﻿250 
  ANNUAL 
  EEPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1929 
  

  

  spectral 
  lines. 
  Owing 
  to 
  the 
  ease 
  with 
  which 
  the 
  lines 
  are 
  masked 
  by 
  

   those 
  of 
  contaminating 
  elements, 
  a 
  careful 
  preliminary 
  separation 
  of 
  

   these 
  elements 
  was 
  necessary, 
  and 
  for 
  the 
  same 
  reason 
  it 
  was 
  found 
  

   more 
  satisfactory 
  to 
  use 
  ''pure" 
  manganese 
  salts 
  than 
  the 
  mineral 
  

   pyrolusite, 
  even 
  though 
  the 
  former 
  contained 
  a 
  far 
  smaller 
  percentage 
  

   of 
  the 
  elements 
  sought 
  than 
  the 
  latter 
  commercial 
  ore. 
  This 
  consider- 
  

   ation 
  has 
  been 
  quoted 
  to 
  throw 
  some 
  doubt 
  on 
  the 
  spectroscopic 
  

   evidence 
  of 
  the 
  German 
  workers, 
  whose 
  preliminary 
  separation 
  

   does 
  not 
  appear 
  to 
  have 
  been 
  sufficiently 
  complete. 
  

  

  Successful 
  support 
  and 
  confirmation 
  of 
  the 
  work 
  of 
  Druce 
  and 
  

   Loring, 
  as 
  well 
  as 
  further 
  illustration 
  of 
  the 
  use 
  of 
  perfected 
  experi- 
  

   mental 
  method, 
  is 
  afforded 
  by 
  the 
  work 
  of 
  the 
  two 
  Czech 
  scientists, 
  

   who 
  had 
  invented 
  an 
  improved 
  type 
  of 
  electrolysis 
  apparatus 
  termed 
  

   ''the 
  dropping-mercury 
  cathode," 
  for 
  which 
  several 
  important 
  advan- 
  

   tages 
  are 
  claimed 
  over 
  the 
  normal 
  type 
  of 
  apparatus. 
  It 
  has 
  a 
  more 
  

   extensive 
  range 
  of 
  utility, 
  permits 
  work 
  to 
  a 
  much 
  greater 
  degree 
  of 
  

   precision, 
  and 
  used 
  in 
  conjunction 
  with 
  a 
  device 
  termed 
  "a 
  polaro- 
  

   graph," 
  photographs 
  a 
  permanent 
  automatic 
  record 
  in 
  the 
  form 
  of 
  

   potential 
  curves, 
  of 
  the 
  electrolytic 
  reaction. 
  A 
  study 
  of 
  the 
  curves 
  

   gives 
  definite 
  indication 
  of 
  the 
  deposition 
  of 
  minute 
  traces 
  of 
  a 
  particu- 
  

   lar 
  product. 
  By 
  the 
  use 
  of 
  this 
  apparatus, 
  Dolejsek 
  and 
  Heyrovsky 
  

   obtained 
  indications 
  of 
  elements 
  43 
  and 
  75. 
  The 
  latter 
  was 
  confirmed 
  

   by 
  subsequent 
  X-ray 
  analysis, 
  although 
  evidence 
  of 
  43 
  was 
  inconclusive. 
  

   The 
  materials 
  used 
  and 
  the 
  results 
  obtained 
  agree 
  completely 
  with 
  the 
  

   work 
  of 
  Druce 
  and 
  Loring 
  and 
  afford 
  valuable 
  independent 
  confir- 
  

   mation 
  and 
  support. 
  

  

  The 
  latest 
  element 
  whose 
  discovery 
  was 
  announced 
  in 
  1926 
  was 
  

   the 
  previously 
  discussed 
  rare-earth 
  metal 
  61. 
  This 
  has 
  been 
  detected 
  

   by 
  Harris, 
  Yntema, 
  and 
  Hopkins 
  in 
  America. 
  

  

  The 
  discovery 
  is 
  of 
  special 
  interest 
  as 
  the 
  group 
  of 
  rare-earth 
  ele- 
  

   ments 
  lying 
  between 
  lanthanum 
  (57) 
  and 
  lutecium 
  (71) 
  is 
  now 
  known 
  

   to 
  be 
  complete. 
  The 
  group 
  finds 
  a 
  natural 
  place 
  in 
  Bohr's 
  generalized 
  

   table 
  of 
  elements, 
  and 
  is 
  beautifully 
  explained 
  in 
  his 
  quantum 
  orbit 
  

   development 
  scheme. 
  As 
  long 
  ago 
  as 
  1902 
  Brauner 
  suggested 
  the 
  

   probability 
  of 
  a 
  missing 
  element 
  between 
  samarium 
  and 
  neodymium 
  

   as 
  the 
  difference 
  in 
  atomic 
  weight 
  between 
  these 
  two 
  elements 
  is 
  greater 
  

   than 
  that 
  between 
  their 
  neighbors. 
  He 
  showed 
  also 
  that 
  a 
  study 
  of 
  

   the 
  periodicity 
  of 
  the 
  hydrides 
  indicated 
  a 
  missing 
  element, 
  according 
  

   to 
  the 
  scheme 
  CsH. 
  Ba 
  H^. 
  La 
  Hg. 
  CH4. 
  Pr 
  H3. 
  Nd 
  H,. 
  (XH). 
  

  

  The 
  main 
  difficulty 
  encountered 
  in 
  this 
  group 
  has 
  been 
  the 
  selec- 
  

   tion 
  of 
  a 
  satisfactory 
  and 
  efficient 
  means 
  of 
  separation, 
  and 
  the 
  method 
  

   employed 
  w^as 
  repeated 
  fractional 
  crystallizations 
  of 
  the 
  double 
  mag- 
  

   nesium 
  bromate 
  instead 
  of 
  the 
  usual 
  procedure 
  by 
  means 
  of 
  the 
  double 
  

   magnesium 
  nitrate. 
  The 
  element 
  was 
  confirmed 
  by 
  its 
  absorption 
  

   spectrum 
  band, 
  which 
  would 
  be 
  masked 
  unless 
  the 
  preliminary 
  separa- 
  

  

  