﻿448 
  F. 
  A. 
  Gooch 
  and 
  T. 
  S. 
  Hart 
  — 
  Detection 
  and 
  

  

  Art. 
  XLYIII. 
  — 
  The 
  Detection 
  and 
  Determination 
  of 
  Potas- 
  

   sium 
  /Spectroscojpically 
  ; 
  by 
  F. 
  A. 
  GrOoeH 
  and 
  T. 
  S. 
  Hart. 
  

  

  [Contributions 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Yale 
  College 
  — 
  X.] 
  

  

  Bunsen 
  and 
  Kirchhoff 
  originally 
  determined 
  the 
  delicacy 
  of 
  

   the 
  spectroscopic 
  test 
  for 
  potassium 
  by 
  exploding 
  in 
  a 
  dark- 
  

   ened 
  room 
  a 
  mixture 
  of 
  potassium 
  chlorate 
  with 
  milk 
  sugar, 
  

   and 
  observing 
  the 
  amount 
  of 
  finely 
  divided 
  chloride 
  which 
  it 
  

   was 
  necessary 
  to 
  diffuse 
  through 
  the 
  given 
  space 
  in 
  order 
  to 
  bring 
  

   out 
  unmistakably 
  the 
  spectrum 
  of 
  the 
  metal. 
  These 
  investiga- 
  

   tors 
  were 
  able 
  to 
  state 
  that 
  the 
  presence 
  of 
  no 
  more 
  than 
  y^-g- 
  

   of 
  a 
  milligram 
  of 
  the 
  potassium 
  salt 
  is 
  sufficient 
  to 
  give 
  to 
  the 
  

   flame 
  the 
  characteristic 
  spectrum 
  of 
  the 
  element. 
  By 
  similar 
  

   methods, 
  the 
  delicacj' 
  of 
  the 
  tests 
  for 
  lithium 
  carbonate 
  and 
  

   sodium 
  chlorate 
  were 
  shown 
  to 
  be 
  a 
  thousand 
  times 
  and 
  three 
  

   thousand 
  times 
  as 
  delicate 
  respectively. 
  Practically, 
  the 
  de- 
  

   tection 
  of 
  lithium 
  and 
  sodium 
  spectroscopically 
  is 
  extremely 
  

   easy 
  and 
  satisfactory, 
  the 
  only 
  difficulty 
  being 
  that 
  the 
  exceed- 
  

   ing 
  delicacy 
  of 
  the 
  sodium 
  test, 
  and 
  the 
  ubiquitousness 
  of 
  

   sodium 
  salts 
  often 
  make 
  a 
  decision 
  doubtful 
  as 
  to 
  whether 
  that 
  

   element 
  is 
  present 
  essentially 
  in 
  the 
  substance 
  under 
  examina- 
  

   tion, 
  or 
  by 
  accident. 
  With 
  potassium 
  the 
  case 
  is 
  different, 
  and 
  

   experience 
  shows 
  that, 
  when 
  the 
  test 
  is 
  to 
  be 
  made 
  for 
  very 
  

   small 
  amounts 
  of 
  potassium, 
  the 
  simple 
  method 
  in 
  vogue 
  for 
  

   developing 
  the 
  luminosity 
  of 
  lithium 
  and 
  sodium 
  — 
  the 
  dipping 
  

   of 
  a 
  single 
  loop 
  of 
  platinum 
  wire 
  in 
  the 
  liquid 
  or 
  solid 
  sub- 
  

   tance, 
  and 
  the 
  placing 
  of 
  the 
  loop 
  in 
  the 
  Bnnsen 
  flame 
  — 
  fails, 
  

   because, 
  as 
  it 
  seems 
  to 
  us, 
  so 
  great 
  a 
  proportion 
  of 
  the 
  material 
  

   is 
  dispersed 
  before 
  the 
  heat 
  of 
  the 
  flame 
  effects 
  the 
  dissociation 
  

   of 
  the 
  metal 
  which 
  precedes 
  the 
  production 
  of 
  the 
  spectrum. 
  

  

  We 
  have 
  endeavored 
  to 
  improve 
  the 
  conditions 
  of 
  exposure 
  

   of 
  the 
  test-substance 
  by 
  making 
  use 
  of 
  more 
  powerful 
  flames 
  

   and 
  by 
  substituting 
  for 
  the 
  single 
  loop 
  the 
  hollow 
  coils 
  of 
  

   platinum 
  wire 
  first 
  recommended, 
  so 
  far 
  as 
  has 
  come 
  to 
  our 
  

   knowledge, 
  by 
  Truchot* 
  in 
  the 
  description 
  of 
  a 
  method 
  for 
  

   the 
  quantitative 
  determination 
  of 
  lithium. 
  Such 
  coils 
  are 
  

   easily 
  made 
  by 
  winding 
  the 
  wire 
  somewhat 
  obliquely 
  about 
  a 
  

   rod 
  of 
  suitable 
  size, 
  pressing 
  the 
  coils 
  close 
  together, 
  and 
  

   gathering 
  the 
  free 
  ends 
  into 
  a 
  twisted 
  handle. 
  The 
  size 
  of 
  

   the 
  coils 
  is 
  adjustable 
  without 
  difficulty, 
  so 
  that 
  each 
  coil 
  may 
  

   be 
  made 
  to 
  hold 
  almost 
  exactly 
  any 
  appropriate 
  amount, 
  and 
  

   to 
  take 
  up 
  this 
  amount 
  with 
  very 
  little 
  variation 
  in 
  successive 
  

   fillings, 
  provided 
  only 
  that 
  the 
  precaution 
  be 
  taken 
  in 
  the 
  pro 
  

   cess 
  of 
  filling 
  to 
  plunge 
  the 
  coil 
  while 
  hot 
  into 
  the 
  liquid, 
  and 
  

   to 
  keep 
  its 
  axis 
  inclined 
  obliquely 
  to 
  the 
  surface 
  of 
  the 
  liquid 
  

  

  * 
  Compt. 
  Rend., 
  lxxviii, 
  1022. 
  

  

  