Am  ju0iy!\§6arm'}  Various  Bleaching  Liquids.  345 
the  above  solutions,  or  even  passing  air  through  them,  almost  all 
the  hypochlorite  is  converted  into  chlorate,  a  small  portion  decom- 
posing into  chloride  and  free  oxygen.  Neither  chlorate  nor  free 
oxygen  (except  traces)  is  formed  when  chloride  of  lime  is  mixed  with 
sulphate  of  magnesia. 
Action  of  Chlorine  on  Zinc  Hydroxide. — With  the  solid  hydroxide 
only  a  trace  of  a  bleaching  compound  is  formed.  With  the  hydroxide 
suspended  in  water,  both  hypochlorite  and  chlorate  are  formed,  the 
latter  in  smaller  proportion  than  in  the  case  of  magnesia.  Heating 
converts  the  hypochlorite  partly  into  chlorate,  but  the  tendency  to 
decompose  into  chloride  and  free  oxygen  is  greater  than  with  mag- 
nesia hypochlorite. 
The  solution  obtained  by  mixing  a  zinc  salt  with  chloride  of  lime 
is  less  stable  than  the  corresponding  magnesian  solution. 
Aluminous  Bleaching  Liquids. — Aluminium  hydroxide  does  not 
absorb  chlorine.  The  solution  obtained  by  double  decomposition 
contains  chiefly  hypochlorite,  but  part  of  this  immediately  splits  up 
into  aluminium  hydroxide  and  free  hypochlorous  acid. 
Alteration  on  keeping. — Chloride  of  lime,  and  the  solutions  con- 
taining magnesium,  zinc,  and  aluminium  obtained  from  it  by  double 
decomposition,  change  very  slowly  in  the  dark,  but  on  exposure  to 
diffused  daylight  in  closed  vessels  rapidly  lose  nearly  the  whole  of 
their  bleaching  power. 
Conversion  of  Chloride  of  Lime  into  Chlorate. — Simple  boiling  is 
insufficient;  the  formation  of  chlorate  progresses  very  slowly,  and 
more  than  half  of  the  hypochlorite  decomposes  into  chloride  and 
oxygen.  If,  however,  the  liquor  is  saturated  with  free  chlorine, 
70  per  cent,  is  at  once  converted  into  chlorate  (with  the  correspond- 
ing chloride)  in  the  cold,  and  although  without  heat  the  further 
progress  of  the  change  is  very  slow,  yet  on  heating  to  boiling  it  is 
completed  without  loss  of  oxygen.  Passage  of  chlorine  during  the 
heating  is  prejudicial. 
Comparative  bleaching  experiments  with  the  bleaching  compounds 
of  the  above  four  metals  shows  that  the  zinc  solution  acts  the  most 
rapidly.  The  passage  of  carbonic  anhydride  for  a  short  time,  or  the 
addition  of  a  minute  quantity  of  acetic  or  oxalic  acid,  accelerates  the 
action  immensely.  When  used  in  excess,  the  three  acids  seem  to  be 
about  equally  active. — Jour.  Chem.  Soc,  1886,  p.  399. — Chem.  Lnd., 
1885,  p.  337. 
