﻿172 
  

  

  Mr. 
  W. 
  H. 
  Johnson 
  on 
  the 
  Action 
  of 
  [Jan. 
  14, 
  

  

  with 
  similar 
  results, 
  as 
  regards 
  increased 
  brittleness, 
  to 
  those 
  which 
  

   accompany 
  the 
  absorption 
  of 
  hydrogen. 
  It 
  also 
  shows 
  how 
  rapidly, 
  by 
  a 
  

   slight 
  change 
  of 
  temperature, 
  zinc 
  may 
  be 
  disengaged 
  from 
  the 
  iron, 
  

   thereby 
  causing 
  it 
  to 
  regain 
  its 
  former 
  toughness. 
  

  

  A 
  piece 
  of 
  galvanized 
  iron 
  wire, 
  of 
  good 
  quality, 
  such 
  that 
  when 
  cold 
  it 
  

   could 
  be 
  bent 
  several 
  times 
  on 
  itself 
  and 
  back 
  again 
  before 
  breaking, 
  was 
  

   raised 
  to 
  a 
  red 
  heat 
  so 
  quickly 
  that 
  the 
  coating 
  of 
  zinc 
  was 
  melted 
  and 
  only 
  

   a 
  small 
  portion 
  vaporized. 
  On 
  attempting 
  to 
  bend 
  it 
  whilst 
  still 
  red-hot, 
  

   it 
  broke 
  off 
  sharp, 
  offering 
  very 
  little 
  resistance 
  to 
  fracture. 
  The 
  fracture 
  

   was 
  of 
  a 
  uniform 
  blue-grey 
  colour, 
  as 
  though 
  the 
  zinc 
  had 
  penetrated 
  into 
  

   the 
  interior 
  of 
  the 
  iron. 
  When 
  cold, 
  the 
  same 
  piece 
  broke 
  with 
  all 
  its 
  

   former 
  toughness 
  and 
  with 
  a 
  long 
  fibrous 
  fracture. 
  The 
  wire 
  was 
  again 
  

   heated 
  till 
  the 
  coating 
  of 
  zinc 
  was 
  completely 
  vaporized, 
  and 
  then 
  it 
  was 
  

   found 
  to 
  be 
  so 
  tough 
  that 
  it 
  was 
  impossible 
  to 
  break 
  at 
  a 
  red 
  heat. 
  "Wire 
  

   in 
  red-hot 
  molten 
  zinc 
  will 
  often 
  break 
  short, 
  though 
  the 
  part 
  out 
  of 
  the 
  

   metal 
  remains 
  quite 
  tough. 
  

  

  It 
  is 
  remarkable 
  that 
  this 
  experiment 
  will 
  not 
  succeed 
  with 
  all 
  kinds 
  

   of 
  iron, 
  some 
  not 
  being 
  made 
  thus 
  "red 
  short" 
  by 
  zinc. 
  

  

  By 
  way 
  of 
  testing 
  the 
  theory 
  that 
  occluded 
  hydrogen 
  is 
  the 
  cause 
  of 
  

   the 
  change 
  in 
  the 
  properties 
  of 
  iron 
  after 
  its 
  immersion 
  in 
  acids, 
  the 
  

   writer 
  determined 
  to 
  dispense 
  with 
  acid 
  altogether, 
  and 
  endeavour 
  to 
  pro- 
  

   duce 
  the 
  same 
  result 
  by 
  subjecting 
  pieces 
  of 
  iron 
  to 
  the 
  action 
  of 
  nascent 
  

   hydrogen. 
  

  

  " 
  With 
  this 
  view 
  two 
  pieces 
  of 
  iron 
  wire 
  *07 
  inch 
  diameter 
  were 
  con- 
  

   nected 
  respectively 
  with 
  the 
  zinc 
  and 
  copper 
  plates 
  of 
  a 
  battery 
  of 
  80 
  

   Daniell's 
  cells, 
  and 
  immersed 
  in 
  a 
  vessel 
  of 
  Manchester 
  town's 
  water 
  at 
  a 
  

   distance 
  of 
  1 
  inch 
  apart. 
  On 
  closing 
  the 
  current, 
  bubbles 
  of 
  hydrogen 
  

   were 
  given 
  off 
  from 
  the 
  wire 
  connected 
  with 
  the 
  zinc 
  plate 
  of 
  the 
  battery, 
  

   but 
  none 
  from 
  the 
  wire 
  connected 
  with 
  the 
  copper 
  plate, 
  the 
  oxygen 
  libe- 
  

   rated 
  there 
  apparently 
  forming 
  oxide 
  of 
  iron, 
  which 
  in 
  12 
  hours 
  formed 
  

   a 
  muddy 
  deposit 
  at 
  the 
  bottom 
  of 
  the 
  vessel. 
  After 
  24 
  hours 
  the 
  surface 
  

   of 
  the 
  wire 
  connected 
  with 
  the 
  zinc 
  plate 
  was 
  unchanged 
  ; 
  but 
  on 
  moisten- 
  

   ing 
  the 
  fracture 
  bubbles 
  were 
  given 
  off, 
  just 
  as 
  if 
  it 
  had 
  been 
  immersed 
  

   in 
  acid. 
  The 
  other 
  wire, 
  though 
  much 
  oxidized 
  and 
  eaten 
  away, 
  did 
  not 
  

   give 
  off 
  bubbles 
  when 
  broken, 
  and 
  had 
  not 
  become 
  brittle. 
  

  

  " 
  A 
  variety 
  of 
  experiments 
  made 
  in 
  the 
  same 
  way 
  with 
  pieces 
  of 
  wire 
  

   varying 
  from 
  3 
  to 
  20 
  inches 
  long, 
  and 
  immersed 
  5 
  to 
  24 
  hours 
  in 
  water, 
  

   yielded 
  similar 
  results. 
  It 
  was 
  found, 
  however, 
  that 
  when 
  the 
  wire 
  con- 
  

   nected 
  with 
  the 
  zinc 
  plate 
  was 
  of 
  steel, 
  no 
  bubbles 
  were 
  visible 
  to 
  the 
  

   naked 
  eye 
  on 
  wetting 
  the 
  fracture 
  with 
  the 
  tongue, 
  precisely 
  as 
  in 
  the 
  

   case 
  of 
  steel 
  after 
  immersion 
  in 
  acid. 
  Twenty-four 
  hours 
  in 
  a 
  warm 
  room 
  

   restored 
  the 
  iron 
  to 
  its 
  original 
  state, 
  and 
  no 
  bubbles 
  were 
  then 
  seen 
  on 
  

   breaking 
  and 
  moistening 
  the 
  fracture. 
  

  

  " 
  The 
  water 
  in 
  the 
  last 
  experiments 
  was 
  then 
  replaced 
  by 
  an 
  aqueous 
  

   solution 
  of 
  caustic 
  soda, 
  when, 
  after 
  two 
  hours, 
  the 
  moistened 
  fracture 
  of 
  

  

  