^°^0cT"i£2^^"^' }  ^ce^afes  of  Chromium^  Iron,  and  Aluminium.  487 
REACTIONS  OF  THE  ACETATES  OF  CHROMIUM,  IRON, 
AND  ALUMINIUM. 
By  B.  Reinitzer. 
Ferric  and  aluminic  salts,  boiled  with  a  quantity  of  sodium  acetate 
sufficient  to  convert  them  into  acetates,  deposit  the  whole  of  the  iron 
and  aluminium  as  basic  acetates,  probably  in  consequence  of  the  reso- 
lution of  the  normal  acetates  formed  in  the  first  instance  into  basic 
salts  and  free  acetic  acid.  Respecting  the  behavior  of  chromic  salts 
under  similar  circumstances,  the  statements  of  different  authors  do  not 
quite  agree.  Schiff  ("  Annalen,''  124,  p.  168)  states  that  when  normal 
chromic  acetate  is  boiled  with  water,  no  decomposition  takes  place ; 
whereas,  according  to  O.  Wallach  Tabellen  zur  chem.  Analyse," 
1880),  chromic  salts,  like  the  salts  of  iron  and  aluminium,  yield,  when 
boiled  with  sodium  acetate,  a  precipitate  of  chromic  acetate. 
According  to  the  author's  experiments  a  solution  of  chloride  or  sul- 
phate, boiled  with  excess  of  sodium  acetate,  yields  no  precipitate.  If 
the  boiling  be  continuel  for  a  short  time  only,  the  solution  turns  violet 
on  cooling ;  and  in  the  solution  thus  altered  no  precipitate  is  formed 
by  potash,  soda,  ammonia,  ammonium  hydrosulphide  or  carbonate,, 
sodium  phosphate,  barium  hydroxide,  or  barium  carbonate.  Potash,, 
soda,  and  baryta  turn  the  solution  green,  and  after  12  to  24  hours 
convert  the  liquid  into  a  green  jelly ;  ammonia  forms  a  violet  jelly. 
The  precipitation  is  accelerated  by  heat  in  all  cases  except  with  sodium 
phosphate,  which  forms  no  precipitate,  even  when  aided  by  heat. 
A  similar  passivity  towards  the  reagents  above  mentioned  is  imparted 
by  the  chromic  solution  to  a  certain  quantity  of  ferric  or  aluminic 
acetate.  Neither  by  heating  to  the  boiling  point  nor  by  addition  of 
caustic  alkalis  or  ammonia,  or  their  salts,  can  ferric  or  aluminic  acetate 
be  detected  in  presence  of  chromic  acetate.  In  such  a  mixed  solution 
ammonium  sulphide  alone  produces  a  slow  but  complete  precipitation 
of  the  iron,  whereas  alumina  is  not  completely  precipitated  in  the  cold 
by  any  reagent  whatever.  A  given  quantity  of  chromium,  however, 
can  protect  from  precipitation  only  a  limited  quantity  of  ferric  oxide 
or  alumina ;  and,  what  is  especially  remarkable,  it  can  protect  a  con- 
siderable quantity  only  when  the  chromic  solution  has  been  boiled 
with  the  sodium  acetate  before  the  addition  of  the  ferric  or  aluminic 
solution.  From  these  results  it  follows  that,  in  presence  of  chromic 
salts,  th(i  method  of  separation  founded  on  tlie  preci})itation  of  iron  and 
