﻿974 
  Mr. 
  E. 
  W. 
  Lawson 
  on 
  the 
  Spectra 
  of 
  

  

  any 
  here 
  possible, 
  and 
  particularly 
  by 
  use 
  of 
  internal 
  elec- 
  

   trodes 
  in 
  silica 
  tubes, 
  the 
  condenser 
  line-spectrum 
  of 
  various 
  

   gases 
  may 
  be 
  produced. 
  It 
  is 
  a 
  noteworthy 
  fact 
  that 
  with 
  

   the 
  external 
  electrode 
  tubes, 
  the 
  elementary 
  line 
  spectrum 
  of 
  

   a 
  gas 
  could 
  not 
  be 
  obtained, 
  using 
  the 
  induction-coil 
  discharge 
  

   from 
  condenser 
  and 
  spark-gap. 
  This 
  was 
  most 
  probably 
  due 
  

   to 
  the 
  high 
  resistance 
  of 
  the 
  discharge 
  tube, 
  this 
  preventing 
  

   the 
  ready 
  charge 
  and 
  discharge 
  of 
  the 
  condenser. 
  The 
  

   spectroscopic 
  observations 
  made 
  on 
  the 
  different 
  gases 
  will 
  

   now 
  be 
  treated 
  under 
  their 
  respective 
  heads. 
  

  

  Nitrogen. 
  

  

  The 
  methods 
  usually 
  used 
  for 
  the 
  production 
  of 
  spectro- 
  

   scopic 
  nitrogen 
  are 
  somewhat 
  unsatisfactory, 
  owing 
  to 
  the 
  

   fact 
  that 
  the 
  evolution 
  of 
  gas 
  takes 
  place 
  spasmodically 
  and 
  

   the 
  action 
  is 
  somewhat 
  violent. 
  The 
  following- 
  method* 
  

   was 
  adopted 
  with 
  great 
  success. 
  Briefly, 
  it 
  consists 
  in 
  pre- 
  

   paring 
  chlorine 
  from 
  a 
  mixture 
  of 
  equal 
  parts 
  by 
  weight 
  of 
  

   sodium 
  chloride 
  and 
  manganese 
  dioxide 
  by 
  adding 
  a 
  solution 
  

   of 
  eleven 
  parts 
  by 
  volume 
  of 
  sulphuric 
  ncid 
  in 
  nine 
  parts 
  of 
  

   water. 
  The 
  chlorine 
  is 
  then 
  passed 
  through 
  strong 
  ammonia 
  

   solution, 
  and 
  nitrogen 
  is 
  liberated, 
  together 
  with 
  hydrochloric 
  

   acid 
  and 
  ammonium 
  chloride. 
  These 
  last 
  are 
  removed 
  by 
  

   repeated 
  washing 
  of 
  the 
  nitrogen 
  in 
  air-free 
  water, 
  by 
  passing 
  

   over 
  solid 
  caustic 
  potash, 
  and 
  after 
  bubbling 
  through 
  con- 
  

   centrated 
  sulphuric 
  acid, 
  the 
  remaining 
  nitrogen 
  is 
  collected 
  

   over 
  mercury. 
  It 
  can 
  then 
  be 
  passed 
  into 
  the 
  adjacent 
  

   drying 
  tube, 
  and 
  from 
  thence 
  into 
  the 
  discharge 
  tube. 
  The 
  

   nitrogen 
  thus 
  prepared 
  has 
  been 
  subject 
  to 
  gas 
  analysis 
  and 
  

   found 
  to 
  be 
  quite 
  pure. 
  Moreover, 
  a 
  steady 
  stream 
  of 
  

   nitrogen 
  could 
  be 
  obtained, 
  and 
  in 
  the 
  present 
  case 
  this 
  was 
  

   allowed 
  to 
  flush 
  the 
  collecting-tube 
  for 
  six 
  hours 
  before 
  a 
  

   sample 
  was 
  collected. 
  By 
  this 
  means 
  the 
  purity 
  of 
  the 
  final 
  

   sample 
  is 
  ensured. 
  

  

  The 
  independence 
  of 
  the 
  spectrum 
  of 
  nitrogen 
  — 
  as 
  excited 
  

   by 
  use 
  of 
  the 
  Poulsen 
  arc 
  — 
  on 
  frequency 
  is 
  clearly 
  shown 
  

   on 
  the 
  first 
  photograph 
  appended 
  (PL 
  XXI.), 
  which 
  corre- 
  

   sponds 
  to 
  a 
  pressure 
  of 
  1'5 
  mm., 
  with 
  current 
  and 
  frequency 
  

   as 
  indicated 
  on 
  the 
  photograph. 
  The 
  external 
  electrode 
  silica 
  

   tube 
  was 
  here 
  used. 
  

  

  Variation 
  of 
  current 
  density 
  and 
  voltage 
  in 
  the 
  discharge 
  

   tube 
  with 
  internal 
  or 
  external 
  electrodes 
  did 
  not 
  produce 
  

   any 
  change 
  in 
  the 
  relative 
  intensity 
  of 
  the 
  nitrogen 
  bands 
  in 
  

  

  * 
  Suggested 
  to 
  the 
  writer 
  by 
  Dr. 
  Paterson, 
  Armstrong 
  College, 
  

   Newcastle. 
  

  

  