394      Hypophosphorous  Acid  and  Hypophosphites.  {^ll^sifm™' 
solubility  of  ferric  hypophosphite  in  presence  of  a  slight  excess  of 
calcium  hypophosphite  the  product  (IV)  of  the  following  process  was 
found  to  be  a  very  pure  salt. 
Calcium  hypophosphite  30  gm. 
Solution  of  ferric  chloride  49"5  gm. 
Distilled  water,  a  sufficient  quantity. 
The  calcium  salt  with  100  cc.  water  is  placed  in  a  flask  and  the 
iron  solution  gradually  added,  shaking  after  each  addition.  The 
ferric  hypophosphite  first  forms  a  magma  but,  after  a  little  time,  sep- 
arates as  an  agglutinated  mass  which  must  be  disintegrated  by  brisk 
agitation.  Agitation  must  be  resorted  to  from  time  to  time  until 
the  precipitate  becomes  crystalline  and  loses  all  tendency  to  cake,  which 
change  will  require  at  least  twenty-four  hours ;  a  better  yield  is  prob- 
ably obtained  by  allowing  to  stand  two  or  even  three  days  before 
filtering  and  washing.  The  washings  are  tested  for  Ca  by  addition  of 
ammonium  oxalate,  and  as  long  as  a  precipitate  is  obtained  washing 
must  be  continued.  It  was  noticed  that  as  the  washings  became  free 
from  Ca  they  came  through  the  filter  a  little  cloudy  and  allowed  to  run 
into  the  vessel  containing  the  first  portions  of  the  filtrate,  after  a  little 
time,  a  distinct  although  a  small  precipitate  was  formed,  due  to  the 
dissolved  ferric  hypophosphite  being  reprecipitated  by  the  presence 
of  a  small  quantity  of  calcium  hypophosphite  in  the  first  filtrate. 
Using  the  above  quantities  and  allowing  to  stand  three  days  before 
filtering  there  was  obtained  a  yield  of  93  per  cent,  based  upon  the 
quantity  of  ferric  chloride  used. 
I.  II.  III.  IV. 
Fe2(H2P02)6  90-32  86-19  93-30  98-80 
H20  2-82  0-71  4-70  0-65 
Fe2(S04)3  3-20  5*92     
Na2S04  3.92  7*31     
Fe2C]6      0-68  0-66 
Fe203      0-85   
CaS04      0-66   
The  U.  S.  P.  tests  appear  to  be  based  upon  the  properties  of  the 
recently  precipitated  salt.  The  solution  of  all  of  the  above  samples 
in  HC1  and  sodium  citrate  solution  was  obtained  only  after  consider- 
able agitation  and  time.  The  effect  of  boiling  acetic  acid  forms  little 
claim  to  the  title  of  solvent ;  whilst  calcium  salts  can  be  tested  for  in 
