PREPARATION  OE  SUCCINIC  ACID  EROM  MALATE  OE  LIME.  353 
to  100  parts  of  salt.    The  crude  succinate  of  lime  is  stirred  up 
with  water  to  form  a  thick  paste,  and  the  necessary  quantity  of 
hydrated  sulphuric  acid  is  added  by  degrees,  with  constant  stir- 
ring, during  which  there  is  of  course  a  great  evolution  of  heat. 
When  the  effervescence  caused  by  the  intermixture  of  carbonate 
of  lime  has  ceased,  the  paste  is  diluted  with  three  or  four  times 
as  much  water  as  the  expected  result  in  succinate  of  lime  em- 
ployed, which  furnishes  nearly  one-third  of  its  weight  of  acid  ; 
and  the  whole  is  digested  until  the  completion  of  the  decomposi- 
tion, which  is  indicated  by  the  formation  of  a  homogeneous  mass. 
The  brown  solution  of  the  acid  is  filtered  away  from  the  sulphate 
of  lime  through  a  pointed  bag  ;  the  sulphate  of  lime  is  freed  as 
much  as  possible  from  adherent  acid  by  repeated  diffusion  in 
water  and  filtering,  and  then  the  fluid  is  evaporated  to  dryness. 
If  a  slight  excess  of  sulphuric  acid  be  not  already  present,  this 
addition  is  made,  and  the  mixture  is  put  into  a  wide-necked  re- 
tort ;  the  neck  of  the  retort  must  be  short,  with  a  loosely-fitting 
receiver,  and  the  body  of  the  retort  surrounded  with  sand  to  a 
considerable  height.    When  the  acid  melts,  water  is  first  con- 
densed into  the  receiver ;  but  as  the  acid  reaches  the  boiling-point, 
it  passes  over  in  oleaginous  drops,  which  solidify  both  in  the  neck 
of  the  retort  and  in  the  receiver.  If  the  acid  passing  over,  which 
is  to  a  certain  extent  anhydrous,  comes  in  contact  with  the  water 
previously  condensed  in  the  receiver,  so  great  an  evolution  of 
heat  is  produced  that  the  mass  appears  to  boil ;  it  must  then  be 
cooled.    The  more  carefully  the  fire  is  regulated,  the  whiter  is 
the  product.    A  second  receiver  may  be  substituted  as  soon  as 
the  acid  begins  to  pass  over.    The  sublimation  is  continued  until 
at  a  high  temperature  white  vapors  begin  to  appear  in  the  retort. 
The  carbonaceous  residue  may  easily  be  removed  from  the  retort, 
so  that  the  latter  may  be  employed  again  for  many  operations. 
The  receiver,  however,  is  generally  destroyed,  as  the  acid  con- 
tained in  it  cannot  be  got  out  without  breaking  it  to  pieces,  un- 
less it  be  desired  to  have  it  crystallized,  when  water  may  be  em- 
ployed.   The  white  or  yellowish  acid  thus  obtained,  broken  into 
fragments,  is  heated  in  a  suitable  vessel  on  the  water  or  sand- 
bath,  until  all  the  sulphurous  acid  which  is  produced  during  dis- 
tillation, as  well  as  the  adherent  moisture,  is  entirely  dispelled. 
If  it  be  desired  to  prepare  the  medicinal,  and  not  a  chemically 
23 
