Am.  Jour  Phartn. ) 
Aug.,  1879.  J 
Peroxide  of  Hydrogen. 
419 
article.  I  have  used  the  following  three  methods  with  satisfactory 
results :  %  / 
1  cc.  was  put  into  Crum's  tube  over  mercury  and  run  underneath  the 
tap;  then  5  cc.  of  a  saturated  solution  of  bichromate  of  potash,  the 
whole  gently  agitated,  the  liberated  oxygen  measured  and  corrected  for 
temperature  and  pressure.  In  working  on  a  certain  sample  as  a  mean 
of  several  experiments,  1  cc.  gave  8  2  cc.  of  oxygen  at  o°C.  and 
760  mm. 
By  a  second  method  10  cc.  of  the  peroxide  were  boiled  with  20  cc. 
-of  sulphurous  acid,  and  the  sulphuric  acid  which  was  formed  precipi- 
tated as  barium  salt  and  weighed  ;  the  sulphuric  acid  existing  as  such 
in  the  sulphurous  acid  being  deducted  from  the  precipitate.  10  cc. 
oxidized  0*46  gram  S02,  or  7*08  grs. 
N 
By  a  third  method  10  cc.  of  the  peroxide  oxidized   146  cc.  — 
10 
protosulphate  of  iron.  Now  if  we  calculate  these  we  shall  find  that  our 
first  method  gives  the  strength  of  the  solution  as  8*2  volumes,  and  they 
all,  when  expressed  as  in  grams  of  oxygen  per  liter,  show  11*72, 
11-53,  u-68. 
For  general  work  the  bichromate  method  is  preferable,  though  when 
extreme  accuracy  is  required  the  iron  method  may  be  employed  if  con- 
ducted in  a  stream  of  carbonic  acid. 
Now,  as  to  the  stability  of  peroxide  of  hydrogen.  It  has  been  stated 
quite  recently,  and  by  one  of  the  members  of  this  Club,  that  it  is  so 
unstable  that  simply  drawing  air  through  a  solution  of  it  will  abstract 
the  whole  of  its  active  oxygen.  I  don't  know  what  amount  of  air  is 
considered  necessary,  but  I  should  say  a  great  deal,  and  neither  do  I 
know  what  tests  he  used  to  ascertain  that  there  was  no  peroxide  left 
undecomposed.  An  alkaline  solution  of  peroxide  is  partly  decomposed 
by  agitation  only,  but  an  acid  or  neutral  solution  is  very  stable.  An 
alkaline  solution  of  peroxide  has  been  used  over  a  very  long  time  in 
connection  with  a  continuous  aspirator,  10  cc.  of  peroxide  and  the 
necessary  quantity  of  water  aspirated  through  at  a  speed  of  15  cubic 
feet  per  twenty-four  hours  has  shown  an  excess  of  peroxide  at  the 
finish  of  the  experiment,  even  when  caustic  soda  was  present  in  excess 
also.  I  have  evaporated  a  10-volume  solution  of  peroxide  to  half  its 
bulk  without  driving  off  more  than  two-thirds  its  active  oxygen,  but 
when  reduced  to  that  bulk  caustic  soda  was  added,  the  elimination  of 
