Am.  Jour.  Pharrn.  \ 
August,  1900.  J 
Gasometric  Analysis. 
371 
mate  of  potassium  solution  in  G  and  2  c.c.  or  4  c.c.  of  hydrogen  dioxide 
in  the  homeo ;  fill  D  and  the  syphon-tube  as  previously  described 
and  proceed.  The  complete  decomposition  does  not  take  more  than 
two  or  three  minutes,  and  has  been  complete  in  one  minute.  It  is 
possible  to  use  the  bichromate  solution  over  and  over  again  ;  simply 
remove  the  homeo,  wash  this,  charge  with  dioxide  and  proceed  again. 
Divide  the  volume  of  the  displaced  water  by  the  volume  of  the 
dioxide  used  for  the  volume  strength  of  the  dioxide.  In  deter- 
mining the  strength  of  the  dioxide  by  the  U.S.P.  assay  process 
and  comparing  it  with  the  one  just  described,  it  was  found  that  the 
latter  gave  high  results,  due  particularly  to  effect  of  tempera- 
ture and  aqueous  tension  ;  the  solubility  of  oxygen  cannot  be  of 
much  consequence,  or  results  obtained  by  conducting  two  assays 
one  after  the  other  with  the  same  bichromate  solution  should  give 
somewhat  higher  results  in  the  second  assay,  but  this  was  not  the 
case.  The  effect  of  barometric  pressure  is  much  less  than  that  of 
the  two  first  mentioned,  and  can  ordinarily  be  left  out  of  considera- 
tion just  as  it  has  been  disregarded  in  the  Pharmacopoeia.  The 
following  corrections  for  temperature  and  tension  of  aqueous  vapor 
are  easily  applied,  and  then  give  results  comparing  very  closely  with 
the  U.S.P.  process : 
Temperature. 
For  Exact  Correc- 
tion Volume  of 
Gas  is  Divided  by 
For  Approximate 
Correction  Subtract 
from  Volume  of  Gas. 
Error  of 
Approximate 
Correction. 
Per  Cent. 
IO°  C. 
I  -0488 
7 
+  o-ii 
15°  C. 
1-0719 
tV 
4-  0-05 
20°  C. 
1*0967  * 
,  tV 
—  0-30 
25°  C. 
1*1236 
\ 
—  OT2 
300  c. 
1 -1533 
\  and  add 
—  o*i6 
35°  C. 
1-1866 
\  and  add  xfo 
—  0-I3 
400  C. 
1-2245 
\  and  add 
—  0*09 
RESULTS  OF  SOME  ANALYSES. 
U.S.P.  Process.1  New  Method. 
Approximate  Correc- 
Per  Cent.     Volumes  Volumes  Oxygen  tion  for  Nearest 
H202.        Oxygen.  Found.  Temperature. 
1   2-94  9-71  II*   at  250  C.  978ato°C. 
2   3-09  10-22  n "5  "  230  C.  10-23  "  o°  C. 
3    374  10*40  1175"  26°C.  10-45  "o°C. 
4   3-11  10-28  11*63"  26°  C.  10*34  "  o°  C. 
1  To  change  percentage  of  hydrogen  dioxide  into  volumes  of  available  oxygen,  divide  the 
percentage  by  o"30275  or  multiply  the  percentage  by  3"303. 
To  change  volume  of  available  oxygen  into  percentage  of  H0O2,  divide  the  volume  by 
3"303  or  multiply  the  volume  by  0'30275. 
