﻿Clarhe 
  and 
  Steiger 
  — 
  Experhnents 
  with 
  Pectolite^ 
  etc. 
  245 
  

  

  Art. 
  XXYII. 
  — 
  Experiments 
  relative 
  to 
  the 
  Constitution 
  of 
  

   Pectolite, 
  Pyrophyllite^ 
  Calamine, 
  and 
  Analcite 
  / 
  bj 
  F. 
  W. 
  

   Claeke 
  and 
  George 
  Steiger. 
  

  

  In 
  a 
  series 
  of 
  investigations 
  by 
  Clarke 
  and 
  Schneider 
  which 
  

   were 
  carried 
  out 
  in 
  the 
  laboratory 
  of 
  the 
  United 
  States 
  Geo- 
  

   logical 
  Survey 
  between 
  1889 
  and 
  1892,^ 
  a 
  number 
  of 
  reac- 
  

   tions 
  were 
  examined 
  which 
  shed 
  some 
  light 
  upon 
  the 
  constitu- 
  

   tion 
  of 
  several 
  natural 
  silicates. 
  The 
  work 
  then 
  begun 
  was 
  

   unfortunately 
  interrupted 
  for 
  several 
  years; 
  but 
  it 
  is 
  now 
  

   resumed, 
  with 
  the 
  hope 
  that 
  it 
  may 
  be 
  pushed 
  considerably 
  

   further. 
  

  

  Two 
  of 
  the 
  reactions 
  studied 
  by 
  Clarke 
  and 
  Schneider 
  were 
  

   of 
  peculiar 
  interest. 
  First, 
  in 
  the 
  case 
  of 
  talc, 
  it 
  was 
  found 
  

   that 
  one-fourth 
  of 
  the 
  silica 
  could 
  be 
  liberated 
  by 
  ignition 
  ; 
  

   and 
  that 
  the 
  fraction 
  thus 
  set 
  free 
  was 
  measurable 
  by 
  solution 
  

   in 
  aqueous 
  sodium 
  carbonate. 
  This 
  reaction 
  suggests 
  that 
  

   other 
  acid 
  metasilicates 
  may 
  behave 
  in 
  a 
  similar 
  way, 
  and 
  that 
  

   we 
  perhaps 
  have 
  a 
  means 
  of 
  discrimination 
  between 
  such 
  salts 
  

   and 
  other 
  compounds 
  which 
  simulate 
  them. 
  In 
  other 
  words, 
  

   an 
  acid 
  metasilicate 
  may 
  be 
  experimentally 
  distinguished 
  from 
  

   a 
  pseudo-metasilicate 
  by 
  the 
  way 
  in 
  which 
  it 
  splits 
  up 
  when 
  

   ignited. 
  Evidence 
  bearing 
  upon 
  this 
  supposition 
  will 
  be 
  found 
  

   in 
  the 
  present 
  paper. 
  

  

  The 
  second 
  of 
  the 
  reactions 
  just 
  referred 
  to 
  is 
  that 
  between 
  

   dry 
  ammonium 
  chloride, 
  at 
  its 
  temperature 
  of 
  dissociation, 
  and 
  

   various 
  silicates.f 
  This 
  involves, 
  in 
  part 
  at 
  least, 
  the 
  action 
  of 
  

   dry 
  gaseous 
  hydrochloric 
  acid 
  upon 
  the 
  compounds 
  which 
  are 
  

   studied 
  ; 
  and 
  different 
  minerals 
  are 
  very 
  differently 
  attacked. 
  

   Some 
  are 
  almost 
  completely 
  decomposed, 
  others 
  are 
  affected 
  

   but 
  slightly 
  ; 
  and 
  here 
  again 
  there 
  seems 
  to 
  be 
  a 
  method 
  of 
  

   diagnosis 
  which 
  deserves 
  further 
  attention. 
  Both 
  reactions 
  

   suggest 
  the 
  main 
  purpose 
  of 
  the 
  investigation 
  ; 
  which 
  is, 
  the 
  

   fractional 
  analysis 
  of 
  silicates 
  by 
  means 
  of 
  various 
  reagents, 
  in 
  

   order 
  to 
  gain 
  evidence 
  bearing 
  upon 
  their 
  chemical 
  structure. 
  

   The 
  evidence 
  at 
  least 
  is 
  of 
  value, 
  whether 
  the 
  interpretation 
  

   of 
  it 
  be 
  right 
  or 
  wrong. 
  Each 
  fact 
  helps 
  to 
  the 
  ultimate 
  solu- 
  

   tion 
  of 
  the 
  central 
  problem, 
  the 
  problem 
  of 
  constitution. 
  

  

  Pectolite. 
  

  

  The 
  pectolite 
  which 
  was 
  chosen 
  for 
  examination 
  was 
  the 
  

   well-known 
  radiated 
  variety 
  from 
  Bergen 
  Hill, 
  N. 
  J. 
  The 
  

   mineral 
  was 
  in 
  long 
  white 
  needles, 
  and 
  apparently 
  quite 
  pure 
  ; 
  

  

  * 
  This 
  Journal, 
  III, 
  vol. 
  xl, 
  pp. 
  303, 
  405, 
  452 
  ; 
  vol. 
  xlii, 
  p. 
  242 
  ; 
  vol. 
  xliii, 
  p. 
  378. 
  

   f 
  Bulletin 
  No. 
  113, 
  U. 
  S. 
  Geological 
  Survey, 
  p. 
  34. 
  

  

  