﻿458 
  Carey: 
  A 
  starch 
  gel 
  

  

  it 
  partly 
  irreversible 
  at 
  the 
  temperature 
  of 
  boiling 
  water. 
  The 
  

   higher 
  the 
  concentration 
  of 
  the 
  sol 
  the 
  quicker 
  the 
  setting 
  takes 
  

   place, 
  so 
  that 
  the 
  starch 
  used 
  in 
  this 
  work 
  was 
  practically 
  set 
  

   when 
  removed 
  from 
  the 
  autoclave. 
  This 
  agrees 
  with 
  examples 
  

   given 
  by 
  Meyer 
  (5), 
  showing 
  that 
  the 
  setting 
  of 
  a 
  sol 
  at 
  a 
  certain 
  

   temperature 
  is 
  more 
  rapid 
  the 
  higher 
  the 
  concentration. 
  

  

  Maquenne 
  and 
  Roux 
  (3, 
  4) 
  found 
  that 
  ordinary 
  starch 
  p^ste 
  

   contained 
  80-90 
  per 
  cent 
  aniylocellulose 
  and 
  the 
  rest 
  amylopectin. 
  

   This 
  they 
  concluded 
  from 
  the 
  results 
  of 
  iodine 
  and 
  saccharifying 
  

   tests. 
  They 
  considered 
  the 
  geling 
  properties 
  of 
  starch 
  were 
  due 
  

   to 
  the 
  amylopectin. 
  The 
  aniylocellulose 
  was 
  partly 
  soluble 
  

   in 
  boiling 
  water 
  and 
  completely 
  liquified, 
  according 
  to 
  Roux 
  (6), 
  

   in 
  excess 
  of 
  water 
  at 
  150° 
  C. 
  and 
  had 
  no 
  geling 
  power. 
  At 
  90° 
  C. 
  

   18 
  per 
  cent 
  of 
  the 
  gel 
  goes 
  into 
  solution, 
  according 
  to 
  the 
  work 
  

   of 
  the 
  writer. 
  It 
  may 
  be 
  that 
  this 
  is 
  all 
  amylopectin 
  of 
  

   Maquenne. 
  

  

  Taylor 
  (7, 
  p. 
  127) 
  mentions 
  the 
  fact 
  that 
  starch 
  sols 
  are 
  like 
  

   silicic 
  acid 
  sols 
  in 
  their 
  behavior, 
  but 
  does 
  not 
  state 
  in 
  what 
  manner. 
  

   The 
  gel, 
  however, 
  seems 
  to 
  simulate 
  more 
  closely 
  the 
  elastic 
  gels 
  

   of 
  agar 
  and 
  gelatine 
  than 
  the 
  rigid 
  one 
  of 
  silicic 
  acid. 
  Even 
  these 
  

   elastic 
  gels 
  have 
  to 
  be 
  heated 
  to 
  a 
  higher 
  temperature 
  than 
  that 
  

   at 
  which 
  gelation 
  occurred 
  before 
  they 
  will 
  again 
  become 
  sols. 
  

   The 
  geling 
  and 
  melting 
  points, 
  in 
  the 
  case 
  of 
  gelatine, 
  however, 
  

   vary 
  with 
  the 
  concentration 
  and 
  are 
  also 
  affected 
  by 
  organic 
  

   substances 
  and 
  salts. 
  

  

  The 
  general 
  averages 
  of 
  the 
  determinations 
  given 
  in 
  the 
  tables 
  

   a:t 
  the 
  end 
  of 
  this 
  paper, 
  under 
  Appendix, 
  are 
  shown 
  in 
  Table 
  II, 
  

   below. 
  In 
  the 
  work 
  carried 
  on 
  by 
  the 
  writer, 
  with 
  the 
  range 
  of 
  

   temperatures 
  used, 
  the 
  higher 
  the 
  temperature 
  the 
  more 
  water 
  was 
  

   absorbed. 
  Thus 
  it 
  is 
  evident 
  from 
  the 
  following 
  figures 
  there 
  was 
  

   no 
  maximum 
  point 
  above 
  which 
  the 
  adsorption 
  decreased, 
  at 
  least 
  

   up 
  to 
  90"" 
  C. 
  For 
  at 
  8.5-10.5'' 
  C. 
  the 
  average 
  adsorption 
  is 
  0.864 
  

  

  dry 
  

  

  C. 
  it 
  has 
  risen 
  to 
  

  

  3.713 
  grams 
  of 
  water, 
  an 
  increase 
  of 
  over 
  four 
  times 
  that 
  at 
  about 
  

   8° 
  C. 
  As 
  the 
  temperature 
  was 
  raised 
  the 
  size 
  of 
  the 
  strips 
  increased 
  

   upon 
  swelling; 
  they 
  became 
  softer 
  and 
  of 
  a 
  less 
  tough 
  and 
  firm 
  con- 
  

   sistency. 
  In 
  some 
  of 
  the 
  solutions 
  at 
  high 
  temperatures 
  there 
  were 
  

   minute 
  shiny 
  particles, 
  the 
  nature 
  of 
  which 
  was 
  not 
  determined. 
  

  

  