PRUSSIAN  BLUE,  OR  HYDROCYANATE  OF  IRON.  401 
It  will  thus  be  seen  that,  although  these  two  samples  of  fer- 
rocyanuret  of  iron  contain,  the  one  11  J,  the  other  8  p.  c.  of 
ferrocyanide  of  potassium  (cryst.),  they  are  insoluble  in  water, 
but  become  so  on  adding  some  prussiate  to  them.  It  is,  there- 
fore, not  merely  the  presence  of  the  potassium  salt  which  causes 
the  solubility,  but  it  is  required  to  be  in  mechanical  admixture 
to  render  Prussian  Blue  soluble.  This  is  precisely  the  case  with 
the  hydrocyanate  examined,  from  which  it  has  not  been  removed 
by  water,  and  the  amount  of  prussiate  is  sufficient  to  hold  this 
basic  ferrocyanide  of  sesquioxide  of  iron  in  solution.  The 
smallness  of  the  dose  explains  itself  by  the  ready  solubility  of 
the  substance. 
[Note. — It  may  be  well  to  append  a  few  words  to  Mr.  Mayer's  paper, 
explanatory  of  our  connection  with  what  has  been  called  "  Dr.  McGuigan's 
Hydrocyanate  of  Iron.  Some  time  previous  to  November,  1854,  Dr. 
McGuigan,  of  Keokuk,  Iowa,  wrote  to  us  in  relation  to  "  Hydrocyanate  of 
Iron,"  which  he  was  desirous  of  procuring  for  use  in  Epilepsy,  for  which 
disease  he  had  seen  it  strongly  recommended,  at  the  same  time  intimating 
that  the  article  wanted  was  not  Prussian  Blue.  In  reply  we  wrote  to  him, 
that  strictly  speaking,  no  such  preparation  had  yet  been  made,  but  that 
the  nearest  approach  to  it  that  we  could  offer,  was  the  precipitate  formed 
by  cyanide  of  potassium,  in  a  proto-salt  of  iron,  freed  from  water  by 
aid  of  alcohol,  but  that  in  the  process  of  drying  it  became  altered.  Such 
as  it  was,  it  was  sent  to  him,  and  afterwards  noticed  at  page  504  of 
this  Journal  for  1854,  with  the  details.  Dr.  McGuigan  afterwards  wrote 
stating  that  he  had  derived  good  results  from  the  use  of  the  powder  sent 
to  him.  He  afterwards,  we  believe,  induced  Tilden  &  Co.  to  prepare  the 
preparation  for  him  and  others.  Our  own  view  of  the  matter  is,  that  the 
substance  originally  intended  by  M.  Roux  and  others,  as  mentioned  by 
C.  Bernard,  is  pure  Prussian  Blue,  (see  Journal  de  Pharmacie,  May,  1853, 
page  388)  because  it  is  there  spoken  of  as  Cyanuret  of  Iron  and  Hydro- 
cyanate of  Iron,  both  of  which  names  are  synonyms  of  Prussian  Blue,  in 
France.  In  the  last  paragraph  it  is  remarked,  "  Let  us  add  that  Cyanuret 
of  Iron,  nearly  abandoned  in  France,  is  in  Germany  and  the  United  States 
considered  as  an  excellent  succedaneum  to  Cinchona,  and  that  it  has  been 
much  employed  as  an  anti-spasmodic,  especially  in  chorea,  hysteria  and 
Epilepsy."  Whether  the  association  of  Ferrocyanide  of  Potassium  with 
Prussian  Blue,  as  shown  by  the  analysis  of  Mr.  Mayer,  adds  to  its  power 
by  giving  it  solubility,  we  are  not  able  to  determine,  but  it  is  probable 
that  it  may  be  true. — Editor  Amer.  Jour.  Pharmacy.] 
