AmMay"i8P94arm-}  Calomel  in  Japan.  241  . 
The  spent  lumps  of  earth  and  salt  are  lifted  out  of  the  pots  by  the 
tool  shown  in  Fig.  4.,  and  when  the  furnace  has  become  still  cooler, 
the  fire  is  made  up  again,  the  furnace  top  freely  wetted,  and  a  new 
operation  set  going  as  before.  The  furnace  is  worked  twice  each  day. 
Nothing  could  well  be  carried  out  with  greater  simplicity  and  less 
expenditure  of  labor  and  time. 
OJ  the  Yield — The  loss,  I  am  told,  is  about  16  per  cent,  of  the 
theoretical  amount  of  calomel,  which  is,  I  believe,  about  twice  as 
much  as  is  lost  in  the  Western  process. 
Experimental. — If  one  of  the  cups  is  removed  a  few  minutes  after 
the  operation  has  been  started,  much  of  the  mercury  is  found  in  it 
as  a  sublimate  of  fine  globules,  mixed  with  only  a  little  almost 
amorphous  calomel,  from  which  it  would  appear  that  the  formation 
of  the  calomel  results  from  reaction  in  the  cup  between  the  mercury 
in  vapor  and  the  active  gases. 
On  dipping  into  the  pot,  uncovered  during  the  process,  a  glass  rod 
with  a  drop  of  water  hanging  to  it  and  then  withdrawing  it,  and  test- 
ing the  remainder  of  the  water  with  potassium  iodide  and  starch,  no 
chlorine  can  thus  be  detected.  The  same  is  true  when  a  drop  of 
solution  of  potassium  hydroxide  is  used.  Nor  can  the  slightest 
odor  of  chlorine  be  detected  in  the  vapors  issuing  from  the  uncovered 
pot. 
On  passing  air,  containing  a  little  hydrochloric  acid  gas,  through 
a  tube  in  which  mercury  is  freely  boiling,  sparkling  calomel  is 
formed  close  to  and  mixed  up  with  the  mercury. 
Red  earth  which  has  been  used  in  the  process  turns  moist,  red 
litmus  paper  blue,  while  fresh  red  earth  is  neutral. 
Theoretical. — The  nature  of  the  materials  used  and  the  observa- 
tions gained  by  the  preceding  experiments  are  sufficient  to  establish 
that  the  calomel  is  formed  by  a  reaction  between  mercury  vapor, 
oxygen  and  hydrochloric  acid  gas,  in  which,  along  with  mercurous 
chloride,  water  is  formed — 4Hg  -f  4HCI  -f  02  =  4HgCl  -f  2H20, 
and  that  the  formation  takes  place  at  a  temperature  near — above  or 
below — the  boiling-point  of  mercury,  and  much  below  that  at  which 
calomel  freely  volatilizes.  The  source  of  the  hydrochloric  acid  is 
certainly  the  magnesium  chloride  of  the  bittern  and  bay-salt  which, 
heated  in  a  moist  atmosphere,  even  in  the  presence  of  sodium 
chloride,  is,  as  is  well  known,  partly  converted  into  magnesia  and 
hydrochloric  acid.    Hence  the  alkalinity  of  used  mitsuchi. 
