ON  THE  PRODUCTION  OP  ALUMINIUM. 
425 
ON  THE  COMBINATION  OF  NITRATE  OF  SODA  WITH  NITRATE 
OF  SILVER. 
By  H.  Rose. 
It  has  long  been  known  that  several  salts  of  soda  have  the 
same  form  as  the  corresponding  salts  of  silver.  It  is  remark- 
able, however,  that  nitrate  of  soda  is  not  isomorphous  with 
nitrate  of  silver,  although,  as  is  well  known,  both  may  easily  be 
prepared  in  very  distinct  crystals  in  the  anhydrous  state. 
Nitrate  of  silver  may  nevertheless  be  made  to  assume  the 
rhombohedric  form  of  the  crystal  of  nitrate  of  soda,  when  the 
two  salts  are  allowed  to  crystallize  from  a  common  solution. 
If  the  solution  contains  an  excess  of  nitrate  of  silver,  and 
it  is  gradually  evaporated  over  concentrated  sulphuric  acid, 
dimetric  crystals  of  this  salt,  containing  no  soda,  first  of  all 
separate.  The  subsequent  crystallization,  however,  have  most 
distinctly  the  rhombohedral  form  of  nitrate  of  soda,  but  contain 
besides  this  nitrate  of  silver,  and  this  in  very  various  propor- 
tions. Once  the  crystals  were  obtained  of  the  composition  AgO 
+N05+2NaO,  NO5:  in  other  crystals  1  atom  of  nitrate  of 
silver  was  combined  with  3-18,  3-74,  and  4-2  atoms  of  nitrate  of 
soda,  so  that  in  these  double  compounds  the  two  bases,  oxide  of 
silver  and  soda,  may  replace  each  other  in  indefinite  propor- 
tions.— Ibid,  from  Berichtder  Akad.  der  Wiss.  zu  Berlin,  1857. 
THE  PRODUCTION  OF  ALUMINIUM. 
M.  Petitjean,  a  French  Chemist,  resident  in  London  (the  in- 
ventor of  an  admirable  method  of  silvering  mirrors  cheaply, 
which  was  brought  to  the  notice  of  the  Royal  Institution  some 
time  since  by  Professor  Faraday,)  has  effected  an  improvement 
in  the  production  of  aluminium,  which  promises  to  still  further 
reduce  the  cost  of  that  valuable  metal  beyond  all  that  has  hitherto 
been  anticipated.  His  invention  consists  in  transforming  so  much 
of  the  aluminium  as  is  present  in  the  substances  with  which  it  is 
found  naturally  combined  into  one  or  more  sulphurets  ;  and  then 
removing  the  sulphur  therefrom  by  the  aid  of  carbon,  or  a  hydro- 
carbon, or  of  a  suitable  metal  or  metals,  mixed  therewith,  and 
exposed  in  a  crucible  to  a  high  temperature,  after  which  the 
