﻿472 
  Seventh 
  Annual 
  Report 
  of 
  the 
  

  

  5, 
  The 
  Amount 
  of 
  Axkali 
  Required 
  to 
  Neutralize 
  the 
  Free 
  

   Acids 
  in 
  the 
  Oil. 
  Acid 
  Figure. 
  

  

  Perfectly 
  pure 
  linseed 
  oil 
  contains 
  only 
  a 
  very 
  small 
  percentage 
  

   of 
  free 
  acids, 
  while 
  rosin 
  is 
  composed 
  principally 
  of 
  free 
  acids, 
  and 
  

   rosin 
  oil 
  usually 
  contains 
  a 
  notable 
  proportion 
  of 
  free 
  rosin. 
  There- 
  

   fore, 
  the 
  free 
  acids 
  in 
  an 
  oil 
  which 
  contains 
  rosin 
  will 
  neutralize 
  

   a 
  larger 
  proportion 
  of 
  alkali 
  than 
  those 
  from 
  pure 
  linseed 
  oil. 
  On 
  

   keeping, 
  the 
  amount 
  of 
  free 
  acid 
  is 
  likely 
  to 
  increase 
  somewhat. 
  The 
  

   free 
  acid 
  found 
  may 
  be 
  partly 
  due 
  to 
  mineral 
  acid 
  used 
  in 
  refining 
  

   the 
  oil. 
  The 
  amount 
  of 
  mineral 
  acid 
  may 
  be 
  separately 
  determined 
  

   by 
  boiling 
  for 
  some 
  time 
  a 
  weighed 
  portion 
  of 
  the 
  oil 
  with, 
  water, 
  

   cooling 
  the 
  mixture, 
  adding 
  neutral 
  potassium 
  iodide 
  and 
  iodate, 
  

   and 
  titrating 
  the 
  liberated 
  iodine 
  with 
  standard 
  sodium 
  thiosulphate. 
  

   After 
  deducting 
  from 
  the 
  total 
  percentage 
  of 
  potash 
  required 
  to 
  

   neutralize 
  the 
  total 
  free 
  acid 
  the 
  percentage 
  required 
  for 
  the 
  min- 
  

   eral 
  acid, 
  the 
  percentage 
  required 
  by 
  the 
  free 
  organic 
  acid 
  is 
  

   found, 
  which, 
  in 
  the 
  case 
  of 
  linseed 
  oil, 
  are 
  almost 
  certain 
  to 
  be 
  

   either 
  the 
  normal 
  fatty 
  acids 
  from 
  the 
  linseed 
  oils 
  or 
  a 
  combina- 
  

   tion 
  of 
  tbese 
  with 
  resin 
  acids. 
  

  

  The 
  method 
  of 
  determining 
  free 
  acids 
  is 
  to 
  weigh 
  5 
  to 
  10 
  gi'ams 
  

   of 
  the 
  oil 
  in 
  a 
  flask, 
  add 
  about 
  50 
  c. 
  c. 
  of 
  alcohol, 
  which 
  is 
  neutral 
  

   to 
  phenolphthalein, 
  heat 
  on 
  the 
  water 
  bath 
  till 
  the 
  alcohol 
  boils, 
  

   shake 
  well 
  and 
  titrate 
  with 
  half-normal 
  alkali. 
  The 
  results 
  of 
  the 
  

   titration 
  are 
  expressed 
  in 
  milligrams 
  of 
  potassium 
  hydroxide 
  re- 
  

   quired 
  per 
  gram 
  of 
  oil, 
  and 
  the 
  result 
  is 
  called 
  the 
  " 
  Acid 
  Figure." 
  

  

  Benedikt 
  gives 
  as 
  the 
  limits 
  observed 
  by 
  Nordlinger, 
  in 
  examin- 
  

   ing 
  ten 
  samples 
  of 
  linseed 
  oil 
  acidities, 
  from 
  .41 
  to 
  4.19 
  per 
  cent 
  

   of 
  oleic 
  acid, 
  corresponding 
  to 
  acid 
  figures 
  from 
  .9 
  to 
  8.3. 
  Mills 
  

   allows 
  a 
  maximum 
  figure 
  of 
  10.0. 
  As 
  will 
  be 
  seen 
  from 
  the 
  figures 
  

   contained 
  in 
  the 
  table, 
  raw 
  linseed 
  oil 
  will 
  usually 
  give 
  an 
  acid 
  

   figure 
  in 
  the 
  neighborhood 
  of 
  3,0. 
  Oil 
  ISTo. 
  1, 
  though 
  pure, 
  has 
  

   7.1, 
  due, 
  no 
  doubt, 
  to 
  the 
  fact 
  that 
  it 
  is 
  several 
  yeai*s 
  old. 
  The 
  

   figures 
  of 
  boiled 
  oil 
  are 
  slightly 
  higher, 
  due, 
  probably, 
  to 
  the 
  

   production 
  of 
  a 
  small 
  quantity 
  of 
  some 
  acid 
  body 
  by 
  the 
  action 
  

  

  