AmAJu°gu:-I?7h9!rm }  Peroxide  of  Hydrogen,  42 1 
works  that  cannot  be  readily  and  accurately  examined  except  by  its 
use  ;  such  as  the  total  alkali  and  crude  soda  liquors  or  in  black-ash,  and 
certain  qualities  of  soda-ash  which  contain  sulphides  or  sulphites.  In 
the  testing  of  chamber  exits  it  is  extremely  useful,  inasmuch  as  sul- 
phurous acid  is  not  an  acid  easily  titrated,  for  the  normal  sulphite  of  an 
alkali  is  not  neutral  to  test-paper,  and  therefore  on  titrating  a  sulphite 
with  standard  acid  the  point  of  neutrality  is  not  clearly  defined  and 
•distinct.  This  want  of  clearness  in  the  ending  has  been  stated  by 
some  chemists  to  be  due  to  the  carbonic  and  nitrous  acids  present  in 
chamber  exits,  but  add  peroxide  of  hydrogen  to  the  solution  and  all 
•difficulty  vanishes,  the  sulphurous  acid  is  oxidized  to  sulphuric,  which 
acid  is  easily  titrated. 
I  will  now  proceed  to  give  examples  of  its  use  in  various  methods 
•of  analysis.  Some  samples  of  soda-ash  contain  so  much  sulphite  of 
soda  that  it  is  impossible  to  estimate  the  amount  of  alkali  accurately 
by  means  of  standard  acid.  As  an  example  of  this  kind  of  ash  I  give 
the  following  analysis  of  a  sample  of  ash  made  from  caustic  salts,  which 
contained  by  the  acid  test  in  the  ordinary  way  30  per  cent,  of  alkali 
without  peroxide  of  hydrogen,  whilst  the  addition  of  a  few  cc.  brought 
down  the  actual  percentage  to  21.  The  escaping  carbonic  acid  carries 
away  a  great  deal  of  sulphurous  acid,  but  it  does  not  do  this  if  per- 
oxide of  hydrogen  is  present. 
Sodium  sulphide, 
0098 
sulphite, 
22982 
sulphate, 
2*207 
chloride, 
33-048 
silicate, 
1-214 
carbonate, 
18-704 
hydrate, 
.  i2-8oo 
Water, 
8747 
99'8°° 
Peroxide  of  hydrogen  is  very  useful  in  the  analysis  of  black-ash  ;  a 
few  cc.  added  to  the  liquor  under  examination  gives  at  once  the  total 
alkali,  which  number  needs  no  correction  for  sulphides,  hyposulphites, 
etc. 
This  reagent  is  very  useful  for  many  laboratory  oxidations,  such  as 
the  oxidation  of  iron  salts,  coloring  matters,  experiments  on  bleach- 
angs,  etc,,  etc.    In  fact  the  applications  of  this  useful  substance  are 
