﻿Application 
  to 
  the 
  Determination 
  of 
  Potassium. 
  447 
  

  

  chloric 
  acid 
  appear. 
  Further 
  loss 
  of 
  perchloric 
  acid 
  is 
  to 
  be 
  

   compensated 
  for 
  by 
  addition 
  of 
  more. 
  The 
  cold 
  mass 
  is 
  then 
  

   well 
  stirred 
  with 
  about 
  20 
  cm 
  3 
  of 
  wash 
  alcohol 
  — 
  97 
  per 
  cent 
  

   alcohol 
  containing 
  0*2 
  per 
  cent 
  by 
  weight 
  of 
  pure 
  perchloric 
  

   acid 
  — 
  with 
  precautions 
  against 
  reducing 
  the 
  potassium 
  per- 
  

   chlorate 
  crystals 
  to 
  too 
  fine 
  a 
  powder. 
  After 
  settling, 
  the 
  

   alcohol 
  is 
  decanted 
  on 
  the 
  asbestos 
  filter 
  and 
  the 
  residue 
  simi- 
  

   larly 
  treated 
  with 
  about 
  the 
  same 
  amount 
  of 
  wash 
  alcohol, 
  set- 
  

   tling 
  and 
  again 
  decanting. 
  The 
  residual 
  salt 
  is 
  then 
  deprived 
  

   of 
  alcohol 
  by 
  gently 
  heating, 
  dissolved 
  in 
  10 
  cm 
  3 
  of 
  hot 
  water 
  

   and 
  a 
  little 
  perchloric 
  acid, 
  when 
  it 
  is 
  evaporated 
  once 
  more 
  

   with 
  stirring, 
  until 
  fumes 
  of 
  perchloric 
  acid 
  rise. 
  It 
  is 
  then 
  

   washed 
  with 
  1 
  cm 
  3 
  of 
  wash 
  alcohol, 
  transferred 
  to 
  the 
  asbestos, 
  

   preferably 
  by 
  a 
  policeman 
  to 
  avoid 
  excessive 
  use 
  of 
  alcohol, 
  

   and 
  covered 
  finally 
  with 
  pure 
  alcohol 
  : 
  the 
  whole 
  wash 
  process 
  

   requiring 
  about 
  50 
  to 
  70 
  cm 
  3 
  of 
  alcohol. 
  It 
  is 
  then 
  dried 
  at 
  

   about 
  130° 
  C. 
  and 
  weighed. 
  

  

  The 
  substitution 
  of 
  a 
  G-ooch 
  crucible 
  for 
  the 
  truncated 
  

   pipette 
  employed 
  by 
  Caspari 
  will 
  be 
  found 
  advantageous 
  ; 
  and 
  

   asbestos 
  capable 
  of 
  forming 
  a 
  close, 
  compact 
  felt 
  should 
  be 
  

   selected, 
  inasmuch 
  as 
  the 
  perchlorate 
  is 
  in 
  part 
  unavoidably 
  

   reduced, 
  during 
  the 
  necessary 
  stirring, 
  to 
  so 
  fine 
  a 
  condition 
  

   that 
  it 
  tends 
  to 
  run 
  through 
  the 
  filter 
  when 
  under 
  pressure. 
  A 
  

   special 
  felt 
  of 
  an 
  excellent 
  quality 
  of 
  asbestos 
  was 
  prepared 
  

   for 
  the 
  determinations 
  given 
  below 
  and 
  seemed 
  to 
  hold 
  the 
  

   finer 
  particles 
  of 
  the 
  perchlorate 
  very 
  satisfactorily. 
  

  

  A 
  number 
  of 
  determinations 
  made 
  of 
  potassium 
  unmixed 
  

   with 
  other 
  bases 
  or 
  non-volatile 
  acids 
  are 
  recorded 
  in 
  the 
  fol- 
  

  

  lowing 
  

  

  table 
  : 
  

  

  

  

  

  

  KCl 
  

  

  Volume 
  of 
  

  

  KC10 
  4 
  

  

  Error 
  on 
  

  

  Error 
  on 
  

  

  Error 
  on 
  

  

  taken. 
  

  

  filtrate. 
  

  

  found. 
  

  

  KCIU4. 
  

  

  KCl. 
  

  

  K 
  2 
  0. 
  

  

  grms. 
  

  

  cm 
  3 
  . 
  

  

  grms. 
  

  

  grms. 
  

  

  grms. 
  

  

  grms. 
  

  

  o-iooo 
  

  

  54 
  

  

  0-1851 
  

  

  0-0008 
  — 
  

  

  0-0004 
  — 
  

  

  0-0003- 
  

  

  o-iooo 
  

  

  58 
  

  

  0-1854 
  

  

  o-ooo„ 
  — 
  

  

  0*0002 
  — 
  

  

  0*0002- 
  

  

  o-iooo 
  

  

  51 
  

  

  0-1859 
  

  

  o-oooo 
  

  

  o-oooo 
  

  

  o-oooo 
  

  

  o-iooo 
  

  

  50 
  

  

  0-1854 
  

  

  0-0005 
  — 
  

  

  0-0002 
  — 
  

  

  0-0002- 
  

  

  o-iooo 
  

  

  48 
  

  

  0-1859 
  

  

  o-oooo 
  

  

  o-oooo 
  

  

  o-oooo 
  

  

  o-iooo 
  

  

  52 
  

  

  0-1854 
  

  

  0-0005 
  — 
  

  

  0-0002 
  — 
  

  

  0-0002- 
  

  

  Considerable 
  difficulty, 
  however, 
  was 
  experienced 
  in 
  obtain- 
  

   ing 
  equally 
  satisfactory 
  determinations 
  of 
  potassium 
  associated 
  

   with 
  sulphuric 
  and 
  phosphoric 
  acids. 
  As 
  Caspari 
  has 
  pointed 
  

   out, 
  the 
  sulphuric 
  acid 
  must 
  be 
  removed 
  by 
  precipitation 
  as 
  

   barium 
  sulphate 
  before 
  the 
  treatment 
  with 
  perchloric 
  acid 
  is 
  

   attempted, 
  and 
  unless 
  the 
  precipitation 
  is 
  made 
  in 
  a 
  strongly 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Third 
  Series, 
  Vol. 
  XL1X, 
  No. 
  294. 
  — 
  June, 
  1895. 
  

   30 
  

  

  