Am.  Jour.  Pharm.  \ 
March,  1900.  J 
Soluble  Ferric  Pyrophosphate. 
127 
therefore  abandoned.  In  this  connection  I  wish  to  call  attention  to 
an  observation  which  I  have  not  heretofore  seen  recorded,  which  is 
that  magnesium  phosphate  and  ammonium  magnesium  phosphate, 
freshly  precipitated,  are  completely  soluble  in  sodium  pyrophos- 
phate in  large  excess,  and  are  not  reprecipitated  by  ammonia,  but 
by  excess  of  the  magnesium  salt. 
The  following  test,  which  is  a  slight  modification  of  the  one  pro- 
posed by  Stieglitz,  was  finally  adopted  as  being  most  satisfactory. 
Very  accurate  results  may  be  obtained  with  it  by  moderate  care, 
and  for  this  reason  I  recommend  it  to  the  notice  of  the  Committee 
of  Revision  of  our  next  Pharmacopoeia. 
Boil  1  gramme  of  the  salt  with  10  c.c.  of  potassium  or  sodium 
hydrate,  T.  S„  to  remove  the  iron.  Filter,  acidulate  the  colorless 
filtrate  with  hydrochloric  acid,  and  add  a  slight  excess  of  ammonia 
water  and  a  solution  of  magnesium  sulphate1  so  long  as  a  precipi- 
tate is  formed ;  slightly  acidulate  with  acetic  acid,  boil  and  filter. 
The  filtrate  should  give  no  precipitate  upon  adding  ammonia  water 
in  slight  excess. 
The  following  results  were  obtained  with  the  above  test  upon  the 
samples  collected  : 
No. 
2 
3 
4 
5 
6 
7 
8 
9 
Author's  Test  for 
Orthophosphate. 
Proved  by  Ammouium 
Molybdate  Test. 
Heavy  precipitate 
Heavy  precipitate 
Very  heavy  precipitate 
Very  heavy  precipitate 
Small 
Small 
Heavy 
Heavy 
Very  heavy  " 
Very  heavy 
Small 
Small 
Proved  by 
Silver  Nitrate. 
Yellow  precipitate 
No.  8  was  prepared  by  the  author.  No.  9  was  handed  the  author 
by  a  fellow-chemist,  and  guaranteed  to  be  free  from  orthophos- 
phate. 
It  is  thus  proved  that  iron  pyrophosphate  soluble  does  not  revert 
1  Magnesium  sulphate,  10  grammes  ;  ammonium  chloride,  20  grammes,  and 
water  a  sufficient  quantity  to  make  120  c.c. 
