^Tug'irst  1883°"'}  Progress  of  Soda  Industry.  427 
mixed  solution  of  sodium  chlorate  and  chloride,  found  that  not  only  does 
the  solubility  of  sodium  chlorate  increase  with  the  temperature,  but  it 
increases  to  such  an  extent  that  mere  concentration  by  evaporation  of  a 
mixture  of  these  salts  will  cause  practically  the  whole  of  the  sodium  chlo- 
ride to  fall  down,  leaving  sodium  chlorate  alone  in  solution.  The  disad- 
vantages of  this  process  are,  the  large  amount  of  sodium  sulphate  required 
by  the  reaction 
CaClaOe  +  5-5CaCl2  +  6-5Na2S04  =  2N'aC103  +  2NaCl  +  e-SCaSO^ ; 
the  unavoidable  loss  of  sodium  chlorate ;  its  separation  from  the  large 
amount  of  calcium  sulphate,  and  the  expense  of  evaporating  the  wash 
waters.  The  presence  of  so  large  a  proportion  of  sodium  chloride  was  a  fur- 
ther cause  of  loss  of  chlorate.  Pechiney  surmounted  these  difficulties  by 
removing  the  5*5  molecules  CaClg,  which  are  unavoidably  formed  in  the 
preparation  of  1  molecule  CaClgOe,  and  thereby  reducing  the  quantity  of 
■calcium  sulphate  and  sodium  chloride  considerably.  The  method  consists 
in  evaporating  the  crude  chlorate  liquor  until  its  density  is  48°  B.  The 
liquor  is  then  cooled  to  12°.  Of  its  5*5  mols.  of  calcium  chloride,  4'3  mols. 
are  thus  caused  to  crystallize  out  as  CaCl2,2H20.  The  concentrated  solution 
must  be  cooled  to  at  least  12°,  or  this  proportion  would  not  be  separated  ;  it 
must  not,  however,  be  cooled  below  10°,  or  calcium  chlorate  would  be 
deposited  as  well.  The  crystals  obtained  between  these  limits  of  tempera- 
ture are  free  from  calcium  chlorate,  and  are  of  a  nature  permitting  them  to 
be  separated  completely  from  their  mother-liquor  by  means  of  the  hydro- 
extractor.  The  mother-liquor  consists  of  1  mol.  CaCl206,  and  1-2  mol. 
CaClj.  It  is  diluted  with  its  own  volume  of  water,  treated  with  three  times 
1-2  mol.  lime,  and  heated  to  80°,  to  determine  the  formation  of  calcium  oxy- 
chloride.  It  is  then  cooled  and  filtered.  The  filtrate  consists  of  a  solution 
of  1  mol  calcium  chlorate  and  only  0*3  mol.  calcium  chloride,  and  thus  con- 
tains one-eighteenth  of  the  proportion  of  calcium  chloride  originally  present, 
so  that  the  abo re-mentioned  loss  is  considerably  reduced. 
In  conclusion,  the  author  discusses  the  recovery  of  sulphur  from  soda- 
waste.  At  iSalindres,  Pechiney  simply  injects  air  into  the  liquor  by  the  aid 
of  Korting's  injector,  and  then  when  oxidation  has  just  reached  the  point 
at  which  treatment  of  the  product  by  an  acid  would  not  cause  evolution 
either  of  sulphuretted  hydrogen  or  of  sulphurous  anhydride,  he  decomposes 
the  product  by  hydrochloric  acid.  During  the  operation  of  oxidizing  the 
liquor,  there  occurs  a  considerable  precipitation  of  lime,  in  a  peculiarly 
dense  state,  and  readily  separable.  Owing  to  this  separation,  the  quantity 
of  hydrochloric  acid  is  appreciably  reduced.  Kingzett  recommends  to  dry 
the  soda-waste  in  the  air,  then  grind  it,  and  finally  melt  it  with  coal-tar 
pitch,  for  the  purpose  of  asphalt-making.  After  referring  to  Mond's  sul- 
phur recovery,  Lunge  describes  and  discusses  at  length  the  process  invented 
by  ShaflTner  and  Helbig,  as  recently  reviewed  by  Weldon  [J.  Sac.  Chem- 
Industry^  1882,  45),  and  Chance  [J.  Soc.  Arts,  1882,  727 ;  and  J.  Soe.  Chem. 
Industry,  1882,  264).— J^.  Chem.  Soc,  1883,  524. 
