AnA5ust^£m'}    Hypophosphorous  Acid  and  Hypophosphites.  387 
.•correction  to  be  made,  otherwise  too  high  results  will  be  obtained.  If 
1  cc.  of  bromine  (the  quantity  usually  taken  for  a  determination 
of  hypophosphite)  be  moderately  warmed  with  100  cc.  water  for  one- 
half  hour  and  then,  by  boiling,  the  bromine  entirely  volatilized, 
while  the  solution  is  neutral  to  litmus  indicating  the  absence  of  acids, 
the  addition  of  a  few  drops  of  phenolphthalein  is  the  cause  of  a  green- 
ish color  and,  after  adding  more  indicator  0*3  cc.  NaOH  had  to  be 
added  to  produce  an  alkaline  reaction.  This  correction  (the  subtrac- 
tion of  0*3  cc.  NaOH  from  the  quantity  of  NaOH  needed  to  neutral- 
ize the  acids  formed  in  the  oxidation)  had  to  be  made  in  the  examination 
of  H3P02,  KH2P02,  NaH2  P02  and  Ca  (H2  P02)2.  When  first  using 
this  method  in  the  examination  of  ferric  hypophosphite  it  was  noticed, 
in  boiling  to  free  the  solution  from  bromine,  that  the  solution  became 
opalescent  without  depositing  a  precipitate  (it  was  since  observed  that 
by  protracted  boiling  a  precipitate  will  form) ;  that  the  opalescence 
was  not  due  to  the  presence  of  ferric  phosphate  was  proven  by  the 
prolonged  boiling  of  the  simulated  mixture,  made  without  the  use  of 
bromine,  giving  a  perfectly  clear  solution.  Discovering  the  impurity  in 
the  bromine  as  described  above,  the  probability  that  the  cause  of  the 
opalescence  was  to  be  found  in  the  bromine  was  verified  by  experiment 
and  at  the  same  time  the  correction  for  ferric  hypophosphite  ascer- 
tained. 10  gm.  of  a  dilute  ferric  chloride  solution  were  precipitated  by 
addition  of  normal  sodium  hydrate  until,  after  boiling,  phenolphthalein 
indicated  an  alkaline  reaction ;  it  required  6.5  cc.  NaOH.  To  10 
gm.  of  the  same  solution  diluted  to  100  cc.  was  added  1  cc.  bromine 
and,  after  one-half  hour's  warming,  the  bromine  expelled  by  boiling ; 
the  opalescence  was  noticed  as  soon  the  solution  boiled  actively ;  it 
required  now  7  cc.  NaOH  to  produce  an  alkaline  reaction  making  a 
correction  of  0*5  cc.  NaOH  necessary  in  the  examination  of  ferric 
hypophosphite. 
Using  only  the  one  sample  of  bromine  in  my  work,  it  is  impossible 
to  state  to  what  extent  this  impurity  is  met  with  in  commercial  bro- 
mine ;  but  the  above  experience  is  sufficient  to  draw  attention  to  a 
possible  source  of  error  in  hypophosphite  determinations. 
The  examination  of  the  officinal  hypophosphites  disclosing  a  number 
of  foreign  substances  some  of  which  are  difficultly  estimated,  the 
methods  used  are  described  as  briefly  as  possible. 
Hypophosphite  determination. — With  the  soluble  salts  no  difficulty 
whatever  is  encountered  either  with  the  HgCJ2  or  the  Br  method. 
