﻿0. 
  Barus 
  — 
  Continuity 
  of 
  Solid 
  and 
  Liquid. 
  131 
  

  

  know 
  : 
  (1) 
  The 
  volume 
  of 
  the 
  charge 
  at 
  a 
  fiducial 
  temperature 
  

   and 
  pressure 
  ; 
  (2) 
  The 
  volume 
  of 
  the 
  plug 
  of 
  mercury 
  under 
  

   the 
  same 
  conditions 
  ; 
  (3) 
  The 
  volume 
  of 
  the 
  central 
  tube 
  kh 
  

   (figure 
  1) 
  per 
  centimeter 
  of 
  length; 
  (4) 
  The 
  resistance 
  of 
  the 
  

   thread 
  of 
  zinc 
  sulphate 
  solution, 
  per 
  centimeter 
  of 
  length, 
  

   under 
  all 
  the 
  stated 
  conditions 
  of 
  temperature 
  and 
  pressure. 
  

   From 
  (3) 
  and 
  (4) 
  there 
  follows 
  at 
  once 
  (5) 
  the 
  resistance 
  of 
  the 
  

   thread 
  of 
  zinc 
  sulphate 
  per 
  unit 
  of 
  volume, 
  under 
  any 
  stated 
  

   conditions 
  of 
  temperature 
  and 
  pressure. 
  Thus 
  it 
  is 
  necessary 
  

   to 
  investigate 
  preliminarily 
  (6) 
  the 
  isopiestic 
  relation 
  of 
  resist- 
  

   ance 
  and 
  temperature 
  of 
  the 
  given 
  concentrated 
  solution 
  of 
  

   zinc 
  sulphate, 
  and 
  (7) 
  the 
  isothermal 
  relation 
  of 
  resistance 
  and 
  

   pressure 
  of 
  the 
  same 
  solution. 
  In 
  other 
  words 
  one 
  must 
  know 
  

   what 
  may 
  be 
  called 
  the 
  isoelectrics 
  of 
  the 
  measuring 
  electrolyte. 
  

   Furthermore 
  it 
  is 
  necessary 
  to 
  find 
  (8) 
  the 
  compressibility 
  of 
  

   the 
  glass 
  in 
  its 
  relation 
  to 
  pressure 
  and 
  temperature 
  and 
  (9) 
  

   the 
  compressibility 
  of 
  mercury 
  under 
  the 
  same 
  conditions 
  ; 
  

   finally 
  (10) 
  the 
  thermal 
  expansion 
  of 
  the 
  glass 
  and 
  (11) 
  the 
  

   thermal 
  expansion 
  of 
  mercury 
  under 
  given 
  conditions 
  of 
  

   pressure. 
  

  

  The 
  measurements 
  (8) 
  to 
  (11) 
  I 
  have 
  not 
  thus 
  far 
  made 
  

   directly. 
  They 
  are 
  here 
  of 
  small 
  importance, 
  seeing 
  that 
  the 
  

   substances 
  on 
  which 
  I 
  operate 
  are 
  all 
  characterized 
  by 
  rela- 
  

   tively 
  large 
  volume 
  changes. 
  Such 
  measurements, 
  however, 
  are 
  

   easily 
  feasible, 
  since 
  both 
  the 
  expansion 
  constants 
  and 
  the 
  

   compression 
  constants 
  of 
  pure 
  mercury 
  (thanks 
  to 
  the 
  recent 
  

   labors 
  of 
  Tait, 
  Amagat* 
  and 
  G-uillaume) 
  are 
  now 
  thoroughly 
  

   known, 
  and 
  it 
  is 
  also 
  known 
  that 
  the 
  thermal 
  changes 
  of 
  the 
  

   elastics 
  of 
  glass 
  are 
  of 
  no 
  relative 
  consequence,f 
  even 
  as 
  far 
  as 
  

   200°. 
  If 
  therefore 
  the 
  tube 
  AB, 
  figure 
  1, 
  be 
  filled 
  with 
  mer- 
  

   cury, 
  replacing 
  the 
  substance 
  EE, 
  the 
  expansion 
  and 
  com- 
  

   pression 
  constants 
  may 
  be 
  found 
  by 
  the 
  method 
  above 
  stated, 
  

   §3, 
  once 
  for 
  all. 
  In 
  the 
  present 
  paper 
  I 
  assumed 
  the 
  compres- 
  

   sibility 
  of 
  my 
  glass;); 
  to 
  be 
  -0000022, 
  that 
  of 
  mercury,§ 
  being 
  

   •0000039 
  ; 
  moreover 
  the 
  coefficient 
  of 
  thermal 
  expansion 
  of 
  the 
  

   glass|| 
  to 
  be 
  .000025, 
  that 
  of 
  mercury! 
  between 
  60° 
  and 
  130° 
  

   being 
  -000182. 
  

  

  8. 
  Volume 
  of 
  the 
  charge. 
  — 
  Clearly 
  the 
  fiducial 
  conditions 
  to 
  

   which 
  the 
  volumes 
  are 
  to 
  be 
  referred, 
  are 
  given 
  by 
  the 
  (normal) 
  

   melting 
  point, 
  under 
  atmospheric 
  pressure. 
  By 
  weighing 
  the 
  

   tube 
  before 
  and 
  after 
  charging, 
  I 
  found 
  for 
  the 
  mass 
  of 
  naph- 
  

   thalene 
  enclosed, 
  '763^. 
  In 
  a 
  special 
  and 
  duplicate 
  set 
  of 
  

   pycnometer 
  measurements, 
  I 
  furthermore 
  found 
  for 
  the 
  density 
  

   of 
  fused 
  naphthalene 
  at 
  82°, 
  '724. 
  Hence 
  the 
  volume 
  of 
  the 
  

  

  * 
  Cf. 
  E. 
  H. 
  Amagat: 
  Ann. 
  ch. 
  et 
  phys., 
  VI, 
  xxii, 
  p. 
  95, 
  1891. 
  

  

  f 
  Ibid., 
  p. 
  136. 
  % 
  Ibid., 
  p. 
  125. 
  § 
  Ibid., 
  p. 
  137. 
  

  

  J 
  Landolt 
  u. 
  Boernstein's 
  tables, 
  1883, 
  p. 
  69. 
  % 
  Ibid 
  , 
  p. 
  37. 
  

  

  