Transition elements
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I am planning my A2 investigation on analysing different methods of calculating the concentration of nickel in a nickel sulphate solution. I am planning on analysing: Redox titrations, Compleximetric titrations, Colorimetry and Gravimetric. I am confused about what solution I would use to titrate the nickel sulphate? And what filter I would use in the colorimetry, as we have not done it before? And also do you have any links etc, to any methods for for the above experiments, that I could use in my research?
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Ulex says
I think redox is a non-starter here because there is no conveniently available alternative oxidation state than the +2.
I have come across a complexiometric method. It is a bit unusual as it is a back-titration. It comes from ‘Experimental Chemistry’ by Rendle, Vokins and Davis (out of print). You could adapt it to your purpose if you can find it.
Determination of nickel by back-titration
Pipette 20 cm3 of 0.05M edta (an excess) to a 5 cm3 portion of approximately 0.1M nickel sulphate. Dilute with about 100 cm3 of de-ionised water and add 4 cm3 of pH10 buffer solution. Add a small portion of Solochrome Black indicator and titrate with 0.05M magnesium sulphate until the colour changes from blue to purple.
Gravimetric analysis is done with dimethyl glyoxime – I expect you know that already.
For colorimetry, you choose the filter by trying lots of different filters until you find the one which gives the biggest difference of reading between you solution and pure water. Sounds unscientific but it is the best way!
Take particular care if you use books published before modern safety standards came into force, or the internet.
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updated: 01 February 2008
