MANUFACTURE  OP  VEGETABLE  OILS. 
501 
veyed  to  the  refinery.  This  is  situated  about  a  quarter  of  a 
mile  down  the  Blackwall  line,  of  which  property  it  occupies 
nine  arches  in  its  rear.  The  premises  are  very  large,  and  are 
used  not  only  for  refining  vegetable  but  also  animal  oils.  The 
casks  of  unrefined  oil  are  hoisted  to  the  upper  floor  by  means 
of  a  crane  worked  by  steam.  Along  this  floor  a  large  vat, 
capable  of  holding  ten  tons,  is  extended.  It  is  lined  with  copper, 
is  fitted  with  a  horizontal  agitator  or  fan,  and  is  called  the 
reception  vat.  Into  this  receptacle  five  tons  of  rape  oil  are 
decanted,  an  equal  quantity  of  water  is  added,  and  the  whole 
treated  by  chemical  process.  The  agitator  is  set  in  motion,  and 
after  four  or  five  hours  the  oil  becomes  thoroughly  washed,  its 
impurities  having  been  removed.  The  agitation  is  then  stopped, 
and  the  water  and  bleaching  ingredients  are  allowed  to  subside. 
The  oil  is  next  drawn  off  into  the  boiling  vat  on  the  next  story. 
This  vat  also  is  lined  with  copper,  fitted  with  fans  or  agitators, 
and  a  coiled  perforated  tube  ;  steam  is  admitted  into  the  tube 
until  a  uniform  temperature  of  212  degrees  is  obtained.  It  is 
kept  in  this  condition  and  continually  agitated  for  about  four 
hours,  when  all  impurities  having  been  thrown  off,  it  is  allowed 
to  cool,  assisted  by  the  fans,  which  bring  every  portion  in  turn 
into  contact  with  the  air.  At  the  end  of  eight  or  ten  hours  it 
is  sufficiently  cool  to  be  drawn  off  into  the  filters,  which  are  on 
the  lower  story.  Each  filter  contains  five  tons.  Having  passed 
through  the  filter,  the  oil,  fully  refined,  is  pumped  into  appro- 
priate tanks  to  be  ready  for  barrelling,  and  receives  the  name 
of  colza  oil,  on  account  of  its  illuminating  properties ;  the  true 
colza  being  an  oil  expressed  from  the  Brassica  oleracea,  a  variety 
of  the  cabbage  plant,  from  whose  seeds  an  oil  much  used  on  the 
Continent  is  expressed. 
Some  idea  may  be  formed  of  the  vast  quantity  of  purified 
rape-oil  consumed  for  lubricating  and  illuminating  purposes, 
when  this  refinery  alone  sends  out  upwards  of  two  thousand  tons 
per  annum.  A  single  railway  company  consumes  three  hundred 
tons  a  year,  and  the  Great  Eastern  requires  a  thousand  gallons 
for  a  single  voyage  to  New  York.  Whale,  seal,  and  sperm  oils 
are  refined  by  a  more  simple  process.  They  are  simply  filtered 
through  flannel  bags  ;  the  residue  of  the  common  kinds  is  called 
foots,  and  is  one  of  the  ingredients  used  in  the  manufacture  of 
