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ON  PHOSPHATE  01  SISQUIOXIDE  OF  IRON. 
ON  PHOSPHATE  OF  SESQUIOXIDE  OF  IRON. 
By  Emile  Hetdenreich. 
(An  Inaugural  Essay.)  ^ 
For  several  years  various  compounds  of  phosphorus,  oxygen 
and  iron,  either  by  themselves  dissolved  in  acids,  or  combined 
with  some  alkaline  salts  have  been  used  to  a  considerable  extent. 
Among  these,  the  compound  syrup  of  the  phosphates  of  iron, 
soda  and  lime,  (the  chemical  food,)  the  so-called  syrup  of  super- 
phosphate of  iron,  and  the  glyceroles  and  syrup  of  hypophosphites 
of  iron  have  been  most  generally  used.  The  pyrophosphate  of 
the  sesquioxide  of  iron  has  also  been  brought  forward  by  some 
French  chemists,  but  did  not  come  into  use  till  it  was  offered  by 
the  late  Mr.  E.  Robiquet,  of  Paris,  in  combination  with  the 
citrate  of  ammonia,  with  which  it  forms  a  soluble  salt.  The 
extended  use  which  this  latter  salt  has  obtained,  and  the  little 
notice  which  had  been  taken  of  the  other  compound  of  phosphoric 
acid  and  sesquioxide  of  iron,  led  me  to  make  some  experiments 
in  this  direction.  The  varied  basic  character  of  the  phosphate 
of  soda,  from  which  corresponding  metallic  salts  may  be  usually 
obtained,  would  naturally  lead  one  to  suppose  that  similar  com- 
pounds of  the  sesquioxide  of  iron  might  be  obtained  by  adding 
to  a  solution  of  them,  solutions  of  a  sesquisalt  of  iron.  This  has 
been  verified  in  the  case  of  the  pyrophosphate  of  iron,  SFe^ 
Og.SPO^:  the  reaction  being  3(2NaO,PO-)+2(Fe2033S03)= 
2(Fe203)3P05-f  6(NaOS03.)  According  to  this,  by  using  the 
tribasic  phosphate  of  soda,  instead  of  ihe  pyrophosphate,  we 
might  expect  the  reaction  to  be  3(2NaO,HO,POJ-f-2(Fe203 
3SO3)  =:(2Fe,03,3HO,3P05)+6(NaO,S03.) 
On  carefully  adding  to  a  solution  of  tribasic  phosphate  of 
soda,  a  solution  of  tersulphate  of  sesquioxide  of  iron  to  satura- 
tion, a  bulky  white  precipitate  was  obtained  ;  the  supernatent 
liquid  was  found  to  be  decidedly  acid  to  litmus  paper.  The 
precipitate  was  washed  by  decantation  several  times,  thrown  on 
a  filter,  allowed  to  drain,  and  finally  pressed  between  bibulous 
paper.  It  was  afterwards  dried  on  a  sand  bath  till  anhydrous, 
when  it  was  analysed  to  ascertain  its  composition  ;  during  the 
washing  and  drying,  the  precipitate  assumed  gradually  a  yellow 
tint. 
