﻿68 
  Scientific 
  Intelligence. 
  

  

  and 
  sulphobenzide, 
  dinaphtbyl 
  sulphides 
  and 
  sulphone. 
  In 
  all 
  

   these 
  cases 
  it 
  was 
  found 
  that 
  a 
  large 
  lowering 
  of 
  the 
  boiling 
  point 
  

   was 
  brought 
  about 
  by 
  the 
  last 
  small 
  reduction 
  of 
  pressure 
  ; 
  the 
  

   difference 
  in 
  the 
  boiling 
  point 
  at 
  15 
  ram 
  pressure 
  and 
  in 
  the 
  Crookes 
  

   vacuum 
  varying 
  from 
  70*5° 
  in 
  the 
  case 
  of 
  cetyl 
  alcohol, 
  78° 
  in 
  

   that 
  of 
  stearic 
  acid 
  and 
  98° 
  in 
  heptacosan 
  C 
  27 
  H 
  66 
  , 
  to 
  102° 
  in 
  the 
  

   case 
  of 
  octadecylbenzene 
  and 
  105° 
  in 
  that 
  of 
  pentadecylxylylke- 
  

   tone. 
  — 
  Ber. 
  Berl. 
  Chem. 
  Ges., 
  xxix, 
  1316, 
  May, 
  1896. 
  g. 
  f. 
  b. 
  

  

  3. 
  On 
  the 
  Formation 
  of 
  Per 
  sulphuric 
  Acid. 
  — 
  The 
  relation 
  

   between 
  the 
  concentration 
  of 
  the 
  sulphuric 
  acid 
  subjected 
  to 
  elec- 
  

   trolysis 
  and 
  the 
  amount 
  of 
  persulphuric 
  acid 
  formed, 
  has 
  been 
  

   studied 
  by 
  Elbs 
  and 
  Schonherk. 
  They 
  determined 
  the 
  persul- 
  

   phuric 
  acid 
  by 
  pouring 
  5 
  to 
  10 
  cc 
  of 
  the 
  liquid 
  into 
  200 
  to 
  300 
  cc 
  

   of 
  cold 
  water, 
  adding 
  a 
  known 
  quantity 
  of 
  ammonium 
  ferrous 
  

   sulphate 
  and 
  then 
  titrating 
  back 
  with 
  potassium 
  permanganate. 
  

   They 
  find 
  that 
  very 
  little 
  persulphuric 
  acid 
  is 
  formed 
  when 
  the 
  

   density 
  of 
  the 
  sulphuric 
  acid 
  used 
  is 
  below 
  1*2 
  ; 
  the 
  maximum 
  yield 
  

   being 
  obtained 
  when 
  this 
  density 
  is 
  1*35 
  to 
  1*5. 
  Since 
  the 
  quan- 
  

   tity 
  of 
  persulphuric 
  acid 
  produced 
  is 
  increased 
  by 
  an 
  increase 
  in 
  

   the 
  strength 
  of 
  the 
  current, 
  it 
  must 
  be 
  formed 
  by 
  the 
  union 
  of 
  

   the 
  HS0 
  4 
  ions 
  at 
  the 
  anode 
  and 
  is 
  not 
  due 
  to 
  oxidation 
  : 
  since 
  

   in 
  the 
  latter 
  case 
  the 
  amount 
  formed 
  would 
  decrease 
  rather 
  than 
  

   increase 
  with 
  the 
  current 
  strength. 
  If 
  the 
  electrolyte 
  be 
  too 
  con- 
  

   centrated 
  2 
  the 
  yield 
  is 
  lessened, 
  because 
  (1) 
  the 
  concentrated 
  acid 
  

   is 
  a 
  bad 
  conductor, 
  (2) 
  the 
  molecules 
  of 
  H 
  2 
  S 
  2 
  8 
  when 
  produced 
  in 
  

   a 
  strong 
  acid 
  are 
  not 
  as 
  free 
  to 
  move 
  as 
  in 
  the 
  more 
  mobile 
  dilute 
  

   acid, 
  and 
  therefore, 
  remaining 
  longer 
  at 
  the 
  anode, 
  are 
  to 
  some 
  

   extent 
  decomposed, 
  and 
  (3) 
  with, 
  concentrated 
  acid, 
  greater 
  heat 
  

   is 
  developed 
  and 
  a 
  greater 
  number 
  of 
  molecules 
  is 
  thereby 
  de- 
  

   stroyed. 
  Increase 
  of 
  temperature 
  diminishes 
  the 
  amount 
  of 
  per- 
  

   sulphuric 
  acid 
  formed, 
  it 
  being 
  decomposed 
  at 
  60° 
  as 
  rapidly 
  as 
  

   it 
  is 
  produced. 
  If 
  the 
  acid 
  be 
  moderately 
  dilute 
  and 
  the 
  current 
  

   strong, 
  it 
  is 
  soon 
  interrupted. 
  On 
  warming, 
  however, 
  the 
  electrol- 
  

   ysis 
  begins 
  anew, 
  the 
  interruption 
  being 
  caused 
  by 
  the 
  forma- 
  

   tion 
  of 
  a 
  non-conducting 
  coating 
  of 
  H 
  2 
  S 
  2 
  8 
  at 
  the 
  anode. 
  If 
  the 
  

   dilute 
  acid 
  have 
  a 
  density 
  less 
  than 
  1*3, 
  no 
  hydrogen 
  peroxide, 
  

   practically, 
  is 
  produced 
  by 
  the 
  decomposition 
  of 
  the 
  persulphuric 
  

   acid. 
  It 
  increases, 
  however, 
  as 
  the 
  strength 
  of 
  the 
  electrolyte 
  

   increases. 
  Persulphuric 
  acid 
  may 
  be 
  diluted 
  with 
  50 
  times 
  its 
  

   volume 
  of 
  cold 
  water 
  without 
  decomposition. 
  

  

  Elbs 
  demonstrates 
  the 
  formation 
  of 
  persulphuric 
  acid 
  and 
  of 
  

   its 
  potassium 
  salt, 
  by 
  filling 
  a 
  wide 
  test 
  tube 
  with 
  the 
  electrolyte, 
  

   placing 
  in 
  it 
  an 
  anode 
  consisting 
  of 
  a 
  platinum 
  wire 
  enclosed 
  in 
  

   a 
  glass 
  tube 
  for 
  the 
  greater 
  part 
  of 
  its 
  length, 
  and 
  a 
  kathode 
  

   made 
  of 
  a 
  platinum 
  ring. 
  The 
  bubbles 
  of 
  gas 
  evolved 
  are 
  col- 
  

   lected 
  in 
  a 
  wider 
  tube 
  surrounding 
  the 
  anode 
  and 
  are 
  thus 
  pre- 
  

   vented 
  from 
  reaching 
  the 
  cathode. 
  The 
  whole 
  apparatus 
  is 
  placed 
  

   in 
  a 
  beaker 
  of 
  cold 
  water 
  and 
  a 
  current 
  is 
  passed 
  through 
  it 
  whose 
  

   density 
  is 
  100 
  amperes 
  per 
  square 
  meter 
  of 
  anode 
  surface. 
  If 
  the 
  

   sulphuric 
  acid 
  have 
  a 
  specific 
  gravity 
  of 
  1*4, 
  persulphuric 
  acid 
  can 
  

  

  