460      Hypop>hosphorous  Acid  and  Hypophosphites.  {Amsiptf,'i?89arni' 
per  cent.  No.  1  was  at  least  six  years  old,  the  others  were  obtained 
at  different  times  within  the  last  eighteen  months.  They-  were  sub- 
mitted to  the  following  tests  : 
Sulphuric  acid  by  use  of  BaCl2  and  HC1. 
Calcium  oxalate  by  making  slightly  alkaline  with  ammonium  hy- 
drate, acidifying  with  acetic  acid  (to  redissolve  calcium  phosphate)  and 
filtering  off  the  calcium  oxalate ;  the  filtrate  is  tested  for 
Calcium  phosphate  by  rendering  slightly  alkaline  with  NH4OH  ; 
an  immediate  flocculent  precipitate  indicating  this  salt.  The  filtrate 
from  the  Ca3(P04)2  is  divided  into  two  parts ;  one  part  is  tested  for 
Other  calcium  salts  (sulphate  and  hypophosphite)  by  addition  of  am- 
monium oxalate  ;  the  other  part  for  free 
Oxalic  acid  by  adding  calcium  chloride. 
Phosphorous  acid  was  not  tested  for  directly,  but  indirectly  by 
noting  the  excessive  acidity  over  the  reducing  value  after  allowing 
for  an  excess  of  calcium  hypophosphite  and  any  free  acid  (sulphuric 
or  oxalic)  which  might  be  present. 
The  neutralizing  power  of  the  various  samples  was  determined  by 
weighing  in  a  small  glass-stoppered  bottle  from  2  to  5  gm.  of  the 
acid  and  afterwards  rinsing  the  stopper  and  bottle  until  the  acid  was 
completely  removed,  adding  a  little  phenolphthalein  as  indicator 
and  titrating  with  normal  NaOH.  Mr.  Lunan  in  the  paper  referred 
to  used  extraordinary  precautions  to  prevent  change  of  the  indicator 
(methyl-orange)  by  the  reducing  properties  of  the  acid ;  the  conditions 
under  which  he  titrated  were  extreme  dilution  and  running  the 
diluted  acid  from  a  burette  into  the  dilute  NaOH  and  indicator.  A 
few  experiments  convinced  me  that  these  fears  were  groundless ;  the 
strong  acid  and  a  very  diluted  acid  giving  the  same  results  on  titration. 
The  reducing  value  was  determined  with  about  0*5  gm.  by  either 
the  mercuric  chloride  or  bromine  method  (with  the  latter  method  the 
precautions  on  pages  332  and  387  must  not  be  forgotten). 
The  results  are  expressed  in  parts  in  one  hundred : 
I.  II.  III.  IV. 
H  po    neutralization  3276  3276  38" 22  4476 
*  reduction       30-10  34-19  3911  45*14 
CaC204      0-36  071 
Ca3(P04)2    0.11    
H2S04  2'69  trace  0'27  0'69 
<CaO  from 
other  Ca  salts  ^ 
