﻿258 
  Scientific 
  Intelligence. 
  

  

  duced 
  into 
  20 
  times 
  its 
  mass 
  of 
  fuming 
  sulphuric 
  acid, 
  warmed 
  

   to 
  20° 
  or 
  25°, 
  containing 
  80 
  per 
  cent 
  sulphuric 
  oxide; 
  the- 
  

   temperature 
  not 
  being 
  allowed 
  to 
  rise 
  above 
  30°. 
  The 
  glycocoll 
  

   goes 
  easily 
  into 
  solution 
  with 
  a 
  yellow 
  color 
  which 
  at 
  once 
  with 
  

   evolution 
  of 
  sulphurous 
  oxide 
  passes 
  into 
  the 
  deep 
  blue 
  color 
  of 
  

   the 
  indigo-solution. 
  To 
  remove 
  the 
  concentrated 
  acid, 
  the 
  mas& 
  

   is 
  diluted 
  with 
  sulphuric 
  acid 
  of 
  66° 
  B. 
  The 
  coloring 
  matter 
  is 
  

   isolated 
  by 
  farther 
  dilution 
  with 
  ice 
  and 
  the 
  addition 
  of 
  salt. 
  

   As 
  so 
  prepared 
  the 
  product 
  is 
  completely 
  pure 
  indigo-carmine. 
  

   The 
  colors 
  obtained 
  in 
  dyeing 
  with 
  it 
  far 
  exceed 
  in 
  brilliancy 
  

   those 
  obtained 
  from 
  the 
  best 
  varieties 
  of 
  commercial 
  indigo. 
  It& 
  

   identity 
  with 
  the 
  natural 
  product 
  was 
  established 
  by 
  means 
  of 
  its 
  

   chemical 
  reactions, 
  by 
  dyeing 
  tests 
  and 
  by 
  spectroscopic 
  exami- 
  

   nation. 
  The 
  yield 
  is 
  about 
  60 
  per 
  cent 
  of 
  the 
  glycocoll 
  taken. 
  — 
  

   Ber. 
  Berl. 
  Chem. 
  Ges., 
  xxiv, 
  1476, 
  May, 
  1891. 
  g. 
  f. 
  b. 
  

  

  4. 
  Lemons 
  sur 
  les 
  M'etanx, 
  professees 
  a 
  la 
  Faculte 
  des 
  Sciences 
  

   de 
  Paris. 
  Par 
  Alfred 
  Ditte, 
  Professeur 
  de 
  Chimie 
  a 
  la 
  Faculte. 
  

   Premier 
  Fascicule. 
  4to, 
  pp. 
  44, 
  lviii, 
  621. 
  Paris, 
  1891. 
  (Vve 
  

   Ch. 
  Dunod.) 
  — 
  To 
  judge 
  from 
  the 
  part 
  of 
  Professor 
  Ditte's 
  book 
  

   now 
  before 
  us, 
  the 
  complete 
  work 
  will 
  be 
  a 
  valuable 
  addition 
  to 
  

   chemical 
  literature. 
  It 
  is 
  written 
  largely 
  from 
  the 
  standpoint 
  of 
  

   energy. 
  In 
  his 
  preface 
  the 
  author 
  says 
  : 
  " 
  The 
  principles 
  of 
  

   Thermo-chemistry 
  and 
  the 
  consequences 
  which 
  flow 
  from 
  them, 
  

   teach 
  us 
  not 
  only 
  to 
  explain 
  reactions, 
  but 
  also 
  frequently 
  to 
  fore- 
  

   see 
  them 
  and 
  to 
  discover 
  in 
  advance 
  what 
  phenomena 
  will 
  be 
  

   produced 
  when 
  two 
  or 
  more 
  substances 
  are 
  put 
  together 
  under 
  

   determined 
  conditions. 
  On 
  the 
  other 
  hand 
  when 
  two 
  reactions 
  

   are 
  simultaneously 
  possible 
  the 
  laws 
  of 
  dissociation 
  enable 
  us 
  to 
  

   define 
  rigorously 
  the 
  conditions 
  of 
  eqilibrium 
  which 
  must 
  be 
  

   established 
  between 
  them. 
  In 
  general 
  a 
  rational 
  application 
  of 
  

   these 
  principles 
  and 
  these 
  laws 
  enables 
  us 
  to 
  say, 
  often 
  even 
  

   before 
  making 
  the 
  experiment, 
  why 
  one 
  given 
  reaction 
  is 
  certain 
  

   to 
  result, 
  while 
  another 
  reaction 
  is 
  impossible 
  ; 
  why 
  an 
  action 
  

   which 
  begins 
  without 
  difficulty, 
  ceases 
  after 
  a 
  time 
  ; 
  and 
  finally 
  

   why 
  a 
  particular 
  phenomenon 
  occurring 
  under 
  certain 
  circum- 
  

   stances, 
  does 
  not 
  take 
  place 
  under 
  other 
  circumstances 
  entirely 
  

   similar 
  apparently 
  in 
  appearance." 
  The 
  introductory 
  portions 
  of 
  

   the 
  book 
  are 
  therefore 
  devoted 
  to 
  calorimetry 
  and 
  the 
  general 
  

   principles 
  of 
  Thermo-chemistry 
  as 
  laid 
  down 
  by 
  Berthelot. 
  In 
  

   the 
  First 
  part, 
  a 
  general 
  study 
  of 
  the 
  metals 
  is 
  given, 
  covering 
  

   about 
  four 
  hundred 
  pages. 
  It 
  includes 
  the 
  principles 
  of 
  metal- 
  

   lurgy, 
  the 
  physical 
  properties 
  of 
  the 
  metals 
  and 
  their 
  alloys, 
  their 
  

   compounds 
  with 
  the 
  non-metals, 
  the 
  action 
  of 
  water, 
  acids, 
  etc., 
  

   on 
  the 
  metals, 
  and 
  lastly 
  metallic 
  salts. 
  The 
  Second 
  part 
  is 
  

   devoted 
  to 
  the 
  study 
  of 
  the 
  metals 
  specially. 
  Throughout 
  the 
  

   book 
  all 
  the 
  reactions 
  are 
  given 
  as 
  energy-reactions, 
  and 
  repre- 
  

   sent 
  the 
  heat-changes 
  concerned, 
  thus 
  : 
  

  

  SnCl 
  2 
  + 
  2HO 
  = 
  Sn0 
  2 
  + 
  2HC1 
  ()16 
  , 
  + 
  [67'9 
  + 
  2.39-3 
  - 
  64'6 
  - 
  2.34'5] 
  

   [+ 
  12-9]. 
  

  

  