MANUFACTURE  OP  CARBONATE  OF  MAGNESIA.  365 
The  preparation  of  carbonate  of  magnesia,  the  Magnesia  Alba 
of  P.  L.  1787,  was  for  several  years  a  considerable  secret  in  the 
possession  of  some  particular  persons.  It  formerly  bore  the  name 
at  Rome  of  Count  Palma's  powder.  Many,  however,  are  of 
opinion  that  the  mode  of  preparation  was  carried  from  Germany 
to  Italy.  Lancisi,  in  1717  (and,  it  is  said,  Yalentini,  in  1707), 
and  afterwards  Hoffman,  in  1722,  made  public  the  process  of 
manufacture.  At  that  time  it  was  extracted  from  the  mother- 
liquor  which  remains  after  the  crystallization  of  rough  nitre 
(chloride  of  magnesium)  by  precipitation  with  a  solution  of  car- 
bonate of  potash  or  soda.  The  name  Miraculum  Chemicum  was 
given  to  it  from  the  circumstance  of  a  precipitate  being  formed 
by  the  admixture  of  two  pellucid  solutions. 
Manufacture  of  Carbonate  of  Magnesia  from  Epsom  Salt. — 
The  manufacture  of  carbonate  of  magnesia  from  sulphate  of 
magnesia,  was  first  made  known  by  Henry,  of  Manchester.  The 
process  communicated  by  him  was  as  follows  : — «  Dissolve  any 
quantity  of  sal  catharticus  amarus  in  its  own  weight  of  water ; 
filter,  and  add  to  it  by  degrees  a  filtered  solution  of  pearl  or 
potashes,  in  an  equal  quantity  of  water,  stirring  them  gently, 
until  the  mixed  liquids  have  acquired  the  appearance  of  a  com- 
plete coagulum.  Then  desist  from  adding  any  more  of  the  al- 
kaline lixivium,  and  immediately  throw  the  mixture  into  a  large 
vessel  of  boiling  water ;  keep  it  boiling  a  quarter  of  an  hour, 
then  take  it  out  and  put  it  into  glazed  earthen  vessels.  As 
soon  as  the  powder  hath  subsided,  and  before  the  water  is  quite 
cold,  pour  it  off,  and  add  a  fresh  quantity  of  boiling  water  ;  re- 
peat these  ablutions  with  hot  water  several  times  until  the  li- 
quor has  entirely  lost  its  saline  taste ;  then  let  it  be  so  agitated 
as  to  suspend  the  finer  parts  of  the  powder,  in  which  state  decant 
it  into  other  vessels,  and  having  separated  the  water  from  the 
magnesia  by  inclination,  put  it  on  large  chalk-stones,  until  a 
considerable  part  of  the  humidity  is  absorbed.  Then  wrap 
it  up  in  sheets  of  white  paper,  and  dry  it  before  the  fire. 
Pour  hot  water  upon  the  remaining  powder,  stir  and  de- 
cant it  in  its  turbid  state,  and  separate  the  magnesia  from 
the  water  as  before;  thus  the  whole,  or  most  of  it,  will  be 
reduced  to  an  equal  degree  of  fineness.  The  larger  the 
quantity  of  water  into  which  the  precipitated  powder  is  cast,  the 
