336  Alkaloidal  Color  Tests.  {AmjuOiy"-i9P03arm' 
changes  for  strychnine  are  perfectly  reliable  when  applied  to  pure 
material;  but  in  the  former  part  of  this  paper  there  are  pointed  out 
some  of  the  difficulties  to  be  encountered  in  isolating  and  rendering 
absolutely  pure  minute  quantities  of  any  alkaloid.  Not  only  is  it 
difficult  to  purify  small  quantities  of  strychnine,  but  there  may  be 
present  in  the  ethereal  or  chloroformic  extracted  material  certain 
undefined  organic  substances  which  will  interfere  so  seriously  with 
the  test  lor  strychnine  that  its  presence  cannot  be  recognized  even 
when  comparatively  large  quantities  of  the  alkaloid  are  present  or 
are  purposely  added. 
Evidence  as  to  the  presence  of  strychnine  depends  on  joining  the 
following  results:  (i)  No  coloration  with  pure  concentrated  sul- 
phuric acid;  (2)  a  purple-blue  color  when  oxidation  results;  (3) 
fading  of  the  purple-blue  color  to  a  bright  cherry-red  tint,  etc. 
There  are  very  few  organic  bodies,  usually  encountered  in  the 
search  for  an  alkaloid,  that  will  comply  strictly  with  the  first  re- 
quisite. Among  these  may  be  mentioned  gelsemine,  acetanilid, 
antipyrin,  salicylic  acid,  benzoic  acid  and  curarine,  the  non-crystal- 
lizable  principle  of  worara,  obtained  from  botanical  sources  allied  to 
those  of  strychnine.  Among  the  above  are  frequently  mentioned 
brucine  and  morphine,  and  occasionally  hydrastine.  The  two 
former  usually  produce  a  slight  rose  tint,  while  the  latter  a  faint 
yellowish  coloration.  After  dissolving  the  strychnine  residue  in 
sulphuric  acid,  the  mixture  ought  to  be  allowed  to  stand  five 
minutes  in  order  to  note  if  any  color  is  developed. 
On  treating  strychnine,  dissolved  in  concentrated  sulphuric  acid, 
with  almost  any  oxidizing  agent,  there  is  produced  a  rich  purple- 
blue,  which  changes  more  or  less  rapidly  through  purple  and  crim- 
son to  a  bright  cherry-red  tint,  this  latter  being  somewhat  persistent. 
The  rapidity  of  the  change  is  largely  influenced  by  the  amount  and 
nature  of  the  oxidizing  agent  employed.  Many  oxidizing  substances 
have  been  recommended  from  time  to  time,  and  each  operator 
seems  to  have  a  distinct  preference  for  one  or  the  other,  probably 
because  of  a  greater  familiarity  with  the  same. 
E.  Marchand,1  in  1843,  showed  that  when  strychnine,  dissolved  in 
sulphuric  acid  containing  a  little  nitric  acid,  is  treated  with  a  small 
amount  of  lead  peroxide,  a  series  ol  colors  was  developed.  Mack, 
xJour.  de  Pharm.,  4,  200. 
