﻿340 
  Fenner 
  — 
  Stability 
  Relations 
  of 
  Silica 
  Minerals. 
  

  

  From 
  the 
  standpoint 
  of 
  the 
  kinetic 
  theory, 
  the 
  question 
  of 
  

   the 
  formation 
  and 
  appearance 
  of 
  a 
  mineral 
  phase 
  may 
  be 
  

   looked 
  upon 
  as 
  a 
  function 
  of 
  two 
  variables 
  ; 
  first, 
  the 
  prob- 
  

   ability 
  of 
  the 
  requisite 
  number 
  of 
  moving 
  particles 
  coming 
  

   together 
  in 
  the 
  pattern 
  appropriate 
  to 
  the 
  structure 
  of 
  the 
  

   mineral 
  in 
  question, 
  and 
  second, 
  the 
  strength 
  of 
  the 
  bonds 
  by 
  

   which 
  the 
  particles 
  thus 
  assembled 
  are 
  held 
  together 
  under 
  the 
  

   impact 
  of 
  other 
  particles 
  or 
  under 
  the 
  stress 
  of 
  intramolecular 
  

   forces. 
  Both 
  of 
  these 
  are 
  again 
  functions 
  of 
  the 
  temperature 
  

   and 
  pressure, 
  but 
  vary 
  with 
  these 
  according 
  to 
  very 
  different 
  

   laws. 
  

  

  Under 
  this 
  conception, 
  when 
  a 
  number 
  of 
  substances 
  enter 
  

   into 
  a 
  reaction, 
  or 
  when 
  a 
  single 
  substance 
  is 
  subjected 
  to 
  a 
  

   change 
  of 
  conditions 
  under 
  which 
  it 
  is 
  no 
  longer 
  stable, 
  a 
  cer- 
  

   tain 
  assemblage 
  of 
  particles 
  characterized 
  by 
  a 
  simple* 
  pattern 
  

   may 
  be 
  formed 
  at 
  a 
  given 
  temperature 
  and 
  pressure 
  in 
  great 
  

   numbers, 
  while 
  a 
  second 
  assemblage 
  characterized 
  by 
  a 
  more 
  

   complex 
  pattern 
  is 
  formed 
  in 
  the 
  same 
  interval 
  in 
  much 
  less 
  

   quantity 
  ; 
  and 
  the 
  relative 
  velocity 
  of 
  formation 
  and 
  destruc 
  

   tion 
  of 
  the 
  two 
  may 
  be 
  such 
  that 
  the 
  phase 
  appropriate 
  to 
  the 
  

   lirst 
  pattern 
  will 
  appear 
  as 
  a 
  new 
  phase 
  of 
  the 
  system, 
  while 
  

   the 
  second 
  is 
  present 
  in 
  only 
  infinitesimal 
  quantity 
  ; 
  but 
  we 
  

   may 
  easily 
  suppose 
  that 
  each 
  group 
  of 
  the 
  second 
  phase, 
  when 
  

   once 
  formed, 
  is 
  relatively 
  indestructible 
  under 
  the 
  given 
  con- 
  

   ditions, 
  while 
  the 
  groups 
  of 
  the 
  first 
  kind 
  are 
  continually 
  

   breaking 
  down 
  and 
  reforming. 
  The 
  result 
  will 
  be 
  that 
  the 
  

   phase 
  which 
  appeared 
  with 
  such 
  rapidity 
  at 
  first 
  will 
  gradually 
  

   yield 
  place 
  to 
  the 
  second 
  phase, 
  which 
  will 
  then 
  be 
  the 
  stable 
  

   phase. 
  The 
  second 
  phase 
  may, 
  however, 
  under 
  some 
  condi- 
  

   tions, 
  be 
  formed 
  with 
  such 
  slowness 
  (on 
  account 
  of 
  the 
  small 
  

   number 
  of 
  free 
  particles 
  which 
  escape 
  from 
  the 
  phase 
  already 
  

   formed 
  or 
  because 
  of 
  the 
  complexity 
  of 
  its 
  pattern) 
  that 
  it 
  will 
  

   not 
  appear 
  in 
  recognizable 
  quantity, 
  and 
  the 
  unstable 
  phase 
  

   will 
  persist 
  indefinitely. 
  

  

  By 
  changing 
  the 
  temperature 
  and 
  pressure, 
  we 
  change 
  the 
  

   two 
  variables 
  according 
  to 
  different 
  laws, 
  and 
  the 
  results 
  

   obtained 
  as 
  regards 
  the 
  phases 
  which 
  first 
  appear 
  and 
  as 
  regards 
  

   the 
  phases 
  which 
  are 
  stable, 
  vary 
  accordingly. 
  At 
  transition 
  

   points 
  the 
  opposing 
  tendencies 
  are 
  in 
  equilibrium, 
  or 
  in 
  other 
  

  

  * 
  Simple 
  and 
  complex, 
  as 
  here 
  used, 
  refer 
  to 
  probability 
  or 
  improbability 
  

   of 
  the 
  particles 
  coming 
  together 
  in 
  the 
  manner 
  to 
  form 
  the 
  pattern 
  in 
  ques- 
  

   tion. 
  

  

  E. 
  J. 
  Strutt 
  (Proc. 
  Eoy. 
  Soc. 
  London, 
  ser. 
  A, 
  lxxxvii, 
  302-9) 
  has 
  made 
  

   some 
  interesting 
  calculations 
  on 
  this 
  sort 
  of 
  molecular 
  statistics. 
  He 
  con- 
  

   cludes 
  that 
  probably 
  a 
  single 
  collision 
  with 
  a 
  silver 
  surface 
  is 
  sufficient 
  to 
  

   destroy 
  a 
  molecule 
  of 
  3 
  , 
  but 
  that 
  a 
  molecule 
  of 
  active 
  N 
  must 
  collide 
  500 
  

   times 
  with 
  an 
  oxidized 
  Cu 
  surface 
  before 
  it 
  is 
  destroyed, 
  and 
  that 
  two 
  mole- 
  

   cules 
  of 
  3 
  at 
  100° 
  must 
  collide 
  6 
  x 
  10 
  n 
  times 
  before 
  the 
  right 
  sort 
  of 
  colli- 
  

   sion 
  occurs 
  for 
  the 
  formation 
  from 
  them 
  of 
  3 
  molecules 
  of 
  O 
  a 
  . 
  (Chem. 
  

   Abstracts, 
  vii, 
  6, 
  923, 
  1913.) 
  

  

  