﻿Mack 
  and 
  Hulett 
  — 
  Water 
  Content 
  of 
  Coal. 
  101 
  

  

  These 
  considerations 
  gave 
  us 
  a 
  fairly 
  definite 
  conception 
  of 
  

   the 
  water 
  content 
  of 
  coal 
  and 
  also 
  indicated 
  the 
  line 
  of 
  attack 
  

   which 
  promised 
  a 
  successful 
  solution 
  of 
  the 
  problem 
  of 
  deter- 
  

   mining 
  the 
  water. 
  "We 
  cannot 
  determine 
  the 
  water 
  content 
  

   of 
  a 
  sample 
  of 
  coal 
  by 
  vacuum 
  desiccation 
  at 
  ordinary 
  temper- 
  

   atures 
  on 
  account 
  of 
  the 
  difficulty 
  of 
  maintaining 
  a 
  sufficiently 
  

   low 
  vapor 
  pressure 
  in 
  the 
  desiccator 
  and 
  especially 
  on 
  account 
  

   of 
  the 
  slowness 
  of 
  the 
  escape 
  of 
  the 
  last 
  but 
  considerable 
  part 
  of 
  

   the 
  water 
  from 
  the 
  coal. 
  If, 
  however, 
  we 
  keep 
  the 
  vapor 
  pres- 
  

   sure 
  low 
  but 
  heat 
  the 
  coal, 
  we 
  increase 
  the 
  vapor 
  pressure 
  of 
  the 
  

   film 
  of 
  adsorbed 
  water, 
  and 
  so 
  may 
  make 
  the 
  time 
  required 
  for 
  

   its 
  removal 
  as 
  short 
  as 
  we 
  wish. 
  Oxygen 
  must 
  of 
  course 
  be 
  ex- 
  

   cluded 
  and 
  in 
  a 
  vacuum 
  the 
  rate 
  of 
  loss 
  of 
  water 
  is 
  somewhat 
  

   greater. 
  We 
  have 
  devised 
  several 
  satisfactory 
  methods 
  for 
  

   accomplishing 
  the 
  desired 
  results, 
  but 
  have 
  studied 
  particularly 
  

   some 
  questions 
  raised, 
  by 
  such 
  procedures. 
  

  

  Our 
  preliminary 
  experiments, 
  Table 
  I, 
  showed 
  that 
  vacuum 
  

   desiccation, 
  with 
  reagents 
  which 
  maintained 
  the 
  vapor 
  pressure 
  

   of 
  water 
  at 
  about 
  'Ol™ 
  1111 
  , 
  still 
  left 
  very 
  considerable 
  portions 
  of 
  

   the 
  water 
  in 
  the 
  coal, 
  which 
  however 
  came 
  off 
  rapidly 
  when 
  the 
  

   coal 
  was 
  raised 
  some 
  100° 
  in 
  temperature, 
  and 
  while 
  it 
  was 
  con- 
  

   cluded 
  that 
  this 
  probably 
  removed 
  most 
  of 
  the 
  water 
  from 
  the 
  

   coal 
  we 
  recognized 
  the 
  possibility 
  that 
  some 
  water 
  could 
  be 
  

   retained 
  until 
  a 
  temperature 
  approaching 
  the 
  critical 
  tempera- 
  

   ture 
  of 
  water 
  was 
  employed 
  — 
  but 
  it 
  was 
  necessary 
  to 
  consider 
  

   another 
  result 
  of 
  heating 
  coal. 
  Coal 
  is 
  a 
  conglomerate 
  of 
  con- 
  

   stituents, 
  some 
  of 
  which 
  at 
  least 
  are 
  decomposing 
  as 
  outlined 
  

   above, 
  and 
  forming 
  among 
  other 
  products 
  water. 
  The 
  rate 
  of 
  

   these 
  reactions 
  at 
  ordinary 
  temperatures 
  is 
  immeasurably 
  slow, 
  

   but 
  Bergius' 
  work 
  shows 
  that 
  the 
  rate 
  doubles 
  for 
  each 
  increase 
  

   of 
  10°. 
  Therefore 
  we 
  must 
  avoid 
  the 
  conditions 
  of 
  tempera- 
  

   ture 
  and 
  time 
  at 
  which 
  the 
  reactions 
  are 
  capable 
  of 
  yielding 
  

   measurable 
  amounts 
  of 
  water. 
  The 
  problem 
  was 
  then 
  to 
  find 
  

   out 
  whether 
  we 
  could 
  heat 
  the 
  coal 
  for 
  a 
  "temperature-time" 
  

   interval 
  such 
  that 
  the 
  water 
  film 
  could 
  be 
  decreased 
  to 
  negligi- 
  

   ble 
  amount, 
  without 
  accelerating 
  the 
  decomposition 
  reactions 
  

   of 
  coal 
  substances 
  to 
  an 
  extent 
  such 
  that 
  a 
  measurable 
  amount 
  

   of 
  water 
  would 
  be 
  formed. 
  

  

  For 
  the 
  question 
  of 
  the 
  preliminary 
  decomposition 
  of 
  coal 
  sub- 
  

   stances 
  we 
  have 
  some 
  data 
  from 
  the 
  work 
  of 
  H. 
  C. 
  Porter 
  and 
  

   Gr. 
  B. 
  Taylor.* 
  These 
  workers 
  determined 
  the 
  amount 
  and 
  

   nature 
  of 
  the 
  volatile 
  products 
  obtained 
  from 
  coal 
  at 
  250°, 
  350° 
  

   and 
  450° 
  when 
  maintained 
  at 
  these 
  temperatures 
  from 
  7 
  to 
  13 
  

   hours 
  and 
  at 
  very 
  low 
  pressure. 
  The 
  following 
  table 
  shows 
  

   some 
  of 
  the 
  results 
  which 
  are 
  of 
  interest 
  here. 
  Four 
  types 
  of 
  

   coal 
  were 
  used. 
  

  

  *Proc. 
  Amer. 
  Gas. 
  Assn., 
  vol. 
  ix, 
  p. 
  234, 
  1914. 
  

  

  