80 
PREPARATION  OF  UREA. 
double  chloride  of  potassium  and  platinum  in  hyposulphite  of 
soda. 
Lastly,  deposits  of  peroxide  of  iron  on  iron  and  steel,  which  are 
already  almost  unalterable  by  air,  will  become  entirely  so  when 
the  pieces  have  been  employed,  as  positive  electrodes  to  decom- 
pose water.- — Chem.  News,  London,  Julyft,  1861,  from  Comptes- 
Rendus. 
ON  THE  PREPARATION  OF   UREA   FROM  FERROCYANID  OF 
POTASSIUM. 
In  the  preparation  of  urea  by  Wohler's  method  the  amount 
obtained  always  falls  short  of  that  which  should  theoretically  be 
produced.  Having  remarked  that  even  when  the  operation  is 
carefully  performed  with  Liebig's  proportions,  the  lixiviate  al- 
ways contains  undecomposed  cyanid  of  potassium,  it  occurred  to 
me  to  try  the  effect  of  a  more  thorough  oxydation,  and  the  result 
proved  very  favorable.    The  following  was  the  course  adopted. 
Of  roasted  ferrocyanid  of  potassium  850  grammes  are  mixed 
with  318  grammes  of  thoroughly  dried  carbonate  of  potash  in 
grains,  and  fused  in  an  iron  vessel.  When  decomposition  is 
complete,  the  vessel  is  a  little  cooled  and  1900  grammes  of  red 
lead  are  to  be  added,  not  all  at  once,  but  300  to  400  grammes 
at  a  time,  with  intervals  of  10  minutes,  stirring  and  keeping  up 
heat  enough  to  retain  the  whole  in  a  state  of  fusion. 
After  the  last  addition  of  red  lead  the  mixture  is  suffered  to 
remain  half  an  hour  on  the  fire  to  complete  the  reaction.  Heat 
is  applied  in  all  for  about  four  hours.  In  this  way  the  cyanid 
of  potassium  becomes  thoroughly  oxydized.  The  process  is 
concluded  in  the  usual  manner,  and  500  grammes  of  urea  are 
obtained.  No  particular  precaution  is  necessary  during  the 
fusion,  or  even  the  lixiviation  with  cold  water,  but  in  evapo- 
rating the  solutions  the  greatest  care  must  be  taken  to  carry 
off  the  vapors. — Sillimari's  Journal,  Sept.  1861. 
