416      DIALYSIS  APPLIED  TO  INVESTIGATION  OF  ALKALOIDS. 
In  the  course  of  this  preliminary  study  I  endeavored  to  find 
some  reaction  as  much  as  possible  characteristic  of  digitaline. 
Hitherto  we  know  no  reaction  for  distinguishing  digitaline  from 
other  vegetable  poisons,  except  the  green  color  obtained  by  dis- 
solving this  substance  in  concentrated  hydrochloric  acid.  This 
reaction,  as  has  been  observed,  cannot  be  taken  as  an  unfail- 
ing indication  of  the  presence  of  digitaline,  for  the  same  color 
is  produced  by  several  other  organic  matters.    The  successive 
action  of  sulphuric  acid  and  bromine  vapors  have  hitherto 
seemed  to  characterize  even  very  small  quantities  of  digitaline. 
Pure  digitaline  takes  a  sienna-brown  color  on  contact  with  con- 
centrated acid,  turning  after  a  time  to  vinous  red,  and  on  the 
addition  of  water  immediately  becoming  dirty  green.  When, 
instead  of  operating  on,  for  instance,  1  centigramme  of  solid 
digitaline  which  has  not  yet  been  in  contact  with  any  liquid, 
we  submit  to  the  action  of  sulphuric  acid  the  residue  of  the 
evaporation  of  several  drops  of  a  diluted  solution  of  digitaline, 
the  color,  instead  of  brown,  is  lighter  or  darker  reddish-brown, 
according  to  the  quantity  of  material  employed.     With  very 
small  quantities  of  digitaline  (0  gr.  0005,  for  instance),  the 
color  is  rose,  like  the  flower  of  the  digitalis.    On  exposing 
digitaline,  moistened  with  sulphuric  acid,  to  bromine  vapors, 
the  mixture  instantly  becomes  violet,  and  the  shade  varies  from 
heartsease  violet  to  mauve,  according  as  there  is  present  more 
or  less  digitaline.    The  coloration  shown  by  sulphuric  acid,  and 
modified  by  bromine  vapors,  is  most  distinct  with  the  residue 
of  the  evaporation  of  1  centimetre  cube  of  water  contain- 
ing 0  gr.  005  of  digitaline  ;  it  is  also  very  clear  with  0  gr. 
0005  of  this  poisonous  substance.     It  is  observable  with 
even  the  very  faintest  traces  of  digitaline.  None  of  the  follow- 
ing substances,  which  I  have  submitted  to  the  same  reaction, 
has  evidenced  this  property  : — Morphine,  narcotine,  codeine, 
narceine,  strychnine,  brucine,  atropine,  solanine,  salicine,  san- 
tonine,  veratine,  phlorhidzine,  diturine,  amygdaline,  asparagine, 
cantharidine,  cafeine. 
Dialysis — and  in  this  consists  its  greatest  value — allows  the 
separation  of  the  vegetable  poisons  from  the  animal  substances 
with  which  they  are  mixed,  in  a  state  sufficiently  pure  to  enable 
us  to  identify  them  by  their  principal  characteristics. — Chem, 
News,  from  Comptes  Bendus,  lviii,  1048. 
