284  Pyrogallic  Acid  as  a  Reagent.  {k^lmT' 
of  mercuric  chloride,  added  to  the  colored  liquid  containing  the  alka- 
loid, causes  immediately  a  black  deposit,  but  a  pyrogallic  solution 
containing  a  glucoside  or  neutral  crystalline  body  is  not  colored  by 
the  addition  of  the  bichloride. 
Some  experiments,  based  upon  this  reaction,  were  made  to  define 
the  relative  alkalinity  of  the  alkaloids.  A  gram  of  pyrogallic  acid 
dissolved  in  10  c.c.  of  alcohol,  added  to  2  c.c.  of  a  saturated  alcoholic 
solution  of  mercuric  chloride,  was  used  as  the  reagent.  Two  or  three 
drops  were  placed  in  a  porcelain  capsule,  and  a  few  crystals  of  the  sub- 
stance to  be  examined  added.  In  some  cases  the  crystals  were  blackened 
immediately  upon  contact ;  others  at  first  took  a  light  tinge,  and  be- 
came more  colored  after  a  few  minutes  ;  whilst  some  alkaloids  only 
became  colored  after  a  slight  elevation  of  temperature.  The  follow- 
ing represents  the  result  of  the  experiments  : — 
In  the  cold  With  heat. 
Atropia.    .    .    Black,  immediately  Black. 
Veratria    .    .       "  "    " 
Codeia      .    .    Brown,  immediately   " 
Quinidia    .    .        "  "  .    .    .  . 
Cinchonidia  "  "  .... 
Thebaina    .     /  Pale  yelloW  '  br0Wn  after  *  of 
an  hour   
Ditto 
ditto 
ditto 
u 
u 
u 
a 
a 
a 
u 
a 
a 
a 
a 
u 
a 
a 
a 
a 
a 
Narcotina  .    .    Ditto  ditto  ditto 
Papaverina     .       "  "  " 
Brucia  /         cnanoe  at  ^rst  »    brown  ) 
\     after  J  of  an  hour    ...  J 
Strychnia  . 
Delphinia  . 
Morphia 
Quinia  . 
Cinchonia  . 
In  operating  with  neutral  crystallizable  bodies  and  glucosides,  and 
heating  the  mixture,  the  black  coloration  was  never  obtained,  and 
even  the  residue  never  presented  a  color  darker  than  that  produced 
by  a  mixture  of  the  body  with  the  bichloride  or  pyrogallol  used  sep- 
arately. 
Picrotoxin,  phlorizin,  salicin,  santonin,  aesculin,  coumarin,  amyg- 
dalin,  meconin,  and  digitalin,  in  no  instance  resembled  the  alkaloids 
in  their  behaviour.    It  would  therefore  appear  that  the  pyrogallo- 
