﻿THE 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [THIRD 
  SERIES.] 
  

  

  Art. 
  XXVIII. 
  — 
  On 
  the 
  Color 
  Relations 
  of 
  Atoms, 
  Ions 
  and 
  

   Molecules; 
  by 
  M. 
  Carey 
  Lea. 
  Part 
  I. 
  (With 
  Plate 
  IV.) 
  

  

  The 
  atoms 
  of 
  which 
  elements 
  are 
  composed 
  differ 
  remark- 
  

   ably 
  in 
  color 
  from 
  the 
  elements 
  themselves 
  ; 
  their 
  colors 
  are 
  

   more 
  important 
  and 
  more 
  characteristic 
  than 
  those 
  of 
  the 
  ele- 
  

   ments, 
  and 
  if 
  we 
  divide 
  the 
  entire 
  series 
  of 
  elements 
  into 
  two 
  

   classes, 
  those 
  whose 
  atoms 
  are 
  always 
  colorless 
  whatever 
  may 
  

   be 
  their 
  valency, 
  and 
  those 
  whose 
  atoms 
  are 
  either 
  sometimes 
  

   or 
  always 
  colored, 
  we 
  shall 
  find 
  that 
  this 
  division 
  harmonizes 
  in 
  

   a 
  striking 
  way 
  with 
  their 
  chemical 
  properties. 
  The 
  colors 
  of 
  

   the 
  elements 
  have 
  no 
  such 
  significance 
  or 
  importance. 
  

  

  This 
  present 
  paper 
  accepts 
  the 
  Arrhenius 
  theory 
  of 
  dissocia- 
  

   tion, 
  the 
  author 
  believing 
  that 
  the 
  evidence 
  in 
  its 
  favor 
  is 
  too 
  

   strong 
  to 
  be 
  resisted. 
  But 
  the 
  facts 
  to 
  be 
  stated, 
  and 
  the 
  con- 
  

   clusions 
  to 
  be 
  drawn 
  therefrom 
  are 
  independent 
  of 
  any 
  theory. 
  

  

  It 
  is 
  somewhat 
  remarkable 
  that 
  it 
  is 
  never 
  possible 
  to 
  deduce 
  

   the 
  color 
  of 
  an 
  atom 
  from 
  that 
  of 
  the 
  element 
  which 
  it 
  forms 
  

   by 
  combining 
  with 
  another 
  similar 
  atom. 
  Between 
  the 
  two, 
  

   the 
  atom 
  and 
  the 
  element, 
  there 
  seems 
  to 
  be 
  no 
  color 
  relation 
  

   whatever. 
  It 
  is 
  from 
  the 
  combinations 
  of 
  an 
  atom 
  with 
  one 
  

   or 
  more 
  dissimilar 
  atoms, 
  kathions 
  with 
  anions, 
  that 
  we 
  can 
  

   with 
  facility 
  and 
  certainty 
  deduce 
  the 
  color 
  of 
  the 
  atoms 
  them- 
  

   selves. 
  

  

  So 
  far 
  I 
  have 
  spoken 
  of 
  atoms 
  only, 
  but 
  the 
  matter 
  in 
  hand 
  

   is 
  simplified 
  by 
  considering 
  dissociated 
  ions 
  also. 
  And 
  as 
  a 
  

   first 
  step 
  it 
  becomes 
  necessary 
  to 
  establish 
  the 
  following 
  propo- 
  

   sition 
  : 
  namely, 
  that 
  in 
  any 
  colored 
  inorganic 
  compound 
  in 
  

   solution, 
  the 
  color 
  belongs 
  essentially 
  to 
  the 
  metallic 
  atom, 
  

   whether 
  it 
  exists 
  in 
  a 
  free 
  state 
  as 
  an 
  ion 
  or 
  combined 
  with 
  a 
  

  

  