122         NEW  PROCESS  OF  MANUFACTURING  SODA,  ETC. 
the  manufacture  of  sulphuric  acid  in  connection  with  that  of 
artificial  soda,  constitutes  a  complete  and  symmetrical  work  in 
which  nearly  all  the  products  are  utilized.  Improvements  that 
have  been  proposed  have  not  been  adopted,  either  because  they 
derange  this  symmetry  of  operations,  or  else  because  of  the  cost 
of  introducing  them,  or  they  are  adapted  only  to  certain  circum- 
stances or  localities.  The  process  now  brought  forward  escapes 
these  objections,  It  is  by  M.  Emile  Kopp,  formerly  Professor 
in  the  School  of  Pharmacy  of  Strasburg,  and  has  already  been 
put  into  practice  in  a  manufactory  in  Lancashire,  England,  at 
Church  near  Manchester. 
The  process  consists  in  decomposing  sulphate  of  soda  by  a 
mixture  of  oxyd  of  iron  and  carbon,  and  treating  the  product  of 
the  reaction  in  the  way  described  below.  The  proportions  em- 
ployed are  as  follows  : — 
Sulphate  of  Soda  (SO3  NaO),        125  kilograms. 
Peroxyd  of  Iron  (Fe203),  80 
Carbon,  55  " 
The  sulphate  of  soda  may  without  inconvenience  contain  some 
common  salt ;  but  then  the  oxyd  of  iron  and  carbon  should  be 
proportioned  only  to  the  pure  and  dry  sulphate  of  soda  present 
in  the  crude  material.  A  furnace  for  calcination  is  used,  taking 
care  to  break  up  the  larger  lumps.  The  oxyd  of  iron  should 
be  weighed  dry  and  in  a  fine  powder,  and  should  be  as  pure  as 
possible. 
For  the  first  operation,  instead  of  the  artificial  or  native  per- 
oxyd of  iron,  the  carbonate  (spathic  iron)  may  be  employed, 
or  the  magnetic  oxyd,  or  even  iron  filings.  But  in  the  case  of 
the  last,  the  quantity  of  carbon  should  be  diminished,  since  me- 
tallic iron  acts  as  a  reducer  of  the  sulphate  of  soda.  It  will  be 
soon  seen,  that  whatever  the  compound  of  iron  used,  there  will 
be  shortly  only  the  peroxyd,  and  this  is  regenerated  constantly 
in  the  operation. 
The  mixture  of  sulphate  of  soda  and  oxyd  of  iron  which  is  ob- 
tained as  a  residue  in  the  process  of  decomposing  common  salt 
by  the  sulphate  of  iron,  is  readily  adapted  to  Kopp's  process, 
since,  if  the  proportions  are  correctly  taken,  it  is  only  necessary 
to  add  the  requisite  quantity  of  carbon.  This  carbon  may  be 
coke,  or  any  other  organic  reducing  substance ;  but  the  quantity 
