﻿in 
  Their 
  Thermodynamic 
  Relations. 
  167 
  

  

  in 
  ray 
  work, 
  consisting 
  of 
  two 
  concentric 
  glass 
  tubes, 
  E, 
  e, 
  

   joined 
  at 
  the 
  ends, 
  the 
  inner 
  snugly 
  enveloping 
  the 
  capillary 
  

   tube 
  ab. 
  Tubulure 
  T 
  holds 
  a 
  thermometer. 
  Tubulure 
  D 
  

   leads 
  to 
  the 
  condenser, 
  which 
  for 
  a 
  charge 
  of 
  naphthaline 
  at 
  h 
  

   (heated 
  by 
  the 
  ringburner 
  R 
  and 
  screen 
  Z) 
  is 
  merely 
  a 
  long 
  

   tube. 
  Cooling 
  in 
  air 
  is 
  sufficient 
  and 
  the 
  operation 
  continuous. 
  

   In 
  experiments 
  like 
  the 
  present 
  it 
  is 
  convenient 
  to 
  join 
  the 
  con- 
  

   centric 
  tubes 
  E 
  and 
  e 
  above, 
  by 
  a 
  gas 
  pipe 
  cap/J 
  cemented 
  to 
  

   the 
  glass 
  with 
  plaster 
  of 
  Paris 
  g. 
  Asbestos 
  jackets 
  envelop 
  

   the 
  tube 
  E 
  except 
  at 
  the 
  longitudinal 
  fissures 
  cut 
  into 
  them 
  

   for 
  observation. 
  After 
  the 
  liquid 
  k 
  boils, 
  the 
  temperature 
  of 
  

   the 
  column 
  of 
  vapor 
  between 
  the 
  plane 
  of 
  ebullition 
  and 
  of 
  

   condensation, 
  both 
  distinctly 
  apparent, 
  is 
  constant. 
  It 
  is 
  thus 
  

   merely 
  necessary 
  to 
  chase 
  the 
  latter 
  into 
  the 
  condenser 
  to 
  

   obtain 
  constancy 
  along 
  8S\ 
  

  

  With 
  well 
  annealed 
  capillary 
  tubes, 
  -02 
  cm 
  to 
  *05 
  cm 
  in 
  diameter 
  

   internally, 
  and 
  '6 
  cm 
  in 
  diameter 
  externally, 
  pressures 
  from 
  400 
  

   to 
  600 
  atms. 
  are 
  admissible. 
  With 
  diameters 
  increased 
  by 
  

   water 
  solution 
  from 
  '04 
  to 
  -07 
  cms 
  (often 
  three 
  times), 
  the 
  pres- 
  

   sure 
  limits 
  are 
  reduced 
  ; 
  less, 
  however, 
  by 
  change 
  of 
  diameter 
  

   than 
  by 
  the 
  continued 
  stress 
  to 
  which 
  the 
  tube 
  has 
  been 
  sub- 
  

   jected. 
  

  

  The 
  phenomena 
  to 
  be 
  observed 
  during 
  the 
  action 
  of 
  hot 
  

   water 
  on 
  glass 
  may 
  be 
  described 
  as 
  follows 
  : 
  Daring 
  heating 
  

   the 
  thread 
  of 
  water 
  expands 
  thermally, 
  but 
  the 
  expansion 
  is 
  

   partial 
  ; 
  before 
  the 
  constant 
  temperature 
  210° 
  is 
  reached 
  the 
  

   thread 
  has 
  begun 
  to 
  contract 
  in, 
  marked 
  degree 
  in 
  consequence 
  

   of 
  the 
  corrosion. 
  The 
  full 
  thread 
  length 
  for 
  210° 
  is 
  not 
  

   reached. 
  

  

  The 
  reaction 
  itself 
  will 
  appear 
  differently 
  according 
  as 
  it 
  

   takes 
  place 
  slightly 
  below 
  or 
  slightly 
  above 
  the 
  solution 
  tem- 
  

   perature. 
  At 
  185° 
  the 
  water 
  glass 
  obtained 
  is 
  rather 
  a 
  coagu- 
  

   luin. 
  The 
  solid 
  swells 
  enormously 
  under 
  the 
  absorption 
  of 
  

   water, 
  like 
  any 
  other 
  colloid. 
  It 
  is 
  apt 
  to 
  remain 
  white 
  and 
  

   turbid, 
  so 
  that 
  the 
  progress 
  of 
  the 
  mercury 
  meniscus 
  is 
  seen 
  

   with 
  difficulty 
  through 
  the 
  semi-translucent 
  thread. 
  The 
  

   water 
  glass 
  remains 
  elastic, 
  i. 
  e., 
  it 
  contracts 
  and 
  expands 
  under 
  

   the 
  influence 
  of 
  pressure. 
  Compressibility 
  slowly 
  but 
  regu- 
  

   larly 
  increases. 
  Contraction 
  of 
  the 
  combined 
  volume 
  of 
  glass 
  

   and 
  water 
  progresses 
  at 
  an 
  accelerated 
  rate. 
  If 
  after 
  long 
  

   reaction 
  (1 
  hour), 
  the 
  cold 
  capillary 
  be 
  broken 
  across 
  and 
  exam- 
  

   ined 
  under 
  the 
  microscope, 
  the 
  capillary 
  canal 
  is 
  found 
  to 
  be 
  

   nearly 
  full 
  of 
  an 
  agate-like 
  warty 
  solid 
  accretion. 
  This 
  is 
  

   water 
  glass 
  in 
  the 
  swollen 
  coagulated 
  state. 
  

  

  At 
  210°, 
  however, 
  the 
  solution 
  temperature 
  is 
  exceeded. 
  

   The 
  preceding 
  phenomenon 
  of 
  swelling 
  passes 
  rapidly 
  into 
  the 
  

   present 
  phenomenon 
  of 
  solution. 
  The 
  water 
  glass 
  gradually 
  

  

  