﻿92 
  Messrs. 
  A. 
  Holt 
  and 
  E. 
  Hopkinson 
  on 
  Decomposition 
  

  

  Aromatic 
  Compounds. 
  

  

  It 
  is 
  found 
  that 
  the 
  possession 
  of 
  ring 
  structure 
  on 
  the 
  

   part 
  of 
  a 
  compound 
  corresponds 
  with 
  an 
  extra 
  contraction 
  — 
  

   that 
  is 
  to 
  say, 
  the 
  atomic 
  volumes 
  in 
  ringed 
  molecules 
  are 
  

   always 
  less 
  than 
  the 
  volumes 
  of 
  similar 
  atoms 
  in 
  straight 
  

   chain 
  compounds, 
  so 
  that 
  the 
  total 
  molecular 
  volume 
  is 
  on 
  

   the 
  whole 
  less 
  than 
  that 
  of 
  a 
  similar 
  complex 
  in 
  the 
  fatty 
  

   series. 
  

  

  The 
  relative 
  volumes 
  of 
  atoms 
  in 
  the 
  nuclei 
  are 
  the 
  same 
  

   as 
  those 
  in 
  straight 
  chain 
  compounds. 
  

  

  Thus 
  it 
  is 
  found 
  that 
  the 
  volumes 
  of 
  benzene 
  and 
  hexa- 
  

   methylene 
  are 
  proportional 
  to 
  their 
  valency 
  numbers 
  from 
  

   the 
  critical 
  point 
  downwards, 
  so 
  that 
  C 
  = 
  4H 
  as 
  before. 
  

  

  The 
  volumes 
  of 
  the 
  atoms 
  in 
  aliphatic 
  side 
  chains 
  are, 
  

   however, 
  the 
  same 
  as 
  in 
  the 
  paraffins. 
  

  

  It 
  has 
  been 
  found 
  that 
  the 
  critical 
  coefficients 
  of 
  benzene 
  

   and 
  its 
  homolooues 
  manifest 
  similar 
  relations 
  to 
  those 
  shown 
  

   by 
  the 
  molecular 
  volumes. 
  

  

  Note. 
  — 
  It 
  should 
  be 
  mentioned 
  that 
  Barlow 
  and 
  Pope 
  take 
  the 
  view 
  

   that 
  the 
  relative 
  -volumes 
  of 
  the 
  atoms 
  in 
  the 
  molecular 
  complexes, 
  

   aromatic 
  as 
  well 
  as 
  aliphatic, 
  are 
  always 
  maintained 
  and 
  that 
  the 
  

   volume 
  of 
  an 
  atom 
  in 
  a 
  compound 
  is 
  always 
  proportional 
  to 
  its 
  fundamental 
  

   valency. 
  

  

  Municipal 
  School 
  of 
  Technology, 
  

   Victoria 
  University, 
  Manchester. 
  

  

  V. 
  The 
  Decomposition 
  of 
  Water 
  Vapour 
  by 
  Electric 
  Sparks. 
  

   By 
  Alfked 
  Holt, 
  Jim., 
  and 
  Edwin 
  Hopkinson 
  *. 
  

  

  THE 
  decomposition 
  of 
  a 
  compound 
  gas 
  such 
  as 
  water- 
  

   vapour, 
  or 
  carbon 
  dioxide, 
  by 
  electric 
  sparks, 
  and 
  the 
  

   separation 
  and 
  arrangement 
  of 
  the 
  resulting 
  products 
  about 
  

   the 
  electrodes, 
  is 
  of 
  special 
  interest 
  since 
  it 
  may 
  be 
  expected 
  

   to 
  show 
  how 
  far 
  the 
  hypothesis 
  of 
  electrolysis 
  in 
  liquids 
  is 
  

   applicable 
  to 
  gases. 
  

  

  Almost 
  half 
  a 
  century 
  ago 
  Perrot 
  [Ann. 
  Cliim. 
  et 
  Phys. 
  

   1861, 
  p. 
  161) 
  showed 
  that 
  the 
  decomposition 
  of 
  water-vapour 
  

   took 
  place 
  along 
  the 
  entire 
  path 
  of 
  the 
  spark 
  and 
  not 
  only 
  in 
  

   tin* 
  neighbourhood 
  of 
  the 
  electrodes, 
  and 
  that 
  the 
  gas 
  col- 
  

   lected 
  from 
  the 
  anode 
  contained 
  an 
  excess 
  of 
  oxygen, 
  while 
  

   that 
  from 
  the 
  cathode 
  contained 
  an 
  excess 
  of 
  hydrogen, 
  

   their 
  amounts 
  being 
  equivalent 
  to 
  the 
  copper 
  deposited 
  in 
  a 
  

   voltameter 
  placed 
  in 
  the 
  same 
  circuit. 
  His 
  experiments 
  

  

  ( 
  Sommunicated 
  by 
  the 
  Authors. 
  

  

  