ON  THE  REVISION  OF  THE  U.  S.  PHARMACOPOEIA.  51 
the  small  proportion  of  sal  prunelle  that  is  often  added  to  the 
so-called  pure  or  "No.  1  caustic"  to  make  it  run  well,  is  de- 
tected in  a  minute  with  equal  certainty. 
A  solution  of  nitrate  of  silver  precipitated  by  hydrochloric 
acid  in  excess  yields  a  precipitate  entirely  soluble  in  ammonia. 
The  clear  supernatant  liquid  evaporated  to  dryness  yields  no 
residue  whatever. 
It  has  been  ascertained  by  Prof.  J.  Lawrence  Smith,  of  Lou- 
isville, Ky.,  that  the  addition  of  a  small  proportion  of  chloride 
of  silver  to  the  nitrate  renders  the  sticks  very  tough  and  hard, 
and  thus  remedies  a  defect  long  felt  in  the  use  of  pure  lunar 
caustic. 
He  adds,  before  fusing,  such  a  proportion  of  chloride  of  so- 
dium that  the  fused  nitrate  may  contain  about  8  per  cent,  of 
chloride  of  silver,  and  considers  this  proportion  as  best  adapted 
to  the  object  in  view.  But  this  method  has  the  serious  objection 
of  introducing  a  very  considerable  proportion  of  nitrate  of  soda 
into  the  preparation,  and  of  diminishing  its  available  strength 
by  the  percentage  of  chloride  of  silver,  plus  the  percentage  of 
nitrate  of  soda  formed.  The  writer  prefers  to  add  a  given  quan- 
tity of  hydrochloric  acid  to  the  nitrate  before  fusing,  or  while 
in  solution  ;  and  thinks  that  such  an  addition  as  will  give  to  the 
nitrate  5  per  cent,  of  the  chloride  of  silver,  will  be  found  suf- 
ficient for  all  useful  purposes.  The  chloride  of  silver  formed  is 
entirely  soluble  in  the  concentrated  solution  of  the  nitrate,  and 
is  therefore  of  course  perfectly  disseminated  through  the  whole 
quantity.  So  hard  and  tough  does  this  admixture  render  the 
sticks  of  fused  nitrate,  that  the  writer  believes  that  they  might 
be  made  of  two- thirds  the  usual  thickness,  and  yet  be  sufficiently 
3trong  for  all  practical  purposes. 
The  formula  proposed  for  this  preparation  is  as  follows  : 
Take  of  Nitrate  of  Silver,  two  ounces. 
Muriatic  Acid,  forty  grains. 
Distilled  Water,  half  a  fluid  ounce. 
Mix  the  acid  and  distilled  water  in  a  suitable  vessel,  add  the 
nitrate  of  silver,  and  by  means  of  a  sand  bath  or  gas  flame  evap- 
orate to  dryness,  fuse,  and  cast  the  fused  mixture  in  suitable 
moulds. 
The  characteristics  and  tests  for  this  preparation  are  the  same 
