548      DEPORTMENT  OF  ALKALOIDS  WITH  REAGENTS,  ETC. 
with  bicarbonate  of  soda,  is  boiled  for  some  time,  a  precipitate 
forms  at  once ;  from  dilute  solutions  this  precipitate  separates 
only  after  concentration. 
6.  Sulphocyanide  of  potassium  produces  in  concentrated  solu- 
tions of  salts  of  strychnia  immediately,  in  dilute  solutions  after 
the  lapse  of  some  time,  a  white  crystalline  precipitate,  which  ap- 
pears under  the  microscope  as  an  aggregate  of  flat  needles, 
truncated  or  pointed  at  an  acute  angle,  and  is  but  little  soluble 
in  an  excess  of  the  precipitant. 
7.  Chloride  of  mercury  produces  in  solutions  of  salts  of  strych- 
nia a  white  precipitate,  which  changes  after  some  time  to  crys- 
talline needles,  aggregated  into  stars,  and  distinctly  visible 
through  a  lens.  Upon  heating  the  fluid  these  crystals  redis- 
solve,  and  upon  subsequent  cooling  of  the  solution  the  double 
compound  recrystallizes  in  larger  needles. 
8.  If  a  few  drops  of  pure  concentrated  sulphuric  acid  are 
added  to  a  little  strychnia  in  a  porcelain  dish,  solution  ensues, 
without  coloration  of  the  fluid.  If  small  quantities  of  oxidizing 
agents  (chromate  of  potassa,  permanganate  of  potassa,  ferricya- 
nide  of  potassium,  peroxide  of  lead,  binoxide  of  manganese)  are 
now  added — best  in  the  solid  form,  as  dilution  is  prejudicial  to 
the  reaction — the  fluid  acquires  a  magnificent  blue-violet  color, 
which,  after  some  time,  changes  to  wine-red,  then  to  reddish- 
yellow.  With  chromate  of  potassa  and  permanganate  of  potassa 
the  reaction  is  immediate ;  on  inclining  the  dish,  blue  violet 
streaks  are  seen  to  flow  from  the  salt  fragment,  and  by  pushing 
the  latter  about,  the  coloration  is  soon  imparted  to  the  entire 
fluid.  With  ferricyanide  of  potassium  the  reaction  is  less 
rapid  ;  but  it  is  slowest  with  peroxides.  The  more  speedy  the 
manifestation  of  the  reaction  the  more  rapid  is  also  the  change 
of  color  from  one  tint  to  another.  I  prefer  chromate  of  potassa, 
recommended  by  Otto,  or  permanganate  of  potassa,  recommended 
by  Guy,  as  the  most  sensitive,  to  all  other  oxidizing  agents. 
Jordan  succeeded,  with  chromate  of  potassa,  in  distinctly  show- 
ing the  presence  of  5o^o^n  grain  of  strychnia.  J.  Erdmann 
prefers  binoxide  of  manganese  in  lentil-sized  fragments.  Metal- 
lic chlorides  and  considerable  quantities  of  nitrates,  also  large 
quantities  of  organic  substances,  prevent  the  manifestation  of 
