Am.  Jour.  Pharm.  \ 
August,  1896.  J 
Solution  of  Lead  Sitbacetate. 
429 
visible.  The  methyl  orange  was  added,  however,  to  each  subse- 
quent sample  titrated  simply  to  approximately  indicate  the  end  of 
the  reaction,  which  was  determined  by  allowing  the  precipitated 
lead  sulphate  to  settle  and  adding  the  volumetric  solution  drop  by 
drop,  until  a  turbidity  was  no  longer  produced  in  the  supernatant 
liquid.  Duplicate  titrations  were  made  with  each  sample  and  the 
average  taken  to  calculate  the  percentage  of  lead  subacetate. 
The  samples  made  with  the  British  proportions  showed  the  follow- 
ing results: 
Per  Cent. 
Samples  1,  2  and  3,  cold  digestion  for  one  day  ....  29*0,  297,  297 
Sample  4,  cold  digestion  for  one  day  (common  lead 
acetate)   25-5 
Sample  5,  cold  digestion  for  two  days   22*9 
Samples  6  and  7,  cold  digestion  for  one  week    ....  294,  304 
Sample  8,  cold  digestion  for  two  and  one-half  weeks  .  307 
Samples  9  and  10,  half-hour's  boiling   31'!,  30*1 
It  will  be  noticed  that,  according  to  the  table,  sample  5  was 
weaker  than  sample  4,  which  was  made  in  a  shorter  time.  This 
seeming  irregularity  came  about  through  the  sample  having  been 
contained  in  a  bottle  having  a  defective  cork  for  two  weeks  before  it 
was  titrated  ;  thus  it  had  been  permitted  to  absorb  carbon  dioxide 
from  the  air  and  become  thereby  deteriorated. 
To  determine  the  rapidity  of  this  change,  experiments  were  made 
on  sample  9,  which,  when  freshly  prepared,  showed  31-1  per  cent,  of 
lead  subacetate  ;  upon  standing  for  one  week  uncorked,  the  sample 
was  found  to  contain  30*1  per  cent.,  and,  after  another  week's  expo- 
sure, but  29  6  per  cent,  was  present.  The  precipitate  which  formed 
during  the  exposure,  proved  to  be  a  carbonate  of  lead. 
With  the  proportions  of  the  United  States  Pharmacopoeia  the  fol- 
lowing results  were  obtained  by  cold  digestion. 
Per  Cent. 
Samples  11  and  12,  one  day  17*0,  17 '6 
Sample  13,  one  day  (common  acetate)   18*3 
Sample  14,  two  days   18*3 
Sample  15,  two  days  (5  percent,  glycerin)   18 "2 
Sample  16,  one  week   18*4 
Sample  17,  two  weeks   19*8 
Samples  18  and  19,  by  half-hour's  boiling  22 '9,  20*5 
The  results  yielded  by  samples  18  and  19  seem  to  indicate  an  im- 
probability of  attaining  the  official  standard  of  25  per  cent,  when 
following  the  official  directions.and  the  other  results  show  the  chances 
