510  Strychnine  and  Brucine  Ferro-cyanides.    {Am' octT,\m&Tm' 
alcohol,  but  dissolves  in  hot  water  with  formation  of  hydrogen  ferro- 
cyanide, giving  rise  to  a  blue  coloration  and  the  formation  of  hydro- 
cyanic acid.  The  salt  has  a  strong  acid  reaction,  decomposes  carbo- 
nates and  is  decomposed  by  ammonia  and  alkalis  with  separation  of 
strychnine.  Normal  brucine  ferrocyanide,  (C^H^^O^T^Fe^N^ 
-j-  4H20,  is  obtained  by  adding  to  a  concentrated  neutral  brucine 
hydrochloride  solution,  a  concentrated  solution  of  potassium  ferrocya- 
nide,  as  tufts  of  yellow,  prismatic  crystals ;  it  gives  yellow  solutions 
with  water  and  alcohol.  In  the  air  it  gradually  passes  into  brucine 
ferricyanide  with  the  separation  of  brucine.  Acid  brucine  ferrocyanide, 
(C23H26N204),H4Fe(CN)6,  the  salt  precipitated  from  a  very  concentrated 
strongly  acid  solution  of  brucine  by  potassium  ferrocyanide,  forms  a 
white,  crystalline  powder,  as  seen  under  the  microscope,  which  in  the 
air  quickly  becomes  blue.  In  less  concentrated  solutions  there  is  no 
change  at  first,  but  after  twelve  to  twenty-four  hours  beautiful,  large, 
white  prisms  form  of  the  same  composition  as  the  powder.  The  salt 
decomposes  when  heated  with  water  with  separation  of  hydrocyanic 
acid. 
Potassium  ferricyanide  gives  only  normal  salts.  Strychnine  ferricy- 
anide, (C2iH22N202)6,H6Fe2(C]N")12+12H20,  precipitated  from  neutral 
and  acid  solutions,  forms  golden-yellow,  flat  prisms,  somewhat 
sparingly  soluble  in  water  to  a  yellow  liquid.  Brucine  ferricyanide, 
(C22H26N204)6,H6Fe2(CN)12+12H20,  is  precipitated  from  acid  or  neu 
tral  solutions  of  brucine  salts  as  greenish-yellow  spangles,  sparingly 
soluble  in  water  to  a  yellow  liquid.  Other  alkaloids  are  now  under- 
going investigation  by  the  authors. 
Estimation  of  strychnine  and  brucine. — The  authors  have  based  a 
volumetric  method  on  Dunstan  and  Short's  observation  that  strych- 
nine is  completely  precipitated  from  aqueous  solution  of  its  sulphate, 
whilst  brucine  is  not.  If  a  0  5  to  1  per  cent,  solution  of  the  two 
alkaloids,  strongly  acidified  with  hydrochloric  acid,  is  treated  with 
potassium  ferrocyanide  until  a  filtered  portion  of  the  solution  gives  a 
blue  stain  with  ferric  chloride  paper,  the  whole  of  the  strychnine  is 
precipitated  as  acid  strychnine  ferrocyanide,  whilst  the  brucine  remains 
in  solution.  The  amount  of  strychnine  can  thus  be  determined  by  using 
a  standard  solution  of  ferrocyanide,  two  hundred  and  forty-four  parts 
potassium  ferrocyanide  corresponding  to  three  hundred  and  thirty-four 
parts  of  strychnine.  If  the  solution  contain  less  than  0'5  per  cent, 
the  separation  is  too  slow ;  also  the  ferric  chloride  paper  should  not 
