THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
DECEMBER,  1875. 
NOTES  ON  DILUTE  PHOSPHORIC  ACID. 
BY  VV.  H.  PILE. 
[Read  at  the  Pharmaceutical  Meeting,  No-vember  iGth.) 
The  subject  of  dilute  phosphoric  acid  has  been  pretty  thoroughly  in- 
vestigated of  late,  and  much  valuable  information  has  been  the  result. 
In  two  particulars  it  has  been  rendered  evident  that  the  second  process 
of  the  U.  S.  Pharmacopoeia  for  preparing  this  acid  is  unfitted  for  that 
purpose,  and  should  consequently  be  expunged  from  our  codex.  The 
proof  of  this  assertion  is  shown  by  the  finished  production  not  being 
free  from  metaphosphoric  or  pyrophosphoric  acids,  and  consequently 
precipitating  a  basic  phosphate  or  pyrophosphate  of  iron,  when  mixed 
with  tincture  of  chloride  of  iron,  as  frequently  prescribed.  A  second 
reason  why  the  process  fails,  arises  from  the  universal  contamination  of 
the  glacial  acid  with  phosphate  of  sodium,  in  some  cases  amounting  to 
30  per  cent.,  as  shown  by  Professor  Remington  in  a  paper  read  before 
the  meeting  of  the  Pharmaceutical  Association,  held  in  Boston  last 
September. 
We  are  thus  thrown  upon  the  first  process  of  the  Pharmacopoeia,  a 
method  which,  when  carefully  performed,  always  proves  satisfactory, 
more  especially  when  ended — but  certainly  annoying  enough  to  deter 
any — but  the  most  persevering  lover  of  chemical  science,  from  repeating 
the  experiment,  not  to  say  anything  of  the  danger  constantly  arising 
from  the  scintillations  of  burning  phosphorus  and  suffocating  vapors  of 
nitrous  acids. 
To  shield  the  conscientious  pharmacist  from  these  serious  conse- 
quences, while  preparing  a  remedy  so  desirable  and  yet  so  seldom  met 
with  (our  esteemed  friend),  Professor  Markoe,  of  Boston,  after  deep 
thought  and  careful  investigation  of  the    interchange    of  chemical 
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