558 
Bromine  in  Analytical  Chemistry. 
f  Am.  Jour.  Pharm». 
\    Dec.  1, 1871. 
not  contain  more  than  J  per  cent,  of  chlorine.  The  employment  of 
gas  is  troublesome,  as  an  apparatus  must  be  arranged  for  every  oxi- 
dation. 
Bromine  therefore  seems  to  me  to  be  the  oxydizing  material  which, 
being  free  from  the  drawbacks  that  prevent  the  general  employment 
of  the  three  above  mentioned  substances,  deserves  a  place  in  qualita- 
tive as  well  as  quantitative  analysis. 
I  employ  the  bromine  principally  in  three  forms,  as  free  bromine, 
as  bromine-water,  and  as  bromine  in  concentrated  hydrochloric  acid. 
Bromine-water,  prepared  by  shaking  an  excess  of  bromine  with  water, 
contains  between  two  and  three  per  cent,  of  bromine.  Concentrated 
hydrochloric  acid,  treated  in  the  same  way,  furnishes  a  solution,  con- 
taining about  thirteen  per  cent,  of  bromine.  In  choosing  for  each, 
case  the  oxidizing  material  as  to  quantity  and  concentration,  an 
excess  may  be  easily  avoided,  and  the  prominent  odor  and  color  of 
bromine  furnish  the  best  means  to  recognize  an  excess,  which  can  be 
driven  off  easily  by  boiling,  on  account  of  the  low  boiling  point  of 
bromine.  Bromine  water  attacks  platinum  neither  in  alkaline  nor 
acid  solutions,  if  the  latter  are  free  from  nitric  acid,  and  it  is,  in  this 
shape  or  dissolved  in  hydrochloric  acid,  without  action  on  paper,  so 
that  a  metallic  sulphide  may  be  dissolved  and  oxidized  in  presence  of 
the  filter  paper  by  means  of  bromine,  when  the  oxide  can  be  com- 
pletely precipitated  by  potassa  or  ammonia. 
I  have  employed  bromine  most  advantageously  for  the  oxidation  of 
sulphur,  sulphydric  acid  and  metallic  sulphides.  For  two  and  a  half 
years  it  has  been  my  solvent  for  sulphur,  magnetic  pyrites,  copper 
pyrites,  mispickel,  nickel  mattes,  and  precipitated  sulphides,  both  for 
the  determination  of  sulphuric  acid  and  the  metals. 
Sulphur,  shaken  with  bromine  and  water,  is  easily  converted  into 
bromohydric  and  sulphuric  acids,  if  for  every  atom  of  sulphur  three 
of  bromine  are  present,  or  fifteen  by  weight  of  bromine  to  one  of  sul- 
phur. If  sulphur  has  to  be  determined  in  this  way  it  is  best  to  add 
all  the  bromine  at  once,  so  that  no  sulphide  of  bromine  can  be  formed. 
In  the  treatment  of  pyrites,  no  necessity  will  exist  for  pulverizing 
them  very  finely,  as  they  are  oxidized  by  bromine  quite  easily  even 
in  larger  pieces,  but  it  is  best  to  add  water  first  and  then  bromine 
with  constant  stirring,  that  the  action  may  not  become  too  violent. 
Bromine-water  is  the  most  convenient  material  for  the  destruction 
of  hydrosulphuric  acid.    A  few  drops  of  it  added  to  a  filtrate  from  a 
