50         ON  THE  REVISION  OF  THE  U.  S.  PHARMACOPOEIA. 
granular  or  homogeneous  fine  grained  fracture,  and  when  of  an 
opaque  or  porcelanic  whiteness,  it  may  be  strongly  suspected  of 
impurity.    As  a  general  rule,  that  presenting  the  handsomest 
appearance  is  most  to  be  distrusted,  or  most  clearly  indicates  the 
necessity  of  examination.    It  is,  perhaps,  better  known  in  the 
pharmaceutical  than  in  the  medical  profession,  that  a  lunar  caus- 
tic "  No.  2  "  is  very  commonly  made  and  sold,  and  is,  as  far  as 
the  writer  has  been  able  to  ascertain,  quoted  upon  the  prices 
current  of  every  manufacturing  chemist  in  the  United  States. 
This  preparation  is  commonly  made  up  of  66  to  75  per  cent,  of 
nitrate  of  silver,  and  33  to  25  per  cent,  of  nitrate  of  potassa. 
It  is  put  up  precisely  as  the  so-called  pure  or  "  No.  1  "  prepara- 
tion, with  the  exception  of  a  shade  of  color  in  the  tint  of  the 
paper  with  which  it  is  wrapped,  or  in  the  wax  with  which  it  is 
sealed.    The  bottle  containing  half  a  pound  or  more  is  often 
marked  "No.  2  "  upon  the  wrapper  or  label,  and  this  sometimes 
with  lead  pencil.    But  the  sticks  carry  with  them,  on  being  dis- 
pensed and  used,  no  indication  of  adulteration,  and  since  "  the 
trade,"  or  the  initiated  only,  know  the  slight  distinctions  men- 
tioned, the  preparation  is  liable  to  be  sold  and  used  as  a  pure 
article.    Whatever  may  be  the  object  of  this  half-masked  adul- 
teration, its  effect  and  drift  are  unmistakably  bad,  and  therefore 
the  means  of  detection  and  control  should  be  so  simple  and  easy 
of  application,  as  to  insure  their  use  as  far  as  practicable. 
The  writer  believes  he  has  been  fortunate  enough  to  find  a 
test  just  applicable  to  this  necessity,  and  which  in  point  of  sim- 
plicity, and  easy  application,  must  leave  little  to  be  desired.  A 
small  fragment  of  nitrate  of  silver,  crushed  to  powder  with  a 
knife  blade  upon  a  piece  of  paper,  the  powder  spread  out  over 
the  paper,  and  the  paper  and  powder  then  rolled  up  into  a  small 
match-like  roll,  twisted,  set  on  fire  and  burned,  leaves  a  tasteless 
residue  of  pure  silver.  But  if  the  nitrate  contains  even  one  per 
cent,  of  any  saline  impurity,  the  residue,  instead  of  being  taste- 
less, will  have  the  sharp  alkaline  taste  of  the  base  of  the  adul- 
terating salt.  The  little  match  burns  rapidly  with  deflagration, 
as  may  be  seen  by  those  near,  the  carbon  of  the  paper  serving 
perfectly  to  reduce  the  silver,  and  in  great  measure  the  base  of 
the  adulterating  salt  also.  With  this  test  no  one  need  be  de- 
ceived by  "No.  2"  lunar  caustic,  nor  by  the  adulteration  of 
the  crystallized  nitrate  with  chlorate  of  potassa,  &c,  and  even 
