﻿K 
  A. 
  Hill 
  — 
  Argon, 
  Proutfs 
  Hypothesis, 
  etc. 
  405 
  

  

  Art. 
  XXXII. 
  — 
  Argon, 
  Proutfs 
  Hypothesis, 
  and 
  the 
  Periodic 
  

   Law 
  ; 
  by 
  Edwix 
  A. 
  Hill. 
  

  

  If 
  Argon 
  be 
  an 
  element, 
  its 
  properties 
  indicate 
  that 
  its 
  place 
  

   in 
  the 
  periodic 
  classification 
  is 
  between 
  F 
  and 
  Xa, 
  with 
  an 
  

   atomic 
  weight 
  of 
  20. 
  Its 
  non-metallic 
  acidic 
  electro-negative 
  

   character, 
  and 
  low 
  melting 
  and 
  boiling 
  points, 
  link 
  it 
  to 
  

   Series 
  2 
  ending 
  with 
  F 
  rather 
  than 
  Series 
  3 
  beginning 
  with 
  

   Xa 
  ; 
  just 
  as 
  Fe 
  is 
  more 
  closely 
  allied 
  to 
  Mn 
  than 
  Cu. 
  Its 
  

   resemblance 
  to 
  the 
  members 
  of 
  transitional 
  Group 
  Till, 
  into 
  

   which 
  it 
  would 
  therefore 
  fall, 
  is 
  shown 
  in 
  many 
  ways. 
  All 
  

   the 
  members 
  of 
  this 
  group 
  have 
  high 
  specific 
  gravities, 
  small 
  

   atomic 
  volumes, 
  very 
  weak 
  chemical 
  affinities, 
  are 
  inert, 
  and 
  

   with 
  basic 
  or 
  acidic 
  properties 
  very 
  weakly 
  developed 
  if 
  at 
  all. 
  

   Argon 
  is 
  as 
  truly 
  transitional 
  from 
  Xa 
  to 
  F 
  as 
  Group 
  YIII 
  in 
  

   general 
  is 
  transitional 
  between 
  the 
  two 
  halves 
  of 
  Mendeleef 
  s 
  

   long 
  periods, 
  and 
  belonging 
  in 
  a 
  short 
  period, 
  is 
  cut 
  off 
  from 
  

   the 
  other 
  long 
  period 
  members 
  of 
  Group 
  YIII 
  by 
  the 
  same 
  

   differences 
  in 
  boiling 
  points, 
  melting 
  points, 
  atomic 
  volumes, 
  

   specific 
  gravities, 
  and 
  other 
  properties, 
  which 
  separate 
  the 
  

   Series 
  F, 
  O, 
  X, 
  from 
  Mn, 
  Cr, 
  V. 
  To 
  assign 
  it 
  an 
  atomic 
  

   weight 
  of 
  40, 
  thus 
  usurping 
  the 
  place 
  of 
  calcium, 
  and 
  placing 
  

   it 
  among 
  elements 
  to 
  which 
  it 
  bears 
  no 
  analogies 
  whatever, 
  

   would 
  violate 
  all 
  the 
  principles 
  of 
  the 
  periodic 
  law 
  as 
  now 
  

   understood 
  ; 
  and 
  the 
  great 
  mass 
  of 
  accumulated 
  evidence, 
  upon 
  

   which 
  that 
  generalization 
  rests, 
  requires 
  us 
  to 
  accept 
  any 
  rea- 
  

   sonable 
  explanation 
  of 
  the 
  supposed 
  inconsistency, 
  between 
  the 
  

   specific 
  heat 
  ratio 
  of 
  1*66 
  and 
  the 
  diatomicity 
  of 
  the 
  molecule, 
  

   rather 
  than 
  the 
  conclusion 
  that 
  it 
  is 
  monatomic. 
  

  

  That 
  is 
  to 
  say 
  the 
  burden 
  of 
  proof 
  is 
  on 
  those 
  who 
  oppose 
  

   the 
  conclusions 
  drawn 
  from 
  the 
  periodic 
  law. 
  

  

  The 
  argument 
  for 
  mon 
  atomicity, 
  briefly 
  stated, 
  is 
  this 
  : 
  The 
  

   Argon 
  molecule, 
  if 
  diatomic, 
  being 
  eccentric, 
  would 
  by 
  molec- 
  

   ular 
  contacts 
  acquire 
  rotational 
  energy, 
  which 
  it 
  does 
  not 
  pos- 
  

   sess, 
  as 
  proved 
  by 
  the 
  specific 
  heat 
  ratio 
  ; 
  hence 
  its 
  molecule 
  

   must 
  be 
  monatomic, 
  and 
  its 
  atomic 
  weight 
  40. 
  The 
  whole 
  

   argument 
  is 
  based 
  on 
  the 
  assumption 
  that 
  a 
  molecular 
  encoun- 
  

   ter 
  involves 
  an 
  actual 
  contact 
  of 
  atoms, 
  or 
  is 
  of 
  the 
  nature 
  of 
  a 
  

   collision 
  between 
  two 
  elastic 
  balls. 
  This, 
  however, 
  is 
  not 
  a 
  

   necessary 
  assumption, 
  nor 
  was 
  it 
  Maxwell's 
  view.* 
  As 
  pointed 
  

  

  * 
  "I 
  have 
  concluded 
  (he 
  says) 
  from 
  some 
  experiments 
  of 
  my 
  own 
  that 
  the 
  col- 
  

   lision 
  between 
  two 
  hard 
  spherical 
  balls 
  is 
  not 
  an 
  accurate 
  representation 
  of 
  what 
  

   takes 
  place, 
  ... 
  a 
  better 
  representation 
  of 
  such 
  an 
  encounter 
  will 
  be 
  obtained 
  

   by 
  supposing 
  the 
  molecules 
  to 
  act 
  on 
  one 
  another 
  in 
  a 
  more 
  gradual 
  manner, 
  so 
  

   that 
  the 
  action 
  between 
  them 
  goes 
  on 
  for 
  a 
  finite 
  ' 
  time 
  during 
  which 
  the 
  centers 
  

   of 
  the 
  molecules 
  first 
  approach 
  each 
  other 
  and 
  then 
  separate." 
  And 
  again: 
  "We 
  

   have 
  evidence 
  that 
  the 
  molecules 
  of 
  gases 
  attract 
  each 
  other 
  at 
  certain 
  small 
  dis 
  

   tances, 
  but 
  when 
  they 
  are 
  brought 
  still 
  nearer 
  they 
  repel 
  each 
  other." 
  

  

  