﻿certain 
  Alloys 
  of 
  Silver 
  and 
  Copper. 
  

  

  483 
  

  

  of 
  silver 
  ; 
  otherwise 
  we 
  should 
  expect 
  a 
  straight 
  line 
  from 
  the 
  alloy 
  

   containing 
  72 
  per 
  cent, 
  of 
  silver 
  to 
  that 
  which 
  contains 
  only 
  10 
  per 
  

   cent. 
  

  

  I 
  now 
  proceed 
  to 
  give 
  the 
  results 
  of 
  my 
  own 
  experiments. 
  

  

  In 
  commencing 
  the 
  inquiry, 
  it 
  seemed 
  probable 
  that, 
  by 
  determining 
  

   the 
  melting-points 
  of 
  a 
  series 
  of 
  the 
  alloys 
  of 
  silver 
  and 
  copper, 
  informa- 
  

   tion 
  of 
  much 
  interest 
  might 
  be 
  gained 
  as 
  to 
  the 
  arrangement 
  which 
  attends 
  

   the 
  solidification 
  of 
  a 
  fluid 
  mass 
  of 
  these 
  metals. 
  I 
  adopted 
  a 
  modifica- 
  

   tion 
  of 
  the 
  plan 
  described 
  by 
  Pouillet*, 
  and 
  employed 
  by 
  him 
  in 
  deter- 
  

   mining 
  the 
  specific 
  heat 
  of 
  platinum 
  at 
  high 
  temperatures. 
  

  

  As 
  soon 
  as 
  the 
  alloy 
  under 
  examination 
  was 
  melted, 
  a 
  wrought-iron 
  

   cylinder 
  of 
  known 
  weight 
  was 
  dropped 
  into 
  it 
  by 
  means 
  of 
  a 
  wire 
  sup- 
  

   port. 
  The 
  crucible 
  was 
  then 
  removed 
  from 
  the 
  furnace, 
  and, 
  when 
  the 
  

   alloy 
  showed 
  signs 
  of 
  solidifying, 
  the 
  iron 
  was 
  transferred 
  to 
  a 
  calori- 
  

   meter, 
  which 
  consisted 
  of 
  two 
  concentric 
  vessels 
  of 
  thin 
  polished 
  brass, 
  

   such 
  as 
  is 
  ordinarily 
  used 
  for 
  determining 
  specific 
  heats 
  by 
  the 
  method 
  of 
  

   mixtures. 
  

  

  It 
  was 
  necessary 
  to 
  determine 
  the 
  mean 
  specific 
  heat 
  of 
  the 
  iron 
  

   employed, 
  between 
  0° 
  C. 
  and 
  a 
  known 
  fixed 
  point 
  near 
  the 
  maximum 
  

   temperature 
  likely 
  to 
  be 
  attained 
  in 
  the 
  course 
  of 
  the 
  experiments* 
  The 
  

   melting-point 
  of 
  silver 
  was 
  a 
  convenient 
  one, 
  and 
  it 
  has 
  been 
  accurately 
  

   ascertained 
  by 
  M. 
  Becquerelf, 
  who 
  placed 
  a 
  wire 
  of 
  pure 
  silver 
  in 
  a 
  

   crucible 
  which 
  was 
  enclosed 
  in 
  a 
  porcelain 
  tube 
  surrounded 
  by 
  the 
  

   vapour 
  of 
  boiling 
  zinc, 
  the 
  temperature 
  of 
  which 
  has 
  been 
  fixed 
  by 
  M. 
  

   Deville 
  at 
  1040° 
  C.+ 
  As 
  the 
  heat 
  was 
  sufficient 
  to 
  partially 
  fuse 
  the 
  

   silver, 
  this 
  temperature 
  may 
  safely 
  be 
  taken 
  as 
  the 
  melting-point 
  of 
  the 
  

   metal. 
  

  

  In 
  order, 
  therefore, 
  to 
  determine 
  the 
  specific 
  heat 
  of 
  the 
  iron, 
  I 
  plunged 
  

   the 
  cylinder 
  into 
  molten 
  silver, 
  and 
  transferred 
  it 
  to 
  the 
  calorimeter. 
  I 
  

   may 
  here 
  observe 
  that 
  the 
  film 
  of 
  oxide 
  which 
  formed 
  on 
  the 
  surface 
  of 
  

   the 
  iron 
  to 
  a 
  great 
  extent 
  protected 
  it 
  from 
  being 
  attacked 
  by 
  the 
  molten 
  

   alloy 
  ; 
  but 
  it 
  was 
  impossible 
  to 
  avoid 
  carrying 
  into 
  the 
  calorimeter 
  a 
  small 
  

   quantity 
  of 
  metal 
  which 
  adhered 
  to 
  the 
  iron. 
  The 
  metal 
  so 
  introduced 
  

   was 
  always 
  collected 
  and 
  allowed 
  for. 
  "With 
  pure 
  silver 
  0*05701 
  was 
  

   taken 
  as 
  the 
  specific 
  heat, 
  while 
  in 
  the 
  case 
  of 
  alloys 
  the 
  necessary 
  cor- 
  

   rection 
  was 
  made 
  by 
  deducing 
  the 
  specific 
  heat 
  of 
  each 
  alloy 
  from 
  the 
  

   specific 
  heats 
  of 
  its 
  constituents 
  ; 
  and 
  the 
  equivalent 
  weight 
  of 
  iron 
  was 
  

   calculated 
  by 
  multiplying 
  the 
  weight 
  of 
  introduced 
  metal 
  by 
  its 
  specific 
  

   heat, 
  and 
  dividing 
  this 
  product 
  by 
  the 
  specific 
  heat 
  of 
  iron 
  as 
  ascertained 
  

   by 
  preliminary 
  experiments. 
  This 
  weight 
  was 
  then 
  added 
  to 
  that 
  of 
  the 
  

   iron 
  employed. 
  

  

  The 
  specific 
  heats 
  of 
  metals 
  at 
  high 
  temperatures 
  have 
  not 
  been 
  deter- 
  

  

  * 
  Elements 
  de 
  Physique, 
  sixienie 
  edition, 
  t. 
  ii. 
  p. 
  564. 
  

   t 
  Ann. 
  Chim. 
  et 
  Phys. 
  (3) 
  t. 
  lxviii. 
  p. 
  74. 
  

   \ 
  Comptes 
  Eendus, 
  t. 
  lvii. 
  p. 
  897. 
  

  

  