﻿148 
  Scientific 
  Intelligence. 
  

  

  The 
  second 
  part 
  of 
  the 
  research 
  was 
  devoted 
  to 
  the 
  question 
  

   whether 
  gold 
  would 
  still 
  permeate 
  lead 
  if 
  the 
  temperature 
  were 
  

   maintained 
  far 
  below 
  the 
  fusing 
  point 
  of 
  the 
  latter 
  metal. 
  In 
  the 
  

   first 
  experiments, 
  thin 
  plates 
  of 
  gold 
  were 
  fused 
  to 
  the 
  lower 
  

   ends 
  of 
  cylindrical 
  rods 
  of 
  lead 
  I4 
  mm 
  in 
  diameter 
  and 
  7o 
  mm 
  long, 
  

   and 
  these 
  cylinders 
  were 
  maintained 
  for 
  thirty-one 
  days 
  in 
  a 
  little 
  

   iron 
  chamber 
  lined 
  with 
  asbestos 
  and 
  kept 
  at 
  250° 
  0, 
  75° 
  below 
  

   the 
  melting 
  point 
  of 
  lead. 
  The 
  cylinders 
  were 
  then 
  measured, 
  cut 
  

   into 
  sections 
  and 
  assayed. 
  Gold 
  was 
  found 
  through 
  the 
  entire 
  

   length 
  of 
  the 
  cylinder, 
  the 
  diffusivity 
  being 
  in 
  one 
  case 
  0*023 
  and 
  

   in 
  another 
  0*03 
  sq 
  cm 
  per 
  diem. 
  At 
  200°, 
  the 
  experiment 
  lasting 
  only 
  

   ten 
  days, 
  the 
  values 
  were 
  0'007 
  and 
  0-008. 
  Since 
  the 
  eutectic 
  

   alloy 
  of 
  gold 
  and 
  lead 
  fuses 
  at 
  200°, 
  experiments 
  were 
  made 
  to 
  

   see 
  if 
  gold 
  would 
  diffuse 
  into 
  solid 
  lead 
  at 
  165°, 
  a 
  temperature 
  

   below 
  this 
  point. 
  The 
  diffusivity 
  was 
  found 
  to 
  be 
  0*005 
  and 
  

   . 
  004 
  sq 
  cm 
  p 
  er 
  di 
  em 
  Even 
  as 
  low 
  as 
  100°, 
  the 
  diffusivity 
  was 
  

   found 
  to 
  be 
  0*00002. 
  Experiments 
  were 
  also 
  made 
  on 
  the 
  diffusion 
  

   of 
  gold 
  into 
  solid 
  silver 
  at 
  800° 
  ; 
  a 
  temperature 
  160° 
  below 
  the 
  

   fusing 
  point 
  of 
  silver 
  and 
  50° 
  below 
  that 
  of 
  the 
  eutectic 
  alloy 
  of 
  

   these 
  metals. 
  The 
  results 
  gave 
  a 
  diffusivity 
  of 
  the 
  same 
  order 
  as 
  

   that 
  of 
  gold 
  in 
  lead 
  at 
  200°. 
  — 
  Phil. 
  Trans., 
  clxxxvii, 
  A, 
  383-415, 
  

   1896. 
  G. 
  F. 
  B. 
  

  

  2. 
  On 
  Optical 
  Rotation 
  in 
  the 
  Crystalline 
  and 
  the 
  Liquid 
  

   States. 
  — 
  The 
  specific 
  rotation 
  of 
  several 
  uniaxial 
  crystals 
  which 
  

   polarize 
  circularly, 
  has 
  been 
  examined 
  by 
  Tkaube, 
  in 
  connection 
  

   with 
  the 
  rotatory 
  power 
  possessed 
  by 
  them 
  in 
  the 
  melted 
  or 
  dis- 
  

   solved 
  states. 
  Thus 
  the 
  hexagonal-trapezohedral-tetartohedral 
  

   crystals 
  of 
  patchouli 
  camphor 
  have 
  a 
  rotation 
  for 
  the 
  D 
  line 
  of 
  

   — 
  1*325° 
  per 
  mm. 
  in 
  the 
  optic 
  axial 
  direction 
  ; 
  while 
  in 
  the 
  fused 
  

   state 
  the 
  specific 
  rotation 
  [a] 
  D 
  = 
  — 
  118° 
  and 
  in 
  alcoholic 
  solution 
  

   [ 
  a 
  ] 
  D 
  — 
  — 
  124*5. 
  Since 
  these 
  values 
  correspond 
  to 
  rotations 
  of 
  

   — 
  1*240° 
  and 
  —1*308° 
  per 
  mm. 
  respectively, 
  it 
  follows 
  that 
  this 
  

   camphor 
  has 
  practically 
  the 
  same 
  specific 
  rotation 
  in 
  the 
  crys- 
  

   talline 
  and 
  amorphous 
  states. 
  The 
  same 
  is 
  true 
  of 
  ordinary 
  

   camphor. 
  Matico 
  camphor 
  on 
  the 
  other 
  hand, 
  although 
  crystal- 
  

   lizing 
  in 
  the 
  same 
  system, 
  gives 
  a 
  rotation 
  of 
  —1*877° 
  for 
  the 
  D 
  

   line, 
  in 
  plates 
  1 
  mm 
  thick; 
  while 
  the 
  melted 
  substance 
  has 
  the 
  

   specific 
  rotation 
  [a] 
  D 
  = 
  — 
  29*17°. 
  Hence 
  the 
  rotatory 
  power 
  is 
  about 
  

   six 
  times 
  as 
  great 
  in 
  the 
  crystalline 
  as 
  in 
  the 
  melted 
  state. 
  

   Rubidium 
  tartrate 
  crystallizes 
  in 
  the 
  hexagonal-tetartohedral 
  

   system, 
  the 
  crystals 
  of 
  the 
  dextrotartrate 
  being 
  lsevorotatory 
  and 
  

   those 
  of 
  the 
  laevotartrate 
  being 
  dextrorotatory. 
  Plates 
  l 
  mm 
  thick 
  

   rotate 
  10*12° 
  to 
  10*24° 
  for 
  the 
  sodium 
  line; 
  while 
  in 
  aqueous 
  solu- 
  

   tion 
  and 
  for 
  a 
  thickness 
  of 
  l 
  mm 
  the 
  rotation 
  is 
  only 
  0*69° 
  and 
  of 
  

   the 
  opposite 
  sign 
  to 
  that 
  of 
  the 
  crystals. 
  Caesium 
  dextrotartrate 
  is 
  

   isomorphous 
  with 
  the 
  rubidium 
  salt, 
  the 
  crystals 
  giving 
  a 
  rotation 
  

   of 
  — 
  1 
  4° 
  to 
  — 
  1 
  9° 
  per 
  mm. 
  for 
  the 
  D 
  line 
  ; 
  this 
  rotation 
  being 
  oppo- 
  

   site 
  in 
  sign 
  to 
  that 
  of 
  the 
  aqueous 
  solution. 
  — 
  Per. 
  Ah. 
  Perl, 
  x, 
  

   195-205, 
  1895 
  ; 
  J. 
  Chem. 
  .Soc, 
  Ixx, 
  ii, 
  509, 
  September 
  1896. 
  

  

  G. 
  F. 
  B. 
  

  

  