﻿Chemistry 
  and 
  Physics. 
  331 
  

  

  makes 
  the 
  very 
  plausible 
  assumption 
  that 
  b 
  2 
  /g 
  == 
  kc 
  where 
  e 
  is 
  

   the 
  electronic 
  value 
  of 
  b 
  2 
  /g 
  (e 
  — 
  183 
  X 
  10 
  8 
  cm/gram) 
  and 
  k 
  is 
  

   the 
  smallest 
  integer 
  compatible 
  with 
  the 
  physical 
  conditions. 
  

   This 
  may 
  be 
  interpreted 
  as 
  meaning 
  that 
  an 
  atomic 
  resonator 
  con- 
  

   sists 
  of 
  k 
  electrons 
  or 
  that 
  each 
  atom 
  contains 
  k 
  dispersive 
  

   electrons. 
  

  

  The 
  practical 
  application 
  of 
  the 
  preceding 
  theoretical 
  outline 
  to 
  

   the 
  case 
  of 
  hydrogen 
  will 
  now 
  be 
  considered. 
  The 
  indices 
  of 
  re- 
  

   fraction 
  for 
  the 
  radiations 
  II 
  a 
  , 
  D, 
  So, 
  and 
  II 
  . 
  , 
  for 
  hydrogen 
  at 
  

  

  0°C. 
  and 
  76 
  cm 
  pressure, 
  are 
  1-0001387, 
  1-0001392, 
  1-0001406, 
  and 
  

   1-0001412. 
  Hence, 
  the 
  well-known 
  formula 
  iV= 
  (/x, 
  2 
  — 
  1) 
  

   (fi 
  2 
  + 
  2)- 
  1 
  Md~ 
  l 
  gives 
  2-074, 
  2082, 
  2*103, 
  and 
  2*112 
  for 
  the 
  cor- 
  

   responding 
  molecular 
  refractivities. 
  (Molecular 
  weight 
  of 
  H^ 
  is 
  

   M— 
  2-016, 
  density 
  = 
  d 
  = 
  8-9873 
  X 
  10~ 
  6 
  grm/cm 
  3 
  .) 
  These 
  values 
  

   of 
  N 
  satisfy 
  the 
  equation 
  JF= 
  2*0445 
  + 
  1*279 
  X 
  10- 
  10 
  /A 
  2 
  very 
  

   satisfactorily 
  (A 
  in 
  cm.). 
  Hence 
  b 
  = 
  2*0445, 
  g 
  = 
  1*279 
  X 
  10~ 
  10 
  . 
  

   It 
  is 
  also 
  found 
  that 
  k 
  = 
  1, 
  so 
  that 
  "we 
  shall 
  attribute 
  one 
  

   dispersive 
  electron 
  to 
  each 
  hydrogen 
  atom." 
  The 
  equation 
  

   b 
  2 
  /g 
  = 
  183 
  X 
  10 
  8 
  when 
  combined 
  with 
  the 
  two 
  equations 
  con- 
  

   necting 
  b 
  and 
  g 
  with 
  b 
  , 
  g 
  Q 
  , 
  and 
  o- 
  leads 
  directly 
  to 
  a-b 
  = 
  0-4932, 
  

   b 
  = 
  0*7719, 
  g 
  = 
  0*3255 
  X 
  10~ 
  10 
  c.g.s. 
  units. 
  Accordingly 
  the 
  

   atomic 
  refractivity 
  of 
  hydrogen 
  is 
  expressed 
  by 
  JV 
  = 
  0*7719 
  + 
  

   0*326 
  X 
  10~ 
  10 
  /A 
  2 
  . 
  The 
  "free" 
  wave-length 
  A 
  of 
  a 
  hydrogen 
  

   atom 
  = 
  649*4 
  A. 
  The 
  central 
  distance 
  between 
  two 
  atoms 
  in 
  a 
  

   hydrogen 
  molecule 
  = 
  M 
  = 
  1*067 
  X 
  10~ 
  8 
  cm. 
  For 
  oxygen 
  k 
  = 
  2, 
  

   X 
  = 
  622*6 
  A, 
  and 
  B 
  = 
  1*265 
  X 
  10 
  _8 
  cm. 
  For 
  nitrogen 
  k 
  = 
  3, 
  

   A 
  = 
  570*5 
  A 
  y 
  and 
  JR 
  = 
  1*493 
  X 
  10 
  _8 
  cm. 
  In 
  conclusion, 
  attention 
  

   should 
  be 
  called 
  to 
  the 
  facts 
  that 
  (i) 
  k 
  agrees 
  with 
  the 
  valency 
  of 
  

   the 
  elements, 
  (ii) 
  A 
  falls 
  near 
  the 
  limit 
  of 
  Lyman's 
  extension 
  of 
  

   the 
  Schumann 
  region 
  so-called, 
  and 
  (iii) 
  the 
  values 
  of 
  R 
  agree 
  

   more 
  closely 
  with 
  the 
  molecular 
  semidiameters 
  derived 
  from 
  data 
  

   on 
  viscosity 
  than 
  these 
  data 
  agree 
  with 
  the 
  radii 
  obtained 
  from 
  

   other 
  consequences 
  of 
  the 
  kinetic 
  theory 
  of 
  gases, 
  such 
  as 
  Boyle's 
  

   law, 
  heat 
  conduction, 
  and 
  diffusion. 
  In 
  fact, 
  the 
  viscosity 
  values 
  

   of 
  R 
  are 
  given 
  respectively 
  as 
  1-024 
  X 
  10" 
  8 
  , 
  1*405 
  X 
  10 
  -8 
  , 
  and 
  

   1*448 
  X 
  10~ 
  8 
  for 
  hydrogen, 
  oxygen, 
  and 
  nitrogen. 
  — 
  Phil. 
  Mag., 
  

   xxxiii, 
  p. 
  215, 
  February, 
  1917. 
  h. 
  s. 
  u. 
  

  

  7. 
  Lubrication 
  of 
  Resistance- 
  Box 
  Plugs. 
  — 
  In 
  making 
  accu- 
  

   rate 
  comparisons 
  of 
  electrical 
  resistances, 
  by 
  the 
  aid 
  of 
  plug 
  or 
  

   dial 
  boxes, 
  it 
  is 
  important 
  to 
  have 
  the 
  surfaces 
  of 
  contact 
  of 
  the 
  

   plugs 
  and 
  lugs 
  maintain 
  sensibly 
  constant 
  resistances. 
  The 
  fact 
  

   that 
  a 
  satisfactory 
  approximation 
  to 
  this 
  condition 
  may 
  be 
  made 
  

   by 
  lubricating 
  box-plugs 
  and 
  switches 
  has 
  been 
  known 
  for 
  at 
  

   least 
  fourteen 
  years, 
  since 
  it 
  has 
  been 
  the 
  custom 
  at 
  the 
  National 
  

   Physical 
  Laboratory 
  (England) 
  to 
  use 
  petroleum 
  or 
  paraffin 
  for 
  

   this 
  purpose 
  during 
  the 
  interval 
  of 
  time 
  specified. 
  Since, 
  how- 
  

   ever, 
  the 
  scheme 
  does 
  not 
  seem 
  to 
  be 
  generally 
  known 
  and 
  as 
  

   quantitative 
  data 
  are 
  apparently 
  lacking, 
  it 
  may 
  not 
  be 
  super- 
  

   fluous 
  to 
  call 
  attention 
  to 
  some 
  of 
  the 
  results 
  recently 
  obtained 
  

   and 
  published 
  by 
  J. 
  J. 
  Ma^nley. 
  

  

  