# Determining the composition of basic copper sulfate by titrimetry

A colleague shared an undergraduate level classical gravimetry/titrimetry experiment on determining the stoichiometry of basic copper sulfate. I am looking for a reference for this type of experiment. Unfortunately, my colleague does not know the original reference and despite our search we could not find any similar experiment on titrating copper sulfate with $$\ce{NaOH}.$$ Has anyone seen this type of experiment in any paper or book?

Here is the gist of the experiment.

Basic salts of metals have structures based on the polymeric metal hydroxide lattice with some of the hydroxide groups replaced by other anions. The formula of basic copper sulfate is $$\ce{Cu_{(x+y)}(OH)_{2x}(SO4)_y}.$$ In this experiment increasing amounts of $$\ce{NaOH}$$ are added to fixed amounts of $$\ce{CuSO4}$$ to form the basic copper sulfate salt according to the following reaction:

$$\ce{(x + y) CuSO4 + 2x NaOH -> Cu_{(x+y)}(OH)_{2x}(SO4)_y + x Na2SO4} \tag{Eq. 1}$$

Increasing amounts of $$\ce{NaOH}$$ are added to different portions of fixed amounts of $$\ce{CuSO4},$$ resulting in variable amounts of $$\ce{CuSO4}$$ remaining in excess for the different portions by iodometric titration.

Using the stoichiometry of the reactions, the amount of excess $$\ce{CuSO4}$$ can be determined. This, together with the original amounts of $$\ce{NaOH}$$ and $$\ce{CuSO4}$$ mixed together, can be used for the determination of the stoichiometric coefficients of reaction (1), allowing the determination of the formula of the basic copper sulfate salt.

• If you want to go all the way back in history, you probably want to mention Pickering's The constitution of basic salts and The interaction of metallic sulphates and caustic alkalis. – andselisk Aug 16 '19 at 14:59
• Thanks, those references are indeed of historical. I have never seen this academic experiment in any commonly used textbook e.g., Vogel or elsewhere. Not sure where they got it and who wrote this experiment. Sadly, no reference is given. – M. Farooq Aug 16 '19 at 18:37