Ammonium Chrome Alum

All compounds of chromium are colored the most important are the chromates of sodium and potassium and the dichromates and the potassium and ammonium chrome alums. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather. 

The mother Hquor from the cmde ferrous sulfate crystallisation contains neady all the chromium. It is clarified and aged with agitation at 30°C for a considerable period to reverse the reactions of the conditioning step. Hydrolysis reactions are being reversed therefore, the pH increases. Also, sulfate ions are released from complexes and the chromium is converted largely to the hexaaquo ion. Ammonium chrome alum then precipitates as a fine crystal slurry. It is filtered and washed and the filtrate sent to the leach circuit the chrome alum is dissolved in hot water, and the solution is used as cell feed. 

Ammonium Chrome Alum (Alum Ammonium Chrome), (NH4)aS04. Cra(S04)3. 24HaO, mw 956.72, mp dec 100°, d 1.72 gm or viol crysts. Can be prepd by treating an aq sold... 

Chrome Ammonium Alum. See Ammonium -Chrome Alum in Vol 1, p AI56-L... 

Anhydrous or dehydrated ammonium chrome-alum was obtained by M. Traube... 

---