210  REVIEW  OE  PHARMACOPOEIA  HELVETICA. 
Pharmacopoeias,  and  thereby  adapts  itself  at  once  to  all  parts  of 
Switzerland,  in  some  sections  of  which  the  old  apothecaries' 
weight  is  used,  while  in  others  the  gramme  is  employed,  perhaps 
exclusively.  The  advantage  of  this  is  very  obvious.  We  cannot 
now  make  preparations  according  to  the  British  Pharmacopoeia, 
nor  are  our  friends  in  Great  Britain  able  to  make  preparations 
of  our  Pharmacopoeia,  in  which  liquids  are  employed,  without 
going  to  the  trouble  of  calculating  the  weights  and  measures. 
But  the  direction  of  all  quantities  in  parts  by  tveight  enables  us 
to  produce  exactly  the  same  preparations,  whether  we  work  with 
grammes,  troy,  avoirdupois,  Nuremberg,  or  any  other  system  of 
weights. 
Acidum  aceticum*  has  a  specific  gravity  of  1*040  at  15°  C. ; 
the  dilute  acetic  acid  is  made  with  one  part  of  the  former  and 
five  of  distilled  water. 
Acidum  hydrochloricum  and  nitricum  are  distilled  from  table 
salt  and  purified  saltpetre  respectively,  with  crude  sulphuric 
acid.  These  pure  acids  have  the  spec.  grav.  =  1*120  and  1*20, 
of  the  dilute  acids  —  1*06  and  1*09  ;  besides  these,  the  crude 
acids  are  likewise  officinal. 
Acidum  sulfuricum  is  made  by  rectifying  the  crude  acids  from 
a  bath  of  ashes  ;  it  is  free  from  bases,  and  from  muriatic  and 
nitric  acids. 
Dilute  sulphuric  acid  has  1*11  spec.  grav.  The  crude  acid, 
diluted  with  ten  parts  of  water,  may  yield  a  slight  precipitate 
with  sulphuretted  hydrogen  ("  hydrosulfur,"  a  short  and  very 
appropriate  name),  but  if  this  is  wholly  or  in  part  dissolved  by 
ammonia,  and  this  solution  precipitated  in  yellow  flocks  by  mu- 
riatic acid  (arsenic),  the  acid  is  unfit  for  use. 
Acidum  phosphoricum,  spec.  grav.  1*130,  is  made  in  glass  re- 
torts ;  after  the  phosphorus  has  been  oxidized  and  the  nitric  acid 
entirely  expelled,  the  arsenic  likely  to  be  present  is  removed  by 
sulphuretted  hydrogen.  Our  Pharmacopoeia  has  no  such  provi- 
sion, and  does  not  even  direct  the  phosphorus  to  be  free  from 
this  frequent  impurity. . 
Acidum  hydrocyanicum  contains  two  per  cent,  by  weight ;  the 
*  We  give  the  names  of  all  preparations  as  officinal  in  the  Swiss 
Pharmacopoeia. 
