﻿456 
  Seventh 
  Annual 
  Report 
  of 
  the 
  

  

  ground 
  to 
  meal 
  in 
  liigli-specd 
  ix>lls, 
  and 
  heated 
  l>y 
  st<?ani. 
  In 
  some 
  

   mills 
  the 
  heating- 
  is 
  done 
  by 
  steam 
  injected 
  directly 
  into 
  the 
  meal 
  

   as 
  it 
  rnns 
  in 
  a 
  stream 
  into 
  a 
  tnh 
  nsed 
  as 
  a 
  reservoir 
  of 
  hot 
  meal. 
  

   In 
  other 
  works 
  the 
  heating-tub 
  is 
  steam- 
  jacketed 
  and 
  no 
  free 
  steam 
  

   is 
  admitted 
  to 
  the 
  meal. 
  From 
  the 
  heating-pan 
  the 
  meal 
  is 
  deliv- 
  

   ered 
  to 
  a 
  machine 
  whicli 
  fills 
  it 
  into 
  canvas 
  forms 
  and 
  ])resses 
  these 
  

   forms 
  lightly 
  to 
  make 
  them 
  keep 
  their 
  shape 
  sufficiently 
  to 
  handle. 
  

   They 
  are 
  tlien 
  placed 
  in 
  hydraulic 
  presses 
  and 
  subjected 
  to 
  high 
  

   pressure, 
  causing 
  the 
  oil 
  to 
  run 
  out. 
  The 
  oil 
  at 
  this 
  stage 
  contains 
  

   various 
  foreign 
  matters, 
  called 
  collectively 
  " 
  foots," 
  which 
  have 
  been 
  

   pressed 
  out 
  witli 
  the 
  oil. 
  These 
  are 
  removed 
  by 
  settling 
  or 
  by 
  filtra- 
  

   tion 
  through 
  cloth 
  and 
  paper 
  in 
  filter-presses, 
  or 
  by 
  both. 
  The 
  

   separation 
  of 
  " 
  foots 
  " 
  on 
  storage 
  goes 
  on 
  for 
  a 
  long 
  time 
  and 
  the 
  oil 
  

   improves 
  by 
  storage 
  and 
  settling, 
  even 
  after 
  careful 
  filtration. 
  

  

  The 
  operation 
  of 
  " 
  boiling 
  oil 
  " 
  is 
  one 
  about 
  which 
  great 
  secrecy 
  

   is 
  observed 
  by 
  the 
  manufacturei-s. 
  When 
  linseed 
  oil 
  is 
  heated 
  to 
  a 
  

   temperature 
  of 
  300° 
  to 
  500° 
  F., 
  its 
  drying 
  properties 
  are 
  increased. 
  

   If 
  salts 
  of 
  lead 
  or 
  of 
  manganese 
  are 
  incorporated 
  into 
  the 
  oil 
  a 
  

   similar 
  result 
  is 
  produced, 
  and 
  the 
  simplest, 
  and 
  in 
  former 
  times 
  the 
  

   universal 
  method 
  of 
  increasing 
  the 
  drying 
  properties 
  of 
  linseed 
  oil, 
  

   was 
  to 
  heat 
  the 
  oil 
  to 
  near 
  the 
  temperature 
  at 
  whicJi 
  it 
  imdergoes 
  

   destructive 
  distillation, 
  550° 
  F., 
  or 
  thereabouts, 
  and 
  stir 
  in 
  at 
  the 
  

   same 
  time 
  oxide 
  of 
  lead, 
  or 
  oxide 
  of 
  manganese, 
  or 
  both. 
  Heating 
  

   the 
  oil 
  to 
  such 
  a 
  high 
  temperature 
  darkens 
  it 
  very 
  much, 
  and 
  as 
  

   light 
  colored 
  oil 
  is 
  often 
  demanded, 
  so 
  that 
  the 
  oil 
  will 
  not 
  discolor 
  

   pigments 
  suspended 
  in 
  it 
  more 
  than 
  necessar)^, 
  and 
  as 
  this 
  higb 
  

   heat 
  is 
  wasteful 
  of 
  oil, 
  time 
  and 
  fuel, 
  it 
  has 
  become 
  the 
  practice 
  

   to 
  make 
  a 
  " 
  drier 
  " 
  of 
  the 
  metallic 
  oxides 
  by 
  heating 
  them 
  Avith 
  a 
  

   small 
  portion 
  of 
  the 
  oil 
  until 
  they 
  are 
  dissolved, 
  and 
  then 
  adding 
  

   this 
  drier 
  to 
  the 
  main 
  body 
  of 
  the 
  oil 
  maintained 
  at 
  a 
  much 
  lower 
  

   temperature, 
  usually 
  not 
  much 
  above 
  the 
  boiling 
  point 
  of 
  water. 
  

   The 
  result 
  of 
  this 
  process 
  is 
  that 
  there 
  is 
  not 
  so 
  great 
  a 
  loss 
  of 
  oil 
  

   during 
  the 
  boiling, 
  and 
  the 
  oil 
  obtained 
  is 
  lighter 
  in 
  color. 
  The 
  

   use 
  of 
  this 
  method 
  of 
  making 
  boiled 
  by 
  adding 
  to 
  raw 
  oil 
  at 
  a 
  com- 
  

   paratively 
  low 
  temperature, 
  a 
  drier 
  made 
  by 
  a 
  separate 
  operation, 
  

  

  