168 
ON  THE  PREPARATION  OP  CINNABAR. 
powdered  sulphur  of  which  four  equivalents  are  required  ;  it  must 
be  well  protected  from  the  atmosphere. 
To  prepare  now  the  cinnabar,  bottles  are  filled  with  10  lbs.  mer- 
cury, 2  lbs.  sulphur,  and  4J  lbs.  of  the  above  liquor ;  they  are 
moderately  heated,  and  placed  in  a  swing  in  boxes,  which  are 
lined  with  straw,  usually  contain  two  such  bottles,  and  are  rocked 
against  a  straw  cushion  to  increase  the  motion.  The  bottles  com- 
mence to  get  warm  after  1^  to  2  hours,  and  the  mixture  assumes 
a  greenish  brown  color;  the  mercury  combines  with  the  sulphur 
of  the  dissolved  sulphide,  which  is  replenished  by  the  sulphur  of 
the  mixture  ;  to  keep  the  latter  in  a  loose  condition,  the  bottles 
ought  to  be  turned  occasionally.  The  combination  is  completed 
in  about  3i  hours,  and  the  color  of  the  mixture  is  now  dark 
brown.  After  having  been  cooled  slowly,  the  bottles  are  placed 
in  a  room,  the  temperature  of  which  is  between  35  and  40^  R., 
(Ill  and  122°  F.)  for  two  or  three  days,  during  which  time  the 
mixture  is  well  agitated  three  or  four  times  daily.  The  tem- 
perature has  an  important  influence  on  the  shade  of  the  color, 
which  is  lighter  the  cooler  the  mixture  has  been  on  being  put  in 
the  swing.  Light  carmine  cinnabar,  with  a  tinge  of  yellow,  is 
obtained  by  exposing  the  bottles  in  winter  to  the  cold  atmosphere 
for  one  hour,  or  by  setting  them  in  summer  in  cold  water  for  the 
same  space  of  time. 
The  cinnabar  is  now  to  be  freed  from  the  excess  of  the  sul- 
phur; about  half-a-quart  of  water  is  added  to  each  bottle,  and 
the  contents  thrown  on  a  filter;  the  cinnabar  is  then  treated  in 
stone  pots  with  caustic  soda,  and  after  the  sulphur  is  dissolved, 
the  liquor  is  decanted  and  the  residue  washed  repeatedly  with 
fresh  water,  which  usually  requires  two  or  three  days.  The  com- 
plete removal  of  the  sulphur  and  of  the  alkaline  liquor  is  most 
important,  the  durability  in  fire  depending  on  the  former,  and 
the  permanence  of  the  color  upon  the  latter.  In  order  to  dry 
the  cinnabar,  it  is  first  transferred  to  the  grate  in  a  drying  closet, 
where  a  very  moderate  heat  is  used  for  desiccation,  until  it  breaks 
into  pieces,  and  does  not  appear  moist  to  the  touch.  Placed 
upon  iron  pans,  it  is  introduced  into  a  drying  oven,  where  it  is 
constantly  turned,  and  gradually  heated  to  50°  R.  (144°. 5  F.) 
This  last  manipulation  is  finished  in  about  five  hours.  By  the 
higher  heat  the  cinnabar  assumes,  temporarily,  a  darker  shade, 
and  its  durability  in  fire  is  much  increased  thereby. 
