122  Compound  Solution  of  the  Hypophosphites.  {     Ma?'^  i8?>'^'"* 
magnesium  liypophosphites  are  incorrectly  stated,  the  correct  formulae 
for  the  salts  being 
re(PHA)2+6HA  Ca(PHA)2,  Mg(PHA)2+6H20. 
This  of  course  involves  a  great  difference  in  the  amount  of  hypo- 
phosphorous  acid  present  in  these  salts,  which  in  the  case  of  the  ferrous 
and  magnesium  salts  is  understated  to  the  extent  of  one-half,  and  in 
the  calcium  salt  to  the  extent  of  three-fourths. 
With  the  view  of  securing  the  iron  in  a  ferrous  condition,  double 
decomposition  with  ferrous  sulphate  and  calcium  hypophosphite  was 
had  recourse  to  (in  preference  to  the  uncertain  method  of  saturating 
the  hydrate,  or  the  slow  process  of  dissolving  metallic  iron  in  hypo- 
phosphorous  acid),  and  having  assured  myself  that  this  could  be 
accomplished,  the  sodium  and  magnesium  hypophosphites  were  made 
in  the  same  way. 
The  only  drawback  to  the  preparation  of  the  various  hypophosphites 
from  calcium  hypophosphite,  and  the  corresponding  sulphates,  is  the 
formation  of  sulphuretted  hydrogen  in  the  solution,  after  it  has  stood 
for  a  little  time.  This  result  you  may  imagine  would  give  consider- 
able annoyance  were  its  formation  not  obviated  by  the  adoption  of  a 
proper  method  to  ensure  double  decomposition  between  the  sulphates 
and  calcium  hypophosphite,  without  the  possibility  of  any  bye-pro- 
ducts, so  to  speak. 
The  sulphuretted  hydrogen  may  arise  in  the  following  manner.  It 
is  well  known  that  hypophosphorous  acid  acts  as  a  powerful  reducing 
agent,  so  that  when  brought  into  the  presence  of  sulphuric  acid  (either 
pure  or  as  sulphate)  the  sulphuric  would  be  reduced  to  sulphurous 
and  the  hypophosphorous  raised  to  phosphorous  acid,  thus, 
HPH  A + H,SO.= H3PO3+ H,S03. 
Sulphurous  acid  again  acting  upon  a  fresh  molecule  of  hypophosphor- 
ous acid  would  raise  it  to  phosphorous  acid  with  liberation  of  sulphur^ 
thus, 
2HPH  A + H^SOs^  2H3PO3 + S  4  Hp. 
But  this  sulphur  would  not  be  found  as  such,  for  being  in  the  pres- 
ence of  a  reducing  agent  of  so  great  power  as  hypophosj^horous  acid, 
the  following  action  will  in  all  likelihood  ensue : 
HPH  A + S + Hp=H3P03 + H^S. 
At  all  events,  it  is  certain  that  sulphuretted  hydrogen  is  formed  in  the 
solution  under  certain  conditions,  and  I  merely  suggest  these  reactions 
as  those  which  may  probably  take  place. 
