﻿German-Silver 
  and 
  Platinoid 
  Wires, 
  161 
  

  

  form 
  of 
  phosphor-tungsten, 
  is 
  first 
  melted 
  with 
  a 
  certain 
  

   quantity 
  of 
  copper. 
  The 
  nickel 
  is 
  next 
  added, 
  then 
  the 
  zinc, 
  

   and 
  finally 
  the 
  remainder 
  of 
  the 
  copper. 
  In 
  order 
  to 
  remove 
  

   phosphorus 
  and 
  a 
  portion 
  of 
  the 
  tungsten, 
  both 
  of 
  which 
  

   separate 
  as 
  dross, 
  the 
  resulting 
  compound 
  is 
  several 
  times 
  

   remelted. 
  It 
  is 
  probable 
  that 
  traces 
  of 
  arsenic 
  and 
  phophorus 
  

   are 
  present 
  in 
  the 
  alloy. 
  

  

  If 
  nickel 
  is 
  in 
  too 
  great 
  proportion 
  in 
  nickel-copper 
  alloys, 
  

   oxygen 
  is 
  absorbed 
  during 
  fusion, 
  and 
  liberated 
  on 
  cooling. 
  

   The 
  result 
  is 
  a 
  porous 
  metal. 
  Again, 
  if 
  the 
  temperature 
  of 
  

   casting 
  is 
  too 
  high, 
  or 
  if 
  the 
  cooling 
  is 
  irregular, 
  cavities 
  may 
  

   be 
  expected 
  in 
  the 
  final 
  alloy. 
  

  

  The 
  surprising 
  diminution 
  in 
  tensile 
  strength 
  produced 
  by 
  

   traces 
  of 
  impurities, 
  for 
  some 
  alloys, 
  has 
  been 
  studied 
  by 
  Prof. 
  

   Roberts-Austen 
  and 
  other 
  metallurgists. 
  A 
  very 
  small 
  per- 
  

   centage 
  of 
  arsenic 
  in 
  nickel-copper-zinc 
  compounds 
  causes 
  

   extreme 
  brittleness. 
  So 
  also 
  does 
  a 
  small 
  addition 
  of 
  lead 
  or 
  

   iron. 
  And 
  as 
  arsenical 
  nickel 
  ore 
  is 
  the 
  source 
  of 
  much 
  of 
  

   the 
  nickel 
  of 
  commerce, 
  the 
  failure 
  of 
  german-silver 
  and 
  

   platinoid 
  may 
  possibly 
  be 
  due 
  to 
  traces 
  of 
  arsenic. 
  

  

  At 
  this 
  point, 
  however, 
  I 
  propose 
  to 
  discriminate 
  between 
  

   two 
  kinds 
  of 
  brittleness, 
  my 
  object 
  being 
  to 
  simplify 
  the 
  dis- 
  

   cussion 
  of 
  the 
  problem. 
  That 
  such 
  a 
  distinction 
  is 
  necessary 
  

   will 
  perhaps 
  be 
  b^st 
  illustrated 
  by 
  an 
  example. 
  Prof. 
  Roberts- 
  

   Austen 
  demonstrated 
  that 
  the 
  addition 
  of 
  1 
  per 
  cent, 
  of 
  lead 
  

   reduces 
  the 
  tensile 
  strength 
  of 
  gold 
  by 
  more 
  than 
  two- 
  thirds. 
  

   Similarly, 
  he 
  observed 
  that 
  arsenic 
  renders 
  gold 
  very 
  fragile, 
  

   and 
  that 
  0*2 
  per 
  cent, 
  of 
  bismuth 
  instantly 
  converts 
  gold 
  into 
  

   an 
  alloy 
  that 
  crumbles 
  under 
  the 
  die. 
  In 
  all 
  these 
  cases, 
  

   brittleness 
  is 
  characteristic 
  of 
  the 
  alloy 
  from 
  the 
  moment 
  of 
  

   solidification 
  ; 
  it 
  may, 
  in 
  fact, 
  be 
  regarded 
  as 
  a 
  definite 
  function 
  

   of 
  the 
  atomic 
  volumes 
  of 
  the 
  constituent 
  elements. 
  I 
  propose 
  

   to 
  call 
  this 
  " 
  primary 
  " 
  brittleness. 
  

  

  But 
  the 
  brittleness 
  of 
  german-silver 
  and 
  platinoid 
  is 
  of 
  a 
  

   different 
  order. 
  It 
  is 
  a 
  subsequent 
  phenomenon. 
  For 
  example 
  : 
  

   the 
  alloys 
  from 
  which 
  electrical 
  wires 
  are 
  made 
  are 
  necessarily 
  

   strong 
  in 
  the 
  first 
  instance 
  ; 
  if 
  they 
  were 
  mechanically 
  weak, 
  

   i. 
  e., 
  if 
  they 
  possessed 
  " 
  primary" 
  brittleness, 
  they 
  would 
  fail 
  

   in 
  the 
  process 
  of 
  " 
  drawing 
  " 
  through 
  the 
  die. 
  Hence, 
  the 
  

   distinction 
  between 
  " 
  primary 
  " 
  and 
  " 
  secondary 
  '' 
  brittleness. 
  

   The 
  one 
  is 
  an 
  accident 
  of 
  birth, 
  the 
  other 
  is 
  a 
  disease 
  that 
  

   develops 
  with 
  age 
  and 
  circumstance. 
  

  

  The 
  fracture 
  of 
  platinoid, 
  as 
  seen 
  under 
  the 
  microscope, 
  

   is 
  granular 
  or 
  crystalline. 
  In 
  new 
  and 
  good 
  specimens 
  the 
  

   colour 
  is 
  silver-grey, 
  and 
  uniform 
  except 
  for 
  a 
  few 
  well- 
  

   defined 
  patches 
  of 
  brown. 
  Occasional 
  specimens 
  of 
  brittle 
  

  

  