AmVune?Sarm'}        The  Pharmacopceial  Standard.  299 
These  results  would  indicate  that  the  decrease  in  strength  is  not 
constant,  but  is  most  rapid  at  first,  and  that  the  preparation  gradu- 
ally approaches  a  state  of  equilibrium. 
(2)  Liquor  Plumbi  Subacetatis  (Goulard's  Extract). 
"An  aqueous  liquid,  containing  in  solution  about  25  per  cent,  of 
lead  sub-acetate  (approximately  Pb20(C2H302)2  =  546'48)."— U.  S.  P., 
1890. 
A  batch  prepared  as  directed  by  the  U.  S.  P.,  1890,  contained  at 
different  periods : 
Per  Cent. 
Basic  Salt. 
April  17,  1895   25-19 
September  26,  1895   23  '40 
February  10,  1896   .  .  .  23*04 
May  7,  1896,  sample   22*99 
May  7,  1896,  bulk  t   22*94 
These  results  would  suggest  the  same  conclusion  as  drawn  in  the 
case  of  Labarraque's  solution  : 
(3)  Acidum  Sulphur osum  (Sulphurous  Acid). 
"A  liquid  composed  of  not  less  than  6  4  per  cent.,  by  weight,  of 
sulphurous  acid  gas  (S02)  and  not  more  than  93-6  per  cent,  of 
water."— U.  S.  P.,  1890. 
Two  lots  were  examined  : 
Per  Cent.  S02. 
(A)  One  gallon,  tested  on  December  10,  1895,  showed  .......  6*55 
Same,  tested  on  January  31,  1896,  showed   6*38 
The  fluid  had  been  placed  in  a  stone  jug,  the  latter  securely  stop- 
pered with  a  paraffined  cork,  put  into  a  cool  place  and  had  never 
been  opened  in  the  interim.  The  decrease  in  strength,  amounting 
to  2*6  per  cent,  of  the  S02  originally  present,  cannot  be  due  alto- 
gether to  oxidation  caused  by  air  contained  in  the  solution,  for  a 
simple  calculation  will  demonstrate  that  were  the  solution  saturated 
even  with  oxygen  at  150  C,  this  amount  could  oxidize  at  most  but 
0-3  per  cent,  of  the  S02  originally  present. 
(B)  A  two-gallon  lot  in  stone  jug,  closed  securely  by  a  cork.  A 
small  part  of  it  was  withdrawn  on  a  purchase  prior  to  March  5th. 
On  March  8th,  it  was  poured  into  three  5-pint  glass-stoppered 
bottles,  the  stoppers  having  been  previously  dipped  into  melted 
paraffine,  was  tested  immediately  after  filling,  and  again  on  May 
