﻿350 
  

  

  On 
  certain 
  Alloys 
  of 
  Silver 
  and 
  Copper. 
  [Mar. 
  18, 
  

  

  The 
  author 
  then 
  described 
  the 
  experiments 
  . 
  he 
  made 
  with 
  a 
  view 
  to 
  

   determine 
  the 
  melting-points 
  of 
  a 
  series 
  of 
  these 
  alloys. 
  He 
  adopted 
  

   Deville's 
  determination 
  of 
  the 
  boiling-point 
  of 
  zinc 
  (1040° 
  C.) 
  as 
  the 
  basis 
  

   of 
  the 
  inquiry, 
  and 
  ascertained, 
  by 
  the 
  method 
  of 
  mixtures, 
  the 
  mean 
  

   specific 
  heat 
  of 
  a 
  mass 
  of 
  wrought 
  iron 
  between 
  0° 
  C. 
  and 
  the 
  melting- 
  

   point 
  of 
  silver, 
  which, 
  as 
  Becquerel 
  showed, 
  is 
  the 
  same 
  as 
  the 
  boiling- 
  

   point 
  of 
  zinc. 
  

  

  The 
  mean 
  of 
  three 
  experiments, 
  which 
  were 
  closely 
  in 
  accordance, 
  

   gave 
  0' 
  15693 
  as 
  the 
  specific 
  heat 
  ; 
  and 
  it 
  should 
  be 
  pointed 
  out 
  that 
  this 
  

   number 
  includes 
  and 
  neutralizes 
  several 
  errors 
  which 
  would 
  affect 
  the 
  

   accuracy 
  of 
  the 
  subsequent 
  determinations. 
  

  

  The 
  melting-points 
  of 
  several 
  alloys 
  were 
  then 
  determined 
  by 
  plunging 
  

   an 
  iron 
  cylinder 
  into 
  them 
  and 
  transferring 
  the 
  iron 
  to 
  a 
  calorimeter. 
  These 
  

   melting-points 
  varied 
  from 
  840° 
  C. 
  to 
  1330° 
  0., 
  or 
  through 
  a 
  range 
  of 
  

   490° 
  C. 
  The 
  alloys 
  which 
  occupy 
  the 
  lowest 
  portion 
  of 
  the 
  curve 
  con- 
  

   tain 
  from 
  60 
  to 
  70 
  per 
  cent, 
  of 
  silver. 
  The 
  results 
  are 
  interesting, 
  as 
  

   they 
  show 
  that 
  the 
  curves 
  of 
  fusibility 
  and 
  electric 
  conductivity 
  are 
  very 
  

   similar. 
  

  

  The 
  author 
  states 
  that, 
  in 
  studying 
  the 
  phenomena 
  of 
  liquation, 
  the 
  

   alloys 
  were 
  cast 
  in 
  red-hot 
  moulds 
  of 
  firebrick 
  in 
  which 
  the 
  metal 
  (about 
  

   50 
  oz.) 
  could 
  be 
  slowly 
  and 
  uniformly 
  cooled. 
  The 
  results 
  showed 
  that 
  

   the 
  homogeneity 
  of 
  Levol's 
  alloy 
  is 
  slightly 
  disturbed 
  by 
  this 
  method 
  of 
  

   casting 
  ; 
  and, 
  on 
  the 
  other 
  hand, 
  that 
  alloys 
  which 
  contain 
  more 
  than 
  

   71'89 
  per 
  cent, 
  of 
  silver 
  hardly 
  show 
  signs 
  of 
  rearrangement 
  when 
  the 
  

   solidification 
  is 
  gradually 
  effected. 
  Two 
  alloys 
  were 
  examined, 
  which 
  

   contained 
  63 
  and 
  33*3 
  per 
  cent, 
  of 
  silver 
  respectively. 
  Both 
  were 
  

   found 
  to 
  be 
  far 
  from 
  homogeneous. 
  In 
  the 
  case 
  of 
  the 
  former 
  the 
  

   arrangement 
  was 
  influenced 
  by 
  gravity, 
  the 
  base 
  of 
  the 
  casting 
  being 
  

   rich 
  in 
  silver. 
  

  

  The 
  density 
  of 
  pure 
  silver 
  and 
  of 
  Levol's 
  homogeneous 
  alloy 
  while 
  in 
  

   the 
  fluid 
  state 
  were 
  then 
  determined 
  by 
  the 
  method 
  described 
  by 
  Mr. 
  

   Bobert 
  Mallet*, 
  the 
  metals 
  being 
  cast 
  in 
  conical 
  vessels 
  of 
  wrought 
  

   iron. 
  The 
  results 
  obtained 
  were 
  as 
  follows 
  : 
  — 
  

  

  In 
  the 
  case 
  of 
  silver, 
  the 
  mean 
  linear 
  expansion 
  deduced 
  from 
  this 
  

   change 
  of 
  density 
  is 
  '00003721 
  per 
  1° 
  C, 
  which 
  is 
  nearly 
  double 
  the 
  

   coefficient 
  at 
  temperatures 
  below 
  100° 
  Q.. 
  

  

  The 
  Society 
  then 
  adjourned 
  over 
  the 
  Easter 
  Becess, 
  to 
  Thursday, 
  

  

  Pure 
  silver 
  . 
  , 
  

   Levol's 
  alloy 
  

  

  Density 
  fluid, 
  

   9-4612 
  

   9-0554 
  

  

  Density 
  solid. 
  

   10-57 
  

   9-9045 
  

  

  April 
  8. 
  

  

  * 
  Vide 
  swprb, 
  p. 
  2Q& 
  

  

  