﻿28 
  

  

  Mr. 
  T. 
  Carlton 
  Sutton 
  on 
  the 
  Value 
  

  

  The 
  results 
  obtained 
  since 
  the 
  year 
  1905 
  are 
  not 
  as 
  concor- 
  

   dant 
  as 
  might 
  have 
  been 
  expected. 
  It 
  may 
  be 
  of 
  interest 
  

   therefore 
  to 
  compare 
  the 
  value 
  of 
  the 
  heat 
  of 
  vaporization 
  of 
  

   water 
  at 
  100° 
  C. 
  obtained 
  electrically 
  at 
  the 
  Reichsanstalt 
  

   by 
  Henning 
  ( 
  Ann. 
  d. 
  Phys. 
  1906-9) 
  with 
  that 
  obtained 
  by 
  

   the 
  author 
  in 
  terms 
  of 
  the 
  mean 
  calorie 
  directly 
  (Proc. 
  Roy. 
  

   Soc. 
  April 
  1917). 
  

  

  Henning's 
  results 
  are 
  shown 
  in 
  the 
  following 
  graph, 
  which 
  

   indicates 
  that 
  the 
  value 
  at 
  100° 
  C. 
  is 
  538*5 
  + 
  0*3. 
  Probably 
  

   the 
  constant 
  errors 
  are 
  even 
  less 
  than 
  0*3. 
  

  

  Henning's 
  work 
  may 
  also 
  be 
  checked 
  by 
  comparing 
  it 
  

   with 
  that 
  of 
  Griffiths' 
  at 
  30° 
  C. 
  The 
  values 
  for 
  the 
  heat 
  of 
  

   vaporization 
  at 
  that 
  temperature 
  are 
  in 
  good 
  agreement, 
  

   579*9 
  and 
  579*3 
  mean 
  calories 
  respectively. 
  

  

  Fig. 
  1. 
  

  

  538-5 
  

  

  538 
  

  

  TemperaZure 
  

  

  The 
  corresponding 
  values 
  obtained 
  by 
  the 
  author 
  (Proc. 
  

   Roy. 
  Soc. 
  April 
  1917) 
  give 
  538*8 
  ±0*1 
  mean 
  calories 
  at 
  

   100° 
  C. 
  

  

  If, 
  then, 
  Henning's 
  mean 
  value 
  is 
  correct 
  to 
  1 
  part 
  in 
  2000, 
  

   the 
  deduced 
  value 
  of 
  the 
  Mechanical 
  Equivalent 
  should 
  be 
  

   correct 
  to 
  within 
  two 
  units 
  in 
  the 
  third 
  decimal 
  figure. 
  

  

  Henning 
  uses 
  the 
  Jager 
  and 
  Steinwehr 
  value 
  of 
  the 
  

   15° 
  calorie 
  to 
  convert 
  joules 
  to 
  calories, 
  and 
  takes 
  the 
  Reiclis- 
  

   anstalt 
  value 
  of 
  the 
  e.m.f- 
  of 
  the 
  Clark 
  Cell. 
  What 
  he 
  

   actually 
  determines 
  as 
  the 
  Energy 
  of 
  Vaporization 
  at 
  100® 
  C. 
  

   is 
  538*5 
  x 
  4*188 
  Reichsanstalt 
  joules. 
  

  

  