  green  stalk,  yielded  noticeable  quantities  of  the  alkaloid, 
but  their  percentage  was  not  determined. 
For  the  purpose  of  identifying  the  alkaloid,  or  bases  carried 
down  by  iodide  of  mercury  from  acidulated  solutions  in  these  sev- 
eral instances,  the  precipitates  were  washed  with  water — (since 
the  test  solution  of  iodohydrargyrate,  besides  containing  a  large 
excess  of  iodide  of  potassium,  is  too  dilute  to  allow  any  trime- 
thylina  to  be  precipitated,  no  attention  needed  to  be  paid  to  any 
possible  decomposition  of  the  precipitate) ;  it  was  then  rubbed 
smooth  in  a  mortar  with  a  concentrated  solution  of  protochloride 
of  tin,  to  which  were  afterwards  added  small  pieces  of  caustic 
potassa,  so  as  to  form  an  alkaline  solution  of  protoxyd  of  tin. 
The  result  in  this  as  well  as  in  the  case  of  all  other  bases,  when 
their  compounds  with  mercury  are  similarly  treated,  is  that  the 
mercury  is  reduced  to  the  metallic  state,  its  iodine  or  chlorine  com- 
bining with  the  tin  ;  the  hydriodate  of  the  base,  then  disengaged, 
is  acted  on  by  the  excess  of  caustic  alkali,  and  the  base,  when 
the  mixture  is  now  agitated  with  ether,  is  a,t  once  taken  up  in  an 
almost  pure  condition. 
After  distilling  off  the  ether,  the  residue  is  dissolved  in  dilute 
hydrochloric  or  oxalic  acid,  filtered,  again  shaken  with  alkali  and 
ether  or  chloroform,  which  will  then  give  a  pure  solution  of  the 
