ON  TOBACCO. 
in  part  as  solution  in  hydrochloric  acid,  a  drop  of  a  solution  of 
iodide  of  potassium  saturated  with  iodide  of  mercury  is  added  to 
part  of  the  acidulated  solution.  Either, 
I.  It  produces  no  'precipitate. — Absence  of  trimethylina,  nico- 
tina,  lobelina,  conia.  To  a  portion  of  the  unchanged  solution 
add  caustic  potassa  in  slight  excess,  which  causes  a  precipitate. 
It  is 
Whitish  and  pulverulent :  anilina. 
Reddish  to  brown  and  flocculent  ;  ammonia. 
II.  A  precipitate  is  produced. — Add  excess  of  the  solution  of 
mercury. 
1.  The  precipitate  re-dissolves  very  readily  :  trimethylina. 
2.  The  precipitate  is  scarcely  soluble  in  excess  of  mercury, 
but  readily,  while  fresh,  in  caustic  potassa :  nicotina, 
conia.    Apply  the  specific  tests. 
3.  The  precipitate  is  scarcely  soluble  in  either :  lobelina. 
Note.— Ammonia. — Its  reactions,  as  for  instance  that  with  cobalt,  are 
rendered  indistinct  by  the  presence  of  carbonic  acid. 
Commercial  trimethylina  (the  medicinal  propylamin)  is  probably  never 
free  from  ammonia,  which  is  readily  ascertained  in  an  acid  solution  by 
the  test  with  iodohydrargyrate  and  caustic  potassa.  It  should  be  per- 
fectly colorless  and  clear,  of  a  faint  odor  of  ergot  rather  than  of  herring, 
and  must  burn  like  alcohol. 
Conia,  when  quite  pure,  is  colorless,  and  has  a  peculiarly  sweet  but 
rancid  or  somewhat  musty  odor.  Lobelina  resembles  it  in  many  respects ; 
has  an  herbaceous  odor,  recalling  that  of  prussic  acid. 
The  alkaloids  tested  were  freshly  prepared  for  the  experiments  by  the 
method  described  further  on  for  nicotina. 
EXAMINATION  OF  TOBACCO. 
The  material  engaged  for  the  experiments  with  fresh  tobacco, 
— a  dozen  plants  in  full  growth,  collected  after  "topping"  the 
buds, — unfortunately,  by  some  delay  in  delivering,  reached  me 
in  so  damaged  a  condition  as  to  reduce  very  considerably  the 
extent  of  my  investigations. 
Of  the  uninjured  leaves,  with  their  petioles  and  ribs,  25  troy 
ounces  were  spread  out  to  dry  until  their  weight  had  been  re- 
duced to  1625  grains, — a  loss  of  86*5  p.  c,  though  they  were 
not  yet  perfectly  air-dry. 
Of  this  weight,  only  245  grains  had  remained  green  through- 
