﻿464 
  Seventh 
  Annual 
  Repokt 
  of 
  ihe 
  

  

  in 
  cracked 
  ice. 
  This 
  causes 
  the 
  formation 
  of 
  a 
  partial 
  vacuum 
  in 
  

   the 
  bottle. 
  The 
  bromine 
  need 
  not 
  be 
  allowed 
  to 
  react 
  with, 
  the 
  oil 
  

   for 
  more 
  than 
  a 
  few 
  minutes, 
  as 
  the 
  reaction 
  between 
  them 
  is 
  nearly 
  

   instantaneous. 
  Twenty-five 
  c. 
  c. 
  of 
  a 
  neutral 
  10 
  per 
  cent 
  solution 
  

   of 
  potassium 
  iodide 
  is 
  introduced 
  into 
  each 
  bottle 
  by 
  slipping 
  a 
  

   piece 
  of 
  rubber 
  tubing 
  of 
  suitable 
  size 
  over 
  the 
  lip 
  of 
  the 
  bottle, 
  

   pouring 
  the 
  iodine 
  solution 
  into 
  the 
  well 
  thus 
  formed 
  and 
  shift- 
  

   ing 
  the 
  stopper 
  slightly 
  so 
  as 
  to 
  allow 
  the 
  solution 
  to 
  be 
  sucked 
  

   into 
  the 
  bottle, 
  or, 
  if 
  the 
  bottle 
  has 
  not 
  been 
  cooled, 
  to 
  cause 
  the 
  

   air 
  as 
  it 
  escapes 
  from 
  the 
  interior 
  to 
  be 
  washed 
  by 
  bubbling 
  through 
  

   the 
  potassium 
  iodide 
  solution. 
  This 
  method 
  of 
  introducing 
  the 
  

   iodide 
  solution 
  effeetually 
  prevents 
  the 
  loss 
  of 
  any 
  bromine 
  or 
  

   hydrobromic 
  acid. 
  As 
  soon 
  as 
  the 
  iodine 
  solution 
  has 
  been 
  intro- 
  

   duced, 
  the 
  bottle 
  is 
  shaken, 
  and 
  preferably 
  set 
  into 
  the 
  ice 
  for 
  a 
  

   couple 
  of 
  minutes 
  more, 
  so 
  that 
  there 
  may 
  be 
  no 
  loss 
  of 
  drops 
  of 
  

   the 
  solution 
  when 
  the 
  stopper 
  is 
  opened, 
  caused 
  by 
  a 
  slight 
  pressure 
  

   inside 
  the 
  bottle. 
  The 
  reaction 
  between 
  the 
  bromine 
  and 
  the 
  iodide 
  

   solution 
  causes 
  some 
  heat 
  and 
  consequent 
  pressure. 
  The 
  free 
  iodine 
  

   is 
  now 
  titrated 
  with 
  neutral 
  tenth-normal 
  sodium 
  thiosnlphate, 
  using 
  

   as 
  little 
  starch 
  as 
  possible 
  as 
  indicator. 
  At 
  the 
  end 
  of 
  this 
  titra- 
  

   tion, 
  5 
  c. 
  c. 
  of 
  a 
  neutral 
  2 
  per 
  cent 
  solution 
  of 
  potassium 
  iodate 
  

   is 
  added, 
  a 
  little 
  more 
  starch 
  solution 
  and 
  the 
  iodine 
  liberated, 
  on 
  

   account 
  of 
  the 
  hydrobromic 
  acid 
  produced 
  in 
  the 
  original 
  reaction 
  

   of 
  bromine 
  on 
  the 
  oil, 
  titrated 
  with 
  thiosnlphate. 
  From 
  the 
  figures 
  

   so 
  obtained, 
  the 
  total 
  percentage 
  of 
  bromine 
  which 
  has 
  disappeared 
  

   is 
  calculated, 
  and 
  the 
  percentage 
  of 
  bromine 
  found 
  as 
  hydrobromic 
  

   acid, 
  called 
  the 
  " 
  Bromine 
  Substitution 
  Figure," 
  is 
  also 
  calcu- 
  

   lated, 
  w*hile 
  from 
  these 
  two 
  tlie 
  " 
  Bromine 
  Addition 
  Figure 
  " 
  is 
  

   obtained 
  by 
  subtracting 
  twice 
  the 
  bromine 
  substitution 
  figure 
  from 
  

   tlie 
  total 
  bromine 
  absorption. 
  A 
  consideration 
  of 
  the 
  figures 
  sub- 
  

   mitted 
  in 
  the 
  table 
  will 
  show 
  that 
  if 
  an 
  oil 
  contains 
  rosin, 
  rosin 
  

   oil, 
  or 
  mineral 
  oil, 
  the 
  fact 
  will 
  be 
  brought 
  out 
  by 
  this 
  process, 
  

   and 
  an 
  indication 
  given 
  by 
  the 
  figures 
  so 
  obtained 
  as 
  to 
  which 
  one 
  is 
  

   present. 
  If 
  the 
  bromine 
  substitution 
  figure 
  is 
  normal, 
  the 
  absence 
  

  

  