﻿152 
  

  

  Mr. 
  J. 
  Gray. 
  

  

  Whereas 
  in 
  normal 
  sea 
  water 
  the 
  cerium 
  produces 
  its 
  effect 
  in 
  less 
  than 
  

   30 
  seconds, 
  in 
  slightly 
  acid 
  sea 
  water 
  the 
  reaction 
  is 
  delayed, 
  and 
  it 
  may 
  be 
  

   several 
  minutes 
  before 
  incomplete 
  precipitation 
  is 
  apparent. 
  

  

  Three 
  drops 
  of 
  undiluted 
  sperm 
  were 
  placed 
  in 
  20 
  c.c. 
  of 
  the 
  following 
  

   solutions, 
  and 
  after 
  15 
  minutes 
  were 
  examined 
  for 
  movement, 
  and 
  tested 
  by 
  

   1 
  cerium 
  (cone. 
  0-001 
  M). 
  

  

  In 
  this 
  particular 
  experiment 
  the 
  flocculation 
  in 
  the 
  solution 
  containing 
  

   0*14 
  c.c. 
  N/10 
  HC1 
  was 
  most 
  marked, 
  and 
  more 
  intense 
  than 
  normal. 
  The 
  

   experiments 
  illustrate 
  very 
  clearly 
  the 
  intense 
  effects 
  of 
  very 
  small 
  changes 
  of 
  

   hydrogen 
  ion 
  concentration. 
  A 
  very 
  slight 
  change 
  beyond 
  the 
  critical 
  value 
  

   stops 
  both 
  movement 
  of 
  spermatozoa 
  and 
  their 
  power 
  of 
  being 
  agglutinated 
  

   by 
  cerium. 
  Both 
  these 
  phenomena 
  are 
  reversible 
  by 
  raising 
  the 
  P 
  H 
  of 
  the 
  

   solution 
  to 
  a 
  value 
  of 
  about 
  6 
  - 
  5. 
  

  

  In 
  the 
  following 
  experiment 
  the 
  P 
  H 
  of 
  several 
  samples 
  (20 
  c.c. 
  each) 
  of 
  the 
  

   same 
  sperm 
  suspension 
  was 
  lowered 
  to 
  the 
  values 
  shown 
  in 
  column 
  1 
  ; 
  after 
  

   20 
  minutes 
  each 
  sample 
  was 
  divided 
  into 
  two 
  equal 
  portions, 
  and 
  to 
  one 
  

   portion 
  an 
  equal 
  bulk 
  of 
  sea 
  water 
  was 
  added. 
  To 
  each 
  tube 
  sufficient 
  cerium 
  

   chloride 
  was 
  added 
  to 
  give 
  a 
  concentration 
  of 
  0*00125 
  M 
  Ce"*. 
  After 
  

   15 
  minutes 
  the 
  degree 
  of 
  agglutination 
  was 
  noted. 
  

  

  Table 
  VII. 
  

  

  I. 
  

  

  Ph 
  of 
  original 
  20 
  c.c. 
  

   of 
  acid 
  suspensions. 
  

  

  II. 
  

  

  Ph 
  of 
  portions 
  of 
  

   original 
  solution 
  after 
  

   dilution 
  with 
  

   sea 
  water. 
  

  

  I. 
  

  

  Degree 
  of 
  agglut. 
  

   by 
  Ce"' 
  in 
  original 
  

   suspensions. 
  

  

  II. 
  

  

  Degree 
  of 
  agglut. 
  

   by 
  Ce 
  - 
  " 
  in 
  diluted 
  

   suspension. 
  

  

  7-6 
  

  

  7-7 
  

  

  + 
  + 
  + 
  

  

  + 
  + 
  + 
  

  

  7 
  3 
  

  

  7 
  5 
  

  

  + 
  + 
  © 
  

  

  + 
  + 
  + 
  

  

  6-5 
  

  

  7 
  3 
  

  

  + 
  © 
  

  

  + 
  + 
  

  

  6-2 
  

  

  6-9 
  

  

  © 
  

  

  + 
  + 
  

  

  5-9 
  

  

  6-6 
  

  

  

  

  + 
  

  

  5-6 
  

  

  6 
  4 
  

  

  

  

  + 
  

  

  5 
  3 
  

  

  6-3 
  

  

  

  

  + 
  

  

  The 
  reversal 
  of 
  the 
  effect 
  of 
  cerium 
  by 
  sodium 
  citrate, 
  and 
  the 
  dependence 
  

   of 
  the 
  agglutination 
  by 
  cerium 
  upon 
  the 
  hydroxyl 
  ion 
  concentration 
  of 
  the 
  

   suspension, 
  are 
  exactly 
  paralleled 
  by 
  the 
  effect 
  of 
  these 
  ions 
  upon 
  a 
  suspension 
  

   of 
  albumen 
  or 
  globulin. 
  In 
  the 
  latter 
  case, 
  there 
  is 
  no 
  cause 
  to 
  doubt 
  the 
  

   conclusion 
  that 
  the 
  degree 
  of 
  dispersal 
  or 
  agglutination 
  caused 
  by 
  acids, 
  

   alkalis, 
  or 
  trivalent 
  ions 
  is 
  dependent 
  upon 
  the 
  surface 
  charge 
  on 
  the 
  particle. 
  

   The 
  point 
  of 
  maximum 
  flocculation 
  coincides 
  with 
  the 
  reduction 
  of 
  the 
  

   surface 
  charge 
  to 
  a 
  minimum 
  (in 
  other 
  words, 
  at 
  the 
  isoelectric 
  point) 
  ; 
  in 
  

   acid 
  solutions 
  the 
  colloid 
  particle 
  is 
  positively 
  charged 
  so 
  that 
  the 
  positively 
  

  

  