﻿300 
  Scientific 
  Intelligence. 
  

  

  uct 
  is 
  black 
  arid 
  is 
  said 
  to 
  consist 
  of 
  a 
  mixture 
  of 
  magnesium 
  

   hydroxide 
  and 
  the 
  hydroxide 
  of 
  lead 
  suboxide. 
  When 
  treated 
  

   with 
  boiling 
  water 
  the 
  alloy 
  evolves 
  hydrogen 
  and 
  the 
  same 
  solid- 
  

   compounds 
  are 
  formed. 
  — 
  Trans. 
  Faraday 
  Soc, 
  14, 
  271. 
  

  

  H. 
  l. 
  w. 
  

  

  5. 
  The 
  Preparation 
  of 
  Organic 
  Compounds; 
  by 
  E. 
  De 
  Barry 
  

   Barnett. 
  8vo, 
  pp. 
  273. 
  Philadelphia, 
  1920 
  (P. 
  Blakiston's 
  

   Son 
  & 
  Co. 
  Price 
  $3.25 
  net). 
  — 
  This 
  is 
  the 
  second 
  edition 
  of 
  a 
  

   very 
  useful 
  laboratory 
  manual 
  of 
  British 
  origin. 
  No 
  very 
  

   extensive 
  changes 
  have 
  been 
  made 
  in 
  the 
  present 
  edition, 
  but 
  

   some 
  descriptions 
  of 
  larger-scale 
  apparatus 
  are 
  among 
  the 
  note- 
  

   worthy 
  additions, 
  and 
  it 
  has 
  been 
  the 
  author's 
  aim 
  to 
  give 
  

   the 
  student 
  an 
  insight 
  into 
  industrial 
  operations 
  in 
  connection 
  

   with 
  the 
  theoretical 
  principles 
  of 
  the 
  subject. 
  

  

  The 
  list 
  of 
  preparations 
  presented 
  is 
  unusually 
  extensive 
  and 
  

   well 
  classified, 
  covering 
  very 
  satisfactorily 
  the 
  various 
  fields 
  of 
  

   organic 
  synthesis, 
  while 
  copious 
  references 
  to 
  the 
  literature 
  are 
  

   given, 
  which 
  should 
  be 
  of 
  much 
  assistance, 
  both 
  to 
  students 
  and 
  

   instructors, 
  in 
  courses 
  of 
  organic 
  preparations. 
  h. 
  l. 
  w. 
  

  

  6. 
  The 
  Value 
  of 
  the 
  Rydberg 
  Series 
  Constant. 
  — 
  In 
  the 
  year 
  

   1914 
  an 
  attempt 
  was 
  made 
  by 
  W. 
  E. 
  Curtis 
  to 
  derive 
  the 
  best 
  

   value 
  for 
  the 
  Rydberg 
  constant 
  N 
  from 
  the 
  most 
  reliable 
  data 
  on 
  

   the 
  wave-lengths 
  of 
  the 
  series 
  lines 
  of 
  hydrogen. 
  The 
  result 
  

   then 
  obtained 
  was 
  109679.22 
  = 
  N. 
  In 
  obtaining 
  this 
  important 
  

   constant 
  the 
  author 
  failed 
  to 
  realize 
  that 
  the 
  tertiary 
  iron 
  stand- 
  

   ards 
  refer 
  to 
  15° 
  C. 
  By 
  using 
  20° 
  C. 
  in 
  the 
  reduction 
  of 
  the 
  

   hydrogen 
  wave-lengths 
  to 
  vacuo 
  he 
  introduced 
  a 
  slight 
  error 
  in 
  

   the 
  final 
  result. 
  Since 
  the 
  first 
  paper 
  of 
  Curtis 
  was 
  published, 
  

   very 
  accurate 
  determinations 
  of 
  the 
  indices 
  of 
  refraction 
  of 
  air, 
  

   for 
  an 
  unusually 
  wide 
  range 
  of 
  wave-lengths, 
  have 
  been 
  made 
  by 
  

   Meggers 
  at 
  the 
  National 
  Bureau 
  of 
  Standards 
  in 
  Washington, 
  

   D. 
  C. 
  

  

  A 
  second 
  paper 
  on 
  the 
  same 
  subject 
  by 
  Curtis 
  has 
  recently 
  

   appeared, 
  and 
  in 
  it 
  he 
  takes 
  advantage 
  both 
  of 
  the 
  latest 
  data 
  

   for 
  the 
  refractive 
  indices 
  of 
  air 
  and 
  of 
  the 
  experience 
  gained 
  in 
  

   his 
  earlier 
  calculations. 
  In 
  this 
  paper 
  six 
  series 
  formulae 
  are 
  

   compared 
  and 
  it 
  is 
  found 
  that 
  a 
  Rydberg 
  expression 
  involving 
  

   two 
  constants 
  is 
  not 
  only 
  capable 
  of 
  representing 
  the 
  hydrogen 
  

   series 
  satisfactorily 
  but 
  that 
  it 
  is 
  appreciably 
  superior, 
  in 
  this 
  

   respect, 
  to 
  the 
  theoretical 
  formulae 
  of 
  Bohr 
  and 
  Allen. 
  The 
  

   probable 
  effect 
  upon 
  the 
  determination 
  of 
  N 
  arising 
  from 
  the 
  

   fact 
  that 
  each 
  of 
  the 
  lines 
  Ha 
  and 
  H(3 
  is 
  a 
  doublet 
  is 
  investigated, 
  

   and 
  shown 
  to 
  be 
  inappreciable. 
  The 
  author 
  suggests 
  the 
  provis- 
  

   ional 
  adoption 
  of 
  the 
  value 
  109678.3 
  for 
  N. 
  By 
  way 
  of 
  com- 
  

   parison, 
  it 
  is 
  desirable 
  to 
  state 
  that, 
  in 
  1918, 
  R. 
  T. 
  Birge 
  discussed 
  

   the 
  same 
  question 
  and 
  arrived 
  at 
  the 
  value 
  109678.705 
  for 
  N. 
  

   It 
  seems 
  clear, 
  therefore, 
  that 
  the 
  seventh 
  digit 
  cannot 
  be 
  finally 
  

   established 
  until 
  more 
  accurate 
  values 
  for 
  the 
  wave-lengths 
  of 
  

  

  