Cuprous Sulfate: A Disagreement with My High School Chemistry Teacher

cuprous sulfate
As a kid, I was excessively shy and retiring – except when it came to matters of science and math. When it came to them, I was generally quiet but I could become quite outspoken if the occasion arose. During senior year, I approached my math instructor and told him an entire chapter in our textbook was wrong. He was reluctant to hear me out, but when he did, he acknowledged I was correct.

On one occasion during junior year, I was listening to my chemistry teacher attentively when he spoke of cuprous sulfate. For those who are unacquainted with terminology, this would have been the old name (the name I still use) for copper(I) sulfate. I informed Mr. D’Alesandro that the only existing copper sulfate was cupric sulfate, CuSO₄, not cuprous sulfate, Cu₂SO₄. Cuprous sulfate didn’t exist.

Was I correct? Mr. D’Alesandro told me he’d tell me more in class the next day.

Cuprous Sulfate: My Comeuppance

And he did. Although one can make cupric sulfate pentahydrate by the simple combination of copper, sulfuric acid, and water,

cuprous sulfate
Cupric sulfate pentahydrate. Image by Crystal Titan CCA-SA4.0 International

Cu + H₂SO₄ + 5 H₂O → CuSO₄•5H₂O + H₂↑

the reaction he wrote on the blackboard was,

Cu₂O + (CH₃)₂SO₄ → (CH₃)₂O + Cu₂SO₄

This reaction reads: cuprous oxide plus dimethylsulfate yields dimethylether plus cuprous sulfate. I’d been wrong. And what was worse, I had questioned his knowledge as an instructor although that was not my intent nor did he accuse me of it. I felt pretty foolish. I acknowledged what he said. We never discussed the matter again.

But just how wrong was I?

Acids, Bases, and Salts

First, this was an introductory chemistry course. The chemistry knowledge I had was all gained by my own effort. Then, too, cuprous sulfate is a most unusual compound of limited use. Although it can be stored in an anhydrous condition, it is not stable in the presence of moisture or of heat. You are quite unlikely to find it on any laboratory shelf.

Regretting the Outcome

Sadly, my instructor was informed he would not be given tenure. When I found this out, I felt guilty, thinking somehow I may have contributed to his departure. I’ve often wondered what ever became of this fellow. Likely he went to a less demanding school. But I still do not know. Maybe I never will.

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