ON  DILUTED  PHOSPHORIC  ACID. 
525 
ON  DILUTED  PHOSPHORIC  ACID. 
By  William  S.  Thompson. 
This  preparation  is  not  an  officinal  of  our  Pharmacopoeia ; 
and  of  the  British  Colleges  only  in  that  of  the  London,  which 
directs  six  drachms  of  phosphorus  to  be  added  to  a  mixture  of 
four  fluid  ounces  of  nitric  acid  sp.  gr.  1.42,  and  eight  fluid 
ounces  of  water,  in  a  retort.  The  retort  is  placed  in  a  sand- 
bath,  and  heat  is  applied  until  six  fluid  ounces  are  distilled, 
which  are  returned  to  the  retort,  and  six  fluid  ounces  more  are 
distilled,  which  are  rejected.  The  dilute  acid  in  the  retort  is 
now  evaporated  in  a  platinum  capsule  until  all  traces  of  nitric 
acid  are  removed,  and  it  is  diluted  with  distilled  water  sufficient 
to  make  it  measure  one  pint,  imperial  measure ;  its  specific 
gravity  is  stated  at  1.064. 
In  the  process,  as  above  conducted,  there  is  no  room  for  loss 
of  phosphorus,  if  the  retort  is  of  sufficient  capacity,  unless  by 
accident ;  consequently,  the  specific  gravity  of  the  resulting 
preparation  is  invariable.  The  process  is  objectionable,  how- 
ever, as  being  tedious  and  troublesome,  and  the  quantity  of 
phosphorus  operated  upon  must  necessarily  be  small ;  it  is,  there- 
fore, desirable  to  substitute  a  process  by  which  a  larger  quantity 
of  acid  can  be  prepared  at  one  operation ;  which  is  attended 
with  but  little  risk,  and  which  affords  a  result  fully  equal  to 
the  process  of  the  London  College  ;  while  at  the  same  time,  it 
is  more  simple  in  the  details  of  its  operation. 
The  process  which  I  now  offer,  for  the  consideration  of  the 
College,  originated  with  Mr.  Geo.  W.  Andrews,  and  it  has  been 
successfully  practised  by  him  and  myself,  in  preparing  large 
quantities  of  phosphoric  acid  for  other  purposes,  for  several 
years  past ;  it  is  as  follows  : — 
Take  of  Phosphorus,    -  4  ounces  Troy, 
Nitric  Acid.  sp.  gr.  1.42,     26  fluid  ounces, 
Water,    -    -  -     54     "  « 
Mix  the  nitric  acid  and  water  in  a  porcelain  dish  of  the  capa- 
city of  not  less  than  six  quarts,  and  add  the  phosphorus  to  the 
mixture.  Having  the  dish  properly  arranged  for  the  applica- 
tion of  heat  by  means  of  a  spirit  lamp,  take  another  dish,  of 
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