#4
It's pH neutral too. And readily available in many places. On the downside, it's electrically conductive and precipitates rusting in iron.
#5
Because it's a polar liquid that can dissolve material with a high electronegativity. Pure ethanol is even better because it has both polar and non-polar features, meaning it can dissolve both stuff with a high electronegativity and stuff with a low electronegativity. Water is cheaper and healthier.

Yeah, I don't know the correct terms in English..
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