﻿450 
  

  

  F. 
  A. 
  Gooch 
  and 
  T. 
  S. 
  Hart 
  — 
  Detection 
  and 
  

  

  a 
  dark 
  handkerchief, 
  and 
  to 
  cover 
  the 
  eye 
  not 
  in 
  use. 
  We 
  

   have 
  found 
  it 
  desirable 
  to 
  use 
  the 
  scale 
  of 
  the 
  instrument, 
  

   illuminated 
  to 
  the 
  lowest 
  degree 
  of 
  visibility, 
  to 
  aid 
  the 
  eye 
  in 
  

   placing 
  barely 
  visible 
  lines. 
  

  

  Upon 
  experimenting 
  with 
  the 
  apparatus 
  described, 
  it 
  was 
  

   found 
  that 
  the 
  largest 
  coil 
  used 
  was 
  best 
  adapted 
  to 
  our 
  pur- 
  

   pose, 
  and, 
  accordingly, 
  in 
  all 
  the 
  experiments 
  made 
  subse- 
  

   quently, 
  and 
  recorded 
  in 
  the 
  following 
  account, 
  coils 
  holding 
  

   ■fo 
  of 
  a 
  gram 
  of 
  water, 
  measuring 
  2 
  mm. 
  in 
  diameter 
  by 
  1 
  cm. 
  in 
  

   length, 
  made 
  of 
  No. 
  28 
  wire 
  (0*32 
  mm. 
  in 
  diameter), 
  and 
  wound 
  

   in 
  about 
  thirty 
  turns, 
  were 
  the 
  ones 
  employed. 
  With 
  these 
  

   coils 
  and 
  the 
  flame 
  adjusted 
  to 
  a 
  height 
  of 
  20 
  cm. 
  we 
  have 
  been 
  

   able 
  to 
  recognize 
  the 
  presence 
  of 
  potassium, 
  taken 
  in 
  the 
  form 
  

   of 
  the 
  chloride, 
  in 
  a 
  coil-full 
  of 
  liquid 
  containing 
  0'00066 
  grm. 
  

   of 
  the 
  metal 
  in 
  10 
  cm. 
  3 
  , 
  when 
  the 
  slit 
  had 
  a 
  width 
  of 
  0*18 
  ram. 
  ; 
  

   and 
  containing 
  0*0005 
  grm. 
  in 
  the 
  same 
  volume 
  of 
  solution, 
  

   when 
  the 
  slit 
  was 
  set 
  0*23 
  mm. 
  wide. 
  That 
  is 
  to 
  say, 
  t 
  ^q 
  mg. 
  of 
  

   potassium 
  to 
  the 
  coil-full 
  produces 
  a 
  line 
  distinctly 
  visible 
  with 
  

   a 
  slit 
  of 
  0*18 
  mm., 
  and 
  T 
  oVo 
  m 
  S 
  with 
  a 
  slit 
  of 
  0*23 
  mm., 
  and 
  

   it 
  is 
  evident 
  that 
  this 
  practical 
  method 
  of 
  producing 
  the 
  

   spectrum 
  of 
  potassium 
  gives 
  results 
  of 
  a 
  delicacy 
  approaching 
  

   that 
  indicated 
  in 
  the 
  experiments 
  of 
  Bunsen 
  and 
  Kirchhoff. 
  

  

  These 
  determinations 
  were 
  made 
  with 
  pure 
  potassium 
  chlo- 
  

   ride 
  carefully 
  prepared 
  from 
  the 
  chlorate, 
  but 
  in 
  practical 
  

   analysis 
  it 
  almost 
  always 
  happens 
  that 
  sodium 
  is 
  also 
  present. 
  

