﻿High 
  Temper 
  atitres. 
  191 
  

  

  Table 
  X 
  givep 
  the 
  values 
  of 
  the 
  E. 
  M. 
  F. 
  for 
  the 
  element 
  T^. 
  

  

  Table 
  X. 
  

   Thermo-element 
  T2. 
  

  

  Microvolts. 
  Microvolts. 
  

  

  500° 
  4141 
  850° 
  7794 
  

  

  550 
  4633 
  900 
  8356 
  

  

  600 
  5135 
  950 
  8927 
  j 
  

  

  650 
  5647 
  1000 
  9507 
  

  

  700 
  6169 
  1050 
  10101 
  

  

  750 
  6700 
  1100 
  10703 
  

  

  800 
  7242 
  1150 
  11315 
  

  

  Expansion 
  coefficient 
  of 
  platin-iridiiivi. 
  — 
  In 
  regard 
  to 
  the 
  

   calculation 
  of 
  the 
  temperatures 
  given 
  bj 
  the 
  gas 
  thermometer 
  

   with 
  the 
  platin-iridium 
  bulb, 
  attention 
  should 
  be 
  called 
  to 
  the 
  

   fact 
  that 
  the 
  round 
  number 
  0'000025 
  has 
  been 
  adopted 
  as 
  the 
  

   coeflScient 
  of 
  volume-expansion 
  of 
  platin-iridium 
  (S;^). 
  

  

  This 
  corresponds 
  for 
  a 
  20 
  per 
  cent 
  alloy 
  to 
  the 
  figures 
  given 
  

   by 
  Benoif^ 
  for 
  observations 
  upon 
  pure 
  platinum, 
  pure 
  iridium, 
  

   and 
  a 
  10 
  per 
  cent 
  alloy 
  for 
  temperatures 
  0°-100°. 
  

  

  It 
  is 
  probable 
  that 
  this 
  coefficient 
  is 
  higher 
  at 
  higher 
  tem- 
  

   peratures, 
  but 
  few 
  trustworthy 
  observations 
  are 
  at 
  hand. 
  

   We 
  have 
  found 
  only 
  the 
  papers 
  of 
  Le 
  Chatelierf 
  and 
  Seli- 
  

   wanow.:}: 
  The 
  former 
  gives 
  as 
  a 
  preliminary 
  result 
  for 
  a 
  10. 
  

   per 
  cent 
  alloy 
  between 
  0° 
  and 
  1000° 
  an 
  expansion 
  coefficient 
  

   some 
  30 
  per 
  cent 
  higher 
  than 
  0°-100° 
  ; 
  the 
  latter 
  for 
  platinum 
  

   0°-1650° 
  gives 
  a 
  result 
  only 
  11 
  per 
  cent 
  higher 
  than 
  at 
  the 
  

   lower 
  temperatures. 
  The 
  temperature 
  measurements 
  is 
  how- 
  

   ever, 
  in 
  the 
  latter 
  case, 
  uncertain. 
  

  

  Table 
  IX 
  shows 
  the 
  values 
  for 
  the 
  ice 
  point 
  (H^) 
  and 
  

   coefficient 
  of 
  expansion 
  («) 
  to 
  be 
  nearly 
  constant. 
  After 
  the 
  

   last 
  heating, 
  made 
  with 
  the 
  first 
  gas 
  filling, 
  a 
  considerable 
  in- 
  

   crease 
  in 
  Hq 
  will 
  be 
  noticed 
  which, 
  however, 
  is 
  solely 
  due 
  to 
  

   the 
  fact 
  that 
  the 
  temperature 
  was 
  carried 
  for 
  the 
  first 
  time 
  up 
  

   to 
  1300°. 
  Afterward 
  when 
  the 
  bulb 
  had 
  been 
  evacuated 
  and 
  

   freshly 
  filled 
  at 
  1300° 
  a 
  second 
  heating 
  to 
  the 
  same 
  point 
  

   showed 
  no 
  change 
  in 
  the 
  ice 
  point 
  whatever. 
  

  

  In 
  order 
  to 
  accomplish 
  this 
  result 
  great 
  care 
  is 
  necessary 
  in 
  

   the 
  choice 
  of 
  the 
  material 
  used 
  in 
  the 
  construction 
  of 
  the 
  oven. 
  

   We 
  include 
  herewith 
  ice 
  points 
  from 
  an 
  earlier 
  series 
  of 
  

   observations 
  where 
  a 
  sudden 
  and 
  sharp 
  increase 
  occurred 
  which 
  

   could 
  be 
  foreseen 
  during 
  the 
  progress 
  of 
  the 
  heating. 
  The 
  

   outer 
  mantle 
  of 
  the 
  then 
  new 
  oven 
  consisted 
  of 
  sun-dried 
  

  

  *Benoit, 
  Trav. 
  et 
  Mem. 
  du 
  Bur. 
  internat., 
  vi, 
  190, 
  1888. 
  

  

  f 
  Le 
  Chatelier, 
  C. 
  R., 
  cviii, 
  1096, 
  1889. 
  

  

  :{: 
  Seliwanow, 
  Journ. 
  d. 
  russ. 
  phys, 
  Ges., 
  xxiii, 
  II, 
  152, 
  1891. 
  

  

  