394 
Gasometric  Analysts. 
( Am.  Jour.  Pharm. 
I     August,  1902. 
Estimation  of  Manganese  Dioxide. — This  substance  should  be  finely- 
powdered  to  facilitate  the  reaction.  0-2  —  0-3  gramme  are  placed 
in  the  generator  along  with  10  c.c.  diluted  H2S04  (if  the  sample  con- 
tains carbonates  allow  the  effervescence  to  cease  before  proceeding) ; 
adjust  funnel-tube  with  H202.  Add  5  c.c.  H202  through  the  funnel- 
tube  and  agitate  repeatedly  until  all  black  particles  disappear  and 
effervescence  ceases. 
0*3404  gramme  of  a  specimen  liberated  56*43  c.c.  gas  corrected  =  64*39  Per  cent. 
0-3164       "       "  "       52-45  "     "  =64-39  " 
0*2226       "       "  "  "       36*89  "     "        "        =64-37  " 
By  a  volumetric  titration  64-40  and  64-52  per  cent,  were  obtained. 
Estimation  of  Barium  Dioxide. — Thoroughly  mix  the  sample  and 
weigh  off  about  2  grammes;  add  10  c.c.  H20  and  then  sufficient  of 
a  cooled  mixture  of  10  c.c.  H3P04  and  30  c.c.  H20  to  make  50  c.c. 
Place  about  0-5  gramme  manganese  dioxide  and  10  c.c.  diluted 
H2S04  in  the  generator  (if  there  is  any  effervescence  wait  until  it 
ceases  before  proceeding) ;  adjust  funnel-tube  with  water.  Add 
5  c.c.  of  the  barium  dioxide,  or  rather  hydrogen  dioxide  solution 
prepared  from  the  barium  dioxide,  through  the  funnel-tube ;  follow 
this  with  10  c.c.  water  to  perfectly  rinse  the  former  solution  into  the 
generator ;  agitate  repeatedly  until  effervescence  ceases.  Subtract 
15  c.c.  from  the  volume  of  water  displaced.  2-7352  grammes  dis- 
solved as  above  gave  85-28,  85-75,  86-75,  85-75,  87-96,  87-71  and 
86-99  per  cent.  Volumetric  titration  before  and  after  the  above 
determinations  gave  86-22  per  cent.  The  varying  figures  are  easily 
explained  when  it  is  remembered  that  for  the  strength  of  solution 
used,  an  error  of  I  c.c.  in  reading  the  volume  of  displaced  water  is 
equivalent  to  2-76  per  cent. 
In  conclusion  the  writer  would  state  that  the  object  of  this  paper 
is  to  show  the  pharmacist  that  it  is  not  essential  to  have  a  well- 
equipped  laboratory  in  order  to  do  a  little  experimenting ;  and  I 
venture  to  say  that  one  taking  up  for  instance  the  hydrogen  dioxide 
assay  will  become  interested  in  this  little  apparatus  and  take  up  < 
some  of  the  other  determinations. 
