﻿224 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OP 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  9 
  

  

  vapor. 
  Roozeboom 
  gave 
  the 
  name 
  "second 
  boiling 
  point" 
  to 
  this 
  higher 
  

   boiling 
  point, 
  which 
  is 
  obtained 
  on 
  cooling 
  as 
  above 
  described. 
  The 
  

   second 
  boiling 
  point 
  of 
  a 
  number 
  of 
  salt 
  solutions 
  has 
  been 
  observed 
  

   by 
  Smits, 
  and 
  others 
  have 
  been 
  observed 
  by 
  the 
  author. 
  The" 
  spit- 
  

   ting" 
  observed 
  when 
  molten 
  silver 
  is 
  cooled 
  in 
  air 
  is 
  another 
  example 
  

   of 
  the 
  second 
  boiling 
  point, 
  in 
  this 
  case 
  in 
  the 
  system 
  silver-oxygen, 
  

   and 
  a 
  similar 
  "spitting" 
  was 
  observed 
  by 
  Prandtl 
  and 
  Murschauser^ 
  

   with 
  alkali 
  vanadates. 
  Jackson^ 
  gives 
  an 
  interesting 
  description 
  of 
  a 
  

   gas 
  evolution 
  on 
  cooling 
  on 
  a 
  much 
  larger 
  scale, 
  which 
  will 
  be 
  quoted 
  : 
  

   "****** 
  For 
  a 
  special 
  optical 
  glass, 
  rich 
  in 
  phosphoric 
  anhydride, 
  

   an 
  experiment 
  was 
  tried 
  with 
  ammonium 
  phosphate 
  to 
  find 
  if 
  this 
  

   substance 
  could 
  be 
  used 
  in 
  the 
  batch 
  mixture 
  for 
  the 
  glass. 
  A 
  nice, 
  

   clear 
  fluid 
  melt 
  was 
  obtained, 
  which 
  was 
  kept 
  fluid 
  for 
  several 
  hours 
  

   after 
  all 
  traces 
  of 
  gas 
  bubbles 
  had 
  gone. 
  The 
  melt 
  was 
  well 
  stirred 
  

   and 
  cooled 
  till 
  it 
  was 
  quite 
  viscous, 
  when 
  it 
  was 
  left 
  to 
  get 
  cold 
  slowly. 
  

   The 
  next 
  morning 
  the 
  furnace 
  top 
  was 
  found 
  forced 
  off, 
  and 
  resting 
  

   on 
  a 
  spongy 
  mass 
  of 
  about 
  thirty 
  times 
  the 
  volume 
  of 
  the 
  original 
  

   glass 
  melt. 
  The 
  changes 
  occurring 
  when 
  solidification 
  was 
  approach- 
  

   ing 
  had 
  evidently 
  been 
  accompanied 
  by 
  the 
  evolution 
  of 
  a 
  large 
  volume 
  

   of 
  gas, 
  no 
  doubt 
  most 
  of 
  it 
  ammonia, 
  since 
  this 
  substance 
  was 
  smelt 
  

   on 
  grinding 
  the 
  spongy 
  mass 
  up. 
  The 
  ground 
  material 
  was 
  then 
  fused 
  

   and 
  gave 
  a 
  stable 
  glass." 
  This 
  is 
  probably 
  to 
  be 
  explained 
  by 
  partial 
  

   crystallization 
  of 
  the 
  glass 
  in 
  the 
  pot. 
  

  

  Experimental 
  data 
  exist 
  for 
  but 
  one 
  system 
  which 
  can 
  fairly 
  be 
  taken 
  

   as 
  analogous 
  to 
  mineral 
  systems, 
  the 
  system 
  H20-K2Si03-Si02.^ 
  The 
  

   cooling 
  of 
  certain 
  mixtures 
  in 
  this 
  system 
  will 
  next 
  be 
  considered. 
  

   With 
  some 
  compositions 
  the 
  second 
  boiling 
  point 
  at 
  atmospheric 
  

   pressure 
  can 
  be 
  demonstrated 
  in 
  a 
  striking 
  manner. 
  If 
  potassium 
  meta- 
  

   silicate 
  at 
  its 
  melting 
  point 
  be 
  saturated 
  with 
  water 
  at 
  one 
  atmosphere 
  

   pressure, 
  it 
  takes 
  up 
  about 
  1 
  per 
  cent, 
  enough 
  to 
  lower 
  its 
  melting 
  point 
  

   about 
  35°. 
  If 
  the 
  saturated 
  liquid 
  be 
  cooled 
  quickly 
  it 
  becomes 
  

   supersaturated; 
  the 
  molten 
  aqueous 
  glass 
  remains 
  liquid 
  until 
  cooled 
  

   several 
  degrees 
  below 
  its 
  melting 
  point. 
  First 
  a 
  few 
  bubbles 
  begin 
  to 
  

   form 
  within 
  the 
  glass; 
  then 
  suddenly 
  the 
  bubble 
  formation 
  becomes 
  

   rapid, 
  the 
  viscous 
  melt 
  swells 
  into 
  a 
  pumiceous 
  mass, 
  increasing 
  in 
  

   volume 
  many 
  times, 
  and 
  overflowing 
  the 
  crucible. 
  This 
  is 
  an 
  exam- 
  

   ple 
  of 
  the 
  second 
  boiling 
  point 
  at 
  atmospheric 
  pressure; 
  of 
  a 
  boiling, 
  

  

  3 
  Zeit 
  anorg. 
  Chem. 
  56: 
  173-208. 
  1908. 
  

  

  * 
  Sir 
  Herbert 
  Jackson, 
  Smithsonian 
  Report 
  for 
  1919, 
  p. 
  245. 
  

  

  s 
  MoREY 
  AND 
  Fenner. 
  Journ. 
  Am. 
  Chem. 
  Soc. 
  39: 
  1173-1229. 
  1917. 
  

  

  