﻿TO 
  Scientific 
  Intelligence. 
  

  

  acid 
  solution. 
  As 
  the 
  nitric 
  oxide 
  produced 
  immediately 
  reacts 
  

   with 
  oxygen, 
  thus 
  forming 
  more 
  nitrous 
  acid, 
  it 
  is 
  essential 
  that 
  

   the 
  first 
  part 
  of 
  the 
  process 
  should 
  be 
  performed 
  in 
  absence 
  of 
  

   air. 
  This 
  is 
  accomplished 
  by 
  bubbling 
  carbon 
  dioxide 
  through 
  

   a 
  first 
  flask 
  containing 
  2 
  g. 
  of 
  KI 
  in 
  50 
  cc. 
  of 
  water, 
  then 
  through 
  

   a 
  second 
  flask 
  containing 
  10 
  cc. 
  of 
  normal 
  H 
  2 
  S0 
  4 
  and 
  finally 
  

   through 
  a 
  third 
  connected 
  flask 
  containing 
  the 
  nitrite 
  to 
  be 
  deter- 
  

   mined. 
  After 
  all 
  the 
  air 
  has 
  been 
  displaced, 
  the 
  tube 
  of 
  the 
  

   first 
  flask 
  is 
  lowered 
  and 
  the 
  solution 
  in 
  it 
  is 
  driven 
  over 
  into 
  the 
  

   second 
  flask 
  by 
  the 
  current 
  of 
  carbon 
  dioxide 
  ; 
  then 
  in 
  the 
  same 
  

   way 
  the 
  liquid 
  in 
  the 
  second 
  flask 
  is 
  passed 
  into 
  the 
  third 
  one 
  r 
  

   then 
  without 
  the 
  introduction 
  of 
  air, 
  10 
  cc. 
  of 
  20 
  per 
  cent 
  

   ammonium 
  carbonate 
  solution 
  are 
  put 
  into 
  the 
  last 
  flask 
  and 
  the 
  

   titration 
  is 
  made 
  with 
  N/70 
  arsenious 
  acid. 
  The 
  author 
  shows 
  

   that 
  the 
  results 
  are 
  very 
  accurate, 
  and 
  evidently 
  the 
  method 
  will 
  

   be 
  a 
  useful 
  one. 
  — 
  Comptes 
  Rendus, 
  167, 
  366. 
  h. 
  l. 
  w. 
  

  

  5. 
  The 
  Volumetric 
  Estimation 
  of 
  Zinc 
  by 
  Acidimetric 
  Titra- 
  

   tion. 
  — 
  To 
  apply 
  this 
  method 
  of 
  R. 
  Howden 
  the 
  zinc 
  should 
  be 
  

   present 
  as 
  chloride 
  and 
  the 
  solution 
  should 
  be 
  free 
  from 
  ammo- 
  

   nium 
  salts, 
  as 
  well 
  as 
  from 
  the 
  salts 
  of 
  other 
  heavy 
  metals. 
  A 
  

   sulphuric 
  acid 
  solution 
  does 
  not 
  give 
  good 
  results. 
  The 
  free 
  

   acid 
  is 
  driven 
  off 
  by 
  evaporation 
  to 
  small 
  volume, 
  then 
  the 
  liquid 
  

   is 
  diluted 
  to 
  20 
  cc, 
  a 
  drop 
  of 
  methyl 
  orange 
  solution 
  is 
  added 
  

   and 
  the 
  liquid 
  is 
  carefully 
  neutralized 
  with 
  decinormal 
  caustic 
  

   soda. 
  As 
  zinc 
  chloride 
  is 
  neutral 
  to 
  methyl 
  orange, 
  this 
  is 
  easily 
  

   done. 
  A 
  few 
  drops 
  of 
  phenolphthalein 
  solution 
  are 
  added 
  and 
  

   the 
  acid 
  in 
  combination 
  with 
  the 
  zinc 
  is 
  titrated 
  with 
  the 
  caustic 
  

   soda 
  solution. 
  Towards 
  the 
  end 
  of 
  the 
  titration 
  the 
  liquid 
  should 
  

   be 
  heated 
  to 
  boiling, 
  and 
  the 
  end 
  of 
  the 
  process 
  is 
  indicated 
  by 
  

   the 
  persistence 
  of 
  a 
  pink 
  color 
  after 
  boiling. 
  The 
  alkali 
  may 
  be 
  

   standardized 
  by 
  means 
  of 
  pure 
  zinc. 
  The 
  precipitate 
  of 
  zinc 
  

   hydroxide 
  does 
  not 
  interfere, 
  the 
  end-point 
  is 
  perfectly 
  sharp, 
  

   and 
  experiments 
  have 
  shown 
  that 
  perfectly 
  concordant 
  results 
  

   can 
  be 
  obtained. 
  — 
  Chem. 
  News, 
  117, 
  322. 
  h. 
  l. 
  w. 
  

  

  6. 
  Diffusion 
  of 
  Light 
  by 
  Gases. 
  — 
  In 
  a 
  recent 
  paper 
  by 
  Ch. 
  

   Fabry 
  it 
  is 
  shown 
  that 
  a 
  number 
  of 
  important 
  optical 
  phenom- 
  

   ena, 
  occurring 
  in 
  nature, 
  may 
  be 
  explained 
  on 
  the 
  hypothesis 
  

   that 
  they 
  are 
  due 
  primarily 
  to 
  the 
  diffusion 
  or 
  scattering 
  of 
  

   light 
  by 
  the 
  molecules 
  of 
  gases 
  in 
  a 
  highly 
  attenuated 
  state. 
  In 
  

   order 
  to 
  distinguish 
  between 
  the 
  scattering 
  of 
  light 
  by 
  particles 
  

   of 
  appreciable 
  size 
  on 
  the 
  one 
  hand, 
  and 
  by 
  gaseous 
  molecules 
  

   on 
  the 
  other, 
  advantage 
  is 
  taken 
  of 
  the 
  following 
  differentiat- 
  

   ing 
  characteristics, 
  (a) 
  Light 
  diffused 
  by 
  a 
  gas 
  is 
  polarized 
  

   while 
  that 
  scattered 
  by 
  particles 
  which 
  are 
  large 
  in 
  comparison 
  

   witli 
  the 
  wave-length 
  is 
  not 
  polarized, 
  (b) 
  The 
  distribution 
  of 
  

   intensity 
  in 
  the 
  spectra 
  of 
  the 
  diffused 
  light 
  will 
  not 
  be 
  the 
  same 
  

   tor 
  systems 
  of 
  large 
  and 
  of 
  small 
  particles 
  when 
  the 
  spectrum 
  

   of 
  11k; 
  incident 
  light 
  embraces 
  a 
  wide 
  range 
  of 
  wave-lengths 
  

  

  