﻿Application 
  to 
  the 
  Determination 
  of 
  Potassium. 
  445 
  

  

  inconsiderable 
  amount 
  of 
  perchlorate, 
  when 
  tested 
  by 
  first 
  heat- 
  

   ing 
  to 
  expel 
  the 
  free 
  acid 
  and 
  then 
  treating 
  the 
  dry 
  and 
  pow- 
  

   dered 
  residue 
  with 
  97 
  per 
  cent 
  alcohol, 
  which 
  dissolves 
  the 
  

   perchlorate 
  of 
  sodium 
  but 
  has 
  little 
  soluble 
  effect 
  on 
  the 
  

   chloride. 
  

  

  The 
  filtrate, 
  containing 
  the 
  perchloric 
  acid 
  with 
  the 
  excess 
  

   of 
  hydrochloric 
  acid 
  and 
  the 
  small 
  per 
  cent 
  of 
  sodium 
  chloride 
  

   which 
  is 
  soluble 
  in 
  the 
  latter, 
  is 
  then 
  evaporated 
  over 
  the 
  steam 
  

   bath 
  till 
  all 
  hydrochloric 
  acid 
  is 
  expelled 
  and 
  the 
  heavy 
  white 
  

   fames 
  of 
  perchloric 
  acid 
  appear, 
  when 
  it 
  is 
  ready 
  for 
  use 
  in 
  

   potassium 
  determinations. 
  Evidently 
  the 
  acid 
  will 
  not 
  be 
  

   chemically 
  pare 
  because 
  the 
  sodium 
  chloride 
  is 
  not 
  absolutely 
  

   insoluble 
  in 
  hydrochloric 
  acid 
  ; 
  but 
  a 
  portion 
  tested 
  with 
  silver 
  

   nitrate 
  will 
  prove 
  that 
  the 
  sodium, 
  together 
  with 
  any 
  other 
  

   bases 
  which 
  may 
  have 
  gone 
  through 
  the 
  filter, 
  has 
  been 
  com- 
  

   pletely 
  converted 
  into 
  perchlorate, 
  and 
  unless 
  the 
  original 
  

   chlorate 
  contained 
  some 
  potassium 
  or 
  on 
  evaporation 
  the 
  acid 
  was 
  

   exposed 
  to 
  the 
  fumes 
  of 
  ammonia, 
  the 
  residue 
  of 
  the 
  evapora- 
  

   tion 
  of 
  a 
  portion 
  is 
  easily 
  and 
  completely 
  soluble 
  in 
  97 
  per 
  cent 
  

   alcohol 
  and 
  its 
  presence 
  is 
  therefore 
  unobjectionable. 
  One 
  

   cubic 
  centimeter 
  of 
  the 
  acid 
  thus 
  obtained 
  gave 
  on 
  evaporation 
  

   a 
  residue 
  of 
  only 
  0*036 
  grm., 
  which 
  was 
  completely 
  soluble 
  in 
  

   97 
  per 
  cent 
  alcohol. 
  

  

  Caspari's 
  acid 
  under 
  similar 
  treatment 
  gave 
  a 
  residue 
  in 
  one 
  

   case 
  of 
  0*024 
  gnus, 
  and 
  in 
  another 
  0*047 
  grms. 
  If, 
  however, 
  a 
  

   portion 
  of 
  pure 
  acid 
  be 
  required, 
  it 
  may 
  be 
  obtained 
  by 
  distill- 
  

   ing 
  this 
  product 
  under 
  diminished 
  pressure 
  and, 
  as 
  Caspari 
  

   has 
  shown, 
  without 
  great 
  loss 
  providing 
  the 
  heat 
  is 
  regulated 
  

   according 
  to 
  the 
  fumes 
  in 
  the 
  distilling 
  flask. 
  

  

  Some 
  modification 
  of 
  the 
  above 
  treatment 
  will 
  be 
  found 
  

   necessary 
  in 
  case 
  the 
  sodium 
  chlorate 
  contains 
  any 
  potassium 
  

   as 
  an 
  impurity, 
  or 
  if 
  the 
  latter 
  has 
  been 
  introduced 
  from 
  the 
  

   vessel 
  in 
  which 
  the 
  fusion 
  was 
  made. 
  Under 
  these 
  circum- 
  

   stances 
  the 
  hydrochloric 
  acid 
  would 
  not 
  suffice 
  for 
  the 
  removal 
  

   of 
  potassium, 
  since 
  a 
  trace 
  might 
  also 
  go 
  over 
  with 
  the 
  sodium 
  

   and 
  thus 
  on 
  evaporation 
  a 
  residue 
  insoluble 
  in 
  97 
  per 
  cent 
  

   alcohol 
  be 
  obtained. 
  To 
  avoid 
  this 
  difficulty, 
  the 
  mixture 
  of 
  

   sodium 
  perchlorate 
  and 
  chloride, 
  after 
  being 
  treated 
  with 
  hydro- 
  

   chloric 
  acid 
  for 
  the 
  reduction 
  of 
  the 
  residual 
  chlorate, 
  being 
  

   reduced 
  to 
  a 
  fine 
  powder, 
  was 
  well 
  digested 
  with 
  97 
  per 
  cent 
  

   alcohol, 
  which 
  dissolves 
  the 
  sodium 
  perchlorate 
  but 
  leaves 
  the 
  

   chloride 
  as 
  well 
  as 
  any 
  potassium 
  salt 
  insoluble. 
  By 
  giving 
  the 
  

   alcohol 
  time 
  to 
  become 
  saturated, 
  which 
  was 
  facilitated 
  by 
  stir- 
  

   ring, 
  it 
  was 
  found 
  on 
  filtering 
  and 
  evaporating 
  that 
  an 
  average 
  

   of 
  about 
  0*2 
  grm. 
  of 
  sodium 
  perchlorate 
  was 
  obtained 
  for 
  every 
  

   cubic 
  centimeter 
  of 
  alcohol 
  and 
  that 
  the 
  product 
  thus 
  obtained 
  

   was 
  comparatively 
  free 
  of 
  chlorides, 
  until 
  the 
  perchlorate 
  was 
  

  

  