﻿1874.] 
  Coefficient 
  of 
  Expansion 
  of 
  a 
  Paraffine. 
  

  

  113 
  

  

  Owing 
  to 
  the 
  great 
  contraction 
  which 
  takes 
  place 
  when 
  a 
  mass 
  of 
  liquid 
  

   paraffine 
  solidifies, 
  it 
  was 
  found 
  to 
  be 
  somewhat 
  difficult 
  to 
  obtain 
  a 
  solid 
  

   mass 
  free 
  from 
  minute 
  cavities 
  and 
  of 
  uniform 
  texture. 
  The 
  plan 
  

   eventually 
  adopted 
  was 
  to 
  take 
  a 
  long 
  column 
  of 
  melted 
  paraffine 
  and 
  to 
  

   cool 
  the 
  lower 
  extremity 
  of 
  it. 
  The 
  supernatant 
  fluid 
  forced 
  its 
  way 
  into 
  

   the 
  central 
  cavity 
  produced 
  by 
  the 
  contraction 
  of 
  the 
  solidifying 
  mass, 
  and 
  

   the 
  result 
  was 
  a 
  mass 
  of 
  paraffine 
  apparently 
  quite 
  compact 
  and 
  free 
  

   from 
  cavities. 
  It 
  was 
  suspended 
  from 
  the 
  balance 
  by 
  horsehair, 
  and 
  

   weighted 
  by 
  a 
  piece 
  of 
  brass, 
  the 
  weight 
  of 
  which 
  in 
  air 
  and 
  water 
  at 
  

   different 
  temperatures 
  was 
  known 
  ; 
  and 
  the 
  whole 
  was 
  finally 
  weighed 
  in 
  

   distilled 
  water 
  which 
  had 
  been 
  well 
  boiled 
  and 
  cooled 
  in 
  a 
  good 
  vacuum. 
  

   After 
  the 
  immersion 
  of 
  the 
  paraffine 
  the 
  whole 
  was 
  again 
  placed 
  in 
  a 
  good 
  

   vacuum. 
  The 
  mass 
  was 
  heated 
  and 
  weighed 
  in 
  water 
  at 
  various 
  tem- 
  

   peratures, 
  between 
  32° 
  F. 
  (0° 
  C.) 
  and 
  142° 
  F. 
  (61°- 
  11 
  C.) 
  ; 
  the 
  melting- 
  

   point 
  and 
  the 
  cubical 
  expansion 
  was 
  found 
  to 
  be 
  as 
  follows, 
  for 
  one 
  

   degree 
  Fahrenheit 
  : 
  — 
  

  

  Between 
  32° 
  F. 
  and 
  60° 
  F. 
  (15°-55 
  C.) 
  .... 
  -00031985 
  * 
  

  

  60° 
  F. 
  „ 
  100° 
  F. 
  (37°-6 
  C.) 
  .... 
  -00039090 
  

  

  100° 
  F. 
  „ 
  120° 
  F. 
  (48°-85 
  C.) 
  .... 
  -00143118 
  

  

  120° 
  F. 
  „ 
  142° 
  F. 
  (61°-11 
  C.) 
  .... 
  -00244358 
  

  

  The 
  considerable 
  increase 
  of 
  the 
  coefficient 
  as 
  the 
  point 
  of 
  fusion 
  is 
  

   approached 
  is 
  explained 
  by 
  the 
  fact, 
  already 
  adverted 
  to, 
  that 
  the 
  solid 
  

   paraffine 
  becomes 
  soft 
  and 
  semisolid 
  like 
  sealing-wax 
  and 
  gutta-percha 
  

   before 
  actually 
  becoming 
  liquid. 
  From 
  the 
  above 
  coefficients 
  we 
  deduce 
  

   the 
  fact 
  that 
  

  

  100 
  volumes 
  of 
  paraffine 
  at 
  32° 
  F. 
  become 
  100-8955 
  at 
  60° 
  F. 
  

  

  „ 
  102-4591 
  „ 
  100° 
  

   „ 
  105-3215 
  „ 
  120° 
  

   „ 
  110-6974 
  „ 
  142° 
  

  

  As 
  the 
  latter 
  temperature 
  is 
  approached 
  the 
  mass 
  may 
  be 
  moulded 
  by 
  

   the 
  hand 
  like 
  a 
  mass 
  of 
  dough 
  or 
  putty 
  ; 
  and 
  on 
  continuing 
  the 
  heat 
  at 
  

   the 
  same 
  temperature, 
  it 
  fuses 
  to 
  a 
  limpid 
  liquid. 
  

  

  Determination 
  of 
  the 
  amount 
  of 
  expansion 
  which 
  paraffine 
  undergoes 
  when 
  

   it 
  passes 
  from 
  the 
  solid 
  condition 
  at 
  142° 
  F. 
  to 
  the 
  liquid 
  condition 
  at 
  the 
  

   same 
  temperature. 
  

  

  Tubes 
  of 
  known 
  weight 
  and 
  capacity 
  were 
  exactly 
  filled 
  with 
  melted 
  

   paraffine 
  at 
  142°. 
  They 
  were 
  then 
  allowed 
  to 
  cool 
  j 
  the 
  cavity 
  produced 
  

   by 
  contraction 
  was 
  accurately 
  filled 
  with 
  mercury, 
  which 
  was 
  weighed 
  

   and 
  the 
  capacity 
  of 
  the 
  cavity 
  deduced 
  therefrom. 
  The 
  results 
  were 
  

   concordant 
  and 
  satisfactory. 
  Thus 
  it 
  was 
  found 
  that 
  volume 
  =100 
  at 
  

   60° 
  F. 
  becomes, 
  in 
  the 
  fluid 
  condition, 
  at 
  142° 
  F. 
  :— 
  

  

  