﻿F. 
  P. 
  Dunnington 
  — 
  Distribution 
  of 
  Titanic 
  Oxide. 
  491 
  

  

  and 
  become 
  permanent 
  members 
  of 
  the 
  solar 
  system, 
  will 
  as 
  a 
  

   rule 
  (but 
  with 
  exceptions) 
  move 
  in 
  orbits 
  of 
  moderate 
  inclina- 
  

   tion 
  to 
  the 
  ecliptic, 
  and 
  with 
  direct 
  motions. 
  

  

  We 
  know 
  as 
  a 
  fact 
  that 
  most 
  short 
  period 
  comets 
  do 
  move 
  

   in 
  orbits 
  having 
  small 
  inclinations 
  and 
  direct 
  motions, 
  while 
  

   long 
  period 
  and 
  parabolic 
  comets 
  move 
  at 
  all 
  possible 
  inclina- 
  

   tions 
  to 
  the 
  ecliptic. 
  If 
  the 
  short 
  period 
  comets 
  have 
  been 
  

   changed 
  by 
  Jupiter 
  and 
  other 
  planets 
  from 
  parabolic 
  orbits, 
  

   the 
  preceding 
  investigation 
  shows 
  why 
  their 
  orbits 
  have 
  now 
  

   small 
  inclinations 
  to 
  the 
  ecliptic, 
  and 
  the 
  comets 
  themselves 
  

   have 
  direct 
  motions. 
  

  

  Art. 
  LIU. 
  — 
  Distribution 
  of 
  Titanic 
  Oxide 
  upon 
  the 
  sur- 
  

   face 
  of 
  the 
  Earth 
  ; 
  by 
  F. 
  P. 
  Dunnington, 
  University 
  of 
  

   Virginia, 
  Charlottesville, 
  Ya. 
  

  

  At 
  the 
  Ann 
  Arbor 
  meeting 
  of 
  the 
  Association 
  for 
  the 
  

   Advancement 
  of 
  Science 
  in 
  1885, 
  I 
  read 
  a 
  short 
  paper* 
  which 
  

   considered 
  the 
  occurrence 
  of 
  titanic 
  oxide 
  in 
  considerable 
  

   amount 
  in 
  certain 
  soil 
  of 
  Albemarle 
  Co., 
  Ya.; 
  and 
  in 
  an 
  article 
  

   publishedf 
  in 
  1888, 
  by 
  Mr. 
  J. 
  F. 
  McCaleb 
  and 
  myself, 
  we 
  

   presented 
  estimations 
  of 
  this 
  substance 
  in 
  sixteen 
  specimens 
  of 
  

   soil 
  from 
  scattered 
  points 
  of 
  the 
  United 
  States. 
  

  

  In 
  view 
  of 
  the 
  unfrequent 
  mention 
  of 
  this 
  element 
  as 
  a 
  con- 
  

   stituent 
  of 
  rocks 
  and 
  the 
  very 
  rare 
  mention 
  of 
  its 
  occurrence 
  

   in 
  soils, 
  I 
  have 
  endeavored 
  to 
  secure 
  samples 
  of 
  soil 
  and 
  some 
  

   rocks 
  from 
  points 
  scattered 
  over 
  the 
  earth's 
  surface 
  ; 
  and, 
  includ- 
  

   ing 
  the 
  before 
  mentioned 
  sixteen, 
  I 
  herewith 
  present 
  the 
  

   results 
  of 
  examining 
  eighty 
  specimens. 
  

  

  The 
  method 
  employed 
  in 
  the 
  recent 
  determinations 
  is 
  the 
  

   following 
  : 
  weigh 
  into 
  a 
  platinum 
  crucible 
  one 
  gram 
  of 
  the 
  

   powdered 
  sample, 
  ignite, 
  again 
  weigh, 
  then 
  moisten 
  with 
  water 
  

   and 
  add 
  2 
  or 
  3 
  c.c. 
  of 
  hydrofluoric 
  acid, 
  J 
  gradually 
  heat 
  to 
  

   dryness, 
  add 
  about 
  7 
  grams 
  of 
  sodium 
  acid 
  sulphate, 
  gradu- 
  

   ally 
  heat 
  to 
  low 
  redness 
  for 
  1 
  or 
  2 
  hours, 
  cool, 
  digest 
  in 
  

   5 
  per 
  cent 
  diluted 
  sulphuric 
  acid 
  for 
  several 
  hours, 
  filter, 
  to 
  

   filtrate§ 
  add 
  about 
  1 
  c.c. 
  of 
  hydrogen 
  peroxide 
  solution 
  and 
  

   compare 
  the 
  color 
  so 
  produced 
  with 
  one 
  similarly 
  obtained 
  

   from 
  a 
  standard 
  solution 
  of 
  titanic 
  oxide. 
  

  

  *Proc. 
  A. 
  A. 
  A. 
  S., 
  xxxiv, 
  182. 
  \ 
  American 
  Chem. 
  Jour., 
  x, 
  36. 
  

  

  % 
  This 
  acid 
  was 
  used 
  before 
  seeing 
  the 
  article 
  of 
  Dr. 
  Noyes 
  in 
  Jour. 
  Anal. 
  

   Chem 
  , 
  v, 
  39. 
  

  

  § 
  Method 
  of 
  A. 
  Weller: 
  Berichte 
  d. 
  deutsch. 
  chem. 
  G-esell., 
  xv, 
  2592. 
  

  

  