74       Chemical  Constitution  of  Bleaching  Powder.  {Km'&x.i^m' 
for  this  as  follows  :  In  presence  of  moisture  a  portion  of  the  com- 
pound 2CaHC102  in  the  already  formed  chloride  is  decomposed  into 
CaCl202  and  CaH202,  the  latter  in  presence  of  more  chlorine,  then 
giving  CaHClCX.  The  following  reaction  may  alse  take  place, 
2CaH202  +  4CI  =  CaCl202  +  CaCl2  +  2H20,  and  when  we  have 
the  two  results,  aCaHCIO,  +  CaCl2  +  2H20  and  CaCl202  +  CaCl2 
+  2H20,  the  strength  of  equal  parts  of  such  a  mixture  (chloride  of 
lime)  would  be  43*5  per  cent,  actual  chlorine  ;  in  the  proportion  of  5  : 
1  =  40*5  per  cent.,  and  in  that  of  10  :  1  =  40*0  per  cent.  It  is  con- 
cluded that,  with  the  help  of  the  water  liberated  from  the  dry 
hydrate  in  its  conversion  into  chloride  of  lime,  together  with  that  con- 
tained in,  and  carried  along  with  the  chlorine  gas,  the  already  described 
decompositions  of  the  chloride  of  lime  may  take  place,  so  that  the 
amount  of  actual  chlorine  in  the  product  will  rise.  This  view  is  sup- 
ported by  the  fact  that  in  a  manufactured  sample  of  chloride  of 
lime,  prepared  from  calcium  hydrate  which  contained  about  8  per  cent* 
of  water  in  excess,  besides  the  compound  CaClH02,  also  calcium 
hypochlorite  occurs  in  varying  quantities.  On  suspending  calcium 
hydrate  in  water,  and  passing  a  current  of  chlorine  through  the  mix- 
ture, till  alkalinity  disappeared,  and  all  the  lime  had  dissolved,  it  was 
found  that  the  following  equation  was  exactly  realized  :  2CaH202  -f- 
4CI  =  CaCl202  +  CaCl2  +  2H20.  This  was  proved  by  estimating 
in  equal  volumes  of  the  solution,  first  the  actual  chlorine,  secondly  the 
lime.  Of  course  the  most  conclusive  proof  of  the  existence  of  calcium 
hypochlorite  in  the  chloride  of  lime  solutions,  is  that  Kingzett  has 
obtained  crystals  of  calcium  hypochlorite  from  such  solutions  by 
evaporation,  in  a  vacuum  over  sulphuric  acid,  or  by  cooling  a  concen- 
trated solution  below  o°.  J.  Kolb  has  observed  that  carbonic  acid 
decomposes  chloride  of  lime,  liberating  hypochlorous  acid  and  leaving 
calcium  carbonate.  The  author  has  had  a  sample  of  chloride  of  lime, 
which  was  thus  reduced  from  25  per  cent,  to  7  per  cent,  actual  chlor- 
ine, the  amount  of  calcium  carbonate  having  risen  to  over  40  per  cent* 
The  workmen  can  distinguish  the  hypochlorous  acid  from  the 
chlorine  by  the  slower  action  which  the  former  exerts  upon  the  lungs, 
and  by  its  sweetish  taste. — Jour.  Chem.  Soc.  [Lond.],  Dec,  1876,  from 
Ding/.  Polyt.  J.,  ccxxi,  243-250. 
