]22 
ON  THE  MANUFACTURE   OF   RESIN  OIL  FROM  ROSIN. 
the  mingled  vapors  passing  into  and  being  condensed  in  the 
worm,  from  whence  they  are  discharged  into  a  suitable  receiving 
vessel.  The  temperature  of  550°  must  be  kept  up  until  the  flow 
of  oil  nearly  or  quite  ceases.  The  bulk  of  oil  should  be  about 
twenty-five  per  cent,  of  the  original  quantity  of  resin. 
The  contents  of  the  still  are  then  raised  to  600°,  when  the  flow 
of  oil  and  moist  vapor  recommences,  and  continues  until  a  second 
quantity  of  oil,  equal  to  about  twenty-five  per  cent,  of  the  resin, 
is  discharged,  when  the  flow  of  oil  will  nearly  cease.  The  tem- 
perature of  the  still  is  then  raised  50°  higher,  when  the  flow  of 
moisture  and  oil  again  commences,  and  continues  under  the  same 
heat  until  a  third  quantity  of  oil  is  discharged,  equal  to  about  12 J 
per  cent,  of  the  bulk  of  the  resin  originally  placed  in  the  still, 
after  which  the  fire  is  extinguished.  The  residue  left  in  the  still 
is  of  a  nature  like  pitch  ;  this  is  drawn  off  through  the  discharge 
pipe.  During  the  process  steam  is  injected  into  the  upper  pipe 
upon  the  oil  whilst  it  is  in  a  state  of  vapor,  thus  producing  a 
purifying  influence  upon  the  oil. 
An  oil  suitable  for  employment  as  a  paint  oil,  is  prepared,  ac- 
cording to  Mr.  Furck's  process,  by  first  placing  in  the  still  some 
of  the  oil  obtained  at  a  temperature  of  650°,  as  before  described, 
and  the  man-hole  of  the  still  having  been  closed  and  luted,  the 
contents  are  then  raised  to  650°,  and  kept  at  that  point  until  the 
process  is  completed.  At  this  temperature  the  oil  passes  over  as 
vapour,  when  steam  is  injected  into  the  still  through  the  upper 
steam  pipe  before  referred  to.  The  oil  thus  obtained  is  condensed 
in  its  passage  through  the  worm,  and  having  been  received  in 
suitable  vessels,  is  next  re-distilled  in  the  same  way,  after  which 
it  is  placed  in  a  kind  of  kettle  or  pot,  in  which  its  temperature  is 
raised  to  about  225°,  by  means  of  steam  blown  in  through  an  open 
pipe  dipping  to  nearthe  bottom  of  the  vessel ;  and  having  attained 
that  point,  steam  is  let  in  through  another  pipe,  the  end  of  which 
is  enlarged  and  perforated  by  numerous  small  apertures,  until  the 
oil  is  freed  from  all  acid  and  coloring  matter,  when  it  will  be 
quite  clear,  and  fit  to  be  boiled  like  linseed  oil  for  painter's 
purposes. 
To  obtain  an  oil  fit  for  the  uses  of  tanners  and  curriers,  some  of 
the  oil  obtained  at  650°,  as  before  described,  is  placed  in  the  still, 
and  about  five  per  cent,  of  slaked  lime  added  ;  the  man-hole  of  the 
