10       Bleaching  Powder  and  Analogous  Compounds.     { Am'janUri884 arm* 
shown  that  calcium  chloride,  when  treated  with  a  mixture  of  hypo- 
chlorous  anhydride  and  carbonic  anhydride,  forms  calcium  carbonate 
thus:  CaCl2+Cl20  +  C02=CaC03+2Cl2,  and  concludes  from  this 
that  calcium  chloride  is  present  as  such  in  bleaching  powder.  But 
the  authors  point  out  that  this  reaction  can  equally  be  explained  by 
the  intermediate  formation  of  bleaching  powder  and  its  subsequent 
decomposition  thus  :  CaCl.OH  +  HOC1  =  H20  +  CaCl.OCl  and 
CaC1.0Cl  +  C02=CaC03-j-Cl2.  To  prove  the  correctness  of  their 
interpretation,  a  series  of  experiments  were  conducted  in  which  pure 
hypochlorous  anhydride  was  passed  over  pure  calcium  hydroxychlo- 
ride,  CaCl.OH,  and  the  chloride ;  in  every  case  the  resultant  material 
always  contains  a  considerable  proportion  of  bleaching  powder  (mixed 
with  unaltered  chloride  and  traces  of  chlorate),  which  can  be  subse- 
quently decomposed  by  carbonic  anhydride.  Kraut's  experiments  are 
therefore  inconclusive. 
Secondly,  Kraut  having  established  that  when  lithium  hydroxide  is 
heated  with  chlorine,  only  half  of  it  is  attacked  with  formation  of 
LiCl-f  LiOCl,  draws  the  conclusion  that  as  the  lithium  hydroxide  is 
an  integral  part  of  the  resultant  compound,  so  calcium  hydroxide  is 
an  integral  part  of  bleaching  powder.  The  authors,  however,  show 
that  80  per  cent,  of  lithium  hydroxide  can  be  converted  into  the  mix- 
ture LiCl-f- LiOCl,  which  is  far  less  stable  than  bleaching  powder  in 
presence  of  excess  of  chlorine,  in  that  it  gives  off  oxygen,  the  presence 
of  which  could  be  recognized.  On  the  other  hand,  the  mixture  LiCl 
-f- LiOCl  is  far  more  stable  than  bleaching  powder  towards  carbonic 
anhydride ;  at  low  temperatures  it  is  practically  unaltered,  whilst  at 
higher  temperatures  the  mixture  is  converted  partly  into  the  chloride 
and  chlorate,  and  is  partly  decomposed  into  the  chloride  and  oxygen. 
The  gas  given  off  is  not  chlorine,  but,  hypochlorous  anhydride.  As 
the  properties  of  the  so-called  chloride  of  lithia  differ  so  markedly  from 
those  of  bleaching  powder,  a  different  constitution  must  be  assigned  to 
each.  Arguments  drawn  from  the  behavior  of  the  one  compound  have 
no  bearing  on  the  constitution  of  the  other. 
The  analogous  compounds  of  barium  and  strontium  were  also  exam- 
ined; that  of  barium  is  very  unstable,  whilst  that  of  strontium  is 
readily  prepared,  and  resembles  bleaching  powder  in  its  decomposition 
by  carbonic  anhydride. — Jour.  Chem.  Soc,  Nov.,  1883,  from  Annalen 
[219],  129-161. 
