﻿with 
  Sodium 
  Peroxide. 
  29 
  

  

  blackened 
  by 
  a 
  fusion 
  with 
  sulphur 
  the 
  heat 
  result 
  is 
  low. 
  

   Acetylene 
  carbon 
  is 
  the 
  ideal 
  substance 
  to 
  use, 
  but 
  difficult 
  to 
  

   obtain. 
  It 
  is 
  constant 
  in 
  composition 
  after 
  heating 
  to 
  expel 
  

   hygroscopic 
  moisture, 
  and 
  any 
  unburned 
  is 
  not 
  dissolved 
  when 
  

   the 
  fusion 
  is 
  treated 
  with 
  water 
  or 
  acid 
  and 
  may 
  be 
  collected 
  

   on 
  a 
  Gooch 
  filter 
  and 
  weighed. 
  Commercial 
  lampblack 
  nearly 
  

   ash 
  free 
  is 
  prepared 
  as 
  follows 
  : 
  It 
  is 
  heated 
  for 
  two 
  or 
  three 
  

   hours 
  to 
  1000° 
  or 
  higher, 
  sifted 
  when 
  cool 
  and 
  shaken 
  in 
  a 
  

   large 
  bottle 
  to 
  ensure 
  uniformity 
  in 
  composition. 
  A 
  portion 
  

   for 
  a 
  calorimetric 
  experiment 
  is 
  heated 
  in 
  a 
  crucible, 
  best 
  in 
  

   an 
  electric 
  furnace, 
  until 
  the 
  top 
  of 
  it 
  is 
  a 
  faint 
  red 
  to 
  expel 
  

   moisture, 
  then 
  allowed 
  to 
  cool 
  in 
  a 
  desiccator. 
  Finally 
  it 
  is 
  

   quickly 
  weighed 
  and 
  placed 
  in 
  a 
  bomb. 
  As 
  the 
  lampblack 
  

   changes 
  in 
  composition 
  with 
  the 
  intensity 
  and 
  time 
  of 
  heating, 
  

   care 
  should 
  be 
  taken 
  to 
  heat 
  the 
  different 
  portions 
  used 
  uni- 
  

   formly. 
  Lampblack 
  gives 
  a 
  quicker 
  combustion, 
  often 
  of 
  

   explosive 
  violence, 
  than 
  acetylene 
  carbon 
  or 
  sulphur. 
  Thus 
  

   far 
  the 
  writer 
  has 
  found 
  no 
  lampblack 
  left 
  in 
  fusion 
  with 
  

   sodium 
  peroxide. 
  

  

  One 
  part 
  of 
  carbon 
  requires 
  13 
  parts 
  of 
  pure 
  sodium 
  perox- 
  

   ide 
  for 
  combustion 
  and 
  it 
  is 
  best 
  to 
  take 
  about 
  20 
  parts 
  in 
  

   determining 
  the 
  heat 
  effect 
  of 
  the 
  carbon 
  or 
  lampblack. 
  For 
  

   the 
  combustion 
  of 
  sulphur 
  double 
  the 
  calculated 
  amount 
  of 
  

   peroxide 
  should 
  be 
  used. 
  Oxygen 
  is 
  often 
  evolved 
  in 
  a 
  com- 
  

   bustion 
  from 
  the 
  action 
  of 
  an 
  acidic 
  oxide 
  on 
  the 
  sodium 
  per- 
  

   oxide 
  and 
  the 
  heat 
  required 
  to 
  set 
  it 
  free 
  from 
  the 
  peroxide 
  is 
  

   added 
  to 
  the 
  observed 
  heat. 
  This 
  correction, 
  1/73 
  g-cal. 
  for 
  

   l 
  cc 
  of 
  oxygen 
  at 
  0° 
  and 
  760 
  mm 
  , 
  is 
  derived 
  from 
  Beketoff's 
  

   Na 
  2 
  + 
  O 
  = 
  100-26 
  Cal. 
  and 
  de 
  Forcrand's 
  Na 
  2 
  + 
  20 
  = 
  119-8 
  

   Cal. 
  The 
  writer 
  has 
  tested 
  and 
  found 
  no 
  carbon 
  dioxide 
  in 
  

   the 
  oxygen 
  given 
  off 
  in 
  considerable 
  quantities 
  from 
  fusions 
  of 
  

   mixtures 
  of 
  sodium 
  peroxide, 
  an 
  acidic 
  oxide 
  and 
  lampblack. 
  

  

  It 
  is 
  best 
  to 
  use 
  large 
  quantities 
  of 
  substances 
  in 
  calorimetric 
  

   determinations, 
  not 
  only 
  because 
  the 
  errors 
  are 
  less, 
  but 
  because 
  

   a 
  large 
  fusion 
  remains 
  liquid 
  longer 
  than 
  a 
  small 
  one 
  and 
  

   hence 
  the 
  combustion 
  is 
  more 
  likely 
  to 
  be 
  complete. 
  A 
  mix- 
  

   ture 
  of 
  20 
  to 
  50 
  grams 
  giving 
  a 
  heat 
  effect 
  of 
  10 
  to 
  20 
  Cal. 
  

   answers 
  well. 
  

  

  The 
  bomb, 
  fig. 
  1, 
  is 
  sterling 
  silver. 
  It 
  is 
  3/32 
  in. 
  in 
  thick- 
  

   ness. 
  The 
  inside 
  diameter 
  at 
  the 
  top 
  is 
  1 
  5/8 
  in., 
  at 
  the 
  bottom 
  

   1 
  4/8 
  in., 
  and 
  the 
  length 
  not 
  including 
  the 
  top 
  is 
  3 
  1/4 
  in. 
  It 
  

   is 
  slightly 
  conical 
  for 
  convenience 
  in 
  fitting 
  the 
  expanded 
  top 
  of 
  

   the 
  cup 
  a, 
  to 
  make 
  a 
  dust-tight 
  joint. 
  A 
  fusion 
  in 
  the 
  cup 
  

   coois 
  more 
  slowly 
  than 
  when 
  in 
  contact 
  with 
  the 
  cold 
  bomb 
  

   and 
  hence 
  the 
  reaction 
  is 
  more 
  complete. 
  The 
  cup 
  is 
  tine 
  sil- 
  

   ver 
  and 
  weighs 
  15 
  to 
  30 
  grams. 
  The 
  top 
  and 
  fittings 
  are 
  

   brass. 
  The 
  top 
  is 
  2 
  3/4 
  in. 
  in 
  diameter 
  and 
  5/8 
  in. 
  thick 
  

  

  