540 
MANUFACTURE  OF  CHLORINE,  ETC. 
by  this  method  ;  but  it  was  soon  found  that,  when  using  lime  to 
decompose  the  chloride  of  manganese,  considerably  more  than 
half  the  protoxide  operated  upon  was  frequently  converted  into 
Mn02.  It  was  found,  eventually,  that  more  than  half  the  pro- 
toxide was  thus  peroxidised  only  when  more  lime  was  used  than 
simply  the  quantity  necessary  to  decompose  the  chloride  of  man- 
ganese, and  when  what  was  treated  vfith  air  was  thus  a  mixture 
of  protoxide  of  manganese  and  lime  ;  and  it  was  also  found  that 
in  all  such  cases  there  was  a  definite  relation  between  the  quantity 
of  lime  associated  with  the  protoxide  of  manganese  and  the  quan- 
tity of  the  protoxide,  in  excess  of  half,  which  became  peroxi- 
dised. This  led  to  the  discovery  that,  whereas  when  protoxide 
of  manganese  by  itself  is  treated  with  air  in  the  wet  way,  one- 
half  is  the  maximum  proportion  of  it  which  can  thereby  be  con- 
verted into  Mn02,  association  of  a  certain  proportion  of  litoe 
mth.  the  protoxide  so  treated  will  enable  the  whole  of  it  to  be- 
come converted  into  Mn02.  It  is  to  this  fact,  together  with 
that  of  the  much  greater  rapidity  with  which  protoxide  of  man- 
ganese can  be  peroxidised  by  treatment  with  air  in  the  wet  way 
when  lime  is  present  than  when  lime  is  not  present,  that  the 
practical  success  of  the  new  method  of  manufacturing  chlorine 
is  mainly  due. 
The  action  of  lime  in  increasing  the  proportion  of  protoxide 
of  manganese  which  can  be  peroxidised  by  treatment  with  air  in 
the  wet  way,  evidently  consists  in  the  lime  substituting  itself  for 
part  of  the  protoxide  which,  when  protoxide  of  manganese  not 
having  any  other  basic  substance  associated  with  it  is  treated 
with  air  in  the  wet  way,  does  not  undergo  peroxidation.  It  would 
seem  that  the  production  of  Mn02  in  the  wet  way  by  direct  com- 
bination between  hydrated  MnO  and  atmospheric  oxygen  abso- 
lutely requires  the  presence  of  a  base  with  which  the  MnOg  can 
combine  as  it  forms.  When  protoxide  of  manganese  not  having 
any  other  basic  substance  associated  with  it  is  treated  with  air 
in  the  wet  way,  a  part  of  the  protoxide  itself  has  to  act  as  the 
required  base ;  and  this  is  the  reason  why,  in  that  case,  not 
more  than  half  of  the  protoxide  can  become  peroxidised,  the 
other  half  being  required  to  combine  as  MnO  with  the  half  which 
becomes  converted  into  MnO^.    When,  however,  the  protoxide 
