554 
OBTAINING  OIL  PROM  BITUMINOUS  COAL. 
manner  as  already  described.  Parafine  oil  obtained  from  the 
last  mentioned  distillation  contains  a  fluid  more  volatile  than 
parafine,  a  considerable  portion  of  which  may  be  separated  from 
the  oil  and  obtained  in  a  separate  state  as  follows : — The  oil  is 
placed  in  an  iron  still  connected  with  a  worm-pipe  passing  through 
a  refrigeratory  apparatus,  and  half  its  bulk  of  water  being  added, 
the  contents  of  the  still  are  boiled  for  about  twelve  hours,  adding 
water  from  time  to  time,  so  as  to  keep  about  the  same  proportions 
of  oil  and  water  in  the  still. 
The  volatile  fluid  will  pas  over  along  with  steam,  and  be  con- 
densed in  the  worm-pipe  by  the  refrigeratory  apparatus.  This 
fluid  will  be  clear  and  transparent,  and  as  it  is  lighter  than  water, 
it  separates,  on  standing,  from  the  water  with  which  it  will  be 
mixed  as  it  leaves  the  worm-pipe  of  the  still.  This  fluid  may  be 
burnt  for  the  purpose  of  illumination,  or  applied  to  any  other 
useful  purpose  to  which  it  may  be  applicable.  The  last-named 
process  will  separate  the  greater  portion  of  the  volatile  fluid 
from  the  oil,  but  a  larger  quantity  may  be  separated  by  pro- 
longing the  operation.  The  oil  left  in  the  still  after  the  com- 
pletion of  the  process  is  then  to  be  carefully  separated  from  all 
the  remaining  water  (upon  which  it  will  float)  and  conveyed  into 
a  leaden  vessel,  where  two  gallons  of  oil  of  vitriol  are  to  be  added 
to  each  100  gallons.  This  mixture  is  to  be  well  stirred  for  six 
or  eight  hours,  after  which  it  is  allowed  to  stand  undisturbed  for 
twenty-four  hours,  in  order  that  the  vitriol  may  settle  to  the 
bottom  of  the  leaden  vessel,  carrying  with  it  all  impurities  with 
which  it  has  combined.  The  supernatant  oil  is  now  to  be  drawn 
off  into  another  vessel,  and  to  each  100  gallons  there  is  added 
28  lbs.  of  chalk,  ground  up  with  a  little  water  into  a  tin  paste. 
The  oil  and  chalk  are  to  be  well  agitated  until  the  oil  becomes 
entirely  freed  from  any  trace  of  sulphurous  acid,  which  may  easily 
be  known  by  heating  a  little  of  it  in  a  glass  retort,  and  testing 
its  vapors  by  moistened  blue  litmus  paper.  If  the  vapors  change 
the  color  of  the  litmus  paper  to  red,  the  oil  must  be  treated  with 
more  chalk.  This  oil  is  to  be  kept  warm — say  at  100°  Fahr. — 
in  any  convenient  vessel,  for  about  a  week,  to  allow  impurities 
to  settle,  and  it  is  then  fit  to  be  used  for  lubricating  purposes, 
either  by  itself  or  mixed  with  an  animal  or  vegetable  oil,  or  it 
may  be  burnt  by  itself  in  Argand  lamps  for  the  purpose  of  illu- 
