﻿258 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  Dr. 
  Milton 
  Whitney 
  24 
  writes 
  : 
  

  

  The 
  investigations 
  of 
  this 
  bureau 
  28 
  show 
  that 
  the 
  absorptive 
  power 
  of 
  a 
  

   soil 
  resides 
  almost 
  wholly 
  in 
  the 
  ultra 
  clay 
  or 
  the 
  colloidal 
  material 
  in 
  the 
  soil. 
  

   This 
  ultra 
  clay 
  is 
  mainly 
  a 
  hydrous 
  silicate 
  of 
  alumina 
  and 
  iron, 
  with 
  hydrated 
  

   oxides 
  of 
  iron 
  and 
  probably 
  alumina 
  and 
  absorbed 
  calcium, 
  magnesium, 
  sodium, 
  

   and 
  potassium. 
  It 
  is 
  of 
  a 
  colloidal 
  nature, 
  and 
  can 
  be 
  separted 
  from 
  the 
  soil 
  

   in 
  the 
  form 
  of 
  minute 
  droplets 
  in 
  dilute 
  colloidal 
  solutions 
  which 
  form 
  into 
  

   colloidal 
  aggregates 
  when 
  the 
  concentration 
  is 
  somewhat 
  over 
  1 
  gram 
  per 
  

   1,000 
  c. 
  c. 
  

  

  The 
  chemical 
  analysis 
  of 
  the 
  soil 
  colloids 
  which 
  we 
  have 
  separated 
  shows 
  

   considerable 
  amounts 
  of 
  lime, 
  potash, 
  soda, 
  and 
  other 
  material 
  which 
  we 
  be- 
  

   lieve 
  to 
  be 
  absorbed 
  in 
  colloidal 
  condition. 
  We 
  believe 
  there 
  is 
  a 
  distribution 
  

   between 
  the 
  amount 
  so 
  absorbed 
  and 
  the 
  concentration 
  of 
  the 
  noncolloidal 
  

   part 
  of 
  the 
  solution. 
  We 
  believe 
  also 
  that 
  the 
  absorption 
  of 
  any 
  one 
  of 
  these 
  

   constituents 
  such 
  as 
  potassium 
  will 
  be 
  influenced 
  by 
  the 
  presence 
  of 
  other 
  salts 
  

   such 
  as 
  sodium 
  or 
  calcium. 
  Under 
  all 
  stable 
  conditions 
  there 
  will 
  be 
  an 
  equi- 
  

   librium 
  between 
  the 
  amount 
  absorbed 
  and 
  the 
  concentration 
  of 
  the 
  surrounding 
  

   liquid. 
  Sodium 
  chloride 
  lowers 
  the 
  absorption 
  of 
  potassium 
  chloride 
  and 
  

   calcium 
  salts 
  lower 
  the 
  absorption 
  of 
  potassium 
  chloride. 
  In 
  general, 
  soils 
  and 
  

   the 
  colloids 
  obtained 
  therefrom 
  absorb 
  the 
  basic 
  ions 
  much 
  more 
  readily 
  than 
  

   they 
  absorb 
  the 
  acid 
  ions. 
  

  

  According 
  to 
  Clarke 
  the 
  earth's 
  crust 
  contains 
  3.28 
  per 
  cent 
  of 
  Na 
  2 
  and 
  

   2.96 
  per 
  cent 
  of 
  K 
  2 
  0. 
  Thirty 
  soils 
  and 
  the 
  colloids 
  obtained 
  from 
  the 
  same 
  

   collected 
  by 
  this 
  bureau 
  contained 
  in 
  the 
  soil 
  1.59 
  per 
  cent 
  of 
  K 
  2 
  and 
  1.45 
  

   per 
  cent 
  in 
  the 
  colloids. 
  The 
  soils 
  contained 
  on 
  the 
  average 
  0.77 
  per 
  cent 
  of 
  

   Na 
  a 
  O 
  and 
  0.29 
  per 
  cent 
  in 
  the 
  colloids. 
  These 
  figures 
  show 
  very 
  clearly 
  the 
  

   greater 
  power 
  possessed 
  by 
  the 
  soil 
  colloids 
  to 
  absorb 
  and 
  to 
  hold 
  back 
  potash 
  

   than 
  they 
  have 
  for 
  sodium. 
  

