﻿THE 
  

   LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  [SIXTH 
  SERIES.] 
  

  

  OCTOBER 
  1908. 
  

  

  XLV. 
  Another 
  Method 
  of 
  Measuring 
  large 
  Molecular 
  Masses. 
  

   By 
  William 
  Sutherland*. 
  

  

  IT 
  has 
  already 
  been 
  proposed 
  to 
  find 
  the 
  masses 
  of 
  mole- 
  

   cules, 
  which 
  are 
  too 
  large 
  for 
  the 
  ordinary 
  methods, 
  by 
  

   determining 
  their 
  radii 
  from 
  their 
  velocities 
  of 
  diffusion 
  or 
  

   their 
  velocities 
  in 
  electrolytic 
  conduction 
  (Phil. 
  Mag. 
  [6] 
  ix. 
  

   p. 
  781 
  and 
  xiv. 
  p. 
  1). 
  These 
  methods 
  have 
  been 
  applied 
  to 
  

   the 
  large 
  molecules 
  of 
  egg 
  albumin 
  and 
  globulin. 
  In 
  the 
  

   latter 
  paper 
  it 
  was 
  shown 
  that 
  they 
  yield 
  for 
  the 
  radius 
  of 
  

   the 
  hvdrogen 
  molecule 
  an 
  absolute 
  value 
  agreeing 
  well 
  with 
  

   that 
  given 
  by 
  the 
  kinetic 
  theory 
  of 
  gases. 
  The 
  latter 
  paper 
  

   contains 
  incidentally 
  also 
  another 
  method 
  of 
  finding 
  large 
  

   molecular 
  masses 
  which 
  will 
  be 
  worked 
  out 
  in 
  the 
  present 
  

   communication 
  and 
  applied 
  briefly 
  to 
  experimental 
  data 
  for 
  

   certain 
  peptones, 
  casein, 
  and 
  globulin. 
  The 
  theoretical 
  

   equation 
  (13) 
  of 
  that 
  paper 
  gives 
  the 
  following 
  connexion 
  

   between 
  the 
  molecular 
  conductivity 
  X 
  and 
  the 
  concentration 
  

   of 
  a 
  solution 
  containing 
  n 
  gram-molecules 
  per 
  cm. 
  3 
  of 
  a 
  

   solute 
  whose 
  molecule 
  yields 
  n 
  x 
  positive 
  ions 
  of 
  valency 
  v 
  1 
  

   and 
  n 
  2 
  negative 
  ions 
  of 
  valency 
  v 
  2 
  , 
  the 
  conductivities 
  of 
  the 
  

   ions 
  at 
  infinite 
  dilution 
  being 
  A 
  01 
  and 
  A 
  02 
  , 
  and 
  at 
  concentra- 
  

   tion 
  n 
  being 
  Aj 
  and 
  A 
  2 
  : 
  

  

  X 
  oVo 
  /\ri 
  = 
  1 
  + 
  27r(Ai 
  + 
  A 
  3 
  )Cv 
  ] 
  y 
  s 
  {n(n 
  1 
  + 
  n 
  2 
  )/h\i 
  /'dKIX^ 
  (1) 
  

  

  in 
  which 
  C 
  is 
  a 
  constant, 
  tj 
  is 
  viscosity 
  of 
  solvent, 
  77 
  of 
  solu- 
  

   tion, 
  h 
  is 
  the 
  mass 
  of 
  the 
  atom 
  of 
  hydrogen, 
  K 
  is 
  the 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

   Phil. 
  Mao. 
  S. 
  6. 
  Vol. 
  16. 
  No. 
  94. 
  Oct. 
  1908. 
  2 
  L 
  

  

  