﻿Mack 
  and 
  Hulett 
  — 
  Water 
  Content 
  of 
  Coal. 
  97 
  

  

  of 
  fungus 
  bacterial 
  ferments 
  to 
  so-called 
  "humus" 
  substances, 
  

   while 
  at 
  the 
  same 
  time, 
  but 
  more 
  slowly, 
  the 
  wax 
  and 
  resin- 
  

   like 
  matter 
  decomposes, 
  giving 
  rise 
  to 
  hydrocarbons. 
  The 
  

   microscopic 
  examination 
  of 
  peat 
  and 
  coals 
  by 
  Thiessen 
  (1. 
  c.) 
  

   has 
  revealed 
  a 
  fine 
  spongy 
  structure 
  made 
  up 
  of 
  a 
  mat 
  of 
  resin 
  

   granules, 
  spores, 
  and 
  pollen 
  exines, 
  humic 
  and 
  woody 
  remains. 
  

   The 
  original 
  plant 
  cells 
  having 
  been 
  collapsed, 
  there 
  remains 
  a 
  

   mass 
  which 
  has 
  passed 
  through 
  various 
  colloidal 
  stages. 
  

  

  In 
  the 
  first 
  stages 
  peat 
  may 
  be 
  largely 
  a 
  hydrosol. 
  Accom- 
  

   panying 
  the 
  slow 
  chemical 
  changes, 
  reactions 
  which 
  take 
  place 
  

   of 
  themselves 
  with 
  a 
  decrease 
  in 
  free 
  energy, 
  there 
  is 
  an 
  elimi- 
  

   nation 
  of 
  water, 
  carbon 
  dioxide, 
  methane, 
  etc., 
  and 
  the 
  mass 
  

   becomes 
  more 
  largely 
  a 
  hydrogel 
  which 
  by 
  the 
  further 
  loss 
  of 
  

   water 
  and 
  volatile 
  products 
  can 
  harden 
  to 
  bituminous 
  coal. 
  

   The 
  chemical 
  reactions 
  involved 
  are 
  generally 
  of 
  the 
  nature 
  of 
  

   the 
  formation 
  of 
  small 
  molecules 
  from 
  larger 
  ones, 
  a 
  change 
  

   almost 
  invariably 
  accompanied 
  by 
  an 
  increase 
  in 
  volume, 
  and 
  

   the 
  effect 
  of 
  pressure 
  in 
  such 
  cases 
  is 
  rather 
  to 
  oppose 
  than 
  aid 
  

   the 
  chemical 
  reactions. 
  

  

  The 
  foregoing 
  considerations 
  indicate 
  the 
  importance 
  of 
  the 
  

   " 
  water 
  content 
  of 
  a 
  coal 
  " 
  in 
  questions 
  concerning 
  its 
  present 
  

   status 
  and 
  constitution. 
  In 
  addition 
  to 
  the 
  water 
  originally 
  

   present, 
  the 
  slow 
  chemical 
  reactions 
  continually 
  form 
  water 
  as 
  

   one 
  of 
  the 
  decomposition 
  products, 
  and 
  consequently 
  there 
  

   must 
  be 
  an 
  elimination 
  of 
  water 
  from 
  the 
  coal 
  beds 
  during 
  the 
  

   slow- 
  transformations 
  from 
  peat 
  to 
  anthracite. 
  Nevertheless 
  

   coals 
  are 
  normally 
  dry. 
  We 
  may 
  dismiss 
  any 
  idea 
  that 
  hydro- 
  

   carbons, 
  resinous 
  bodies, 
  waxes, 
  carbon 
  residues 
  and 
  humus 
  

   substances 
  combine 
  with 
  water 
  in 
  any 
  such 
  way 
  as 
  water 
  of 
  crys- 
  

   tallization, 
  but 
  if 
  these 
  substances 
  form 
  a 
  colloidal 
  solution 
  with 
  

   water 
  as 
  one 
  of 
  the 
  phases 
  the 
  matter 
  is 
  entirely 
  comprehensible. 
  

   The 
  organic 
  substances 
  from 
  peat 
  to 
  anthracite 
  are 
  in 
  an 
  ex- 
  

   ceedingly 
  finely 
  divided 
  state 
  and 
  present 
  an 
  enormous 
  surface 
  

   for 
  the 
  water 
  phase. 
  It 
  is 
  generally 
  recognized 
  that 
  at 
  the 
  

   surface 
  of 
  heterogenous 
  phases 
  there 
  is 
  a 
  concentration 
  layer, 
  

   and 
  in 
  the 
  case 
  of 
  a 
  colloid 
  the 
  total 
  surface 
  is 
  so 
  great 
  that 
  the 
  

   actual 
  amount 
  of 
  water 
  concentrated 
  in 
  the 
  film 
  may 
  be 
  a 
  con- 
  

   siderable 
  percent 
  of 
  the 
  total 
  mass. 
  Some 
  interesting 
  estimates 
  

   have 
  been 
  made 
  of 
  the 
  thickness 
  and 
  density 
  of 
  such 
  films. 
  

   For 
  the 
  thickness 
  Lewis* 
  assigns 
  5 
  X 
  10~ 
  6 
  cm. 
  

  

  This 
  seems 
  rather 
  large, 
  for 
  taking 
  the 
  diameter 
  of 
  the 
  water 
  

   molecule 
  as 
  0*2 
  - 
  1*0 
  X 
  10" 
  8 
  cm.,f 
  we 
  have 
  a 
  film 
  500-2500 
  

   times 
  as 
  thick 
  as 
  a 
  water 
  molecule. 
  A 
  more 
  reasonable 
  

   figure 
  is 
  that 
  of 
  Taylor,;); 
  # 
  6 
  X 
  10" 
  8 
  cm. 
  Sutherland 
  gives 
  

  

  * 
  W. 
  C. 
  McC. 
  Lewis, 
  On 
  the 
  Nature 
  of 
  the 
  Transition 
  Layer 
  between 
  Two 
  

   Adjacent 
  Phases, 
  Phil. 
  Mag., 
  xx, 
  p. 
  509, 
  1910. 
  

  

  fW. 
  Sutherland, 
  The 
  Molecular 
  Constitution 
  of 
  Water, 
  Phil. 
  Mag., 
  Nov. 
  

   1900, 
  p. 
  473 
  ; 
  and 
  W. 
  Ostwald, 
  Grundriss 
  der 
  Kolloidchemie, 
  1912, 
  p. 
  32. 
  

  

  {W. 
  W. 
  Taylor, 
  The 
  Chemistry 
  of 
  Colloids, 
  1915, 
  p. 
  225. 
  

  

  