﻿E 
  T. 
  Long 
  — 
  Formation 
  of 
  Salt 
  Crystals. 
  291 
  

  

  hot 
  brine. 
  During 
  the 
  first 
  step 
  of 
  the 
  experiment, 
  a 
  second 
  

   glass 
  tube 
  was 
  run 
  through 
  the 
  stopper 
  (X) 
  in 
  the 
  right 
  hand 
  

   side 
  neck 
  of 
  B 
  without 
  rubber 
  tube 
  connection, 
  at 
  the 
  outer 
  

   end 
  of 
  which, 
  however, 
  there 
  was 
  a 
  connection 
  on 
  which 
  

   another 
  stopcock 
  was 
  placed. 
  During 
  the 
  second 
  step, 
  instead 
  

   of 
  the 
  glass 
  tube, 
  a 
  common 
  rubber 
  finger 
  was 
  used. 
  It 
  was 
  

   punctured 
  at 
  the 
  tip 
  and 
  a 
  small 
  glass 
  tube 
  inserted, 
  while 
  the 
  

   open 
  end 
  was 
  stretched 
  over 
  the 
  same 
  rubber 
  stopper, 
  X. 
  

  

  The 
  most 
  effective 
  temperature 
  to 
  bring 
  about 
  deposition 
  

   from 
  the 
  hot 
  brine 
  was 
  found 
  to 
  be 
  between 
  70° 
  and 
  75° 
  C. 
  

   Below 
  that, 
  there 
  was 
  not 
  enough 
  NaCl 
  absorbed 
  for 
  an 
  

   appreciable 
  deposition, 
  and 
  above 
  75° 
  recrystallization 
  went 
  

   on 
  in 
  B. 
  As 
  enough 
  hydrostatic 
  pressure 
  could 
  not 
  be 
  

   obtained 
  by 
  raising 
  A 
  so 
  that 
  the 
  passage 
  through 
  the 
  stopper 
  

   at 
  X 
  could 
  be 
  kept 
  open, 
  it 
  had 
  to 
  be 
  frequently 
  cleared 
  by 
  a 
  

   steel 
  rod 
  with 
  a 
  right-angle 
  turn 
  run 
  through 
  the 
  top 
  neck 
  of 
  B. 
  

   This 
  stopper 
  was 
  also 
  removed 
  to 
  replenish 
  the 
  supply 
  of 
  salt, 
  

   but 
  otherwise 
  B 
  was 
  kept 
  air-tight 
  to 
  prevent 
  crystallization 
  

   by 
  evaporation. 
  

  

  After 
  five 
  or 
  six 
  days 
  the 
  hot 
  brine 
  became 
  sufficiently 
  

   saturated 
  to 
  begin 
  the 
  formation 
  of 
  crystals 
  at 
  C, 
  the 
  first 
  point 
  

   where 
  crystallization 
  took 
  place, 
  and 
  therefore 
  the 
  point 
  where 
  

   it 
  was 
  always 
  farthest 
  advanced. 
  At 
  the 
  end 
  of 
  a 
  few 
  weeks 
  

   the 
  crystals 
  had 
  grown 
  so 
  that 
  they 
  completely 
  filled 
  the 
  tube 
  

   and 
  stopped 
  the 
  flow 
  entirely. 
  Figure 
  2 
  shows 
  the 
  conditions 
  

   at 
  this 
  stage 
  of 
  the 
  experiment. 
  The 
  hydrostatic 
  pressure 
  was 
  

   increased 
  but 
  no 
  seepage 
  could 
  be 
  forced 
  through. 
  This 
  run 
  

   was 
  repeated 
  several 
  times 
  under 
  slightly 
  different 
  conditions, 
  

   but 
  the 
  result 
  was 
  always 
  the 
  same 
  even 
  though 
  the 
  time 
  

   varied 
  somewhat. 
  

  

  The 
  second 
  step 
  was 
  then 
  started 
  : 
  to 
  make 
  the 
  crystals 
  grow 
  

   against 
  pressure, 
  in 
  this 
  case 
  a 
  rubber 
  finger. 
  This 
  was 
  so 
  

   successful 
  that 
  after 
  a 
  month, 
  one 
  crystal 
  expanded 
  the 
  rubber 
  

   wall 
  of 
  its 
  prison 
  so 
  far 
  as 
  to 
  puncture 
  it. 
  The 
  tiny 
  hole 
  was 
  

   cemented 
  over 
  and 
  effectually 
  closed, 
  but 
  in 
  a 
  few 
  days 
  another 
  

   crystal 
  went 
  through 
  at 
  a 
  different 
  point, 
  this 
  time 
  making 
  a 
  

   much 
  larger 
  hole. 
  

  

  On 
  page 
  550 
  of 
  Mr. 
  Taber's 
  article 
  he 
  says, 
  " 
  The 
  tendency 
  

   to 
  form 
  crystals 
  is 
  much 
  stronger 
  in 
  some 
  substances 
  than 
  in 
  

   others, 
  but 
  it 
  is 
  never 
  so 
  strong 
  as 
  to 
  cause 
  growth 
  on 
  a 
  face 
  

   which 
  is 
  not 
  in 
  contact 
  with 
  a 
  supersaturated 
  solution, 
  and 
  

   even 
  if 
  a 
  growing 
  surface 
  is 
  in 
  contact 
  with 
  a 
  supersaturated 
  

   solution, 
  the 
  relative 
  rate 
  of 
  growth 
  is 
  chiefly 
  controlled 
  by 
  the 
  

   rapidity 
  with 
  which 
  the 
  material 
  for 
  growth 
  is 
  made 
  avail- 
  

   able." 
  

  

  The 
  results 
  of 
  the 
  two 
  series 
  of 
  experiments 
  thus 
  indepen- 
  

   dently 
  worked 
  out 
  would 
  therefore 
  seem 
  to 
  establish 
  without 
  

  

  