﻿1874.] 
  Coefficient 
  of 
  Expansion 
  of 
  a 
  Paraffine. 
  

  

  Ill 
  

  

  out 
  when 
  the 
  thermometer 
  immersed 
  in 
  the 
  water 
  read 
  141° 
  F., 
  but 
  it 
  

   rose 
  to 
  148° 
  F. 
  (six 
  degrees 
  above 
  the 
  point 
  of 
  fusion 
  of 
  the 
  paraffine), 
  

   and 
  a 
  very 
  small 
  amount 
  of 
  paraffine 
  at 
  the 
  surface 
  melted 
  ; 
  hence, 
  with 
  

   the 
  exterior 
  surface 
  actually 
  fusing 
  at 
  148° 
  F., 
  it 
  will 
  be 
  seen 
  that 
  the 
  

   imbedded 
  thermometer, 
  separated 
  from 
  the 
  fused 
  surface 
  by 
  only 
  8 
  millims. 
  

   of 
  paraffine, 
  read 
  48° 
  F. 
  lower. 
  Further, 
  it 
  will 
  be 
  noticed 
  that 
  the 
  tem- 
  

   perature 
  of 
  the 
  water 
  rose 
  steadily 
  to 
  148° 
  F. 
  and 
  then 
  sank 
  at 
  the 
  rate 
  

   of 
  about 
  one 
  degree 
  in 
  a 
  minute, 
  while 
  the 
  paraffine 
  acquired 
  heat 
  in- 
  

   creasingly 
  till 
  the 
  water 
  ceased 
  to 
  be 
  heated, 
  then 
  less 
  quickly, 
  until 
  when 
  

   the 
  paraffine 
  had 
  acquired 
  a 
  temperature 
  of 
  130° 
  F. 
  the 
  temperatures 
  

   coincide, 
  half 
  an 
  hour 
  after 
  the 
  commencement 
  of 
  heating. 
  Then 
  the 
  

   temperature 
  of 
  the 
  paraffine 
  begins 
  to 
  fall 
  gradually, 
  and 
  less 
  quickly 
  

   than 
  that 
  of 
  the 
  water, 
  until 
  at 
  90 
  o, 
  5 
  F. 
  there 
  is 
  once 
  again 
  coincidence, 
  

   one 
  hour 
  and 
  twenty-seven 
  minutes 
  from 
  the 
  commencement 
  of 
  heating. 
  

   After 
  this 
  the 
  temperatures 
  read 
  alike, 
  and 
  the 
  thermometers 
  continue 
  to 
  

   fall 
  pari 
  passu. 
  In 
  the 
  column 
  of 
  differences, 
  minus 
  differences 
  signify 
  that 
  

   the 
  temperatures 
  of 
  the 
  paraffine-thermometer 
  were 
  below 
  those 
  of 
  the 
  

   water-thermometer, 
  plus 
  differences 
  that 
  the 
  former 
  were 
  above 
  those 
  of 
  

   the 
  latter. 
  

  

  It 
  will 
  be 
  noticed 
  that 
  the 
  two-minute 
  observations 
  cease 
  at 
  12.10 
  p.m., 
  

   and 
  that 
  the 
  last 
  four 
  are 
  made 
  at 
  intervals 
  of 
  12, 
  25, 
  19, 
  and 
  68 
  

   minutes. 
  

  

  In 
  regard 
  to 
  the 
  fluid 
  paraffine, 
  a 
  mass 
  of 
  from 
  20 
  to 
  30 
  grammes 
  takes 
  

   two 
  or 
  three 
  hours 
  to 
  cool 
  down 
  from 
  just 
  below 
  its 
  fusiug-point 
  to 
  the 
  

   temperature 
  of 
  the 
  air 
  — 
  that 
  is, 
  to 
  cool 
  through 
  about 
  80° 
  F. 
  The 
  bulb 
  

   of 
  a 
  thermometer 
  was 
  surrounded 
  by 
  8 
  millimetres 
  of 
  liquid 
  paraffine 
  

   at 
  150° 
  F., 
  and 
  was 
  plunged 
  in 
  a 
  bath 
  kept 
  at 
  245° 
  F. 
  ; 
  at 
  the 
  end 
  of 
  

   half 
  an 
  hour 
  the 
  mass 
  of 
  about 
  30 
  grammes 
  had 
  barely 
  acquired 
  the 
  tem- 
  

   perature 
  of 
  the 
  bath. 
  In 
  heating 
  a 
  vessel 
  of 
  paraffine 
  there 
  is 
  always 
  a 
  

   marked 
  difference 
  between 
  the 
  temperatures 
  of 
  the 
  upper 
  and 
  lower 
  

   levels. 
  The 
  convection-currents 
  part 
  with 
  their 
  heat 
  so 
  slowly 
  that 
  a 
  

   uniform 
  temperature 
  throughout 
  the 
  mass 
  seems 
  to 
  be 
  altogether 
  unat- 
  

   tainable 
  without 
  constant 
  and 
  complete 
  agitation. 
  During 
  the 
  heating 
  

   of 
  about 
  half 
  a 
  litre 
  of 
  the 
  liquid 
  paraffine 
  in 
  a 
  cylindrical 
  copper 
  vessel 
  

   75 
  millimetres 
  (about 
  3 
  inches) 
  diameter 
  by 
  150 
  millimetres 
  high, 
  the 
  

   following 
  results 
  were 
  obtained 
  : 
  — 
  The 
  upper 
  thermometer 
  was 
  placed 
  

   with 
  its 
  bulb 
  a 
  centimetre 
  from 
  the 
  surface, 
  the 
  lower 
  thermometer 
  with 
  

   its 
  bulb 
  a 
  centimetre 
  from 
  the 
  bottom. 
  The 
  fluid 
  mass 
  was 
  directly 
  

   heated 
  by 
  a 
  Bunsen 
  burner 
  from 
  below. 
  In 
  the 
  column 
  of 
  differences, 
  

   minus 
  differences 
  signify 
  that 
  the 
  temperature 
  of 
  the 
  lower 
  thermometer 
  

   is 
  below 
  that 
  of 
  the 
  upper 
  thermometer, 
  and 
  plus 
  differences 
  that 
  the 
  

   temperatures 
  of 
  the 
  former 
  are 
  above 
  those 
  of 
  the 
  latter. 
  The 
  gas 
  was 
  

   turned 
  out 
  at 
  6 
  p.m., 
  the 
  highest 
  temperature 
  being 
  attained 
  by 
  the 
  lower 
  

   thermometer 
  (361° 
  F.) 
  at 
  6.1 
  p.m., 
  while 
  the 
  highest 
  temperature 
  attained 
  

   by 
  the 
  upper 
  thermometer 
  was 
  354° 
  F. 
  at 
  the 
  same 
  time. 
  

  

  k2 
  

  

  