412  ON  THE  SOLUBILITY  OF  PHOSPHATE  OF  IRON. 
a  syrup  in  which  acid  phosphate  of  ammonia  is  the  solvent  of 
phosphate  of  iron,  and  which  he  considers  a  permanent  prepara- 
tion. In  Mr.  Maisch's  letter  a  step  further  is  taken  ;  he  as- 
certains that  citrate  of  ammonia  will  dissolve  and  retain  the 
ordinary  phosphate  of  iron  in  solution,  and  that  in  presence  of 
citrate  of  ammonia  the  oxide  of  iron  cannot  be  precipitated 
from  the  sesquichloride  of  iron  in  solution.  The  latter  observa- 
tion has  been  made  before  by  Rose,  (see  Gmelin's  Hand.  xi.  447,) 
so  far  as  citric  acid  in  a  free  state  is  concerned. 
In  a  paper,  which  has  reached  us  since  the  above  was  written, 
by  Mr.  A.  F.  Haselden,  on  names  in  connection  with  Pharmaco- 
poeial  usage,  (Pharmaceutical  Journal,  August,  1859,)  we  find 
the  following  ;  alluding  to  "  syrup  of  phosphate  of  iron,  some- 
times called  syrup  of  superphosphate  of  iron,  and  sometimes 
syrup  of  phosphate  of  iron,  I  have  no  doubt  that  generally  the 
same  preparation  is  looked  for  ;  but  in  the  first,  if  prepared  as 
the  name  would  imply,  an  opaque  syrup  of  an  insoluble  com- 
pound is  the  result ;  in  the  last  two,  an  excess  of  acid  to  the 
phosphate  enables  the  operator  to  produce  a  clear  preparation, 
but  this  is  uncertain  in  its  strength  and  unstable  in  its  nature. 
In  order  to  meet  this  difficulty,  the  General  Apothecaries'  Com- 
pany have  introduced  a  preparation  by  the  assistance  or  addition 
of  citrate  of  ammonia  to  the  phosphate  of  iron,  and  thus  a  prepa- 
ration in  scales  is  obtained  like  the  ammonio-citrate  of  iron, 
which  still  sails  under  the  name  of  the  pyrophosphate  of  iron, 
and  with  which  a  light  brown  or  dark  straw  colored  syrup  is 
prepared,  bearing  the  title  of  syrup  of  pyrophosphate  of  iron." 
From  this  it  appears  that  Mr.  Maisch  is  anticipated  in  regard 
to  citrate  of  ammonia  dissolving  phosphate  of  iron.  By  trial 
we  have  ascertained  that  citric  acid  in  a  free  state  is  a  perfect 
solvent  for  recently  precipitated  phosphate  of  iron,  and  the  ad- 
dition of  an  alkali  afterwards  does  not  precipitate  the  phos- 
phate. This  naturally  suggested  a  trial  with  the  blue  com- 
mercial ferroso-ferric  phosphate.  When  equal  parts  of  citric 
acid  and  of  this  blue  phosphate  are  triturated  with  four  parts  of 
water  and  allowed  to  stand  several  hours  with  occasional  agi- 
tation, the  blue  color  gradually  disappears,  the  phosphate  is  dis- 
solved, and  forms  a  greenish  brown  solution,  which  on  dilution 
is  not  precipitated,  nor  does  ammonia  or  potash  throw  down 
