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Cobalt Oxide Testing Method

Taking Hydrochloride Acid as the decomposition sample, dissolving acidity should be limited at 5% hydrochloride acid. The precipitating agent α-nitroso-β-naphthol reacting with Cobalt will yield nitroso-β-naphthol cobalt. Weighing the Cobalt tetroxide after filtered and burned.
Equipment & Regents:
The million electric analytical balance
Generic drugs balance
Beakers: 250ml and 500ml, two of each
The long-necked funnel: two
Hydrochlorid acid with specific gravity 1.19
Glacial acetic acid
α-nitroso-β-naphthol
Procedures:
Weighing exactly 0.2 gram sample after dried at 105~110℃,adding it into 250ml beaker together with 15-20 ml concentrated hydrochloride acid. Heating to dissolve it on the electric stove. Diluting it in 250ml volumetric flask after filtered up to the mark, shared up for use.
Taking 25ml above solution, adding 8-10ml concentrated hydrochloride acid, and then filtering to 200ml. Controlling the acidity at 5% hydrochloride acid. Heated to 60℃, and then adding 15mlα-nitroso-β-naphthol acetic acid solution( this solution is prepared with 1 gram α-nitroso-β-naphthol dissolved in 15ml Glacial acetic acid ) , stirring it rapidly for 1 min. Cooling down to room temperature and keeping it on standing for 1 h. Filtering with middle-speed filer paper, and washing 10-12 times with 5:95 warm hydrochloride acid solution. Putting the precipitation with the filter papers into 30 ml constant weight porcelain crucible and ashing. Cooling 40 mins and weighing. Going on igniting 30 minutes and then weighting till the weight doesn’t change. Finally, the Cobalt oxide weight would be got.
Calculating:
Co%= (precipitation +porcelain crucible weight)X Multiple X 0.734 X 100/Sample weight
CoO%=(precipitation +porcelain crucible weight)X Multiple X 0.734 X 1.2715 X 100/Sample weight
P.S. 0.734=Co3O4 to Co 1.2715=Co to CoO
Testing data:
Gravimetric method 97.10% ,97.05%
Average: 97.085%
Volumetric method 97.01%, 97.10%
Average: 97.06%
Discussion & Conclusion:
According to the testing result. Colorimetry: As Cobalt content in the sample is high, the result error is large when multiplied by a multiple of the solution.
Volumetric method: the impurities in the sample interfere the result stability when titration.
Weight method: Potassium Nitrite and Cobalt generate Cobalt Potassium Nitrite precipitation. But judging the CoO content from the precipitation weight is still ideal.
This method useα-nitroso-β-naphthol as precipitating agent to generate nitroso-β-naphthol cobalt. It is relatively pure, with high sensitivity and good reproducibility. The result is reliable and suitable for scientific research and industry production.
Note:
When decomposing the sample, heating it slowly till turning clear, to avoiding the splashing.
Controlling the acidity at 5% hydrochloride acid in the precipitation process.
Burning or drying on the electric stove should control the temperature avoiding splashing.

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