344  NOTE  ON  SYRUP  OF  HYPOPHOSPHITE  OF  IRON. 
It  became  necessary,  however,  for  the  trustworthiness  of  this 
method,  to  ascertain  whether  commercial  hypophosphite  of  lime 
is  sufficently  pure  and  definite  to  .effect  always  an  exact  decompo- 
sition of  the  sulphate  of  iron.  I  therefore  analyzed  several 
samples  of  the  salts,  and  found  that  the  amount  of  real  hypo- 
phosphite  (Ca(PH202)2)  varied  from  92  to  94  per  cent.,  the 
remainder  consisting  chiefly  of  water,  with  a  little  carbonate  and 
phosphate  of  lime. 
This  variation  in  composition  I  regard  as  too  slight  to  be  of 
any  material  importance.  In  calculating  the  quantity  of  salts 
necessary  for  the  reaction,  the  lime  salt  may  be  regarded  as  con- 
taining 90  per  cent,  of  real  calcic  hypophosphite,  a  slight  excess 
of  the  latter  being  preferrable  to  any  surplus  of  the  sulphate  of 
iron.  The  proportions  to  be  then  employed  for  320  grs.  of 
ferrous  hypophosphite,  Fe(PH202)2  are  480  grs.  of  crystallized 
sulphate  of  iron  and  326  grs.  of  commercial  hypophosphite  of  lime. 
If  the  two  salts  are  triturated  with  oz.  of  water,  the  resulting 
paste  pressed  out,  and  the  filtered  liquid  mixed  with  seven  times 
its  volume  of  simple  syrup,  the  product  contains  2  grs.  of  hypo- 
phosphite of  iron  in  each  fluid  drachm. 
But  the  syrup  so  produced  does  not  keep  long  unless  atmos- 
pheric air  is  thoroughly  excluded.  After  a  few  hours'  exposure, 
a  precipitate  begins  to  form  at  the  surface,  and  gradually  passes 
downwards.  To  prevent  this,  it  is  necessary  to  introduce  a  free 
acid,  and  phosphoric  or  citric  acid  is  best  suited  for  the  purpose. 
The  former  is  preferrable,  because  it  is  more  in  chemical  accord- 
ance with  the  other  constituents  of  the  syrup.  I  have  tried  the 
use  of  free  hypophosphorous  acid,  but  it  does  not  answer  well, 
being  a  very  bad  solvent  for  the  insoluble  ferric  hypophosphite 
which  forms  after  a  time  in  the  syrup.  The  process  I  follow, 
therefore,  stands  as  follows  : — 
Granulated  Sulphate  of  Iron  .    .    .  480  grs. 
Hypophosphite  of  Lime     ....  326  grs. 
Dilute  Phosphoric  Acid     -    .    .    .  1  fl.  oz. 
Water  1J  oz. 
Syrup  q.  s. 
Dissolve,  without  heat,»the  sulphate  of  iron  in  the  phosphoric 
