ON  THE  SOLUBILITY  OF  PHOSPHATE  OF  IRON.  411 
the  ordinary  phosphate;  no  precipitate  of  phosphate  of  iron 
occurs. 
A  solution  of  sesquichloride  of  iron,  after  being  mixed  with  a 
solution  of  citrate  of  ammonia,  is  likewise  not  precipitated  by 
the  ordinary  phosphate  of  ammonia,  or  of  soda ;  but  the  phos- 
phate of  potassa  produces  a  precipitate  immediately.  If,  how- 
ever, a  sufficient  quantity  of  phosphate  of  ammonia  had  been 
previously  added,  the  further  addition  of  the  potassa  phosphate 
will  not  disturb  the  clear  solution. 
I  inferred  from  these  experiments  that,  not  only  pyrophos- 
phate, but  also  the  other  phosphates  of  iron,  will  enter  into  a 
permanently  clear  solution  with  citrate  of  ammonia;  in  accord- 
ance with  this  inference,  I  prepared  some  ordinary  phosphate  of 
the  sesquioxide  of  iron,  and  found  it  in  its  recent  state  entirely 
soluble  in  the  ammoniacal  citrate.  It  would  appear,  therefore, 
an  easy  matter  for  a  physician  to  give  phosphate  of  iron  in  so- 
lution by  simply  ordering  citrate  of  iron  and  phosphate  of  am- 
monia, the  solution,  no  doubt,  will  contain  the  citrate  and  phos- 
phate of  both  bases. 
My  time  being  so  much  occupied,  I  have  not  had  time  to  make 
any  more  experiments  at  present,  and  the  few  above  related  are 
not  calculated  to  answer  the  question,  whether  or  not  a  soluble 
double  phosphate  of  ammonia  and  sesquioxide  of  iron  may  exist, 
or  whether  Robiquet's  syrup  of  pyrophosphate  of  iron  is  merely 
a  solution  of  an  insoluble  phosphate  in  citrate  of  ammonia. 
I  remain  yours,  very  respectfully,  J.  M.  Maisch. 
[Note. — The  employment  of  citrate  of  ammonia  as  a  solvent 
for  pyrophosphate  of  iron,  originated,  we  believe,  with  M. 
Robiquet,  who  suggested  it  as  a  better  agent  than  the  pyro- 
phosphate of  soda  for  that  purpose ;  and  at  pages  401-4  of  this 
Journal  for  1857,  his  process  will  be  found  noticed.  Subse- 
quently, (January,  1858,)  J.  G.  Richardson,  of  Philadelphia,  in 
a  new  process  for  Compound  Syrup  of  the  Phosphates,  uses 
citrate  of  ammonia  as  a  solvent  for  pyrophosphate  of  iron, 
which  he  introduces  into  that  preparation  in  lieu  of  the  ordinary 
phosphate,  and  at  the  same  time  effects  the  solution  of  the  phos- 
phate of  lime  by  free  citric  acid.  Joseph  Roberts,  of  Baltimore, 
(see  Maryland  Journal  of  Pharmacy,  March  4th,  1858,)  suggests 
24 
