How to recognize glycerin, formalin and ethanol with one reagent?

Methods of analytical chemistry are used to identify substances. Let’s analyze these substances.

Glycerin is a trihydric alcohol (propanetriol-1,2,3). A qualitative reaction for polyhydric alcohols is the reaction with Cu (OH) 2. A complex compound (chelate complex) of copper glycerate is formed, which has a characteristic light blue color.

Formalin is an aqueous solution of formaldehyde (HCOH) stabilized with a solution of methanol. Can also use Cu (OH) 2 for recognition:

HCOH + 2Cu (OH) 2 = HCOOH + Cu2O + 2H2O

A characteristic red precipitate of copper oxide I forms.

Ethanol does not react with copper hydroxide. Therefore, in the absence of a reaction, we can distinguish it from the other two substances.

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