Am.  Jour.  Phartn. ) 
February,  1902.  1 
Seidlitz  Powders. 
75 
subject,  and,  if  possible,  present  a  method  of  analysis  which  it 
would  be  practicable  for  the  average  pharmacist  to  carry  out. 
The  most  able  effort  on  the  subject  which  has  come  to  the  writer's 
notice  is  a  paper  by  Joseph  Huntington,  which  was  published  in 
the  American  Journal  of  Pharmacy,  1900,  p.  461,  and  reprinted  in 
a  number  of  other  pharmaceutical  journals. 
In  this  the  U.S.P.  method  of  titration  with  potassium  hydrate 
volumetric  solution  was  used  for  tartaric  acid.  An  indistinct  end 
reaction  is  here  encountered,  unless  carried  out  in  hot  solution,  on 
account  of  a  precipitate  of  potassium  bitartrate. 
The  method  for  the  estimation  of  the  Seidlitz  mixture  consists  in 
first  estimating  the  sodium  bicarbonate  by  adding  an  excess  of 
sulphuric  acid  volumetric  solution  and  titrating  back  with  potassium 
hydrate  volumetric  solution.  Second,  another  portion  of  the  Seid- 
litz mixture  is  ignited,  taken  up  with  water,  and  titrated  as  in  the 
previous  case.  The  amount  of  solution  required  for  the  sodium 
bicarbonate  alone  is  then  subtracted,  the  remainder  representing  the 
Rochelle  salt. 
This  method  gave  31*44  per  cent,  sodium  bicarbonate  and  85-86 
per  cent.  Rochelle  salt,  making  a  total  of  117*3  Per  cent. 
The  17-3  per  cent.,  which  this  runs  high,  was  accounted  for  from 
the  fact  that  the  work  had  been  done  in  a  warm  room,  which  had 
caused  a  loss  of  moisture.  No  experiments  were  made,  however, 
to  prove  the  latter  theory. 
As  can  be  seen,  the  working  of  this  method  is  not  at  all  satisfac- 
tory, and  the  inaccuracy  of  the  final  result  does  not  justify  the  effort 
required. 
The  experiments  which  the  writer  has  carried  out  on  the  subject 
will  here  be  described  and  the  conclusions  reached  noted. 
A  series  of  experiments  were  carried  out  with  chemically  pure  salts 
to  ascertain  the  possibilities  and  to  afford  a  means  of  comparison  for 
the  work  on  the  samples  to  follow. 
Sodium  hydrate  volumetric  solution  was  used  for  the  titration  of 
the  tartaric  acid,  the  precipitation  thus  being  avoided,  and  perfectly 
satisfactory  results  being  obtained  in  the  cold. 
Experiments  were  then  made  with  the  ingredients  of  Seidlitz 
mixture  to  ascertain  the  effect  of  exposure  under  various  condi- 
tions. Quantities  of  Rochelle  salt  and  sodium  bicarbonate,  corre- 
sponding to  the  weights  given  by  the  U.S.P.  for  one  powder,  also 
