Which substance,when added as an adulterant to ethanol used as an intoxicating drink,causes a person to lose their vision?

$(i)$ How will you bring about the following reactions? Write the concerned chemical equations:
$(a)$ Ethanol to Ethene.
$(b)$ Ethanol to Ethanoic acid.

$(a)$ Write chemical equations for the reactions of ethanoic acid with:
$(i)$ Sodium
$(ii)$ Sodium carbonate
$(iii)$ Ethanol in the presence of conc. $H_{2}SO_{4}$.
$(b)$ State the role of concentrated sulphuric acid in the esterification reaction.
$(c)$ Write one use of ethanoic acid.

State whether the following statement is true or false:
Heating ethanol at $443 \,K$ with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene.

Describe a chemical test to distinguish between ethanol and ethanoic acid.

What is the molecular formula of vinegar used as a preservative?