﻿528 
  

  

  Mr. 
  F. 
  Soddy 
  on 
  

  

  the 
  Production 
  of 
  

  

  Number 
  

   of 
  Test. 
  

  

  Helium 
  in 
  

   tenth-grms. 
  

  

  Quality 
  of 
  

   Experiment. 
  

  

  Observation 
  

   ofD 
  3 
  . 
  

  

  Remarks. 
  

  

  Lead-glass 
  spectrum-tubes, 
  0*04 
  c.c. 
  volume. 
  

  

  CI 
  

  

  09 
  

   1-8 
  

  

  1-64 
  

   33 
  

   168 
  

   Blank 
  test. 
  

  

  Perfect. 
  

  

  Good. 
  

  

  Perfect. 
  

  

  Good. 
  

  

  Good. 
  

  

  Perfect. 
  

  

  Not 
  seen. 
  

   Seen 
  clearly. 
  

  

  Ditto. 
  

  

  Ditto. 
  

  

  D 
  a 
  the 
  

  

  brightest 
  line. 
  

  

  No 
  line 
  like 
  

  

  D 
  3 
  . 
  

  

  Certainly 
  below 
  limit, 
  

   Fairly 
  bright 
  argon 
  also. 
  

  

  D 
  3 
  less 
  bright 
  than 
  argon 
  

  

  lines. 
  

   D 
  3 
  not 
  much 
  brighter 
  

  

  than 
  in 
  last 
  test. 
  

   Exceptionally 
  strong 
  

  

  argon 
  spectrum. 
  

   *02o 
  c.c. 
  of 
  air 
  added. 
  

  

  CII 
  

  

  CXI 
  

  

  C 
  XII 
  .... 
  

   CXIII... 
  

   CXIV 
  ... 
  

  

  Soda-glass 
  spectrum-tubes, 
  0*04 
  c.c. 
  volume. 
  

  

  C 
  III 
  

  

  CIV 
  

  

  CV 
  

  

  C 
  VI 
  

  

  1-4 
  

   1-8 
  

   22 
  

   36 
  

  

  Good. 
  

   Good. 
  

   Fair. 
  

   Good. 
  

  

  Not 
  seen. 
  

  

  Seen 
  for 
  a 
  

   moment 
  only. 
  

   Seen 
  for 
  a 
  

  

  short 
  time. 
  

   Seen 
  well. 
  

  

  Sodium 
  lines 
  strong. 
  

   Sodium 
  lines 
  interfere. 
  

  

  Not 
  enough 
  to 
  be 
  

   depended 
  upon. 
  

  

  But 
  for 
  some 
  time 
  D 
  3 
  

   was 
  hardly 
  visible. 
  

  

  Soda-glass 
  spectrum-tubes, 
  0*3 
  c.c. 
  volume. 
  

  

  CVII 
  ... 
  

   CVIII... 
  

  

  CIX 
  

  

  C 
  X 
  

  

  36 
  

   4-1 
  

  

  8-2 
  

   16-4 
  

  

  Bad. 
  

   Fair. 
  

   Good. 
  

   Good. 
  

  

  Not 
  seen. 
  

   Not 
  seen. 
  

   Not 
  seen. 
  

   Seen 
  clearly. 
  

  

  Strong 
  hydrocarbon 
  

   spectrum 
  at 
  first. 
  

   Certainly 
  below 
  limit. 
  

  

  Ditto. 
  

  

  About 
  the 
  limit. 
  

  

  this 
  line 
  is 
  still 
  excessively 
  faint. 
  The 
  characteristic 
  colour 
  

   of 
  the 
  helium 
  glow 
  appeared 
  with 
  about 
  6 
  times 
  ; 
  and 
  the 
  

   tube 
  began 
  to 
  conduct 
  easily, 
  the 
  spark-gap 
  falling 
  below 
  2 
  cms. 
  

   with 
  about 
  150 
  times 
  the 
  minimum 
  quantity. 
  In 
  these 
  experi- 
  

   ments 
  arrangements 
  were 
  made 
  to 
  admit 
  small 
  quantities 
  of 
  

   water-vapour 
  when 
  the 
  tube 
  became 
  non-conducting. 
  Then, 
  

   by 
  making 
  the 
  furnace 
  very 
  hot, 
  the 
  hydrogen 
  of 
  the 
  calcium 
  

   hydride 
  formed 
  exerts 
  an 
  appreciable 
  tension 
  of 
  dissociation 
  

   so 
  that 
  the 
  discharge 
  will 
  pass. 
  The 
  degree 
  of 
  vacuum 
  and 
  

   the 
  amount 
  of 
  hydrogen 
  present 
  did 
  not, 
  within 
  the 
  limits 
  

   tried, 
  have 
  any 
  appreciable 
  effect 
  on 
  the 
  various 
  quantities 
  

  

  