Am.  Jour.  Pharm.) 
August,  1902.  J 
Gasometric  Analysis. 
393 
(3)  CaOC!2  -f  H202  =  CaCl2  +  H20  +  02. 
(4)  BaG2  -f  2H3?04  =  BaH4  (P04)2  -f  H202. 
(5)  Mn02  +  H2S04  +  H202  =  MnS04  +  2HaO  -f  02. 
The  strength  ot  the  hydrogen  dioxide  is  not  material,  providing 
a  sufficient  quantity  be  used;  this  is  best  determined  by  making  a 
gasometric  estimation  of  the  sample  of  H202  to  be  used.  The  quan- 
tity of  gas  evolved  should  exceed  that  evolved  in  the  estimations 
of  available  chlorine  in  chlorine  water,  chlorinated  lime  and  Labar- 
raque's  solution ;  in  the  estimations  of  manganese  dioxide  and 
barium  and  dioxide  one-half  of  the  evolved  gas  is  to  be  compared 
with  the  volume  evolved  from  the  H202. 
AVAILABLE  CHLORINE  ESTIMATIONS. 
In  Chlorine  Water. — Place  5  c.c.  solution  of  soda  (5  per  cent.)  and 
20  c.c.  chlorine  water  in  generator;  adjust  funnel-tube  with  H202. 
Add  5  c.c.  H202  through  funnel-tube  as  rapidly  as  possible,  agitate 
the  generator  for  a  few  seconds  only,  and  as  soon  as  the  dropping 
of  the  displaced  water  ceases  (the  apparatus  for  the  determination 
of  available  chlorine  should  be  raised  so  that  the  end  of  the  siphon- 
tube  will  not  be  immersed  in  the  displaced  water),  measure  the  dis- 
placed water.  After  standing  less  than  two  minutes  a  slow  decom- 
position of  the  excess  of  H202  commences,  which  is  to  be  diregarded. 
An  old  specimen  of  chlorine  water  by  volumetric  titration  gave 
0-0669  per  cent. ;  by  the  gasometric  method  0-062,  0-069  and  0-0655 
per  cent ;  a  more  recent  specimen  017  per  cent,  by  titration,  against 
01 79,  0-172  and  0-172  per  cent,  by  gasometric  method. 
In  Solution  of  Chlorinated  Soda. — Place  5  c.c.  Labarraque's  solu- 
tion and  5  c.c.  H20  in  the  generator;  adjust  funnel-tube  with  H202. 
Add  5  c.c.  H2Oa  and  proceed  as  under  chlorine  water. 
With  a  specimen  (sp.  gr.  1-050)  i-io  per  cent,  available  chlorine 
was  found  against  1094  per  cent,  by  volumetric  titration. 
In  Chlorinated  Lime. — This  substance  varying  considerably  in 
strength  in  different  portions  of  the  same  lot,  about  2  grammes  are 
to  be  weighted  off  after  mixing,  triturated  in  a  mortar  with  water 
and  finally  made  up  to  100  c.c.  Place  10  c.c.  of  this  turbid  mixture 
in  the  generator;  adjust  the  funnel-tube  with  H202.  Add  5  c.c. 
H202  and  proceed  as  under  chlorine  water. 
1-8352  grammes  treated  as  above  gave  uniformly  30-07  per  cent, 
against  30-08  per  cent,  by  volumetric  titration. 
