﻿446 
  Dr. 
  H. 
  S. 
  Allen 
  on 
  Molecular 
  

  

  Compounds 
  containing 
  water 
  of 
  crystallization 
  have 
  not 
  

   been 
  included, 
  as 
  in 
  such 
  cases 
  it 
  is 
  often 
  difficult 
  to 
  decide 
  

   whether 
  the 
  recorded 
  temperature 
  is 
  a 
  true 
  melting-point 
  or 
  

   the 
  temperature 
  at 
  which 
  the 
  solid 
  dissolves 
  in 
  the 
  water 
  

   of 
  crystallization. 
  

  

  Group 
  I. 
  

  

  Of 
  inorganic 
  compounds 
  for 
  which 
  the 
  density 
  and 
  the 
  

   melting-point 
  are 
  known, 
  a 
  larger 
  proportion 
  belongs 
  to 
  the 
  

   first 
  group 
  than 
  to 
  any 
  other 
  group 
  in 
  the 
  Periodic 
  Table. 
  

   With 
  a 
  small 
  number 
  of 
  exceptional 
  or 
  doubtful 
  cases, 
  the 
  

   results 
  show 
  good 
  agreement 
  with 
  the 
  suggested 
  relations. 
  It 
  

   is 
  noteworthy 
  that 
  when 
  the 
  temperature 
  of 
  the 
  melting-point 
  

   is 
  known 
  accurately, 
  the 
  agreement 
  is 
  better 
  than 
  when 
  this 
  

   temperature 
  is 
  uncertain. 
  

  

  For 
  several 
  of 
  the 
  lithium 
  compounds 
  the 
  melting-point 
  

   has 
  not 
  been 
  determined 
  with 
  great 
  accuracy, 
  yet 
  the 
  values 
  

   of 
  v 
  A 
  do 
  not 
  differ 
  widely 
  from 
  the 
  mean 
  value 
  which 
  is 
  

   20'7 
  x 
  10 
  12 
  sec. 
  -1 
  The 
  mean 
  value 
  for 
  the 
  elements, 
  given 
  

   in 
  a 
  former 
  paper*, 
  was 
  20'9 
  x 
  10 
  12 
  sec. 
  -1 
  , 
  when 
  the 
  same 
  

   factor 
  was 
  employed 
  in 
  Lindemann's 
  formula 
  as 
  that 
  here 
  

   used. 
  It 
  has 
  been 
  pointed 
  out 
  previously 
  t 
  that 
  the 
  chance 
  

   of 
  these 
  results 
  for 
  the 
  lithium 
  compounds 
  (including 
  

   Li 
  3 
  P0 
  4 
  . 
  H 
  2 
  0) 
  agreeing 
  accidentally 
  was 
  about 
  1 
  in 
  280. 
  

  

  Group 
  I. 
  

   Lithium 
  Compounds 
  (N 
  = 
  3). 
  

  

  Name. 
  Formula. 
  N. 
  J>X 
  10-12 
  NvXlO"12. 
  

   Lithium 
  

  

  amide 
  LiNH 
  2 
  12 
  6073 
  3|x20'8 
  

  

  bromide 
  LiBr 
  38 
  3-234 
  6 
  x20-5 
  

  

  carbonate 
  Li„C0 
  3 
  36 
  3435 
  6 
  x20"6 
  

  

  chloride 
  (a) 
  LiCl 
  20 
  5079 
  5 
  X203 
  

  

  fluoride 
  LiF 
  12 
  9-207 
  5^x201 
  

  

  iodide 
  Lil 
  56 
  2-227 
  6 
  X208 
  

  

  nitrate 
  LiN0 
  3 
  34 
  2821 
  4|x21'3 
  

  

  perchlorate 
  LiC10 
  4 
  52 
  T742 
  4|x20'l 
  

  

  silicate 
  (b) 
  Li 
  2 
  Si0 
  3 
  44 
  3'756 
  8 
  x208 
  

  

  sulphate 
  acid 
  LiHS0 
  4 
  52 
  1-636 
  4 
  X21-3 
  

  

  sulphate 
  Li 
  2 
  S0 
  4 
  54 
  2-680 
  7 
  X20-7 
  

  

  (a) 
  Richards 
  and 
  Meldrum 
  (1917) 
  give 
  the 
  melting-point 
  of 
  pure 
  

   lithium 
  chloride 
  as 
  613° 
  C. 
  This 
  makes 
  for 
  better 
  agreement, 
  giving 
  

   NvXlO~ 
  12 
  = 
  5x20-6. 
  

  

  (b) 
  The 
  melting-point 
  of 
  lithium 
  silicate 
  is 
  given 
  as 
  a 
  standard 
  tem- 
  

   perature 
  (121)1° 
  0.) 
  in 
  the 
  Smithsonian 
  Physical 
  Tables. 
  

  

  * 
  H. 
  S. 
  Allen, 
  Phil. 
  Mag. 
  vol. 
  xxxiv. 
  p. 
  478 
  (1917). 
  

   t 
  H. 
  S. 
  Allen, 
  Phil. 
  Mag. 
  vol. 
  xxxv. 
  p. 
  338 
  (1918). 
  

  

  