AmFe°b.?i7h7arm"}  Chemical  Constitution  of  Bleaching  Powder.  73 
ing  it  in  contact  with  water  it  splits  up  into  calcium  hypochlorite  and 
(hydrate  : 
(1)  .  3CaH202    +  4CI     =  2CaHC102  +  CaCl2  +  2H20. 
(2)  .  2CaHC102  +  Water  =  CaCl202  +  CaH202. 
Experiments  led  to  verification  of  the  results  of  Graham,  Bolley, 
Tschigianjanz,  Fricke  and  Reimer,  that  some  calcium  hydrates,  dried 
at  100°,  absorbed  scarcely  any  chlorine,  whereas  others  under  the 
same  conditions  yielded  good  products.  Dried  over  sulphuric  acid, 
the  limes  absorbed  chlorine  readily.  In  the  latter  cases,  however,  it 
is  considered  that  a  small  quantity  of  water  is  still  present  in  the 
hydrate,  which  is  a  necessary  condition  for  the  absorption  of  the  gas. 
o*4  per  cent,  of  water  or  more  in  the  hydrate  is  sufficient,  so  that 
chloride  of  lime  may  be  formed  at  0°,  but  if  the  hydrate  has  been  dried 
at  ioo°  to  1300,  it  cannot  be  converted  into  chloride  of  lime,  unless 
the  latter  undergoes  a  rise  in  temperature.  In  his  experiments  the 
author  worked  upon  quite  pure  materials,  and  with  scientific  exactness. 
A  low  temperature  was  found  to  be  unfavorable  to  the  formation  of 
chloride  of  lime,  or  at  least  to  impede  it.  It  was  found  difficult  to 
account  for  the  indisposition  of  certain  limes  to  absorb  chlorine  gas. 
A  calcium  hydrate  with  a  slight  excess  of  free  water  gave  a  chloride 
of  lime  no  stronger  than  when  a  dry  hydrate  was  used,  but  the  former, 
under  favorable  conditions,  might  be  made  to  absorb  more  chlorine, 
and  finaily  attain  a  strength  indicated  by  39  per  cent,  of  available 
chlorine.  It  was  also  found  that  a  quick-lime,  which  slaked  with 
difficulty,  is  less  to  be  recommended  for  chloride  of  lime  manufacture 
than  one  which  slakes  quickly.  A  lime  of  the  former  description 
absorbed  the  chlorine  much  more  slowly,  and  gave  a  chloride  of  lime 
of  only  31  to  35  percent. 
The  following  formula  represents  the  formation  of  chloride  of  lime 
as  bearing  out  the  experimental  results  obtained  : 
3CaH202  +  4C1  =  2CaHC102  +  CaCl2  +  2H20. 
That  water  was  liberated  from  perfectly  dry  calcium  hydrate,  on  treat- 
ment with  chlorine,  was  made  manifest  by  the  drops  of  water  collected 
in  the  in-let  tube.  In  certain  cases  a  chloride  of  lime  is  obtained  con- 
taining upwards  of  40  per  cent,  of  chlorine.  Gopner,  by  passing  the 
chlorine  through  warm  water  of  6o°  to  700,  obtained  ■  a  chloride  of 
lime  of  4o'2,  and  another  of  42^84  per  cent.    The  author  accounts 
