THE 
AMERICAN  JOURNAL  OF  PHARMACY. 
MAY,  1  8  60. 
ANALYSIS  OF  COMMERCIAL  GLACIAL  PHOSPHORIC  ACID. 
By  John  M.  Maisch. 
Within  a  few  years  past,  phosphoric  acid  and  its  compounds 
have  attracted  the  attention  of  medical  practitioners,  and  are  now 
extensively  used,  frequently  in  the  form  of  solutions  and  syrups, 
in  which  free  phosphoric  acid  is  employed  for  keeping  the  earthy 
and  metallic  phosphates  in  solution.  In  many  of  the  formulas 
of  these  preparations,  the  glacial  phosphoric  acid,  as  it  occurs  in 
commerce,  is  assumed  to  be  the  monohydrated  HO,  P05;  but 
those  who  have  made  them  will  have  frequently  noticed  that 
sometimes  the  phosporic  acid  employed  is  unable  to  dissolve  the 
same  quantity  of  phosphates  which  at  other  times  is  taken  up 
by  it.  As  a  reason  for  this,  we  generally  assign  the  presence 
of  variable  proportions  of  fixed  earthy  matters,  which  cannot  be 
volatilized  by  the  fusion  of  the  acid  ;  and  it  is  a  fact  that  almost 
all  of  it,  the  way  we  meet  with  it  in  commerce,  yields  a  white 
precipitate  on  being  oversaturated  with  ammonia. 
At  the  suggestion  of  Professor  Procter,  I  have  taken  up  the 
subject  with  the  view  of  ascertaining  the  nature  and  the  amount 
of  these  impurities,  and  the  state  in  which  the  acid  exists 
ordinarily. 
In  the  first  place  my  inquiries  were  directed  to  obtain  glacial 
phosphoric  acid  from  different  manufacturers ;  in  this  I  was 
unsuccessful.  By  inquiring  of  a  number  of  friends,  I  ascer- 
tained that  they  are  all  using  an  article  made  by  Merck,  of 
Darmstadt,  a  number  of  whose  chemicals  enjoy  a  well  merited 
reputation  among  us.  This  induced  me  to  select  at  random 
from  a  larger  lot  of  this  acid,  three  specimens,  which  were 
washed  with  cold  water,  and  dried  by  means  of  bibulous  paper. 
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