﻿450 
  Dr. 
  H. 
  S. 
  Allen 
  on 
  Molecular 
  

  

  been 
  included, 
  as 
  the 
  density 
  corresponds 
  to 
  a 
  crystalline 
  

   form 
  different 
  from 
  that 
  to 
  which 
  the 
  melting-point 
  applies. 
  

  

  No 
  results 
  are 
  available 
  for 
  compounds 
  of 
  gold. 
  

  

  The 
  melting-point 
  and 
  the 
  density 
  are 
  known 
  for 
  the 
  

   greater 
  number 
  of 
  the 
  halogen 
  derivatives 
  of 
  Group 
  I., 
  so 
  

   that 
  it 
  is 
  possible 
  to 
  institute 
  a 
  comparison 
  between 
  the 
  

   frequency 
  numbers 
  for 
  this 
  group 
  of 
  compounds. 
  The 
  

   results 
  are 
  collected 
  in 
  the 
  Table 
  following, 
  wLich 
  contains 
  

   the 
  atomic 
  or 
  molecular 
  number 
  in 
  italics 
  and 
  the 
  product 
  

   N«/ 
  < 
  10 
  ~ 
  12 
  in 
  roman 
  numerals. 
  The 
  values 
  for 
  the 
  thallium 
  

   compounds 
  have 
  been 
  added 
  as 
  they 
  resemble 
  closely 
  the 
  

   corresponding 
  rubidium 
  compounds*. 
  A 
  close 
  examination 
  

   or! 
  the 
  table 
  will 
  reveal 
  many 
  interesting 
  relationships 
  ; 
  the 
  

   close 
  resemblance 
  between 
  the 
  sodium 
  and 
  the 
  potassium 
  

   salts 
  is 
  at 
  once 
  evident 
  ; 
  the 
  frequency 
  numbers 
  for 
  these 
  

   compounds 
  exceed 
  the 
  corresponding 
  numbers 
  for 
  the 
  

   lithium 
  salts 
  by 
  unity 
  (the 
  bromide 
  excepted) 
  ; 
  the 
  fre- 
  

   quency 
  numbers 
  for 
  cuprous 
  chloride, 
  bromide, 
  iodide 
  form 
  

   the 
  sequence 
  6, 
  7, 
  8; 
  the 
  frequency 
  numbers 
  for 
  silver 
  

   chloride, 
  bromide, 
  iodide 
  form 
  the 
  sequence 
  7, 
  7|, 
  8. 
  

   Further, 
  it 
  will 
  be 
  noticed 
  that 
  silver 
  chloride, 
  cuprous 
  

   bromide, 
  sodium 
  iodide 
  have 
  the 
  same 
  frequency 
  number, 
  7; 
  

   caesium 
  chloride, 
  rubidium 
  bromide, 
  potassium 
  iodide 
  form 
  a 
  

   similar 
  chain 
  with 
  frequency 
  number, 
  7. 
  

  

  Monohalides 
  of 
  Group 
  I. 
  

  

  Element. 
  Fluoride 
  Chlorfde 
  Bromide 
  Iodide 
  

  

  Y 
  = 
  D. 
  C\=17. 
  Br=35. 
  1=53. 
  

  

  U=3 
  

  

  12 
  

  

  5|X 
  20-1 
  

  

  20 
  

  

  5x20-3 
  

  

  38 
  

  

  6x20-5 
  

  

  56 
  

  

  6x20-8 
  

  

  Na=li 
  

  

  20 
  

  

  6^x20-9 
  

  

  28 
  

  

  6x20-6 
  

  

  46 
  

   6fx20-8 
  

  

  64 
  

  

  7X207 
  

  

  K 
  = 
  19 
  

  

  28 
  

  

  6|x20-6 
  

  

  36 
  

  

  6x20-9 
  

  

  54 
  

   6fx20-6 
  

  

  72 
  

  

  7x20-4 
  

  

  Gi\ 
  = 
  29 
  

  

  38 
  

  

  46 
  

  

  6x20-9 
  

  

  64 
  

  

  7x207 
  

  

  82 
  

  

  8x210 
  

  

  Kb 
  =37 
  

  

  46 
  

  

  (HX214 
  

  

  54 
  

  

  6x20-8 
  

  

  72 
  

  

  7x20-5 
  

  

  90 
  

  

  7x20-8 
  

  

  Ag=47 
  

  

  56 
  

  

  7x21-0 
  

  

  64 
  

  

  7x21-4 
  

  

  82 
  

   7^x21-2 
  

  

  100 
  

   8x207 
  

  

  Cs 
  = 
  55 
  

  

  64 
  

  

  72 
  

  

  7X211 
  

  

  90 
  

  

  108 
  

   7^x21-3 
  

  

  Tl= 
  81 
  

  

  90 
  

  

  98 
  

  

  6x211 
  

  

  116 
  

   8x21-3 
  

  

  134 
  

  

  8x20-9 
  

  

  * 
  Tutton, 
  Roy. 
  Soc. 
  Proc. 
  vol. 
  lxxix. 
  p. 
  351 
  (1907). 
  

  

  