544  MANUFACTURE  OF  CHLORINE,  ETC.  " 
manganese  is  converted  into  MnOg;  and  this,  of  course,  would 
be  a  very  important  consideration,  even  if  the  transformation  of 
chloride  of  manganese  into  manganite  of  calcium  occupied  the 
same  time  as  its  transformation  into  manganite  of  manganese. 
Really,  however  (and  this  is  the  second  reason),  the  former 
operation,  in  which  all  the  manganese,  is  converted  into  MnOg, 
does  not  occupy  more  than  one-fifth  of  the  time  required  for  the 
latter  operation,  in  which  only  half  the  manganese  is  converted 
into  MnOg ;  and  hence,  while  the  manufacture  of  chlorine  by 
means  of  perpetually-regenerated  manganite  of  calcium  effects 
the  very  considerable  economy  above  stated,  it  is  questionable 
whether  chlorine  could  be  manufactured  by  means  of  manganite 
of  manganese  regenerated  by  the  same  method  so  cheaply  as  by 
means  of  manganese  ores. 
The  length  of  time  Avhich,  when  protoxide  of  manganese  by 
itself  is  treated  with  air  in  the  wet  way,  is  required  for  its  com- 
plete conversion  into  sesquioxide  is  very  remarkable,  and  the 
fact  that  hydrated  protoxide  of  manganese  is  somewhat  freely 
soluble,  alike  in  ^'ater  and  in  neutral  solution  of  chloride  of 
calcium,  would  seem  to  have  something  to  do  with  it.  It  is  a 
curious  fact  that  the  peroxidation  of  protoxide  of  manganese  by 
treatment  with  air  in  the  wet  way  is  greatly  retarded  by  the 
presence  in  the  medium  in  which  the  protoxide  is  suspended  of 
any  proto-compound  of  manganese  in  the  state  of  solution.  Thus, 
in  a  solution  of  either  chloride  or  any  other  proto-salt  of  man- 
ganese, peroxidation  will  go  on  only  extremely  slowly  ;  and 
solution  of  the  protoxide  itself,  which  will  be  present  until  the 
very  end  of  the  operation  when  protoxide  alone  is  treated  with 
air  in  the  wet  way,  has  the  same  retarding  influence.  On  the 
other  hand  when  treating  with  air  a  mixture  of  protoxide  of 
manganese  and  lime  suspended  in  solution  of  chloride  of  calcium, 
there  are  formed  solutions  containing  peroxide  of  manganese, 
in  the  presence  of  which  peroxidation  goes  on  with  extreme  ra- 
pidity. All  these  solutions  are  more  or  less  deeply  colored, 
solution  of  the  protoxide  being  without  color.  I  exhibit  a  sam- 
ple of  one  of  the  colored  solutions,  called  by  the  workmen  "  the 
port-wine  solution.''  The  nature  of  these  colored  solutions  has 
not  yet  been  fully  investigated,  but  I  believe  them  to  consist  of 
