10 
Liquor  Sodii  Phosphatis  Compositus. 
(Am.  Jour.  Pharni 
|    January,  1909. 
A  NOTE  ON  LIQUOR  SODII  PHOSPHATIS  COMPOSITUS. 
By  John  K.  Thum,  Ph.G., 
Pharmacist  at  the  German  Hospital,  Philadelphia. 
There  is  considerable  dissatisfaction  and  complaint  among  retail 
pharmacists  about  the  U.  S.  P.  compound  solution  of  phosphate  of 
sodium.  When  first  made  the  solution  seems  perfect,  but  after  stand- 
ing for  a  few  days,  especially  at  a  low  temperature,  crystals  of 
sodium  phosphate  appear  on  the  bottom  of  the  container.  With 
the  object  of  preventing  this  deposit  of  crystals  from  taking  place, 
the  writer  experimented  by  changing  the  U.  S.  P.  formula  in  va- 
rious ways. 
The  plan  of  using  double  the  amount  of  citric  acid  was  tried  with 
apparent  great  success,  the  solution  being  subjected  to  a  low  tem- 
perature without  any  recrystallization  occurring  whatever,  but  on 
testing  the  solution  it  was  found  to  be  decidedly  acid.  From  this 
point  of  view,  and  a  most  important  one,  it  was  a  failure. 
Physicians  use  sodium  phosphate  because  of  its  alkalinity  quite 
as  much  as  for  its  laxative  and  purgative  properties.  Keeping  this 
in  mind,  the  writer  endeavored  to  make  a  solution  which  would 
not  crystallize,  and  would  also  be  free  of  acidity  or  in  which  the 
acidity  would  be  very  slight. 
Citric  acid  to  the  amount  of  13  per  cent,  is  called  for  in  the 
U.  S.  P.  formula;  this  was  increased  to  15  per  cent.,  and  the  sodium 
nitrate  omitted,  with  the  object  of  finding  if  the  sodium  nitrate 
played  an  important  part  in  aiding  or  facilitating  solution  of  the 
sodium  phosphate.  With  the  aid  of  a  water-bath  complete  solu- 
tion took  place  very  readily  and  sufficient  distilled  water  was  added 
to  make  up  to  the  proper  volume.  On  being  subjected  for  some 
time  to  a  very  low  temperature  and  carefully  watched  it  was  noticed 
that  the  first  crystals  to  appear  were  "  colorless  translucent,  right 
rhombic  prisms,"  typical  of  citric  acid.  On  continued  exposure  to 
this  temperature  sodium  phosphate  appeared  in  considerable  quan- 
tity. While  it  required  some  time  for  recrystallization,  in  this  in- 
stance, to  take  place,  the  addition  of  the  U.  S.  P.  amount  of  sodium 
nitrate  caused  recrystallization  to  take  place  very  rapidly  at  the  same 
temperature.  This  seemed  to  prove  that  the  U.  S.  P.  quantity  of 
sodium  nitrate  facilitated  recrystallization. 
Although  the  citric  acid  and  sodium  phosphate  combination  kept 
