THE  AMEEICAJST 
JOURNAL  OF  PHARMACY 
•   L  %  S\  
APRIL,  igij 
V     •  >       ^4  — 
THE  ASS  AY  W  HYPOPHOSPHOROUS  ACID. 
i£y  Horace  North, 
Analyst  with  Lehn  &  Fink,  New  York. 
It  is  proposed  to  neutralize  hypophosphorous  acid  with  barium 
hydroxide,  collect  any  precipitate  that  forms  on  a  filter  and  weigh 
after  ignition.  The  weight  in  milligrams  per  gram  of  absolute  acid 
is  termed  the  barium  number.  By  this  means,  samples  containing 
excessive  amounts  of  foreign  acids  (sulphuric,  oxalic,  tartaric, 
phosphoric,  phosphorous)  are  readily  detected.    In  the  writer's 
Analyses  of  Commercial  Hypophosphorous  Acid. 
Sample 
Acidity  as  hypophosphorous 
acid 
Barium  number 
No.  3548  
29 . 73  per  cent. 
5-1 
No.  3592  
31 .33  per  cent. 
6.9 
No.  3636  
31 .42  per  cent. 
36.6 
No.  3979  
31 .33  per  cent. 
12.3 
No.  4400  
31 .20  per  cent. 
3-4 
No.  4634  
31 . 19  per  cent. 
4-4 
opinion,  an  acid  fit  for  use  in  medicinal  preparations  should  have 
a  barium  number  not  greater  than  5.  Analyses  of  six  commercial 
lots  are  given  in  the  table.  The  details  of  the  method  are  as  follows  : 
Put  1  c.c.  of  hypophosphorous  acid  in  a  tared,  stoppered  Erlen- 
meyer  flask  and  weigh  accurately.  Add  20  c.c.  of  water  recently 
boiled  to  expel  C02  and  cooled  and  a  few  drops  of  phenolphthalein 
solution.  Titrate  the  liquid  with  N/s  Ba(OH)2  (standardized 
against  N/o  HQ)  until  a  permanent  pink  color  is  produced.  Put  the 
flask  in  a  water:oven  for  an  hour,  then  collect  any  precipitate  that 
may  have  formed  on  a  7  cm.   Swedish  filter,  washing  with  hot  water 
(i47) 
