Am.  Jour.  Pharm. 
May,  1894. 
Calomel  in  Japan. 
243 
One  thing  to  which  attention  may  be  called  is  that  the  Chinese 
are  stated  to  add  some  nitre  to  a  similar  mixture  when  employed  to 
give  corrosive  sublimate.  For  that  being  the  case,  it  is  seen  that 
free  chlorine  which  would  here  be  developed  from  the  salt,  nitre  and 
alum,  is  necessary  for  the  production  of  the  higher  chloride,  and  that 
air  and  hydrochloric  acid  can  only  yield  the  lower  chloride,  a  differ- 
ence of  much  theoretical  interest,  and  indeed  of  practical  moment 
also.  It  is  known  that  re-sublimation  of  calomel  generates  some 
corrosive  sublimate,  and,  although  authorities  are  not  quite  agreed  as 
as  to  whether  reaction  occurs  between  gold  leaf  and  calomel  vapor,  it  is 
hardly  to  be  doubted  that  such  reaction  does  occur.  Now  I  have 
found  that  if  in  the  Japanese  apparatus  the  temperature  of  the  cover 
be  raised  sufficiently  to  volatilize  much  of  the  calomel  the  remaining 
calomel  is  no  longer  free  from  corrosive  sublimate.  It  must,  there- 
fore, be  borne  in  mind  that  the  calomel  formed  in  the  Japanese  process 
is  not,  and  cannot  be,  the  result  of  true  sublimation,  but  of  precipi- 
tation as  fast  as  formed  from  the  three  gaseous  bodies  which  give 
rise  to  it.  At  the  temperature  at  which  mercury  boils,  calomel  is 
either  quite  fixed  or,  at  most,  has  a  vapor  of  exceedingly  small  ten- 
sion. In  the  two  facts,  that  the  three  gases  do  not  react  to  yield 
corrosive  sublimate  and  that  the  calomel  is  not  heated  to  its  volatiliz- 
ing point,  lie  the  explanation  and,  at  the  same  time,  the  assurance 
that  Japanese  (and  Chinese)  calomel  contains  no  corrosive  sublimate. 
Summary. — The  Japanese  prepare  calomel  pure,  above  all  things 
free  from  corrosive  sublimate.  They  heat  balls  of  porous  earth  and 
salt  soaked  in  bittern  along  with  mercury,  in  iron  pots  lined  with 
earth.  The  heat  forms  hydrochloric  acid  from  the  magnesium 
chloride  in  the  bittern,  and  the  mercury  sublimes  into  the  closely- 
fitting  but  unattached  clay  covers  of  the  pots.  Air  enters  by  diffu- 
sion and  oxygen  and  hydrochloric  acid  gas  act  together  in  the 
hollow  cover  on  the  vapor  given  off  from  the  sublimate  of  mercury 
there  formed.  The  cover  thus  becomes  filled  with  a  network  of 
micaceous  particles  of  calomel,  precipitated  at  a  temperature  below 
its  subliming  point  at  the  moment  of  its  formation. 
This  investigation  of  an  interesting  product  of  Japanese  industry 
has  been  carried  out  under  the  authority  of  the  Imperial  University 
of  Japan.  I  cannot  acknowledge  fully  enough  the  indispensable 
assistance  I  have  received  from  my  colleague,  Assistant-Professor 
Haga,  F.C.S. 
