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PREPARATION  OF  UREA. 
ON  THE  PREPARATION  OF  UREA. 
By  John  Williams,  F.C.S. 
Having  had  occasion  to  prepare  rather  large  quantities  of 
Urea,  I  found  that  the  result  constantly  fell  considerably  short 
of  what  I  considered  a  satisfactory  one.  This  led  me  to  con- 
sider if  the  ordinary  mode  of  preparation  could  not  be  improved 
upon. 
The  result  of  my  experiments  is,  that  cyanate  of  lead  is 
better  adapted  for  the  purpose  than  the  mixture  of  salt  generally 
present  in  solution,  when  the  usual  process  is  adopted.  I  pro- 
ceed in  the  following  manner  : — 
I  prepare  cyanate  of  lead  by  fusing  cyanide  of  potassium  of 
the  best  commercial  quality  (containing  about  90  per  cent,  of 
real  cyanide)  at  a  very  low  red  heat,  in  a  shallow  iron  vessel ; 
red  lead  is  added  in  the  usual  manner,  by  small  quantities  at  a 
time  with  constant  stirring,  so  as  to  prevent  the  temperature 
rising  too  much  during  the  operation.  I  prefer  cyanide  of 
potassium  to  ferrocyanide  for  many  reasons,  but  mainly  because 
the  temperature  can  be  kept  down  to  the  lowest  point. 
The  cooled  and  finely-powdered  product  is  exhausted  with  suc- 
cessive portions  of  cold  water,  the  liquid  filtered,  and  nitrate  of 
barium  added.  Carbonate  of  barium  is  thus  precipitated.  The 
mother-liquid,  treated  with  nitrate  of  lead,  yields  pure  cyanate 
of  lead ;  this  can  be  washed  thoroughly,  and  dried  at  a  gentle 
heat,  and  preserved  for  use.  Unlike  cyanate  of  potassium,  it  is 
a  permanent  salt,  and  could  be  produced  at  a  moderate  price,  if 
required. 
To  prepare  urea,  it  is  simply  necessary  to  digest  with  suffi- 
cient water  at  a  gentle  heat,  equivalent  quantities  of  cyanate  of 
lead  and  sulphate  of  ammonium,  filter  and  evaporate.  I  have 
found  the  result  most  satisfactory. 
The  compound  ureas  may,  in  like  manner,  be  produced  by  sub- 
stituting the  sulphates  of  the  compound  ammonias  for  the 
ordinary  sulphate  of  ammonium ;  the  experiment  has  been  tried 
and  found  successful. — Chemist  and  Druggist,  March,  1868. 
