﻿370 
  Mr. 
  R. 
  A. 
  Lehfeldt 
  on 
  a 
  Numerical 
  Evaluation 
  of 
  

  

  manner 
  indicated 
  by 
  Mendeleef 
  for 
  air; 
  but 
  that 
  correction 
  

   would 
  be 
  too 
  small 
  to 
  bring 
  them 
  into 
  agreement 
  ; 
  while 
  only 
  

   Jolly's 
  number 
  is 
  at 
  all 
  consistent 
  with 
  that 
  recently 
  found 
  at 
  

   the 
  Bureau 
  International. 
  Ohappuis 
  gives 
  these 
  values 
  : 
  — 
  

  

  0*00372477, 
  with 
  initial 
  pressure 
  995 
  mm. 
  

   371634, 
  „ 
  870 
  „ 
  

  

  they 
  may 
  be 
  represented 
  by 
  the 
  equation 
  

  

  /9= 
  0-00370893 
  + 
  0-00005126 
  (p 
  - 
  1), 
  

  

  p 
  being, 
  as 
  before, 
  expressed 
  in 
  terms 
  of 
  the 
  density 
  at 
  N.T.P. 
  

   as 
  unit. 
  We 
  may 
  perhaps 
  best 
  make 
  use 
  of 
  the 
  last-mentioned 
  

   numbers, 
  but 
  it 
  is 
  remarkable 
  that 
  the 
  discrepancies 
  in 
  the 
  

   measurement 
  of 
  /3 
  should 
  be 
  about 
  four 
  times 
  as 
  great 
  as 
  for 
  

   air. 
  The 
  expressions 
  given 
  above 
  must 
  not, 
  of 
  course, 
  be 
  

   relied 
  upon 
  either 
  for 
  large 
  densities 
  or 
  for 
  very 
  small. 
  

  

  Specific 
  Heat. 
  — 
  The 
  specific 
  heat 
  and 
  specific 
  volume 
  of 
  the 
  

   gases 
  need 
  only 
  be 
  known 
  approximately, 
  as 
  they 
  only 
  enter 
  

   into 
  the 
  expression 
  for 
  the 
  absolute 
  temperature 
  in 
  the 
  small 
  

   correction 
  term. 
  The 
  well-known 
  experiments 
  of 
  Regnault 
  

   and 
  E. 
  Wiedemann 
  afford 
  the 
  necessary 
  information 
  on 
  the 
  

   specific 
  heat 
  at 
  constant 
  pressure. 
  The 
  former 
  used 
  as 
  unit 
  

   of 
  heat 
  the 
  capacity 
  of 
  water 
  between 
  12° 
  and 
  15°, 
  the 
  latter 
  

   between 
  16° 
  and 
  24°. 
  Following 
  the 
  table 
  recently 
  given 
  by 
  

   Griffiths, 
  the 
  unit 
  used 
  by 
  Regnault 
  is 
  equal 
  to 
  41,920,000 
  ergs, 
  

   that 
  of 
  Wiedemann 
  41,830,000. 
  The 
  results 
  are, 
  accordingly, 
  

   for 
  hydrogen 
  

  

  3-409 
  calories, 
  or 
  142,900,000 
  ergs 
  (Regnault), 
  

   3-410 
  „ 
  142,640,000 
  „ 
  (E.Wiedemann), 
  

  

  mean 
  142,770,000 
  ergs 
  ; 
  this 
  quantity 
  is 
  sensibly 
  independent 
  

   of 
  temperature 
  and 
  pressure 
  over 
  the 
  range 
  considered. 
  

   For 
  air 
  

  

  0-23754 
  Dal., 
  or 
  9,958,000 
  ergs 
  (Regnault), 
  

   0-2389 
  „ 
  9,993,000 
  „ 
  (Wiedemann), 
  

  

  mean 
  9,975,000 
  ergs, 
  also 
  sensibly 
  independent 
  of 
  pressure 
  

   and 
  temperature. 
  

  

  For 
  nitrogen 
  (atmospheric, 
  containing 
  argon) 
  

  

  0*24348 
  cal., 
  or 
  10,207,000 
  ergs 
  (Regnault), 
  

  

  also 
  independent 
  of 
  temperature 
  and 
  pressure. 
  

  

  For 
  carbon 
  dioxide 
  the 
  experiments 
  show 
  the 
  specific 
  heat 
  

   to 
  be 
  practically 
  independent 
  of 
  the 
  pressure 
  (for 
  such 
  pres- 
  

  

  