Don protective equipment. Wear a pair of rubber gloves, goggles and a lab coat over your clothing. When working with chemicals, safety is of the utmost importance.
Form your reagent by mixing equal parts of an alkyl halide with magnesium metal. This forms a dry ether layer. Ensure no water touches your ingredients or the ether layer will be ruined.
Mix your reagent with finely crushed dry ice in an ether solvent. This begins the synthesis of your benzoic acid.
Extract the ether solvent from your mixture once it has become liquid. To do this add 5 percent NaOH to the mixture. This removes all ether solvent from your acid. The mixture will then dry into a fine, granulated salt known as carboxylate salt.
Add mineral acid once all dry ice has evaporated to melt down your Carboxylate salt into acid form. Allow it to dry and crystallize.