236  Calomel  in  Japan. 
it  is  almost  entirely  decomposed  by  sulphuric  acid,  either  in  some 
days  in  the  cold  or  quickly  by  heat.  It  is  also  largely  acted  upon 
by  hot  hydrochloric  acid;  and,  heated  in  sealed  tubes  with  this  acid 
to  I20°-I50°,  it  is  almost  as  fully  decomposed  as  by  sulphuric  acid. 
It  contains  practically  no  silica  soluble  in  hot  sodium  carbonate  solu- 
tion, but  after  acid  treatment  yields,  of  course,  much  silica  to  this 
reagent.  The  composition  of  the  earth,  as  found  in  use  at  the  works, 
but  rendered  anhydrous,  is  as  follows: 
Quartz,   38*4 
Combined  silica,   24*2 
Alumina,   26*3 
Ferric  oxide,     10*5 
Magnesia,   0*3 
997 
The  magnesia  is  only  got  by  fusion  of  the  finely-ground  earth 
with  alkali  carbonate,  aud  belongs  to  the  particles  of  mica  scattered 
through  it.  Only  doubtful  traces  of  phosphoric  acid  could  be  found, 
and,  what  is  specially  to  be  noted,  no  lime  whatever.  The  earth  is 
thus  nothing  but  quartz,  kaolin,  ferric  hydroxide,  and  a  very  little 
biotite,  and  is  probably  valuable  to  the  calomel  maker,  not  only  for 
its  highly  porous  texture,  but  also  for  its  negative  chemical  quali- 
ties. 
The  bittern  and  even  the  rough  bay-salt  contain  magnesium 
chloride,  and  this  rather  than  sodium  chloride  must  be  the  source  of 
hydrochloric  acid  in  the  process.  That  air  finds  a  graduated 
entrance  to  the  other  materials  by  diffusion  during  the  process,  will 
become  evident  from  a  consideration  of  the  set-up  of  the  apparatus, 
Of  the  Plant. — The  apparatus  for  making  Japanese  calomel  con- 
sists of  a  table-furnace  supporting  60  cast-iron  pots  lined  and  sur- 
mounted with  the  Shunakayama  earth  or  mitsuchi,  on  which  rest, 
as  covers  and  condensers  and  receivers  of  the  calomel,  unglazed  clay 
cups,  bottom  upwards. 
In  Fig.  1  the  furnace  as  it  is  when  in  action  is  seen  from  the 
working  side;  10  pots  on  the  left  side  are  shown  still  to  be  charged 
and  covered.  The  wooden  step  in  front  is  to  enable  the  workmen 
to  reach  over  the  table  easily  when  charging  the  pots  or  emptying 
them.  In  Fig.  2  the  furnace  is  seen  from  the  back  or  firing  side, 
and  with  the  walls  broken  away  to  show  its  interior  and  the  method 
f  Am.  .Tour.  Pharm. 
t        May,  1894. 
