﻿248 
  Mr. 
  L. 
  \ 
  egard 
  : 
  Researches 
  upon 
  

  

  §i- 
  

  

  2. 
  The 
  constructions 
  o£ 
  the 
  various 
  pieces 
  of 
  apparatus 
  

   that 
  have 
  been 
  tried 
  have 
  (all 
  of 
  them) 
  been 
  made 
  upon 
  the 
  

   principle 
  that 
  the 
  solution, 
  and 
  consequently 
  the 
  pressure, 
  

   was 
  to 
  be 
  placed 
  outside 
  the 
  cell. 
  This 
  arrangement 
  allows 
  

   a 
  better 
  tightening 
  of 
  the 
  cell, 
  and 
  at 
  the 
  same 
  time 
  the 
  

   latter 
  will 
  be 
  more 
  capable 
  of 
  resisting 
  great 
  pressures, 
  as 
  

   by 
  a 
  proper 
  construction 
  we 
  can 
  always 
  arrange 
  matters 
  so 
  

   that 
  the 
  cell 
  substance 
  is 
  only 
  subject 
  to 
  compression. 
  The 
  

   same 
  principle 
  with 
  other 
  arrangements 
  has 
  been 
  used 
  by 
  

   Berkeley 
  and 
  Hartley. 
  

  

  The 
  construction 
  of 
  the 
  apparatus 
  finally 
  used 
  is 
  shown 
  in 
  

   PI. 
  VIII. 
  figs. 
  1, 
  2, 
  3. 
  It 
  consists 
  essentially 
  of 
  three 
  parts 
  : 
  

   The 
  osmometer 
  itself 
  (fig. 
  1), 
  the 
  compressor 
  (fig. 
  2), 
  and 
  

   the 
  manometer 
  (fig. 
  3). 
  

  

  The 
  osmometer 
  again 
  chiefly 
  consists 
  of 
  three 
  parts 
  : 
  the 
  

   cell 
  C 
  and 
  the 
  two 
  pieces 
  A 
  and 
  B 
  made 
  of 
  cast-steel. 
  

  

  The 
  cup 
  A, 
  which 
  has 
  an 
  inner 
  volume 
  of 
  118 
  cm. 
  3 
  , 
  can 
  

   be 
  fixed 
  to 
  the 
  disk 
  B 
  by 
  means 
  of 
  six 
  set-screws 
  with 
  nuts 
  

   passing 
  through 
  perforations 
  equally 
  distributed 
  round 
  the 
  

   circular 
  edge 
  of 
  the 
  cup 
  and 
  the 
  disk. 
  The 
  tap 
  (c) 
  that 
  

   serves 
  for 
  fastening 
  the 
  cell 
  forms 
  a 
  part 
  of 
  the 
  disk 
  B, 
  and 
  

   is 
  cast 
  in 
  the 
  same 
  piece. 
  

  

  The 
  cell 
  has 
  at 
  the 
  top 
  a 
  cylindrical 
  form, 
  but 
  the 
  bottom 
  

   is 
  made 
  spherical 
  as 
  to 
  ensure 
  that 
  the 
  cell 
  is 
  only 
  acted 
  

   upon 
  by 
  stresses 
  tending 
  to 
  compress 
  it. 
  The 
  upper 
  part 
  of 
  

   the 
  cell 
  is 
  glazed. 
  The 
  fastening 
  of 
  the 
  cell 
  to 
  the 
  osmometer 
  

   is 
  easily 
  seen 
  from 
  fig. 
  1. 
  I 
  have 
  used 
  the 
  principle 
  to 
  let 
  

   the 
  osmotic 
  pressure 
  itself 
  take 
  care 
  of 
  the 
  fastening 
  

   .and 
  tightening. 
  To 
  this 
  end 
  the 
  steel 
  tap 
  as 
  well 
  as 
  the 
  

   glazed 
  part 
  of 
  the 
  cell 
  are 
  covered 
  with 
  a 
  piece 
  of 
  rubber 
  

   tubing 
  of 
  a 
  suitable 
  diameter. 
  By 
  this 
  arrangement 
  it 
  is 
  

   ensured 
  that 
  the 
  pressure 
  will 
  have 
  no 
  tendency 
  to 
  produce 
  

   any 
  leak 
  between 
  the 
  steel 
  tap 
  and 
  the 
  cell. 
  An 
  increase 
  of 
  

   pressure, 
  on 
  the 
  contrary, 
  will 
  only 
  cause 
  the 
  cell 
  to 
  be 
  

   pressed 
  with 
  a 
  great 
  force 
  up 
  to 
  the 
  steel 
  tap, 
  and 
  at 
  the 
  

   same 
  time 
  the 
  extensible 
  rubber 
  is 
  pressed 
  with 
  the 
  whole 
  

   pressure 
  up 
  to 
  the 
  walls 
  of 
  the 
  cell 
  and 
  the 
  steel 
  tap. 
  

  

  In 
  order 
  to 
  prevent 
  every 
  possibility 
  of 
  leak 
  at 
  this 
  point 
  

   the 
  ends 
  of 
  the 
  rubber 
  tubing 
  during 
  the 
  experiments 
  have 
  

   been 
  tied 
  round 
  with 
  a 
  cotton 
  thread. 
  

  

  By 
  the 
  arrangement 
  here 
  shown 
  one 
  of 
  the 
  corrections 
  

   required 
  by 
  the 
  method 
  of 
  Berkeley 
  and 
  Hartley 
  has 
  been 
  

   eliminated, 
  namely, 
  the 
  so-called 
  " 
  guard-ring 
  leak." 
  

  

  The 
  disk 
  B 
  besides 
  the 
  six 
  screws 
  already 
  mentioned 
  has 
  

   three 
  other 
  cylindric 
  perforations 
  (a, 
  a 
  f 
  , 
  b) 
  for 
  three 
  glass 
  

  

  