   Experiments 
  were 
  therefore 
  made 
  to 
  determine 
  the 
  influence 
  of 
  

   varying 
  amounts 
  of 
  the 
  latter 
  upon 
  the 
  visibility 
  of 
  the 
  potas- 
  

   sium 
  line. 
  The 
  dilution 
  of 
  the 
  potassium 
  chloride 
  was 
  ad- 
  

   justed 
  nearly 
  to 
  the 
  last 
  limit 
  of 
  visibility, 
  so 
  that 
  a 
  coil-full 
  

   of 
  the 
  liquid 
  should 
  contain 
  y^- 
  rag., 
  or 
  TT 
  \ 
  ? 
  mg. 
  of 
  the 
  element, 
  

   according 
  as 
  the 
  slit 
  was 
  0*18 
  mm. 
  or 
  0*23 
  mm. 
  wide; 
  to 
  this 
  

   solution 
  were 
  added 
  weighed 
  amounts 
  of 
  pure 
  sodium 
  chloride 
  

   twice 
  reprecipitated 
  and 
  washed 
  by 
  hydrochloric 
  acid 
  ; 
  and 
  the 
  

   spectroscopic 
  tests 
  were 
  carried 
  out 
  as 
  before, 
  the 
  sodium 
  line 
  

   being 
  kept 
  within 
  the 
  field 
  of 
  view 
  with 
  the 
  potassium 
  line. 
  

  

  Weight 
  of 
  K 
  

  

  Weight 
  of 
  Na 
  

  

  Ratio 
  

  

  Width 
  

  

  Number 
  

  

  Characteristic 
  

  

  in 
  a 
  

  

  in 
  a 
  

  

  

  of 
  

  

  of 
  

  

  of 
  

  

  coil-full. 
  

  

  coil-full. 
  

  

  Na:K. 
  

  

  slit. 
  

  

  trials. 
  

  

  line. 
  

  

  0-0010 
  mg. 
  

  

  0-0000 
  mg. 
  

  

  0: 
  1 
  

  

  23 
  mm. 
  

  

  3 
  

  

  visible 
  

  

  0-0010 
  " 
  

  

  0-0020 
  '• 
  

  

  2 
  :1 
  

  

  0-23 
  " 
  

  

  3 
  

  

  visible 
  

  

  o-ooio 
  " 
  

  

  o-oioo 
  " 
  

  

  10:1 
  

  

  0-23 
  " 
  

  

  3 
  

  

  visible 
  

  

  o-ooio 
  " 
  

  

  0-0200 
  " 
  

  

  20: 
  1 
  

  

  023 
  " 
  

  

  3 
  

  

  visible 
  

  

  o-ooio 
  " 
  

  

  0-0400 
  " 
  

  

  40: 
  1 
  

  

  0-23 
  '• 
  

  

  3 
  

  

  visible 
  

  

  0-0010 
  " 
  

  

  0-0500 
  " 
  

  

  50: 
  1 
  

  

  023 
  " 
  

  

  4 
  

  

  very 
  faint 
  or 
  none 
  

  

  o-ooio 
  " 
  

  

  1000 
  " 
  

  

  100: 
  1 
  

  

  023 
  " 
  

  

  3 
  

  

  none 
  

  

  o-ooio 
  " 
  

  

  0-2000 
  " 
  

  

  200: 
  1 
  

  

  23 
  " 
  

  

  3 
  

  

  none 
  

  

  0-0014 
  " 
  

  

  o-oooo 
  " 
  

  

  0: 
  1 
  

  

  018 
  " 
  

  

  3 
  

  

  visible 
  

  

  0-0014 
  " 
  

  

  0-0560 
  " 
  

  

  40: 
  1 
  

  

  18 
  " 
  

  

  3 
  

  

  visible 
  

  

  0-0014 
  " 
  

  

  0-0700 
  " 
  

  

  50: 
  1 
  

  

  0-18 
  " 
  

  

  3 
  

  

  visible 
  

  

  S 
  0014 
  " 
  

   { 
  0-0014 
  " 
  

  

  01400 
  " 
  

  

  100 
  : 
  1 
  

  

  0-18 
  " 
  

  

  2 
  

  

  visible 
  

  

  0-1400 
  " 
  

  

  100: 
  1 
  

  

  0-18 
  " 
  

  

  2 
  

  

  none 
  

  

  