﻿certain 
  Alloys 
  of 
  Silver 
  mid 
  Copper. 
  487 
  

  

  Melting-points 
  of 
  Silver-Copper 
  Alloys 
  (continued). 
  

  

  No. 
  

  

  Parts 
  of 
  pure 
  

   silver 
  in 
  1000 
  

   parts 
  of 
  the 
  

   alloy. 
  

  

  Approximate 
  

   formula. 
  

  

  Melting-points, 
  

   in 
  degrees 
  Centigrade. 
  

  

  Observed. 
  

  

  Mean. 
  

  

  14. 
  

  

  497 
  

  

  

  940-2 
  

   973-0 
  

  

  Jo 
  1 
  O 
  

  

  955-6 
  

  

  962-6 
  

  

  10. 
  

  

  

  tu 
  2 
  

  

  953-5 
  

  

  963- 
  9 
  

  

  964- 
  1 
  

  

  960-8 
  

  

  16. 
  

  

  250-5 
  

  

  AgCu 
  5 
  

  

  1080-8 
  

   1141-8 
  

   1114-9 
  

   1119-1 
  

  

  1114-1 
  

  

  17. 
  

  

  

  

  (pure 
  copper). 
  

  

  

  

  1330 
  

  

  These 
  melting-points 
  are 
  graphically 
  represented 
  by 
  the 
  accompanying 
  

   curve 
  (next 
  page) 
  ; 
  the 
  coordinates 
  are 
  the 
  amounts 
  of 
  silver 
  in 
  the 
  several 
  

   alloys 
  and 
  their 
  melting-points. 
  

  

  It 
  will 
  be 
  observed 
  that 
  the 
  curve 
  exhibits 
  a 
  somewhat 
  rapid 
  decrement 
  

   from 
  pure 
  silver 
  to 
  the 
  alloy 
  which 
  contains 
  925 
  parts 
  of 
  silver, 
  the 
  one 
  

   employed 
  for 
  the 
  British 
  silver 
  coins. 
  In 
  it 
  the 
  relation 
  between 
  the 
  

   amounts 
  of 
  metals 
  present 
  is 
  approximately 
  represented 
  by 
  the 
  formula 
  

   Ag 
  7 
  Cu. 
  

  

  The 
  alloys 
  numbered 
  7 
  and 
  8 
  are 
  of 
  singular 
  interest. 
  The 
  first, 
  which 
  

   contains 
  718*93 
  parts 
  of 
  silver, 
  is 
  Levol's 
  homogeneous 
  alloy 
  ; 
  and 
  I 
  anti- 
  

   cipated 
  that 
  it 
  would 
  have 
  the 
  lowest 
  melting-point 
  ; 
  but 
  the 
  results 
  

   showed 
  that 
  the 
  alloy 
  containing 
  630*29 
  parts 
  of 
  silver 
  (JNo. 
  8) 
  melts 
  at 
  a 
  

   point 
  which 
  is 
  23*7 
  degrees 
  lower. 
  In 
  this 
  alloy 
  a 
  very 
  simple 
  relation 
  

   exists 
  between 
  the 
  atoms 
  of 
  the 
  constituent 
  metals, 
  the 
  formula 
  being 
  

   AgCu. 
  Additional 
  interest 
  is 
  imparted 
  to 
  it 
  by 
  Matthiessen's 
  curve 
  of 
  

   electric 
  conductivity 
  having 
  shown 
  that 
  the 
  arrangement 
  of 
  an 
  alloy 
  of 
  

   this 
  composition 
  would 
  probably 
  be 
  peculiar. 
  Prom 
  this 
  point 
  the 
  curve 
  

   passes 
  through 
  the 
  points 
  representing 
  alloys 
  in 
  which 
  base 
  metal 
  pre- 
  

   dominates 
  to 
  1330° 
  C, 
  the 
  melting-point 
  of 
  pure 
  copper. 
  

  

  Further 
  evidence 
  as 
  to 
  the 
  melting-points 
  of 
  Nos. 
  7 
  and 
  8 
  was 
  afforded 
  

   by 
  placing 
  strips 
  of 
  them 
  in 
  small 
  covered 
  crucibles 
  surrounded 
  by 
  the 
  

   vapour 
  of 
  boiling 
  cadmium, 
  the 
  temperature 
  of 
  which 
  has 
  been 
  fixed 
  by 
  

   Deville 
  at 
  860° 
  C. 
  Both 
  alloys 
  melted, 
  the 
  first 
  partially, 
  the 
  second 
  com- 
  

   pletely. 
  I 
  am 
  convinced, 
  therefore, 
  that 
  the 
  melting-points 
  of 
  the 
  alloys 
  

   generally 
  are 
  not 
  inaccurately 
  indicated 
  by 
  the 
  curve. 
  It 
  is, 
  however, 
  not 
  

   improbable 
  that 
  the 
  examination 
  of 
  a 
  more 
  extended 
  series 
  of 
  alloys 
  may 
  

  

  