58     ON  THE  PEEPARATION  OF  PYROPHOSPHATES  OF  IRON. 
ON  THE  PREPARATION  OF  PYROPHOSPHATES  OF  IRON. 
By  Samuel  P.  Duffield,  Ph.  D. 
Query  No.  26. — It  is  found  that  the  process  of  the  Pharmacopoeia  for 
pyrophosphate  of  iron  yields  a  preparation  which  it  is  sometimes  impossi- 
ble to  scale.    Can  a  better  process  be  devised? 
Pyrophosphate  of  iron  rendered  soluble  by  means  of  citrate 
of  ammonia,  was  first  proposed,  by  M.  E.  Robiquet,  to  the 
Academy  of  Medicine  at  Paris.  As  prepared  by  him  the  gela- 
tinous precipitate  was  dissolved  in  citrate  of  ammonia  solution, 
and  a  syrup  was  made  from  this  solution.  This  process  was 
improved  by  Prof.  Procter ;  the  result  was  also  a  syrup.  The 
formula,  as  it  occurs  at  present  in  the  United  States  Pharmaco- 
poeia, is  that  of  Dr.  E.  R.  Squibb,  and  exhibits  the  finished 
product  in  scales. 
The  pharmacopoeia  process  is  to  ignite  the  2NaO,  HO,  PO5+ 
24HO,  thereby  converting  it  into  the  2NaO,  PO5.  This  is  dis- 
solved in  water  and  mixed  with  solution  of  tersulphate  of  iron, 
at  a  temperature  not  exceeding  50°  Fahr. ;  the  resulting  pulpy 
precipitate  washed  thoroughly  and  dissolved  in  solution  of  citrate 
of  ammonia. 
This  process  I  have  been  disappointed  in  ;  it  scales  but  imper- 
fectly, and  sometimes  not  at  all. 
I  am  not  alone  in  my  complaint ;  several  have  tried  the  same 
process  and  failed  to  get  satisfactory  results.  After  having 
tried  faithfully  for  four  times  this  process,  I  devised  a  slight 
modification,  which  gave  me  the  most  satisfactory  results,  never 
failing  once  to  scale  handsomely. 
The  process :  Take  of  the  magma  obtained  from  8J  oz.  of 
pyrophosphate  of  soda  (which  is  about  6|  times  as  much  by 
weight) : 
Aqua  ammonise,       ....       1  pint. 
Citric  acid,  .       .       .       .       6  oz. 
Mix  the  pyrophosphate  of  iron  (the  magma)  with  the  ammonia 
and  digest  at  a  gentle  water-bath  heat  for  6  to  8  hours ;  then 
gradually  add,  constantly  stirring,  the  6  oz.  of  citric  acid,  dis- 
solved in  two  pints  of  distilled  water,  until  the  ammonia  is 
neutralized  and  the  precipitate  dissolved.    Eilter  or  decant,  if 
