ON  THE  MANUFACTURE   OF  RESIN  OIL   FROM  ROSIN. 
121 
small  holes  for  the  escape  of  the  steam  during  the  time  the  steam  is 
used  in  the  distilling  process.  A  spiral  or  any  other  form  may  be 
given  to  the  perforated  terminating  portion  of  the  steam-pipe.  As 
the  careful  conducting  of  the  operation  depends  on  the  due  regula- 
tion of  the  heat  employed,  a  thermometer  is  inserted  into  the  still 
in  the  usual  way,  so  as  to  indicate  the  temperature  of  the  contents 
of  the  interior. 
In  conducting  the  process  of  distillation,  a  sufficient  quantity  of 
resin  is  put  into  the  still  to  fill  nearly  two-thirds  of  its  interior 
space  ;  the  fire  is  then  lighted  under  the  still,  and  a  sufficient  quan- 
tity of  steam  is  also  blown  in  to  moisten  the  resin  ;  the  moveable 
connecting  pipe  placed  between  the  neck  of  the  still  and  the  worm, 
being  detached  before  the  fire  is  made.  During  the  early  stages 
of  raising  the  temperature  of  the  resin,  during  which  the  acid 
and  water  are  driven  off,  a  considerable  agitation  and  frothing 
up  occurs,  during  which  the  resin  is  liable  to  overflow,  and  if 
allowed  to  pass  into  the  worm,  would  choke  it  up,  and  impede 
future  operations  ;  it  is  therefore  better  to  drive  off  the  acid  and 
water  to  waste  in  the  way  above  mentioned.  The  acid  will  begin 
to  escape  when  the  thermometer  indicates  the  temperature  of  the 
resin  to  be  325°  Fahr.,  at  which  point  the  fire  must  be  carefully 
regulated,  and  the  temperature  maintained  from  300°  to  325°, 
until  all  the  acid  has  ceased  to  flow  from  the  neck  of  the  still. 
The  connecting  pipe  is  then  attached  to  the  neck  of  the  still  and 
the  worm,  and  the  joints  well  luted.  Steam  is  now  blown  in 
through  the  pipe  into  the  bottom  of  the  still,  the  temperature 
being  kept  at  about  the  point  before  mentioned.  As  the  steam 
rises  through  the  melted  resin,  it  takes  up  and  carries  the  naphtha 
with  it,  in  the  form  of  vapor,  the  mingled  vapors  passing  off  into 
the  worm,  where  they  are  condensed,  and  the  product  collected  in 
a  suitable  receiver.  This  operation  is  continued  until  the  naphtha 
ceases  to  come  over,  which  is  indicated  by  the  appearance  of  the 
product,  or  when  about  15  per  cent,  of  the  bulk  of  the  contents  of 
the  still  has  been  distilled. 
As  soon  as  the  naphtha  has  ceased  to  flow  from  the  worm  of 
the  still,  the  fire  is  increased  until  the  contents  of  the  still  are 
raised  to  500°  ;  the  steam  all  the  while  being  allowed  to  flow  in, 
and  kept  flowing  in  during  the  remainder  of  the  process.  The  oil 
commences  to  rise  with  the  steam  when  the  heat  is  raised  to  550°, 
