282 
Alkaloids  in  Belladonna  Root. 
Am.  Jour.  Pharm. 
May,  1884. 
chloroform-alcohol  mixture.  The  separation  of  the  water  from  the 
mixture  is  instantaueous  and  entire  if  the  mixture  is  gently  warmed ; 
nearly  the  whole  of  the  coloring  matter  remains  dissolved  in  the 
chloroform,  whilst  the  water  retains  the  alcohol  and  the  alkaloidal  salts. 
By  rendering  the  aqueous  solution  alkaline  with  ammonia  and  agitating 
with  chloroform  the  atropine  and  hyoscyamine  were  obtained  after 
evaporation  in  an  apparently  pure  state ;  that  is  to  say,  the  residue  was 
entirely  soluble  in  dilute  acids,  and  when  dissolved  in  chloroform  and 
the  solvent  spontaneously  evaporated  the  alkaloid  remained  as  a  mass 
of  white  silky  crystals.  However,  one  of  the  most  important  points 
to  be  demonstrated  in  such  investigations  as  these  is  the  perfect  purity 
of  the  final  alkaloidal  residue,  and  yet  this  is  a  point  which  is  gene- 
rally assumed  and  not  proved  by  workers  in  this  field. 
On  a  previous  occasion1  one  of  us  has  proposed  a  method  for  ascer- 
taining the  purity  of  residues  of  strychnine  and  brucine,  which  is 
founded  upon  the  complete  precipitation  of  these  alkaloids  (when 
nearly  free  from  other  organic  substances)  by  a  solution  of  tannin 
rendered  faintly  alkaline  with  ammonia.  This  process  was  tried  with 
atropine  and  hyoscyamine,  but  with  negative  results,  for  the  precipi- 
tate at  first  formed  was  soluble  in  excess  of  the  reagent.  Other  reagents 
were  now  experimented  with.  Potassium  mercuric  iodide  was  found 
to  be  by  no  means  a  complete  precipitant  of  atropine,  and  is  useless 
for  its  detection  when  present  in  small  quantity.  Picric  acid  is  also 
useless  alike  for  the  detection  and  estimation  of  atropine;  even  when 
considerable  quantities  of  the  alkaloid  are  present  in  solution  this 
reagent  fails  to  afford  any  indication.  Phosphotungstic  and  phospho- 
molybdic  acids  are  far  more  delicate  than  the  former  reagents,  but 
even  these  are  not  sufficiently  exact  for  quantitative  use.  As  far  as  the 
detection  of  atropine  and  hyoscyamine  is  concerned  a  very  delicate 
test  is  the  dilating  action  upon  the  eye's  pupil  which  is  distinctly 
yielded  by  mere  traces  of  the  alkaloids.  After  attempting  the  quanti- 
tative application  of  many  of  the  alkaloid  precipitants  with  no  success, 
we  found  one  reagent  which  is  admirably  adapted  for  quantitative  use. 
A  solution  of  iodine  in  potassium  iodide  completely  precipitates  even 
traces  of  atropine  and  hyoscyamine,  from  a  solution  in  dilute  hydro- 
chloric acid,  as  the  dark  green  periodides.  When  other  acids  are  pre- 
sent the  precipitation  is  not  quite  so  complete.    After  a  great  number 
^unstan  and  Short,  "The  Analysis  of  some  Authentic  Specimens  of 
JSTux  Vomica"  ("Pharm.  Jour.,"  [3],  xiii,  1053). 
