312 
ON  THE  HYPOPHOSPHITES  OF  IRON. 
which  was  appended.  I  was  aware,  at  that  time,  of  some 
peculiar  characters  of  the  ferric  salt,  and,  among  other  points, 
with  its  comparatively  great  solubility  in  water  at  the  ordinary 
temperature,  yet  this  quality  was  overlooked  in  speaking  of  the 
salt,  as  the  notice  was  very  concise. 
If  a  small  quantity  of  the  recent  hypophosphite  of  iron  is 
thrown  on  a  filter,  it  may  be  entirely  dissolved  away  by  repeated 
ablutions  of  water,  affording  a  colorless  solution  precipitated  deep 
blue  by  ferrocyanide  of  iron.  Practically,  in  making  the  hypo- 
phosphite  of  sesquioxide  of  iron,  I  have  used  a  strong  solution 
of  sesquisulphate  of  iron,  (containing  about  100  grs.  of  sesqui- 
oxide to  the  fluid  ounce),  kept  for  the  purpose  of  obtaining  sesqui- 
oxide. The  hypophosphite  of  soda  is  dissolved  in  about  five 
times  its  weight  of  water,  and  the  ferruginous  solution  added 
until  it  ceases  to  thicken  the  magma.  The  latter  is  then  imme- 
diately thrown  on  a  muslin  strainer  and  expressed  with  the  hand, 
and  then  mixed  with  its  bulk  of  cold  water  and  again  expressed. 
The  resulting  salt  is  very  compact,  and  by  standing  seems  to 
contract  and  force  out  from  its  pores  a  part  of  the  absorbed 
liquid.  There  still  adheres  to  it  traces  of  persulphate  of  iron 
and  sulphate  of  soda,  but  the  latter  is  unimportant,  and  the  for- 
mer is  instantly  converted  into  hypophosphite  on  the  addition 
of  the  magma  to  the  other  hypophosphites  in  the  preparation  of 
the  compound  syrup. 
Since  then,  Mr.  William  S.  Thompson,  of  Baltimore,  in  a 
paper  which  has  been  copied  at  page  317,  of  this  number,  has 
noticed  that  in  the  presence  of  sugar  this  salt  is  de-oxidized  and 
reduced  to  the  state  of  a  protosalt  in  the  compound  syrup  alluded 
to,  and  that  the  change  was  not  peculiar  to  this  salt,  but  that 
persulphate  and  other  persalts  of  iron  were  in  like  manner 
changed  to  protosalts.  Happening  to  have  several  specimens 
of  the  compound  syrup  of  hypophosphites  of  various  ages,  it 
occurred  to  me  to  try  them  with  the  two  ferrocyanurets  of  iron, 
and  I  found  the  statements  of  Mr.  Thompson  to  accord  with  my 
results,  viz :  the  oldest  syrup  was  most  affected  by  the  ferrid- 
cyanide,  and  the  recent  syrup  the  least ;  and  the  ferrocyanide 
produced  deep  coloration  with  the  recent,  and  only  caused  a 
greenish  color  with  the  oldest  syrup. 
Assuming  this  change  to  be  inevitable,  Mr.  T.  adopts  the  idea 
