''^"kiT'^isg?'™  }  Compound  Solution  of  the  Hypophosphites.  12S 
In  order  to  obviate  these  objectionable  reactions,  I  have  adopted  the 
plan  of  dissolving  all  the  salts  in  hot  water,  since  if  decomposition 
takes  place  in  the  cold  it  is  prolonged,  and  may  give  rise  to  the  above 
reactions ;  whereas  by  the  employment  of  hot  water  the  change  ensues 
immediately,  and  thus  contact  between  the  acids  is  avoided. 
It  will  be  observed  in  the  undernoted  formula,  that  the  hypophos- 
phorous  acid  is  stated  as  containing  30  per  cent.  HPH2O2 ;  this  has 
been  found  to  be  about  the  usual  strength  of  the  acid  supplied  by  the 
wholesale  houses.^  The  acid  also  usually  contains  traces  of  sulphuric 
acid,  which  slightly  interferes  with  the  finished  product  by  precipi- 
tating a  little  lime  as  sulphate  from  the  calcium  hypophospliite  added 
at  the  end  of  the  process. 
The  working  formula  is  as  follows : 
2  oz.  382  grs.  FeSO^THp+l  oz.  332  grs.  Oa(PHA)2=2-77 
5  oz.  364  grs.  Na2SO„10H2O+3  oz.  35  grs.  Ca(PH202)2=3-5 
]>sraPH202,H20 
2  oz.  22  grs.  MgS04,7H20-f  1  oz.  182  grs.  Ca(PH202)2=l-99 
Mg(PH202)2,  6H2O. 
3  oz.  3()8  grs.  Ca(PH202)2=3-5  Ca(PH202)2. 
51  fl.  oz.  HPH2O2,  70H2O=l-66  HPH2O2. 
Method  of  Procedure. — Dissolve  the  whole  of  the  calcium  hypo- 
phosphite  required  to  decompose  the  sulphates  (6  ounces  112  grains) 
in  50  ounces  of  water ;  bring  the  solution  nearly  to  boiling  point,  and 
acidify  with  half  an  ounce  of  the  hypophosphorous  acid ;  then  stir  in 
the  ferrous,  sodium  and  magnesium  sulphates ;  double  decomposition 
ensues  almost  immediately.     After  stirring  two  or  three  minutes, 
throw  the  whole  on  a  paper  filter,  and  wash  the  precipitate  with  hot 
water  to  70  ounces. 
Dissolve  the  3  ounces  368  grains  calcium  hypophosphite  in  25  ounces 
of  water ;  filter,  mix  the  filtrates,  add  to  the  solution  the  remaining  5 
ounces  of  hypophosphorous  acid,  and  make  up  with  water  to  100  ounces. 
^  The  percentage  was  determined  in  the  following  manner :  a  known 
quantity  of  freshly  calcined  lead  oxide  was  mixed  with  a  known  quantity 
of  tlie  commercial  acid ;  to  this  a  little  nitric  acid  was  added,  and  the  whole 
evaporated  and  calcined ;  the  weight  of  the  product,  after  deducting  the- 
amount  of  PbO,  gave  the  amount  of  acid  present  as  P.^Oa,  from  which  the 
amount  of  HPH.^O,^  was  calculated. 
Voluinetric  solution  of  soda  gives  a  nearly  similar  result. 
