302 
The  Pharmacopceial  Standard. 
f  Am.  Jour.  Pbarm. 
I       June,  1896. 
These  results,  in  part,  seem  to  confirm  those  obtained  in  the  case 
of  spirit  of  ammonia,  inasmuch  as  the  use  of  paraffine  in  connection 
with  glass- stoppered  bottles  does  not  completely  prevent  the  escape 
of  ammonia.  The  loss  is  not  so  marked  in  this  case,  probably 
because  the  percentage  (8-15  per  cent,  by  volume)  is  lower  than  in 
the  case  of  the  spirit  of  ammonia,  which  was  10-47  Per  cent,  by 
weight. 
It  will  be  observed  that  such  substances  as  those  herein  enumer- 
ated, under  class  A,  must  necessarily  deviate  from  the  pharmaco- 
pceial standard.  The  question  to  be  determined  is  what  latitude 
should  be  permitted,  a  point  upon  which  the  writer  has  purposely 
aimed  not  to  commit  himself,  as  it  would  manifestly  be  out  of  place 
for  him  to  do  so.  In  the  case  of  some  members  belonging  to  this 
class,  e.  g.,  Labarraque's  solution  and  Goulard's  extract,  the  rate  of 
deterioration  as  shown  by  these  experiments  is  rapid  at  first,  but  de- 
creasingly  so  thereafter,  and  yet  other  shop  conditions  might  give  dif- 
ferent results.  Spirit  of  nitrous  ether  is  a  conspicuous  member  of 
this  class,  but  is  not  reported  herein,  as  the  writer  hopes  to  make 
that  substance  the  subject  of  a  special  paper  for  another  occasion. 
CLASS  B. 
A  representative  of  this  class  of  substances  may  be  sufficient  to 
cite : 
Liquor  Ferri  Subsulphatis  (Monsel's  solution)  and  Liquor  Ferri 
Tersidphatis  (solution  of  ferric  sulphate). 
The  direction  given  by  the  U.  S.  P.  for  making  these  preparations 
must  be  considered  rather  vague  and  indistinct  if  the  finished  pro- 
duct should  conform  to  the  tests  which  immediately  follow  them. 
For  example,  the  boiling  liquid  may  be  "free  from  nitrous  odor," 
and  still  not  stand  the  test  for  the  absence  of  nitric  acid  demanded 
subsequently. 
These  tests  may  be  construed  to  demand  the  strict  absence  of  both 
an  excess  of  nitric  acid  and  ferrous  salt,  a  demand  not  easily  com- 
plied with ;  for  while  it  is  an  easy  matter  to  entirely  exclude  either, 
leaving  a  slight  excess  of  the  other,  it  is  impractical,  to  say  the  least, 
to  exclude  them  both  to  that  exactness  which  the  wording  of  the 
tests  of  the  U.  S.  P.  implies.  In  our  experience  it  has  occurred  that 
the  liquid,  holding  in  solution  a  slight  yet  perceptible  excess  of  fer- 
rous salt  and  a  very  slight  excess  of  nitric  acid,  still  showed  reaction 
for  both  substances  after  prolonged  boiling. 
