﻿certain 
  Alloys 
  of 
  Silver 
  and 
  Copper. 
  

  

  489 
  

  

  point 
  to 
  the 
  necessity 
  of 
  slightly 
  modifying 
  its 
  form. 
  This 
  critical 
  

   examination 
  is 
  especially 
  necessary 
  in 
  the 
  region 
  of 
  the 
  497 
  alloy 
  ; 
  

   for 
  not 
  only 
  do 
  the 
  results 
  obtained 
  on 
  it 
  diverge 
  widely 
  among 
  them- 
  

   selves, 
  but 
  their 
  mean 
  is 
  far 
  removed 
  from 
  the 
  probable 
  line 
  of 
  the 
  

   curve. 
  

  

  I 
  am 
  not 
  satisfied 
  with 
  the 
  results 
  I 
  have 
  obtained 
  on 
  an 
  alloy 
  which 
  

   contains 
  773*2 
  parts 
  of 
  silver. 
  This 
  alloy 
  is 
  of 
  special 
  interest 
  ; 
  its 
  

   formula 
  is 
  Ag 
  2 
  ' 
  Cu", 
  silver 
  being 
  monatomic. 
  

  

  [Since 
  the 
  above 
  was 
  submitted 
  to 
  the 
  Eoyal 
  Society, 
  I 
  have 
  made 
  

   additional 
  experiments 
  on 
  alloys 
  in 
  these 
  two 
  portions 
  of 
  the 
  curve. 
  The 
  

   calorimeter 
  used 
  was 
  of 
  thin 
  polished 
  silver, 
  capable 
  of 
  holding 
  1200 
  

   grammes 
  of 
  water, 
  which 
  were 
  never 
  raised 
  through 
  more 
  than 
  15° 
  C. 
  

   The 
  water-equivalent 
  of 
  the 
  instrument 
  was 
  only 
  15*72 
  grammes. 
  The 
  

   masses 
  of 
  iron 
  used 
  were 
  such 
  as 
  had 
  been 
  employed 
  as 
  carriers 
  of 
  

   heat 
  in 
  the 
  first 
  experiments 
  : 
  the 
  mean 
  of 
  several 
  very 
  concordant 
  

   results 
  gave 
  '15003 
  as 
  the 
  specific 
  heat 
  of 
  the 
  iron 
  when 
  this 
  new 
  calori- 
  

   meter 
  is 
  employed 
  ; 
  and, 
  as 
  has 
  already 
  been 
  pointed 
  out 
  (p. 
  484), 
  this 
  

   number 
  includes 
  and 
  neutralizes 
  several 
  errors. 
  

  

  The 
  results 
  are 
  distinguished 
  by 
  an 
  asterisk 
  in 
  the 
  Table, 
  and 
  have 
  

   been 
  added 
  to 
  those 
  originally 
  indicated 
  in 
  the 
  Diagram. 
  They 
  confirm 
  

   the 
  direction 
  originally 
  given 
  to 
  the 
  curve 
  in 
  the 
  region 
  of 
  the 
  alloys 
  

   which 
  contain 
  from 
  718 
  to 
  800 
  parts 
  of 
  silver 
  ; 
  but 
  the 
  existence 
  of 
  a 
  

   cusp 
  has 
  been 
  detected 
  at 
  the 
  point 
  which 
  represents 
  the 
  alloy 
  No. 
  11 
  

   ( 
  Ag 
  3 
  Cu 
  4 
  ). 
  It 
  may 
  be 
  interesting 
  to 
  point 
  out 
  that 
  the 
  results 
  from 
  which 
  

   Matthiessen's 
  curve 
  of 
  electric 
  conductivity 
  was 
  developed 
  appear 
  to 
  

   prove 
  the 
  presence 
  of 
  a 
  cusp 
  at 
  the 
  point 
  which 
  represents 
  the 
  alloy 
  

   459-4 
  (AgCu 
  2 
  ).— 
  im 
  May, 
  1875.] 
  

  

  It 
  may 
  be 
  useful 
  to 
  compare 
  these 
  results 
  with 
  those 
  obtained 
  by 
  

   Eudberg 
  on 
  alloys 
  of 
  lead 
  and 
  tin. 
  He 
  found 
  that 
  when 
  a 
  thermometer 
  

   is 
  placed 
  in 
  a 
  molten 
  alloy 
  of 
  these 
  metals 
  two 
  distinct 
  stationary 
  points 
  

   are 
  indicated 
  during 
  the 
  passage 
  from 
  the 
  liquid 
  to 
  the 
  solid 
  state. 
  One 
  

   of 
  these 
  points 
  is 
  always 
  187° 
  C. 
  ; 
  and 
  in 
  the 
  alloy 
  Pb 
  Sn 
  6 
  the 
  two 
  points 
  

   coincide 
  at 
  this 
  temperature 
  — 
  a 
  fact 
  which 
  led 
  Eudberg 
  to 
  conclude 
  that 
  

   it 
  was 
  the 
  only 
  alloy 
  in 
  which 
  the 
  whole 
  of 
  the 
  metals 
  were 
  chemically 
  

   combined. 
  I 
  hope, 
  in 
  continuing 
  this 
  inquiry, 
  to 
  be 
  able 
  to 
  ascertain 
  

   whether 
  the 
  change 
  of 
  state 
  in 
  the 
  case 
  of 
  silver-copper 
  alloys 
  also 
  termi- 
  

   nates 
  at 
  a 
  constant 
  temperature. 
  I 
  may 
  mention 
  that 
  M. 
  A. 
  Eich* 
  

   determined 
  the 
  melting-points 
  of 
  certain 
  alloys 
  of 
  tin 
  and 
  copper 
  by 
  

   means 
  of 
  Becquerel's 
  thermo-electric 
  pyrometer 
  ; 
  and 
  he 
  obtained 
  con- 
  

   cordant 
  results 
  with 
  the 
  alloys 
  Sn 
  Cu 
  3 
  and 
  Sn 
  Cu 
  4 
  ; 
  but 
  with 
  all 
  other 
  

   alloys 
  the 
  results 
  differed 
  widely 
  among 
  themselves. 
  

  

  It 
  is 
  at 
  present 
  difficult 
  to 
  show 
  the 
  direct 
  bearing 
  of 
  these 
  results 
  on 
  

   the 
  phenomena 
  of 
  liquation 
  in 
  alloys 
  of 
  silver 
  and 
  copper 
  ; 
  but 
  the 
  curve 
  

   is 
  valuable, 
  as 
  it 
  proves 
  that 
  the 
  alloys 
  Nos. 
  7 
  and 
  8 
  occupy 
  positions 
  in 
  

   * 
  Ann. 
  Chim. 
  et 
  Phys. 
  t. 
  xxx. 
  p. 
  351. 
  

  

  