NEW  PROCESSES  FOR  COVERING  METALS,  ETC.  .173 
same  way.  Mr.  Hunter  has  found  a  very  cheap  one,  indeed. 
He  has  discovered  that  lime,  by  far  the  cheapest  of  all  alkaline 
bodies,  will  separate  the  sulphuric  acid  from  sulphate  of  sodium 
in  solution,  provided  that  the  solution,  after  the  lime  has  been 
added  to  it,  be  subjected  to  a  pressure  considerably  exceeding 
that  of  the  atmosphere.  He  states  that  u  either  hydraulic,  steam, 
or  mechanical  pressure,"  will  answer  equally  well.  Unless  the 
application  of  the  necessary  pressure,  on  the  large  scale,  should 
prove  to  be  attended  with  greater  difficulties  than  there  seems 
any  reason  to  anticipate,  his  discover}7"  will  revolutionize  the 
soda  manufacture ;  and  by-and-by,  all  the  carbonate  of  sodium 
produced  will  be  obtained  by  the  direct  combination  of  caustic 
soda  with  carbonic  acid,  the  caustic  soda  being  obtained  by  a 
process  embracing  only  two  operations  :  (1)  the  decomposition  of 
chloride  of  sodium,  or  common  salt,  by  sulphuric  acid,  as  in  Le- 
blanc's  process  ;  and  (2)  the  decomposition  of  the  resulting  sul- 
phate of  sodium  by  lime. — Am.  Drug.  Circ,  Feb.,  1866,  from 
Mechanics  Magazine. 
NEW  PROCESSES  FOR  COVERING  METALS  WITH  AN  AD- 
HERING AND  BRILLIANT  COATING  OF  OTHER  METALS. 
By  M.  Fred.  Weil. 
The  author  begins  by  observing  that  the  galvano-plastic  pro- 
cesses employed  for  depositing  metals  one  on  the  other  have  the 
disadvantage  of  being  expensive,  and  requiring  apparatus  ex- 
pensive to  keep  in  repair,  and  which,  as  is  usually  the  case  with 
cyanuretted  baths,  are  unhealthy  for  the  workmen. 
The  process  proposed  and  employed  by  M.  Weil,  consists  in 
the  use  of  baths  formed  of  metallic  salts  or  oxides  held  in  alka- 
line solution,  (sodic  or  potassic,)  and  usually  in  presence  of  or- 
ganic matters,  such  as  tartaric  a?id,  glycerin,  albumen,  or  any 
other  inoffensive  substance  which  prevents  the  precipitation  of 
the  oxide  by  the  fixed  alkali.  The  deposit  generally  takes  place 
at  the  ordinary  temperature,  but  sometimes  at  a  higher  tempera- 
ture. According  to  the  author,  his  processes  of  the  coppering 
and  bronzing  of  iron,  cast  iron  and  steel,  are  of  special  import- 
ance ;  he  can,  moreover,  vary  at  will  the  colors  and  tones,  and 
