Which substance is formulated as a chemical germicide for use on skin?

The correct choice is antiseptic because it is specifically designed to kill or inhibit the growth of microorganisms on the skin. Antiseptics are used in various settings, including hospitals and beauty salons, to reduce the risk of infection and promote cleanliness. They can come in various forms, such as liquids, creams, and gels, and are routinely applied to minor cuts, scrapes, and other skin abrasions to prevent the spread of bacteria.

In contrast, acetone is primarily a solvent used in beauty treatments for removing nail polish and is not formulated to kill germs on the skin. A styptic pencil is used to stop bleeding from minor cuts and may contain antiseptics, but its primary purpose is not as a germicide. Brittle nails remedy is specifically focused on treating and conditioning nails that are weak or prone to breakage, which does not pertain to germicidal action on the skin. Thus, antiseptic stands out as the proper option as it directly fulfills the requirement of being a chemical germicide specifically for skin use.