﻿372 
  On 
  the 
  Action 
  of 
  Heat 
  on 
  Saline 
  Solutions. 
  [Apr. 
  22, 
  

  

  April 
  22, 
  1875. 
  

  

  JOHN 
  EVANS, 
  Esq., 
  Vice-President, 
  in 
  the 
  Chair. 
  

  

  The 
  Eight 
  Hon. 
  Eussell 
  Gurney, 
  Q.C., 
  whose 
  certificate 
  had 
  been 
  sus- 
  

   pended, 
  as 
  prescribed 
  by 
  the 
  Statutes, 
  was 
  elected 
  a 
  Eellow 
  of 
  the 
  

   Society. 
  

  

  The 
  Presents 
  received 
  were 
  laid 
  on 
  the 
  table, 
  and 
  thanks 
  ordered 
  for 
  

   them. 
  

  

  The 
  following 
  Papers 
  were 
  read 
  : 
  — 
  

  

  t. 
  " 
  On 
  the 
  Action 
  of 
  Heat 
  on 
  the 
  Absorption-Spectra 
  and 
  

   Chemical 
  Constitution 
  of 
  Saline 
  Solutions/'' 
  By 
  Walter 
  

   Noel 
  Hartley, 
  E.C.S., 
  Demonstrator 
  of 
  Chemistry, 
  King's 
  

   College, 
  London. 
  Communicated 
  by 
  Prof. 
  Stokes, 
  Sec. 
  R.S. 
  

   Received 
  March 
  10, 
  1875. 
  

  

  (Abstract.) 
  

  

  The 
  effects 
  of 
  heat 
  on 
  absorption-spectra 
  were 
  recorded 
  in 
  the 
  preli- 
  

   minary 
  notice 
  of 
  this 
  paper, 
  published 
  in 
  the 
  ' 
  Proceedings 
  of 
  the 
  Eoyal 
  

   Society' 
  for 
  1874 
  (vol. 
  xxii. 
  p. 
  241). 
  

  

  The 
  contents 
  of 
  the 
  present 
  communication 
  consist 
  of 
  : 
  — 
  1st, 
  historical 
  

   notes 
  ; 
  2nd, 
  method 
  of 
  working 
  ; 
  3rd, 
  the 
  spectrum 
  -measurements 
  of 
  dif- 
  

   ferent 
  solutions 
  ; 
  4th, 
  conclusions 
  as 
  to 
  the 
  effect 
  of 
  heat 
  on 
  coloured 
  

   liquids, 
  and 
  the 
  following 
  deductions 
  as 
  to 
  the 
  constitution 
  of 
  salts 
  when 
  

   dissolved 
  in 
  water 
  : 
  — 
  

  

  I. 
  

  

  "When 
  a 
  simple 
  metallic 
  salt 
  is 
  dissolved 
  in 
  water, 
  it 
  is 
  not 
  decomposed 
  

   in 
  such 
  a 
  way 
  that 
  an 
  oxide 
  and 
  an 
  acid 
  is 
  produced, 
  nor 
  does 
  a 
  compound 
  

   of 
  the 
  metallic 
  oxide 
  with 
  the 
  acid 
  result. 
  

  

  II. 
  

  

  When 
  a 
  metallic 
  salt 
  is 
  dissolved 
  in 
  water 
  to 
  form 
  a 
  saturated 
  solution, 
  

   it 
  does 
  not 
  necessarily 
  attain 
  its 
  maximum 
  state 
  of 
  hydration. 
  

  

  III. 
  

  

  "When 
  a 
  simple 
  hydrated 
  metallic 
  salt 
  is 
  dissolved 
  in 
  water 
  to 
  form 
  a 
  

   saturated 
  solution, 
  the 
  crystalline 
  molecule 
  remains 
  chemically 
  intact, 
  

   except 
  in 
  the 
  case 
  of 
  certain 
  compounds 
  which 
  readily 
  part 
  with 
  their 
  

   water 
  of 
  crystallization, 
  when 
  dehydration 
  takes 
  place 
  to 
  form 
  a 
  molecule 
  

   of 
  greater 
  stability 
  ; 
  or, 
  in 
  other 
  words, 
  solution 
  facilitates 
  chemical 
  

   change 
  in. 
  this 
  as 
  in 
  most 
  other 
  cases. 
  

  

  