246 
ON  CRYSTALLIZED  ACETATE  OF  MAGNESIA. 
of  considerable  size,  especially  when  a  large  volume  of  fluid  was 
employed,  this  greatly  facilitating  the  slow  cooling.  The  forma- 
tion of  crystals  takes  places  in  this  case  with  acid,  as  well  as 
with  more  neutral  solutions.  The  author  did  not  succeed  in  add- 
ing to  the  size  of  ready-formed  crystals,  because  when  these 
were  placed  in  freshly-concentrated  solutions  they  became  crusted 
with  a  new  formation  of  small  crystals,  without  increasing  in 
their  original  form.  Solutions  containing  an  excess  of  acid  fur- 
nished more  distinctly-developed  crystals,  with  bright  shining 
surfaces;  those  formed  in  more  neutral  solutions  are  larger,  but 
generally  less  transparent.  The  salt  obtained  is  not  so  very 
deliquescent  as  is  generally  supposed.  At  the  ordinary  tempera- 
ture of  a  room  the  crystals  may  be  readily  dried  on  blotting- 
paper,  and  they  exhibit  no  alteration  even  when  kept  for  months. 
In  closed  vessels  they  may  be  kept  with  still  less  danger  of 
deliquescing,  The  composition  of  the  salt  was  found  to  agree 
withjthe  formula  C4  H3  Mg04-f-4HO.  Its  analysis  gave  18.73 
and  18.75  per  cent,  of  magnesia,  which  was  determined  by  the 
calcination  of  the  salt. 
For  the  purpose  of  this  analysis,  the  salt  was  dried  at  the  ordi- 
nary temperature  of  the  room.  An  analysis  of  crystals  which 
had  already  been  kept  for  some  months  gave  the  same  results. 
When  dried  over  sulphuric  acid,  the  salt  effloresced.  When 
heated  on  the  water-bath,  it  lost  its  4  atoms  of  water  of  crystal- 
lization almost  entirely  ;  but  this  required  a  considerable  time. 
The  loss  of  weight,  whilst  drying  at  212°  F.,  took  place  as 
follows : — 
1.115  grm.  weighed  after  4  hours  0.907  grm.=18.65  per  cent.  loss. 
  9    ...    0.837  ...  =24.93 
  15    ...    0.783    ..  =29.77 
  19    ...    0.766  ...  =31.30 
  24    ...    0.750  ...  =32.73 
It  appears  also  that  when  this  heat  is  so  long  continued,  a 
certain,  although  very  small  quantity  of  acetic  acid  is  expelled 
with  the  water,  for  when  the  salt  dried  in  this  manner  was  dis- 
solved in  water,  it  left  a  small  residue.  When  more  strongly 
heated,  it  behaved  like  the  other  acetates,  first  losing  its  water 
and  swelling  up  strongly,  evolving  acetic  acid  and  afterwards 
acetone,  and  finally  smouldering  away  wThen  heated  to  redness. 
Its  crystals  belong  to  the  monoclinohedric  system. — -Ohem.  Gfaz. 
from  Jahb.  der  K.  K.  Cfeolog.  Reichsanstalt. 
