Nickel Case Study In Chemistry

Nickel as a mineral does not normally occur in water systems. The water effluents from the steel and allied alloys, electro platting, paints, ceramics and food industry are largely the source of this contamination. Nickel is used in metallurgy of alloys, magnets, protective coating, catalysts, and batteries. The toxicity of nickel to aquatic life varies widely and is influenced by nickel compounds, pH, synergetic effects, and other factors. The average abundance of Ni in the earth’s crust is 1.2 ppm; in soils it is 2.5 ppm; in streams it is 1μg/L, and in groundwater it is <0.1 mg/L. Nickel is obtained chiefly from pyrrhotite and garnierite. The common aqueous species is Ni2+. In reducing conditions insoluble sulphide can form, while in aerobic

1.00 ml  10 g Ni

(iii) Hydrochloric acid (L.R. grade) 1.0 N : Dilute 100 ml concentrated hydrochloric acid to 1000 ml with grade I distilled water.

(iv) Bromine water : Saturate distilled water with bromine to prepare Bromine water.

(v) Heptoximereagent : Dissolve 0.1 g 1,2 –cycloheptanedionedioxime (heptoxime) in 100 ml 95 % ethyl alcohol.

(vi) Sodium tartrate solution : Dissolve 10g sodium tartrate (Na2C4H4O6.2 H2O) in 90 ml distilled water.

(vii) Cupferronsolution : Dissolve 1 g cupferron in 100 ml distilled water. Store in refrigerator or prepare fresh for each series of determinations.

(viii) Hydroxylamine – Hydrochloride solution : Dissolve10 g NH2OH.HCl in 90 ml distilled water. This has to be prepared fresh.

Procedure :

(a) Preparation of calibration curve :(i) Pippet portions of standard NiSO4 solution into 100 ml volumetric flask. Use a series from 50 to 250 µg Ni. (ii) Add 25 ml 1.0 N HCl in 5 ml bromine water. (iii) Cool with cold running tap water and add 10 ml concentrated Ammonium hydroxide. (iv) Immediately add 20 ml heptoxime reagent. (v) Add 20 ml ethyl alcohol. (vi) Dilute to volume with distilled water and mix. (vii) Measure absorbance at 445 nm, 20 min after adding reagent, using a reagent blank as

(ii) Acidify to methyl orange end point with concentrated H2SO4. (iii) Add 5 ml concentrated HNO3. (iv) Add 2 ml 30% H2O2 . (v) Evaporate on a hot plate to 15 to 20 ml.

(vi) Transfer the concentrate and any precipitate to a 250 ml conical flask using 5 ml concentrated HNO3. (vii) Add 10 ml concentrated H2SO4 and a few boiling chips or glass beads. Evaporate on a hot plate in a hood until dense white fumes of SO3 just appear. (viii) If solution does not clear, add another 10 ml concentrated HNO3 and repeat the evaporation to obtain fumes of SO3. Remove all HNO3 before continuing treatment. All HNO3 will be removed when the solution is clear and no brownish fumes are evident. Do not let the sample dry during this digestion.

(ix) Cool and dilute to about 50 ml with water. Heat to almost boiling to dissolve soluble salts slowly. Filter if