ON  PYROPHOSPHATE  OF  IRON. 
327 
so-called)  pyrophosphate  of  iron,  a  salt  more  beautiful  in  appear- 
ance than  the  ammonio-citrate,  or  any  other  of  the  scaled  salts 
before  introduced.  Its  color  varies  according  to  the  manufac- 
ture ;  may  be  made  from  a  decided  green  to  a  greenish  hue, 
yellow,  or  more  or  less  of  a  reddish  tint.  Water  dissolves  it 
readily.  In  taste  it  has  nothing  to  indicate  its  ferruginous  char- 
acter, but  is  rather  that  of  a  pleasant  saline,  so  that  the  young- 
est children,  or  the  most  fastidious  in  palate  of  a  larger  growth, 
cannot  object  to  its  use.  With  regard  to  its  efficacy  as  a  tonic, 
when  compared  with  other  preparations  of  iron,  that,  of  course, 
can  only  be  decided  by  medical  men. 
The  name  given  to  the  above  is  decidedly  objectionable.  The 
science  of  chemistry  within  the  last  few  years  has  made  such 
rapid  progress  that  there  is  scarcely  a  day  but  some  new  com- 
pound is  announced  to  the  scientific  world,  some  of  which  com- 
pounds have  such  long  and  formidable  names  that  it  requires 
more  courage  than  many  possess  to  attempt  even  to  pronounce 
them;  others  are  more  simple,  yet,  from  their  immense  number, 
but  few  memories  can  command  them  at  pleasure.  I  think  it, 
therefore,  a  pity  when  a  new  preparation  is  introduced  of  rather 
an  indefinite  composition  to  increase  the  necessary  difficulties 
already  existing  by  giving  it  the  name  of  a  definite  chemical 
compound  well  known.  The  salt  in  question  physically  bears  no 
relation  to  pyrophosphate  of  iron,  and  all  that  can  be  said 
chemically  is,  that  the  latter  is  one  of  its  constituents. 
Pyrophosphate,  or  bibasic  phosphate  of  iron,  is  obtained  by 
adding  a  solution  of  persulphate  or  perchloride  of  iron  to  a  solu- 
tion of  bibasic  or  pyrophosphate  of  soda.  A  white  precipitate 
is  thrown  down,  quite  insoluble  in  water  and  dilute  acids.  Pyro- 
phosphate of  soda  is  obtained  by  simply  igniting  to  redness  in  a 
crucible  the  bibasic  or  ordinary  phosphate  of  soda.  The  two 
are  best  distinguished  by  nitrate  of  silver,  which  gives  with  the 
former  a  white,  and  with  the  latter  a  yellow,  precipitate. 
Recently  precipitated  pyrophosphate  of  iron,  obtained  as 
above,  is  readily  dissolved  by  pyrophosphate  of  soda  and  the 
alkaline  citrates — viz.  potash,  soda,  and  ammonia. 
When  pyrophosphate  of  soda  is  used  as  the  solvent,  and  the 
solution  allowed  to  evaporate  spontaneously  in  shallow  vessels  in 
a  warm  place,  a  nice-looking  transparent  salt  is  obtained,  which 
