4i8 
Peroxide  of  Hydrogen. 
(  Am.  Jour.  Pharm, 
I      Aug.,  1879. 
watery  one  below,  a  cream  in  the  centre,  and  an  oily  stratum  at  the  top. 
After  the  lapse  of  several  hours  this  resolves  itself  into  two  layers. 
H  Ol.  Terebinth., 
Acid.  Acetic, 
Lin.  Camph.,. 
Tinct.  Quillaiae,  aa  partes  aequales. 
Shake  together  the  tincture,  camphor  liniment  and  oil  of  turpentine, 
and  then  add  the  acetic  acid  and  again  shake. — Pharm.  your.  Trans. 
[Lond.],  June  21,  1879. 
PEROXIDE  OF  HYDROGEN.1 
By  George  E.  Davis. 
Most  books  tell  us  that  H202  is  made  by  a  roundabout  process  with 
Ba02  and  HC1 ;  this  might  have  been  in  days  gone  by,  but  now  it  is 
made  principally  by  means  of  barium  peroxide  and  hydrofluoric  or  fluo- 
silicic  acids.  An  insoluble  fluoride  of  barium  or  fluosilicate  is  formed, 
which  separates  at  once  and  peroxide  of  hydrogen  remains. 
Now,  if  hydrofluoric  or  hydro-fluosilicic  acids  have  been  used,  we 
need  not  expect  to  find  hydrochloric,  as  this  latter  can  only  be  present 
when  impure  fluoride  is  used,  impure  acids  or  impure  water.  Of  course 
it  is  absolutely  necessary  to  examine  carefully  every  sample  of  peroxide 
of  hydrogen  which  may  be  purchased,  for  many  statements  have  been 
made  at  various  times  respecting  the  purity  of  the  bought  article.  One 
chemist  assured  me  that  the  first  lot  he  purchased  was  full  of  hydro- 
chloric acid,  whilst  another  chemist  actually  assured  me  that  peroxide 
of  hydrogen  would  not  oxidize  sulphide  of  sodium  in  vat  liquors.  More 
statements  than  these  have  been  made  respecting  the  efficiency  of  this 
reagent,  but  in  each  and  every  case  it  would  have  been  more  credit- 
able to  the  author  of  the  statement  had  he  examined  thoroughly  the 
facts  of  the  case  before  making  complaint  against  one  of  the  most  use- 
ful articles  used  in  chemical  analysis. 
Now,  the  first  thing  which  requires  to  be  estimated  is  the  active 
oxygen,  and  this  may  be  seen  when  I  state  that  the  sample  which  would 
not  oxidize  sulphide  of  sodium  contained  only  a  trace  of  active  oxygen. 
Many  methods  may  be  devised  for  estimating  the  strength  of  this 
1A  paper  read  before  the  Faraday  Club. 
