﻿1875.] 
  Hydrogen 
  and 
  Acids 
  on 
  Iron 
  and 
  Steel. 
  175 
  

  

  large 
  numbers 
  of 
  iron 
  articles 
  are 
  now 
  coated 
  with 
  a 
  covering 
  of 
  copper 
  

   four 
  thousandths 
  of 
  an 
  inch 
  in 
  thickness. 
  

  

  In 
  connexion 
  with 
  this 
  subject, 
  I 
  wish 
  to 
  refute 
  a 
  statement 
  made 
  by 
  

   Professor 
  Reynolds, 
  in 
  a 
  paper 
  read 
  before 
  the 
  Lit. 
  and 
  Phil. 
  Society 
  of 
  

   Manchester, 
  Feb. 
  24th, 
  1874, 
  an 
  abstract 
  of 
  which 
  appeared 
  in 
  the 
  

   ' 
  Journal 
  of 
  the 
  Chemical 
  Society,' 
  June 
  1874, 
  p. 
  546, 
  and 
  other 
  journals. 
  

   The 
  Professor 
  states 
  that 
  I 
  did 
  not 
  attribute 
  the 
  frothing 
  of 
  iron 
  after 
  

   immersion 
  in 
  acid 
  to 
  the 
  escape 
  of 
  hydrogen, 
  but 
  to 
  the 
  action 
  of 
  acid. 
  

   In 
  my 
  first 
  paper 
  on 
  this 
  subject 
  (Proc. 
  Lit. 
  and 
  Phil. 
  Soc. 
  Manchester, 
  

   p. 
  80, 
  1873) 
  the 
  following 
  passage 
  occurs 
  : 
  — 
  " 
  It 
  seems 
  probable 
  that 
  a 
  

   part 
  of 
  the 
  hydrogen 
  produced 
  by 
  the 
  action 
  of 
  the 
  acid 
  on 
  the 
  iron 
  may 
  

   be 
  absorbed 
  by 
  the 
  iron, 
  its 
  nascent 
  state 
  facilitating 
  this. 
  And 
  when 
  the 
  

   iron 
  is 
  heated, 
  by 
  the 
  effort 
  of 
  breaking 
  it, 
  the 
  gas 
  may 
  bubble 
  up 
  through 
  

   the 
  moisture 
  on 
  the 
  fracture." 
  This 
  shows 
  that 
  in 
  my 
  first 
  paper 
  I 
  com- 
  

   prehended 
  the 
  true 
  nature 
  of 
  the 
  phenomenon. 
  

  

  Change 
  produced 
  in 
  the 
  breaking-strain 
  and 
  ultimate 
  elongation 
  of 
  iron 
  

   and 
  steel 
  by 
  hydrogen 
  occluded 
  in 
  it 
  after 
  immersion 
  in 
  hydrochloric 
  

   and 
  sulphuric 
  acids. 
  

  

  In 
  the 
  earlier 
  part 
  of 
  this 
  paper 
  some 
  few 
  of 
  the 
  changes 
  in 
  the 
  pro- 
  

   perties 
  of 
  iron 
  produced 
  by 
  occluded 
  hydrogen 
  have 
  been 
  examined. 
  The 
  

   degree 
  of 
  this 
  change 
  it 
  has 
  not 
  always 
  been 
  possible 
  to 
  determine. 
  In 
  the 
  

   case 
  of 
  the 
  diminution 
  of 
  toughness, 
  for 
  example, 
  no 
  exact 
  and 
  easily 
  

   applied 
  test 
  has 
  yet 
  been 
  devised 
  by 
  which 
  we 
  can 
  obtain 
  with 
  precision 
  

   ; 
  numerical 
  result 
  expressing 
  the 
  relative 
  toughness 
  of 
  any 
  two 
  samples 
  ; 
  

   consequently 
  we 
  must 
  be 
  content 
  with 
  less 
  definite 
  results. 
  This 
  difficulty 
  

   is 
  fortunately 
  not 
  met 
  with 
  in 
  the 
  examination 
  of 
  the 
  change 
  in 
  elasticity 
  

   and 
  tensile 
  strength 
  ; 
  for 
  the 
  breaking- 
  weight 
  and 
  maximum 
  elongation 
  

   of 
  any 
  number 
  of 
  samples 
  can 
  be 
  pretty 
  easily 
  ascertained, 
  with 
  great 
  

   accuracy, 
  and 
  numerically 
  expressed, 
  thus 
  making 
  comparison 
  easy. 
  

  

  Bearing 
  in 
  mind 
  the 
  numerous 
  uses 
  of 
  iron 
  and 
  steel, 
  and 
  the 
  proba- 
  

   bility 
  that 
  at 
  times 
  hydrogen 
  may 
  be 
  occluded 
  in 
  them, 
  altering 
  their 
  

   strength 
  in 
  a 
  way 
  little 
  anticipated, 
  it 
  seemed 
  of 
  some 
  importance 
  to 
  de- 
  

   termine 
  these 
  changes 
  — 
  and 
  the 
  more 
  so, 
  as 
  any 
  experiments 
  of 
  this 
  kind 
  

   could 
  not 
  fail 
  to 
  throw 
  some 
  light 
  on 
  the 
  molecular 
  arrangement 
  of 
  the 
  

   metal 
  in 
  different 
  qualities 
  of 
  iron 
  and 
  steel, 
  a 
  subject 
  in 
  itself 
  of 
  much 
  

   interest. 
  With 
  this 
  object 
  upwards 
  of 
  350 
  experiments 
  have 
  been 
  made 
  

   at 
  various 
  times 
  with 
  a 
  very 
  accurate 
  machine, 
  by 
  which 
  any 
  weight 
  could 
  

   be 
  brought 
  to 
  bear 
  on 
  the 
  wire 
  to 
  be 
  tested 
  without 
  the 
  least 
  jar 
  — 
  a 
  very 
  

   important 
  point, 
  though 
  difficult 
  of 
  attainment, 
  in 
  experiments 
  on 
  tensile 
  

   strength. 
  The 
  elongation 
  at 
  any 
  moment 
  could 
  also 
  be 
  easily 
  read 
  off. 
  

   The 
  length 
  of 
  the 
  pieces 
  tested 
  was 
  in 
  all 
  cases 
  the 
  same, 
  viz. 
  10 
  inches 
  

   between 
  the 
  dies, 
  and 
  the 
  temperature 
  at 
  the 
  time 
  of 
  experiment 
  about 
  

   16° 
  C. 
  I 
  mention 
  these 
  points, 
  as 
  any 
  variation 
  in 
  the 
  length 
  or 
  tempe- 
  

  

  