Separation of Copper and Estimation of Nickel Gravimetrically as Nickel dimethylglyoximate

Estimation of Ni from the mixture of Ni2+ and Cu2+ solution

Procedure

  1. Pipette 25 mL given solution quantitatively into a 200 or 250 mL beaker. Acidify the solution with 1-2 mL of conc. HCl, warm the solution and pass H2S carefully to precipitate copper sulfide (black ppt.) completely.
  2. Remove H2S by boiling the solution gently (test with lead acetate paper). Cool the solution to 70-800C.
  3. Add 30-35 mL of dimethylglyoxime(dmg) solution and immediately add dilute ammonium solution drop-wise with constant stirring until the precipitation(ppt) of the complex (red color ppt.) is complete and then in slight excess.
  4. Allow the mixture to stand on a steam bath for 20-30 minutes and test the solution for complete precipitation of Ni2+.
  5. Then allow the precipitate to stand for 1 hour, cooling at the same time. Filter the mixture through a sintered glass crucible that has been previously cleaned.
  6. Dried at 100-1200C and weighed after cooling in a desiccator. Wash the precipitate with cold water until free from chloride and sulfate and finally with a few mL of rectified spirit. Dry it at 100-1200C for about an hour, cool it in a desiccator and weigh. Repeat the process until constant weight is attained.

               Hints for calculation: 1g complex = 0.2032g Ni

 

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This post was submitted by

Md. Emon Ali
B.Sc.(Hons.)
Department of Chemistry
RU.




November 2018
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