ON  PHOSPHATE  OF  SESQUIOXIDE  OF  IRON. 
295 
One  hundred  grains  were  fused  with  some  carbonate  of  soda, 
the  mass  left  after  ignition  was  removed  from  the  crucible,  in- 
troduced into  a  dish  with  some  water,  and  every  portion  of  oxide 
of  iron  carefully  washed  from  the  crucible ;  this  mixture  was 
allowed  to  boil,  and  sufficient  acetic  acid  added  to  neutralize  the 
excess  of  carbonate  of  soda.  By  this  means,  all  the  sesquioxide 
of  iron  was  precipitated,  while  the  clear  liquid  contained  the 
phosphate  of  soda  with  some  acetate  of  soda.  The  sesquioxide 
of  iron  was  collected  on  a  filter,  washed  and  ignited ;  to  the 
solution  of  phosphate  and  acetate  of  soda,  a  solution  of  chloride 
of  ammonium,  of  sulphate  of  magnesia  and  of  ammonia  was  added  ; 
by  this  means  the  double  phosphate  of  magnesia  and  ammonia 
was  precipitated,  which  by  ignition  furnished  the  pyrophosphate 
of  magnesia,  from  which  the  phosphoric  acid  was  calculated. 
The  result  of  two  analyses  carefully  performed  was : 
1st  Exp.       Fe203    52.50,       2d  Exp.       Fe.O.  52.00 
"     2MgO,P05     73.00,  2MgO,P05  74.00 
112  parts  2MgO,P05  being  equal  to  72  parts  of  PO^,  the 
following  is  the  result : 
1st  Exp.    Fe.fi,  52.50  ) 
"        PO,  46.92  /^^-^-^ 
2d  Exp.    FeA  52.00  1 
PO,  47.57  r^'^^ 
These  results  correspond  in  composition  with  the  phosphate 
of  sesquioxide  of  iron  Fe^OgPO.,  mentioned  by  Will  in  his  "  Out- 
lines of  Chemical  Analysis,"  and  by  Dr.  Graham,  in  his 
''Elements  of  Chemistry."  The  reaction,  therefore,  must  be 
between  one  equivalent  of  phosphate  of  soda,  and  one  of  ter- 
sulphate  of  sesquioxide  of  iron,  by  which  are  formed:  one  eq. 
phosphate  of  sesquioxide  of  iron,  2  eq.  of  sulphate  of  soda,  and 
one  of  sulphuric  acid,  which  remains  in  the  water:  2NaO,HO, 
PO,+Fe203,3S03^Fe203,PO,+2(NaO,S03)+S03,HO. 
Some  further  experiments  were  now  tried  to  ascertain  its 
solubility  in  some  solvent,  which  might  render  it  useful  in  medi- 
cine. 
In  hydrochloric  and  nitric  acids,  it  is  readily  soluble ;  in 
phosphoric  acid  it  is  insoluble  ;  in  citric  and  tartaric  acids,  it 
is  slightly  soluble,  more  so  on  the  application  of  heat,  forming 
green  solutions.    In  phosphate  of  soda  it  is  insoluble,  even 
