Noun used with modifier

• %: Closed patch tests with 8 % olibanum in petrolatum was found to be non-irritant to human skin.

Modifies a noun

• gum: Olibanum gum applied to intact or abraded rabbit skin for 24 hours under occlusion was found to be moderately irritating.

Preposition: in

• petrolatum: Closed patch tests with 8 % olibanum in petrolatum was found to be non-irritant to human skin.