286  Manufacture  of  Sulphuric  Acid.  {Amjj££ifo£arm' 
although  there  is  no  difference  in  the  fundamental  chemical  reaction. 
It  merely  replaces  the  gaseous  carrier  of  oxygen  by  the  use  of  a 
solid  contact  material,  which  by  its  catalytic  action  brings  about  the 
same  change  of  sulphur  dioxide  to  sulphur  trioxide.  There  is  this 
advantage,  however,  that  these  contact  substances,  acting  at  a  higher 
temperature,  can  bring  about  the  change  in  the  absence  of  water  and 
thus  produce  at  once  a  stronger  acid  than  chamber  acid,  or  even 
sulphuric  anhydride  itself  as  a  direct  product. 
In  an  address  before  the  German  Chemical  Society,  delivered 
October  19,  1901,  and  printed  in  full  in  the  Berichte  det  Deutschen 
Chemischen  Gesellschaft,  34,  p.  4069,  Dr.  R.  Knietsch,  of  the  Badische 
Anilin-  und  Soda-Fabrik,  gives  an  account  of  the  manufacture  of 
sulphuric  acid  by  the  new  "Contact  Method"  as  developed  and 
patented  by  his  company  and  now  manufactured  by  them  on  a  large 
scale.  As  this  is  the  first  detailed  account  of  the  new  process,  now 
being  largely  adopt-d  by  the  manufacturers  of  sulphuric  anhydride, 
and  promising  to  replace  the  time-honored  lead-chamber  process 
for  all  grades  of  sulphuric  acid,  wherever  new  plants  are  being 
designed,  it  will  be  well  to  give  its  substance  for  general  information. 
The  first  discovery  of  the  catalytic  action  of  a  solid  body  in  the 
formation  of  sulphuric  acid  was  made  by  Peregrine  Philips,  Jr.,  of 
Bristol,  Eng.,  who  took  out  a  patent  for  the  use  of  platinum  in  this 
connection.  Seventeen  years  later,  Schneider,  a  Belgian  chemist, 
announced  the  catalytic  action  of  pumice  stone  and  thought  that  he 
had  solved  the  problem  of  the  ready  formation  of  sulphuric  oxide 
by  its  means,  but  the  promise  was  not  realized.  In  1846,  Jullion 
patented  the  use  of  platinized  asbestos  as  a  catalytic  agent,  but  it 
was  not  used  in  connection  with  the  manufacture  of  sulphuric  acid 
until  later. 
Wbhler  and  Mahla  later  discovered  the  catalytic  action  of  the 
oxides  of  copper,  iron  and  chromium,  but  the  discovery  did  not 
lead  to  any  practical  process. 
The  next  step  in  advance  was  made  by  Clemens  Winkler,  who 
used  an  exact  mixture  of  two  volumes  of  sulphur  dioxide  and  one 
volume  of  oxygen  to  form  the  trioxide,  which  could  then  be  com- 
bined with  much  or  little  water,  according  to  the  strength  of  acid 
desired.  This  method  was  successfully  applied  to  the  manufacture 
of  fuming  sulphuric  acid.  For  this  purpose  he  heated  ordinary 
sulphuric  acid,  which  on  decomposing  formed  water,  oxygen  and 
