44 
Ferrous  Citrate  and  Double  Salts. 
(  Am.  Jour.  Pharm 
1      Jan.,  1883. 
able  amorphous  salts,  the  one  a  double  citrate  of  sodium  and  iron,  the 
other  a  citro-phosphate  of  these  metals.  Their  generation  is  repre- 
sented by  the  following  equation  : 
2(FeNaCi) + H3Ci + Na2HP04=FeNa2H2Ci2 + FeNa^H^  CiPO^. 
The  hydro-sodioferrous  citrate  and  citrophosphate  may  also  be  writ- 
ten thus : 
Fe=Ci  Fe^PO^ 
/  / 
Nag  Nag 
\  \ 
Hg^zCi  Hg^^Ci 
This  saline  mixture  admits  of  scaling,  but  not  so  readily  and  ele* 
gantly  as  the  sodioferrous  citrate  above  described. 
The  object  in  preparing  these  compounds  was  to  employ  them  in 
the  various  phosphatized  and  citrated  mixtures  where  permanency  of 
solution  is  a  desideratum.  Hence  their  behavior  towards  phosphoric 
acid  is  interesting. 
Phosphoric  acid,  when  added  to  any  of  these  salts  in  moderate  pro- 
portion, discharges  their  color  to  a  great  extent,  but  wholly  when 
added  in  sufficient  excess.  The  acidulated  solution  is  apparently  per- 
manent ;  however,  with  a  certain  inferior  proportion  of  acid,  a  slight 
precipitate  of  ferrous  phosphate  appears ;  but  the  sodioferrous  citrate 
comports  itself,  in  a  particularly  special  manner,  distinct  from  all  the 
rest  of  these  compounds.  A  sufficient  excess  of  phosphoric  acid  added 
at  once  to  this  salt  produces  a  clear,  permanent  and  perfectly  colorless 
solution ;  yet,  when  phosphoric  acid  is  added  in  such  amount  as  to 
leave  the  solution  lightly  green,  a  profuse  cream-colored  granular  pre- 
cipitate of  the  noteworthy  triferrous  phosphate,  Fe3(P04)28H20,  is 
produced.  This  precipitate,  when  once  formed,  requires  a  much  larger 
proportion  of  phosphoric  acid  for  solution,  and  also  considerable  time. 
Chlorhydric  acid  dissolves  it  more  freely,  yet  slowly.  Nitric  acid 
attacks  it  with  difficulty  after  much  time.  Normal  monad  citrates  are 
also  indifferently  active.  The  reason  for  its  formation  under  such 
peculiar  conditions  is  that  the  salt  which  yields  it  contains  no 
hydrogen. 
Ferrous  citrate  is  best  prepared  by  heating  for  about  three  hours,  or 
until  reaction  ceases,  56  parts  of  very  fine  iron  filings  with  210  parts 
of  citric  acid  and  a  nearly  constant  1,500  parts  of  water.  As  the  iron 
always  contains  carbon,  the  quantity  will  practically  have  to  be  about 
