550    EXTRACTION  OF  OIL  BY  MEANS  OF  SULPHIDE  OF  CARBON. 
After  having  carefully  closed  the  vats  with  covers,  the  sul- 
phide of  carbon  is  conducted  into  them  from  a  higher  reservoir; 
about  7000  kilos,  being  required  for  the  daily  manufacture,  of 
which,  however,  only  28  kilos,  are  lost,  that  is  to  say  about  *4 
per  cent.  Erom  the  bottom  of  the  vat,  the  solution  of  oil  in  the 
sulphide  of  carbon  trickles  out  in  a  thread-like  manner,  and 
becomes  clearer,  until  at  last  the  sulphide  runs  quite  pure.  This 
indicates  the  precise  moment  when  the  seed  is  completely  de- 
prived of  oil,  and  steam  is  then  substituted  for  the  sulphide,  of 
which  it  entirely  removes  all  traces. 
The  vats  are  now  uncovered  and  reversed,  in  order  to  eject 
the  exhausted  matter,  which  is  taken  up  by  the  lifts  and  passed 
successively  through  three  mill-hoppers  heated  by  steam  ;  lastly, 
it  is  again  ground,  when  it  forms  an  alimentary  powder,  con- 
taining 5*3  per  cent,  of  nitrogen,  and  saleable  at  15*15  francs 
the  hundred  kilos.  The  mixture  of  oil  and  sulphide  of  carbon 
extracted  from  the  vat  washings  is  purified  with  steam,  distilled 
twice,  and  cooled  in  three  large  worms  passed  through  refrigera- 
tors. It  is  then  rectified,  which  renders  it  capable  of  employ- 
ment in  new  operations,  after  being  restored  to  the  original 
reservoir.  The  trade  price  of  sulphide  of  carbon  is  from  0*79  fr. 
to  0*85  fr.  the  kilogramme,  but  costs  the  manufactory  of  Moabit 
rather  less,  as  it  is  made  on  the  premises.  The  oil  thus  obtained 
is  sold  as  lamp  oil  after  being  deprived  of  color ;  and  by  sub- 
mitting it  to  a  chemical  process,  a  superior  oil  for  purposes  of 
lubrication  is  produced,  possessing  the  advantage  of  being  and 
remaining  extremely  fluid.  Another  oil  is  also  manufactured, 
specially  adapted  to  the  lubrication  of  railway-carriage  axles, 
inspissating  at  -a  very  low  temperature  only.  Four  large  wrought- 
iron  reservoirs  of  7*416  cubic  metres  each  hold  large  quantities 
of  oil,  and  a  steam-engine  of  12-horse  power,  with  two  boilers 
and  a  pressure  of  two  atmospheres,  give  all  the  power  and  steam 
necessary  for  operation,  transport,  &c.  The  daily  fabrication  of 
2*570  kilos,  only  requires  the  work  of  six  men  ;  and  the  careful 
analyses  of  MM.  Birner,  of  Regenwalde,  and  Karsten,  of  Kiel, 
could  only  find  in  the  residue  2  per  cent,  of  oil  and  7  per  cent, 
of  water,  whilst  in  the  residue  from  the  common  method  of  pres- 
sing, 9  per  cent,  of  oil  and  15  per  cent,  of  water  were  discovered. 
