﻿232 
  MR 
  HENRY 
  HOW 
  ON 
  CERTAIN 
  SALTS 
  AND 
  

  

  The 
  crystals 
  contain 
  in 
  addition 
  eight 
  atoms 
  of 
  water. 
  

  

  14-380 
  grains 
  air-dry 
  salt 
  lost 
  at 
  250° 
  

  

  2*775 
  . 
  . 
  . 
  water, 
  and 
  

   11-665 
  grains 
  air-dry 
  substance 
  lost 
  at 
  250° 
  

  

  2-180 
  ... 
  water. 
  

  

  { 
  

  

  the 
  mean 
  of 
  these 
  numbers, 
  when 
  calculated 
  on 
  100 
  parts, 
  

  

  J_ 
  o 
  YL. 
  Mean. 
  

  

  19-29 
  18-77 
  19-03 
  

  

  agrees 
  perfectly 
  with 
  that,— 
  18-88,— 
  corresponding 
  to 
  the 
  formula 
  

  

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

  

  The 
  crystallized 
  salt 
  when 
  boiled 
  in 
  water 
  is 
  converted 
  into 
  a 
  basic 
  com- 
  

   pound, 
  which 
  loses 
  no 
  water 
  at 
  a 
  temperature 
  of 
  250°. 
  A 
  portion, 
  which 
  had 
  been 
  

   so 
  dried, 
  gave 
  on 
  analysis 
  54-5 
  per 
  cent, 
  of 
  baryta 
  ; 
  this 
  is 
  considerably 
  more 
  than 
  

   would 
  correspond 
  with 
  a 
  normal 
  neutral 
  salt 
  entirely 
  free 
  from 
  water. 
  

  

  Salts 
  of 
  Magnesia 
  with 
  Comenic 
  Acid. 
  

  

  Acid 
  Comenate 
  of 
  Magnesia.— 
  -This 
  salt 
  is 
  much 
  more 
  soluble 
  than 
  the 
  corre- 
  

   sponding 
  salts 
  of 
  lime 
  and 
  baryta 
  ; 
  it 
  crystallizes 
  out 
  after 
  some 
  time, 
  in 
  perfect 
  

   small 
  rhombs, 
  when 
  strong 
  cold 
  solutions 
  of 
  bicomenate 
  of 
  ammonia 
  and 
  sulphate 
  

   of 
  magnesia 
  are 
  mixed. 
  When 
  obtained 
  from 
  dilute 
  solutions, 
  by 
  spontaneous 
  or 
  

   very 
  slow 
  artificial 
  evaporation, 
  these 
  crystals 
  are 
  of 
  very 
  large 
  size, 
  and 
  when 
  

   possessing 
  the 
  yellow 
  colour 
  so 
  apt 
  to 
  adhere 
  to 
  salts 
  of 
  comenic 
  acid, 
  they 
  very 
  

   much 
  resemble 
  regular 
  crystals 
  of 
  ferrocyanide 
  of 
  potassium. 
  They 
  are 
  readily 
  

   soluble 
  in 
  hot 
  water, 
  and 
  react 
  strongly 
  acid. 
  The 
  following 
  is 
  the 
  analysis, 
  the 
  

   magnesia 
  being 
  estimated 
  as 
  sulphate, 
  by 
  ignition 
  with 
  sulphuric 
  acid 
  :— 
  

  

  r 
  7-426 
  grains 
  dried 
  at 
  240° 
  Fahr. 
  gave 
  

   } 
  10-517 
  ... 
  carbonic 
  acid, 
  and 
  

   [ 
  1-988 
  ... 
  water. 
  

  

  f 
  5-613 
  grains 
  dried 
  at 
  240° 
  Fahr. 
  gave 
  

   \ 
  1-863 
  ... 
  sulphate 
  of 
  magnesia. 
  

  

  Carbon, 
  

   Hydrogen, 
  

   Oxygen, 
  . 
  

  

  Magnesia, 
  

  

  100-00 
  100-00 
  185-67 
  

  

  from 
  which 
  it 
  appears 
  that 
  two 
  atoms 
  of 
  water 
  are 
  retained 
  in 
  combination 
  at 
  

   the 
  temperature 
  of 
  240" 
  Fahr. 
  ; 
  the 
  composition 
  of 
  the 
  so-dried 
  salt 
  being 
  ex- 
  

   pressed 
  by 
  the 
  formula 
  

  

  MgO, 
  Ho, 
  C 
  12 
  H 
  2 
  8 
  + 
  2 
  HO. 
  

  

  Experiment. 
  

  

  Ci 
  

  

  ilculation. 
  

  

  

  38-62 
  

  

  38-77 
  

  

  C 
  12 
  

  

  72 
  

  

  2-97 
  

  

  2-69 
  

  

  H 
  5 
  

  

  5 
  

  

  

  47-41 
  

  

  On 
  

  

  88 
  

  

  11-10 
  

  

  11-13 
  

  

  MgO 
  

  

  20-67 
  

  

  