AmM0aT,'i887arm'}      Commercial  Hypophosphorous  Acid.  247 
temperature  of  60°  C.  for  some  time,  then  throwing  on  a  tared  and 
dried  filter,  washing,  drying  at  100°  C,  and  weighing  the  calomel. 
The  equation  is  H3P02+4HgCl2+2H20=H3P04+4HgCl-f  4HC1. 
It  was  specified  in  the  process  that  the  temperature  must  not  exceed 
70°  C,  as  in  that  case  some  of  the  calomel  might  be  reduced  to  the 
metallic  state.  Practically,  however,  it  was  found  that  barely  one- 
half  of  the  reducing  power  of  the  samples  was  exhausted  by  digestion 
for  nearly  an  hour  at  60°  C.  A  quantity  of  the  acid  heated  to  100°C. 
with  excess  of  HgCl2  produced  a  white  precipitate  which  showed  no 
signs  of  reduction,  either  to  mercurous  oxide  or  to  metallic  mercury, 
and  as  it  was  proved  that  the  filtrate  could  be  boiled  indefinitely  with- 
out producing  the  slightest  further  precipitation  it  was  deemed  that 
this  process  would  work  practically  with  the  alteration  of  the  diges- 
tion at  60°  C.  to  heating  to  the  boiling  point  100°  C. 
As  an  example  of  this  process  20  cc.  of  a  solution  of  sample  (A) 
containing  10  cc.  in  500  cc,  which  would  be  equal  to  *4  cc.  of  the  origi- 
nal solution,  weighing  (seeing  the  specific  gravity  was  1-1332)  '45468 
gram,  was  taken ;  to  this  was  added  a  known  excess  of  5  per  cent, 
solution  of  HgCl2,  3  cc.  of  HC1,  and  the  whole  diluted  to  about  100 
cc.  with  distilled  water,  and  heated  to  100°  C. 
The  calomel  separated  as  a  lustrous  purely  white  precipitate,  which 
when  thrown  on  a  tared  filter,  well  washed  and  dried,  weighed  1*8989 
gram. 
Now  by  the  equation  942  grams  of  calomel  are  produced  by  66 
grams  of  H3P02,  so  that  calculation  proved  that  '45328  gram  of  the 
sample  contained  *133  gram  of  pure  H3P02  which  is  equal  to  29 '48 
per  cent. 
The  quantitative  estimation  is  tabulated  below : — 
Percentage  of  H3P02 
Sample.  Sp.gr.      NaHO  estimation.    Reduction  of  HgCl2  to  HgCl. 
A.  .    .       1-1332  29-12  28-48 
B.  .    .       1-1367  29-95  29*95 
C.  .    .       1*0442  8'87  8*87 
D.  .    .       1-0353  8*07  8.07 
If  any  reliance  can  be  placed  on  the  qualitative  estimations  sub- 
mitted to  you,  it  would  seem  that  the  acid  cannot  be  prepared  free 
from  calcic  oxalate  if  the  lime  and  oxalic  acid  process  is  used  for  its 
preparation. 
As  there  cannot  be  any  doubt  but  that  freshly  precipitated  oxalate 
