392 
Gasometric  Analysis. 
I  Am.  Jour.  Pharru. 
\     August,  1902. 
No  correction  is  applied  for  the  volume  of  gas  being  under  other 
than  normal  conditions,  for  the  reason  that  in  the  decomposition  of 
urea  there  is  involved  a  loss  of  about  9  per  cent,  nitrogen,  and  this 
loss  is  just  about  balanced  by  the  effect  of  temperature,  pressure 
and  tension  of  aqueous  vapor  under  ordinary  conditions. 
In  the  following  estimations  in  which  oxygen  is  evolved*,  a  cor- 
rection has  to  be  made  tor  the  increase  in  volume  of  the  gas  through 
the  influence  of  temperature  and  the  tension  of  aqueous  vapor.  The 
following  table  is  taken  from  the  previous  paper : 
Error  of 
For  Exact  Correc- 
For Approximate 
Approximate 
tion.  Volume  of 
Correction,  Subtract 
Correction. 
Temperature. 
Gas  is  Divided  by 
from  Volume  of  Gas. 
Per  Cent. 
IO°  C. 
I-0488 
1 
2"2 
4-  o*ii 
15°  C. 
1-0719 
1 
T5 
+  0-05 
2O0  C. 
1-0967 
TT 
—  0-30 
25°  C. 
1-1236 
1 
9  - 
—  0'12 
30°  C. 
1*1533 
\  and  add  Tl  Q 
—  o-i6 
35°  C. 
r  1866 
I  and  add  T^ 
—  013 
•  400  C. 
1-2245 
£  and  add  -5\ 
—  0-09 
V  0-0030385  H20.2 
1  c.c.  oxygen  under  normal  conditions  is  equiva-  j  0-0031684  CI 
lent  to  1  0-0038841  Mn02 
0-0075613  Ba02 
Estimation  of  Hydrogen  Dioxide. — Place  10  to  20  c.c.  of  a  satu- 
rated solution  of  potassium  bichromate  in  generator ;  adjust  funnel- 
tube  with  hydrogen  dioxide.  Add  5  c.c  hydrogen  dioxide  through 
funnel-tube ;  agitate  and  allow  to  stand  until  the  solution  in  the 
generator  assumes  its  original  color.  Example :  67  c.c.  water  dis- 
placed less  5  c.c.  liquid  added  through  funnel-tube  gives  62  c.c.  gas 
at  250  C.  cr  55-12  c.c.  corrected;  55-12  5  (c.c.  H202  used)  = 
11-02  volume  or  55-12  X  -0030385  =  015557  H202  in  5  c.c.  or 
3.349  per  cent. 
As  the  potassium  bichromate  suffers  no  permanent  change  in  this 
estimation,  quite  a  number  of  determinations  of  the  same  H202  can 
be  made  by  simply  filling  up  the  reservoir  again,  as  the  water  in 
this  runs  low,  before  adding  the  next  portion  of  H202  through  the 
funnel-tube. 
The  following  determinations  are  made  possible  by  the  ready 
decomposition  of  hydrogen  dioxide  in  the  presence  of  other  chem- 
icals, thus  we  have: 
.  (L)  Cl2  -f  2NaOH  =  NaOCl  +  NaCl  +  H20. 
(2)  (NaOCl  +  NaCl)  +  H202  =  2NaCl  +  H20  4-  02. 