  

  A 
  diffusion 
  experiment 
  with 
  a 
  soil 
  colloid 
  lasting 
  over 
  two 
  months 
  in 
  which 
  

   large 
  volumes 
  of 
  distilled 
  water 
  were 
  allowed 
  to 
  act 
  showed 
  a 
  loss 
  of 
  25 
  per 
  

   cent 
  of 
  total 
  K 
  2 
  and 
  over 
  95 
  per 
  cent 
  of 
  the 
  total 
  Na 
  2 
  0. 
  

  

  There 
  is 
  no 
  question 
  that 
  the 
  soil 
  colloids 
  are 
  able 
  to 
  absorb 
  NaCl. 
  This 
  

   is 
  shown 
  by 
  the 
  ancient 
  experiments 
  of 
  making 
  sea 
  water 
  drinkable 
  by 
  filter- 
  

   ing 
  through 
  soil 
  filters. 
  

  

  Data 
  and 
  references 
  examined 
  show 
  that 
  under 
  conditions 
  of 
  leaching 
  by 
  

   rain 
  water 
  where 
  equilibrium 
  conditions 
  are 
  changed 
  potassium 
  is 
  largely 
  re- 
  

   tained 
  by 
  the 
  soil 
  but 
  sodium 
  is 
  largely 
  leached 
  out. 
  

  

  M 
  Milton 
  Whitney, 
  Chief, 
  Bureau 
  of 
  Soils, 
  U. 
  S. 
  Department 
  of 
  Agriculture. 
  Personal 
  

   communication. 
  

  

  28 
  These 
  include 
  numerous 
  publications 
  containing 
  many 
  analyses 
  as 
  well 
  as 
  special 
  

   discussions, 
  but 
  as 
  in 
  all 
  agricultural 
  publications 
  the 
  constituents 
  that 
  most 
  concern 
  

   plant 
  life 
  receive 
  most 
  attention 
  and 
  data 
  relative 
  to 
  sodium 
  is 
  incidental. 
  The 
  following 
  

   may 
  be 
  cited 
  : 
  

  

  Cameron, 
  F. 
  K., 
  and 
  Bell, 
  J. 
  M., 
  " 
  The 
  mineral 
  constituents 
  of 
  the 
  soil 
  solution," 
  U. 
  S. 
  

   Dept. 
  Agr., 
  Bur. 
  Soils, 
  Bull. 
  30, 
  1905. 
  

  

  Cameron, 
  F. 
  K., 
  and 
  Patten, 
  H. 
  B., 
  " 
  The 
  distribution 
  of 
  solute 
  between 
  water 
  and 
  

   soil," 
  Jour, 
  of 
  Phys. 
  Chem., 
  vol. 
  II, 
  pp. 
  581-93, 
  1907. 
  

  

  " 
  Patten, 
  H. 
  E„ 
  " 
  Some 
  surface 
  factors 
  affecting 
  distribution," 
  Trans. 
  Anier. 
  Electrochem. 
  

   Soc, 
  vol. 
  10, 
  pp. 
  67-74, 
  1906. 
  

  

  Patten, 
  H. 
  E., 
  and 
  Gallagher, 
  F. 
  E., 
  " 
  Absorption 
  of 
  vapors 
  and 
  gases 
  by 
  soils," 
  U. 
  S. 
  

   Dept. 
  Agr., 
  Bur. 
  Soils, 
  Bull. 
  51, 
  1908. 
  

  

  Patten, 
  H. 
  E., 
  and 
  Waggaman, 
  W. 
  H., 
  " 
  Absorption 
  by 
  soils," 
  U. 
  S. 
  Dept. 
  Agr., 
  Bur. 
  

   Soils, 
  Bull. 
  52, 
  1908. 
  

  

  Schreiner, 
  Oswald, 
  and 
  Failyer, 
  G. 
  H., 
  " 
  The 
  absorption 
  of 
  phosphates 
  and 
  potassium 
  

   by 
  soils," 
  TJ. 
  S. 
  Dept. 
  Agr., 
  Bur. 
  of 
  Soils, 
  Bull. 
  32, 
  1906. 
  

  

  Parker, 
  E. 
  G., 
  " 
  Selective 
  adsorption 
  by 
  soils," 
  Jour, 
  of 
  Agr. 
  Research, 
  Dept. 
  Agr., 
  

   vol. 
  I, 
  no. 
  3 
  (Dec. 
  10, 
  1913). 
  

  

  