﻿Chemistry 
  and 
  Physics. 
  479 
  

  

  SCIENTIFIC 
  INTELLIGENCE. 
  

  

  I. 
  Chemistey 
  and 
  Physics. 
  

  

  1. 
  On 
  the 
  Relation 
  of 
  Refraction 
  to 
  Density. 
  — 
  It 
  is 
  well 
  known 
  

   that 
  Kopp 
  distinguished 
  between 
  real 
  and 
  apparent 
  molecular 
  

   volume 
  by 
  denning 
  the 
  former 
  as 
  the 
  space 
  actually 
  occupied 
  by 
  

   the 
  molecule 
  and 
  the 
  latter 
  as 
  this 
  quantity 
  increased 
  by 
  the 
  space 
  

   in 
  which 
  the 
  molecule 
  moves. 
  Traube 
  prefers 
  to 
  call 
  the 
  former 
  

   the 
  molecular 
  nucleus-volume 
  and 
  the 
  latter 
  the 
  molecular 
  vibra- 
  

   tion-volume 
  ; 
  the 
  nucleus-volume 
  being 
  the 
  sum 
  of 
  the 
  atomic 
  

   nucleus-volumes, 
  and 
  the 
  vibration-volume 
  being 
  the 
  sum 
  of 
  the 
  

   atomic 
  vibration-volumes, 
  increased 
  by 
  the 
  space 
  in 
  which 
  the 
  

   molecule 
  itself 
  vibrates. 
  Hence 
  for 
  this 
  molecular 
  vibration-vol- 
  

   ume, 
  which 
  is 
  the 
  quotient 
  obtained 
  by 
  dividing 
  the 
  molecular 
  

   mass 
  by 
  the 
  density, 
  we 
  have 
  V 
  m 
  = 
  %nO 
  + 
  Cov 
  ; 
  i. 
  e., 
  the 
  sum 
  of 
  

   the 
  products 
  of 
  the 
  vibration-volumes 
  of 
  the 
  separate 
  atoms 
  by 
  

   their 
  number, 
  increased 
  by 
  the 
  molecular 
  co-volume, 
  which 
  is 
  con- 
  

   stant 
  and 
  has 
  the 
  value 
  25*9. 
  In 
  a 
  previous 
  paper 
  the 
  author 
  had 
  

   shown 
  that 
  the 
  molecular 
  co-volumes 
  of 
  liquids, 
  and 
  probably 
  of 
  

   solids 
  also, 
  are 
  equal, 
  so 
  that 
  the 
  laws 
  of 
  Avogadro 
  and 
  Gay 
  Lus- 
  

   sac 
  apply 
  to 
  these 
  states 
  of 
  matter. 
  While 
  therefore 
  the 
  passage 
  

   from 
  the 
  solid 
  to 
  the 
  liquid 
  state 
  is 
  not 
  accompanied 
  by 
  any 
  

   change 
  in 
  the 
  molecular 
  co-volume, 
  this 
  value 
  decreases 
  when 
  the 
  

   liquid 
  becomes 
  a 
  gas, 
  the 
  decrease 
  being 
  greater 
  the 
  higher 
  the 
  

   temperature. 
  Hence 
  for 
  every 
  substance 
  there 
  must 
  be 
  a 
  particu- 
  

   lar 
  temperature 
  at 
  which 
  the 
  co-volumes 
  of 
  the 
  liquid 
  and 
  the 
  gas 
  

   are 
  the 
  same. 
  This 
  obviously 
  is 
  the 
  critical 
  temperature. 
  Traube 
  

   has 
  now 
  shown 
  that 
  if, 
  according 
  to 
  the 
  Clausius-Mosotti 
  dielec- 
  

   tric 
  theory, 
  v 
  be 
  the 
  space 
  actually 
  filled 
  with 
  matter, 
  and 
  k 
  

   the 
  dielectric 
  constant, 
  the 
  molecules 
  being 
  supposed 
  spherical, 
  

   v 
  = 
  (k— 
  1)/ 
  (k 
  + 
  2). 
  But 
  the 
  dielectric 
  constant, 
  on 
  the 
  electro- 
  

   magnetic 
  theory 
  of 
  light, 
  is 
  equal 
  to 
  the 
  square 
  of 
  the 
  index 
  of 
  

   refraction 
  la 
  for 
  waves 
  of 
  very 
  great 
  length. 
  Hence 
  as 
  Exner 
  has 
  

   proved 
  v 
  = 
  (/x 
  2 
  — 
  l)/(/x 
  2 
  -f 
  2). 
  Moreover 
  as 
  above 
  stated, 
  this 
  

   value 
  is 
  comparable 
  to 
  the 
  expression 
  SiC/V 
  Bl 
  ; 
  so 
  that 
  the 
  quo- 
  

   tient 
  of 
  2,nC/Y 
  m 
  divided 
  by 
  (/x 
  2 
  — 
  l)/(/x 
  2 
  + 
  2) 
  should 
  be 
  a 
  constant 
  

   quantity. 
  From 
  the 
  tabulated 
  results 
  of 
  a 
  long 
  series 
  of 
  calcu- 
  

   lated 
  values 
  of 
  this 
  ratio 
  it 
  appears 
  that 
  the 
  atomic 
  vibration-vol- 
  

   ume 
  calculated 
  from 
  the 
  molecular 
  mass 
  and 
  the 
  density 
  are 
  equal 
  

   to 
  the 
  atomic 
  nucleus-volumes, 
  obtained 
  from 
  atomic 
  refraction, 
  

   multiplied 
  by 
  a 
  constant 
  which 
  varies 
  only 
  with 
  the 
  wave 
  length 
  

   of 
  light 
  and 
  this 
  within 
  narrow 
  limits. 
  For 
  D, 
  this 
  constant 
  is 
  

   3'44 
  ; 
  for 
  Cauchy's 
  constant 
  A, 
  it 
  is 
  3*53. 
  — 
  Ber. 
  Berl. 
  Chem. 
  Ges., 
  

   xxix, 
  2732-2742, 
  December, 
  1896. 
  g, 
  f. 
  b. 
  

  

  2. 
  On 
  the 
  Properties 
  of 
  Free 
  Hydrazine. 
  — 
  According 
  to 
  Lobry 
  

   de 
  Bruyjst, 
  free 
  hydrazine 
  is 
  best 
  prepared 
  by 
  the 
  action 
  of 
  barium 
  

   oxide 
  on 
  hydrazine 
  hydrate. 
  The 
  barium 
  oxide 
  is 
  contained 
  in 
  

   a 
  flask 
  provided 
  with 
  a 
  neck 
  about 
  50 
  cm 
  long 
  bent 
  at 
  right 
  angles 
  

  

  