﻿Lea 
  — 
  Color 
  Relations 
  of 
  Atoms, 
  Ions 
  and 
  Molecules. 
  367 
  

  

  Transitional 
  Elements. 
  

  

  Intermediate 
  between 
  the 
  two 
  divisions 
  is 
  a 
  small 
  class 
  of 
  

   eleven 
  transition 
  als. 
  These 
  elements 
  have 
  ions 
  which 
  at 
  some 
  

   valencies 
  are 
  colored 
  and 
  others 
  colorless. 
  

  

  Transitional 
  Elements. 
  

  

  Ti 
  4.8 
  

  

  

  m 
  9u 
  

  

  

  

  Cu 
  68-3 
  . 
  

  

  

  Ag 
  108 
  

  

  Vol 
  

  

  

  Mom 
  

  

  

  GeU2 
  

  

  Ta 
  182 
  

  

  W184 
  

  

  T1204. 
  

   Bi 
  210 
  

  

  (As 
  to 
  tantalum 
  and 
  niobium, 
  satisfactory 
  information 
  is 
  

   deficient 
  and 
  they 
  are 
  placed 
  here 
  provisionally.) 
  

  

  An 
  inspection 
  of 
  the 
  table 
  will 
  show 
  that 
  the 
  metals 
  com- 
  

   posing 
  it 
  have 
  little 
  relation 
  with 
  one 
  another. 
  

  

  Most 
  of 
  them 
  on 
  the 
  contrary 
  are 
  noticeable 
  as 
  having 
  each 
  

   some 
  marked 
  peculiarity. 
  Titanium 
  when 
  heated 
  combines 
  

   with 
  atmospheric 
  nitrogen. 
  Vanadium 
  forms 
  a 
  compound 
  

   radical 
  simulating 
  a 
  metal 
  so 
  completely 
  that 
  all 
  chemists 
  were 
  

   deceived 
  until 
  Roscoe 
  detected 
  the 
  fact. 
  Copper 
  forms 
  a 
  solu- 
  

   tion 
  which 
  has 
  the 
  property 
  of 
  dissolving 
  cellulose. 
  Silver 
  can 
  

   assume 
  a 
  condition 
  in 
  which 
  it 
  is 
  freely 
  soluble 
  in 
  water 
  ; 
  it 
  is 
  

   also 
  remarkable 
  for 
  the 
  high 
  sensitiveness 
  to 
  light 
  of 
  some 
  of 
  

   its 
  compounds. 
  Tungsten 
  is 
  remarkable 
  amongst 
  inorganic 
  

   substances 
  for 
  the 
  unexampled 
  complexity 
  of 
  its 
  compounds, 
  

   as 
  first 
  observed 
  by 
  Gibbs. 
  Thallium 
  is 
  noted 
  for 
  uniting 
  in 
  a 
  

   singular 
  way 
  the 
  properties 
  of 
  an 
  alkaline 
  and 
  those 
  of 
  a 
  heavy 
  

   metal. 
  

  

  The 
  relations 
  of 
  this 
  peculiar 
  group 
  are 
  chiefly 
  with 
  the 
  ele- 
  

   ments 
  having 
  colorless 
  atoms 
  only, 
  as 
  shown 
  in 
  Table 
  II. 
  Into 
  

   this, 
  they 
  enter 
  as 
  it 
  were 
  in 
  a 
  block, 
  at 
  the 
  center, 
  increasing 
  

   the 
  number 
  of 
  groups 
  to 
  thirteen, 
  or 
  twelve 
  if 
  we 
  take 
  the 
  first 
  

   two 
  as 
  constituting 
  a 
  double 
  group 
  of 
  univalent 
  elements. 
  In 
  

   this 
  way 
  as 
  we 
  follow 
  the 
  groups 
  downwards 
  the 
  valency 
  in- 
  

   creases 
  successively 
  from 
  one 
  to 
  six. 
  then 
  begins 
  at 
  one 
  again 
  

   and 
  increases 
  regularly 
  from 
  one 
  to 
  six 
  again. 
  This 
  will 
  be 
  

   better 
  seen 
  by 
  referring 
  to 
  Table 
  II. 
  In 
  every 
  group 
  each 
  

   member 
  has 
  the 
  same 
  valency. 
  

  

  "Whether 
  it 
  is 
  probable 
  that 
  all 
  the 
  blanks 
  represent 
  so 
  many 
  

   elements 
  remaining 
  to 
  be 
  discovered 
  seems 
  doubtful. 
  But 
  it 
  

   is 
  certainly 
  the 
  opinion 
  of 
  many 
  chemists 
  that 
  the 
  number 
  of 
  

   existing 
  elements 
  as 
  yet 
  unknown, 
  is 
  large.* 
  

  

  * 
  Cf. 
  Ramsay, 
  InorgaDic 
  Chemistry, 
  p. 
  87. 
  

  

  