POTASSIUM  PERCHLORATE.  491

Potassium  chlorate  crystallizes  in  lustrous  crystals  of
the  monocliriic  system.  Its  taste  is  somewhat  like  that
of  saltpeter.  It  melts  at  a  comparatively  low  tempera-
ture (334°),  and  at  352°  begins  to  decompose,  with  evolu-
tion of  oxygen.  At  ordinary,  temperatures  100  parts  of*
water  dissolve  6  parts  of  the  salt,  and  at  the  boiling  tem-
perature 60  parts.  In  consequence  of  the  ease  with
which  it  gives  up  its  oxygen,  the  chlorate  is  an  excellent
oxidizing  agent,  and  it  is  constantly  used  in  this  capacity
in  the  laboratory.  Its  oxidizing  action  is  well  illus-
trated by  grinding  a  very  little  of  it  in  a  mortar  with  a
little  sulphur,*  when  an  explosion  takes  place.  With
phosphorus  the  action  is  exceedingly  violent.
The  chief  uses  of  potassium  chlorate  are  for  the  prep-
aration of  oxygen,  and  in  the  manufacture  of  matches
and  fireworks.  The  tips  of  Swedish  safety  matches  are
made  of  potassium  chlorate  and  antimony  sulphide.
The  surface  upon  which  they  are  rubbed  to.  ignite  them
contains  red  phosphorus.  The  chlorate  is  frequently
used  in  medicine,  particularly  as. a  gargle  in  cases  of
sore  throat.
