HOTE  OK  THS   PREPARATION  OF  UHANIUM.  247 
NOTE  ON  THE  PREPARATION  OF  URANIUM. 
By  E.  Peligot. 
In  1842  the  author  showed,  that  by  treating  protocliloride  of 
cranium  with  potassium,  uranium  was  obtained  partly  in  the 
form  of  a  black  powder,  and  partly  in  silvery  metallic  plates  ; 
but  as  the  sudden  elevation  of  temperature  produced  by  the  re- 
action prevented  the  employment  of  earthen  crucibles,  and 
Tendered  the  use  of  platinum  vessels  necessary.,  the  metallic  scales 
were  always  alloyed  with  platinum. 
Since  sodium  has  been  so  easily  procurable,  the  author  has 
renewed  his  experiments,  substituting  sodium  for  potassium.  He 
proceeds,  in  the  following  manner  : 
The  quantity  of  sodium  necessary  to  decompose  the  green  pro- 
tochloride  of  uranium  (prepared  by  submitting  one  of  the  oxides  of 
this  metal  to  the  simultaneous  action  of  chlorine  and  charcoal) 
is  put  into  a  glazed  porcelain  crucible.  The  sodium  is  covered 
with  very  dry  chloride  of  potassium,  and  then  with  a  mixture  of 
the  latter  salt  and  chloride  of  uranium.  The  crucible,  closed 
with  its  lid,  is  placed  in  a  luted  earthen  crucible,  which  is  filled 
with  charcoal-powder,  and  also  closed  with  an  earthen  cover. 
The  object  of  the  addition  of  chloride  of  potassium  is  to  render 
the  reaction  less  instantaneous  and  violent. 
The  crucible  is  heated  until  the  reaction  takes  place,  which  is 
known  by  the  sound  produced  at  that  moment ;  it  is  then  imme- 
diately removed  into  a  blast-furnace,  and  kept  at  a  white  heat 
for  a  quarter  of  an  hour  or  twenty  minutes  ;  on  cooling  it,  a  fused 
cinder  is  found  in  the  porcelain  crucible,  and  this  encloses  several 
globules  of  uranium. 
Thus  prepared,  uranium  possesses  a  certain  degree  of  mallea- 
bility ;  it  is  hard,  but  may  easily  be  scratched  with  steel ;  and  its 
color  resembles  that  of  nickel  or  iron.  In  the  air  it  acquires  a 
slight  yellowish  tint,  in  consequence  of  a  slight  oxidation  of  the 
surface.  When  heated  to  redness,  it  exhibits  a  brilliant  incan- 
descence, and  becomes  covered  with  a  voluminous  black  oxide, 
in  the  interior  of  which  a  portion  of  the  metal  is  found  unchanged 
if  the  action  of  heat  has  been  stopped  in  time.  Its  density  is 
18.4,  so  that  next  to  platinum  and  gold  it  is  the  heaviest  body 
wifch  which  we  are  acquainted.    This  specific  gravity  may  per- 
