﻿PRODUCTS 
  OF 
  DECOMPOSITION 
  OF 
  COMENIC 
  ACID. 
  231 
  

  

  Hence 
  the 
  composition 
  of 
  the 
  salt 
  dried 
  at 
  212° 
  is 
  expressed 
  by 
  the 
  formula 
  

  

  BaO 
  HO 
  C 
  12 
  H 
  2 
  8 
  . 
  

  

  In 
  the 
  crystals, 
  as 
  appears 
  from 
  the 
  following 
  experiments, 
  two 
  equivalents 
  of 
  

   this 
  substance 
  are 
  combined 
  with 
  thirteen 
  of 
  water. 
  

  

  f 
  14-815 
  grains 
  air-dry 
  substance 
  lost 
  at 
  212° 
  

   ( 
  3-105 
  ... 
  water. 
  

  

  f 
  10-721 
  grains 
  air-dry 
  substance 
  lost 
  at 
  212° 
  

   I 
  2-228 
  ... 
  water. 
  

  

  The 
  per-centage 
  calculation 
  from 
  which, 
  

  

  I. 
  II. 
  Mean. 
  

  

  20-95 
  20-78 
  20-86 
  

  

  agrees 
  well 
  with 
  the 
  number, 
  20*73, 
  required 
  by 
  the 
  formula 
  

  

  2 
  (BaO, 
  HO, 
  C 
  12 
  H 
  2 
  8 
  ) 
  + 
  13 
  aq. 
  

  

  Neutral 
  Comenate 
  of 
  Baryta. 
  — 
  An 
  alkaline 
  ammoniacal 
  solution 
  of 
  comenic 
  

   acid 
  causes 
  an 
  immediate 
  precipitate 
  in 
  chloride 
  of 
  barium, 
  of 
  minute 
  radiated 
  

   crystals. 
  In 
  dilute 
  solutions 
  these 
  do 
  not 
  appear 
  immediately, 
  but 
  in 
  a 
  very 
  short 
  

   time 
  they 
  commence 
  forming, 
  and 
  their 
  quantity 
  increases 
  till 
  the 
  whole 
  fluid 
  is 
  

   filled. 
  Under 
  these 
  circumstances 
  they 
  present 
  a 
  very 
  beautiful 
  appearance, 
  being 
  

   in 
  individual 
  groups, 
  whose 
  silky 
  needles 
  radiate 
  regularly 
  from 
  a 
  centre. 
  Under 
  

   the 
  microscope 
  these 
  needles 
  are 
  seen 
  to 
  be 
  square 
  prismatic 
  crystals. 
  

  

  This 
  salt 
  is 
  insoluble 
  in 
  boiling 
  water, 
  and 
  does 
  not 
  lose 
  its 
  water 
  of 
  crystalli- 
  

   zation 
  at 
  a 
  temperature 
  of 
  212\ 
  When 
  dried 
  at 
  250°, 
  it 
  is 
  almost 
  pyrophoric 
  on 
  

   ignition, 
  blowing 
  up 
  in 
  a 
  light 
  fiery 
  cloud 
  ; 
  for 
  this 
  reason 
  the 
  base 
  was 
  deter- 
  

   mined 
  as 
  sulphate 
  in 
  the 
  analysis 
  which 
  follows, 
  by 
  ignition 
  with 
  a 
  little 
  sul- 
  

   phuric 
  acid. 
  

  

  (5-418 
  grains 
  dried 
  at 
  250° 
  Fahr. 
  gave 
  

   4-584 
  ... 
  carbonic 
  acid, 
  and 
  

   0-721 
  ... 
  water. 
  

  

  ( 
  5-556 
  grains 
  dried 
  at 
  250° 
  Fahr. 
  gave 
  

   \ 
  4- 
  1 
  94 
  ... 
  sulphate 
  of 
  baryta. 
  

  

  Carbon, 
  

   Hydrogen, 
  

   Oxygen, 
  

   Baryta, 
  

  

  Experiment. 
  

  

  

  Calculation. 
  

  

  

  23-07 
  

  

  23-27 
  

  

  o 
  12 
  

  

  72 
  

  

  1-47 
  

  

  1-29 
  

  

  H 
  4 
  

  

  4 
  

  

  

  25-89 
  

  

  °io 
  

  

  80 
  

  

  49-54 
  

  

  49-55 
  

  

  2 
  BaO 
  

  

  153-28 
  

  

  100-00 
  100-00 
  309-28 
  

  

  From 
  the 
  above 
  it 
  appears 
  that 
  this 
  salt, 
  like 
  the 
  corresponding 
  one 
  of 
  lime, 
  

   retains 
  two 
  equivalents 
  of 
  water 
  at 
  this 
  temperature, 
  its 
  formula 
  being 
  

  

  2 
  BaO, 
  C 
  12 
  H 
  2 
  8 
  + 
  2 
  HO. 
  

  

  