﻿DiaZkyljphosplioric 
  and 
  Benzenedisulplionic 
  Acids. 
  61 
  

  

  expressed 
  by 
  the 
  following 
  equations 
  : 
  C 
  6 
  H 
  4 
  N 
  2 
  S0 
  3 
  + 
  KS.CS.- 
  

   OEt 
  = 
  C.HJSO.K.SCSOEt 
  4- 
  ]ST 
  a 
  , 
  and 
  C 
  6 
  H 
  4 
  S0 
  3 
  K.SCSOEt 
  + 
  

   H 
  2 
  = 
  C 
  6 
  H 
  4 
  SH.S0 
  3 
  K 
  + 
  COS 
  + 
  EtOH. 
  Hydrolysis 
  was 
  com- 
  

   pleted 
  by 
  evaporating 
  the 
  reaction 
  mixture 
  to 
  dryness 
  on 
  the 
  

   steam 
  bath, 
  during 
  which 
  process 
  the 
  thiophenolsulphonate 
  

   was 
  oxidized 
  by 
  the 
  air 
  chiefly 
  to 
  the 
  disulphide, 
  KS0 
  3 
  C 
  6 
  H 
  4 
  S.- 
  

   SC 
  6 
  H 
  4 
  S0 
  3 
  K. 
  

  

  The 
  disulphide 
  prepared 
  as 
  described 
  always 
  contained 
  an 
  

   orange-red 
  dye 
  resulting 
  from 
  the 
  diazo 
  reaction. 
  This 
  dye 
  is 
  

   soluble 
  in 
  alcohol 
  while 
  the 
  disulphide 
  is 
  not. 
  The 
  disulphide 
  

   was 
  therefore 
  purified 
  from 
  the 
  dye 
  by 
  twice 
  precipitating 
  the 
  

   disulphide 
  from 
  its 
  saturated 
  aqueous 
  solution 
  by 
  the 
  addition 
  

   of 
  alcohol. 
  The 
  trace 
  of 
  color 
  still 
  remaining 
  could 
  be 
  removed 
  

   later 
  by 
  means 
  of 
  animal 
  charcoal. 
  On 
  oxidation 
  the 
  disul- 
  

   phide 
  yields 
  the 
  corresponding 
  benzenedisulphonate. 
  The 
  oxi- 
  

   dation 
  was 
  best 
  effected 
  by 
  the 
  use 
  of 
  hot 
  saturated 
  aqueous 
  

   potassium 
  permanganate, 
  which 
  was 
  added 
  in 
  about 
  theoretical 
  

   amount 
  in 
  small 
  portions 
  in 
  the 
  course 
  of 
  20 
  to 
  30 
  minutes 
  to 
  

   the 
  cold 
  dilute 
  aqueous 
  solution 
  of 
  the 
  disulphide. 
  The 
  reac- 
  

   tion 
  evolved 
  considerable 
  heat 
  but 
  the 
  temperature 
  was 
  not 
  at 
  

   any 
  time 
  allowed 
  to 
  rise 
  above 
  60°. 
  Toward 
  the 
  end 
  of 
  the 
  

   oxidation 
  the 
  solution 
  retained 
  the 
  purple 
  color 
  of 
  the 
  perman- 
  

   ganate 
  for 
  10 
  to 
  15 
  minutes 
  on 
  the 
  steam 
  bath. 
  This 
  slight 
  

   excess 
  of 
  permanganate 
  was 
  finally 
  destroyed 
  by 
  the 
  addition 
  

   of 
  a 
  few 
  drops 
  of 
  alcohol. 
  The 
  reaction 
  mixture 
  was 
  some- 
  

   what 
  diluted 
  by 
  the 
  addition 
  of 
  water 
  and 
  allowed 
  to 
  

   stand 
  on 
  the 
  steam 
  bath 
  until 
  the 
  hydrated 
  oxide 
  of 
  

   manganese 
  had 
  well 
  settled 
  out. 
  The 
  oxide 
  of 
  manga- 
  

   nese 
  was 
  then 
  easily 
  removed 
  by 
  filtration 
  with 
  suc- 
  

   tion 
  and 
  was 
  well 
  washed 
  with 
  hot 
  water 
  on 
  the 
  porcelain 
  

   funnel. 
  The 
  combined 
  filtrates 
  were 
  concentrated 
  on 
  the 
  

   steam 
  bath 
  to 
  crystallization 
  and 
  allowed 
  to 
  stand 
  over 
  night 
  

   for 
  the 
  potassium 
  benzenedisulphonate 
  to 
  crystallize 
  out. 
  If 
  

   any 
  of 
  the 
  reddish 
  dye 
  persisted 
  at 
  this 
  stage 
  it 
  was 
  removed 
  

   by 
  animal 
  charcoal. 
  The 
  jy-benzenedisulphonate 
  was 
  further 
  

   purified 
  by 
  recrystallization 
  from 
  water. 
  A 
  60 
  per 
  cent 
  yield 
  

   of 
  potassium 
  ^-benzenedisulphonate 
  may 
  be 
  obtained 
  from 
  

   sulphanilic 
  acid 
  by 
  the 
  xanthate 
  process 
  under 
  favorable 
  condi- 
  

   tions. 
  A 
  convenient 
  method 
  for 
  the 
  purification 
  of 
  the 
  <9-ben- 
  

   zenedisulphonic 
  acid 
  is 
  to 
  convert 
  the 
  potassium 
  salt 
  into 
  the 
  

   barium 
  salt 
  by 
  the 
  action 
  of 
  saturated 
  aqueous 
  barium 
  chloride, 
  

   and 
  recrystallization 
  of 
  the 
  barium 
  salt 
  from 
  hot 
  water. 
  This 
  

   method 
  was 
  described 
  by 
  J. 
  J. 
  Polak.* 
  

  

  The 
  6>-benzenedisulphonic 
  acid 
  was 
  prepared 
  from 
  6>-amido- 
  

   benzenesulphonic 
  acid 
  by 
  the 
  xanthate 
  method. 
  The 
  amido- 
  

   sulphonic 
  not 
  being 
  obtainable 
  in 
  the 
  market, 
  it 
  became 
  

  

  * 
  Polak, 
  Rec. 
  trav. 
  chim. 
  Pays-Bas, 
  xxix, 
  418, 
  1910. 
  

  

  