﻿Van 
  Name 
  and 
  Brown 
  — 
  Freezing 
  Point 
  Lowering. 
  113 
  

  

  receiver 
  and 
  from 
  time 
  to 
  time 
  returned 
  by 
  hand 
  to 
  the 
  freez- 
  

   ing 
  mixture. 
  

  

  A 
  side 
  branch 
  in 
  the 
  tube 
  which 
  conveys 
  the 
  brine 
  to 
  the 
  

   apparatus 
  is 
  connected 
  with 
  the 
  water 
  main 
  so 
  that 
  when 
  

   desired 
  the 
  brine 
  temperature 
  may 
  be 
  raised 
  by 
  admitting 
  

   water 
  in 
  regulated 
  amounts. 
  To 
  insure 
  thorough 
  mixing 
  of 
  

   the 
  two 
  liquids 
  they 
  pass, 
  just 
  beyond 
  their 
  point 
  of 
  meeting, 
  

   through 
  a 
  roll 
  of 
  tine 
  wire 
  gauze, 
  so 
  arranged 
  as 
  to 
  be 
  easily 
  

   accessible 
  for 
  cleaning 
  (fig. 
  2, 
  G). 
  After 
  each 
  determination, 
  

   the 
  ice 
  which 
  has 
  separated 
  is 
  melted 
  by 
  shutting 
  off 
  the 
  brine 
  

   altogether 
  and 
  permitting 
  water 
  alone 
  to 
  flow 
  through 
  the 
  cool- 
  

   ing 
  tube 
  for 
  a 
  short 
  time. 
  

  

  The 
  stirrer 
  is 
  driven 
  by 
  a 
  motor, 
  and 
  except 
  for 
  a 
  brief 
  

   interval 
  at 
  the 
  time 
  of 
  inoculation, 
  is 
  kept 
  in 
  motion 
  through- 
  

   out 
  the 
  experiment. 
  The 
  successive 
  steps 
  in 
  determining 
  the 
  

   freezing 
  point 
  of 
  a 
  solution 
  are 
  as 
  follows 
  : 
  The 
  solution 
  (of 
  

   known 
  concentration) 
  is 
  placed 
  in 
  the 
  apparatus, 
  the 
  stirrer 
  set 
  

   in 
  motion 
  and 
  the 
  flow 
  of 
  brine 
  started. 
  When 
  the 
  desired 
  

   degree 
  of 
  undercooling 
  has 
  been 
  reached 
  the 
  inner 
  tube 
  of 
  the 
  

   cooling 
  device 
  is 
  lowered 
  to 
  the 
  position 
  shown 
  in 
  fig. 
  1. 
  After 
  

   waiting 
  a 
  short 
  time 
  for 
  temperature 
  equilibrium 
  the 
  thermom- 
  

   eter 
  is 
  read 
  (this 
  reading 
  is 
  used 
  only 
  in 
  calculating 
  the 
  degree 
  

   of 
  undercooling) 
  and 
  the 
  inoculation 
  effected 
  in 
  the 
  usual 
  way, 
  

   whereupon 
  the 
  temperature 
  rises 
  and 
  becomes 
  constant 
  at 
  the 
  

   freezing 
  point. 
  Owing 
  to 
  the 
  good 
  heat 
  insulation 
  the 
  con- 
  

   stancy 
  of 
  the 
  freezing 
  point 
  is 
  almost 
  as 
  perfect 
  when 
  working 
  

   with 
  a 
  solution 
  as 
  it 
  is 
  with 
  pure 
  water. 
  This 
  eliminates 
  the 
  

   necessity 
  for 
  considering 
  the 
  so-called 
  " 
  convergence 
  tempera- 
  

   ture," 
  and 
  makes 
  the 
  calculation 
  of 
  the 
  correction 
  for 
  under- 
  

   cooling 
  simple 
  and 
  free 
  from 
  uncertainty.* 
  

  

  The 
  effective 
  heat 
  insulation 
  is 
  due 
  not 
  only 
  to 
  the 
  use 
  of 
  

   the 
  Dewar 
  vessel 
  but 
  also 
  to 
  the 
  fact, 
  mentioned 
  above, 
  that 
  

   the 
  flow 
  of 
  brine 
  through 
  the 
  upper 
  part 
  of 
  the 
  cooling 
  tube 
  

   tends 
  to 
  compensate 
  for 
  the 
  heat 
  leakage 
  and 
  the 
  heat 
  gener- 
  

   ated 
  by 
  stirring. 
  

  

  With 
  regard 
  to 
  the 
  possibility 
  of 
  using 
  this 
  form 
  of 
  apparatus 
  

   for 
  very 
  accurate 
  measurements 
  we 
  would 
  call 
  attention 
  to 
  the 
  

   fact 
  that 
  by 
  suitable 
  provision 
  for 
  a 
  closer 
  regulation 
  of 
  the 
  

   temperature, 
  rate 
  of 
  flow, 
  and 
  path 
  of 
  the 
  brine, 
  this 
  compen- 
  

   sation 
  could 
  be 
  made 
  approximately 
  complete, 
  thus 
  permitting 
  

   the 
  temperature 
  readings 
  to 
  be 
  made 
  under 
  practically 
  ideal 
  

   conditions. 
  The 
  accuracy 
  would 
  then 
  be 
  limited 
  only 
  by 
  that 
  

   of 
  the 
  temperature 
  measurements. 
  

  

  * 
  This 
  correction 
  is 
  based 
  on 
  the 
  degree 
  of 
  undercooling, 
  the 
  heat 
  of 
  fusion 
  

   of 
  the 
  solvent, 
  and 
  the 
  heat 
  capacities 
  (a) 
  of 
  the 
  liquid, 
  and 
  (b) 
  of 
  the 
  con- 
  

   tainer, 
  stirrer, 
  thermometer, 
  etc. 
  In 
  practice 
  (a) 
  is 
  so 
  large 
  compared 
  with 
  

   (6) 
  that 
  a 
  rough 
  estimate 
  of 
  the 
  latter 
  is 
  generally 
  amply 
  sufficient 
  for 
  the 
  

   purpose. 
  

  

  