Some corrosives possess other chemical properties which may extend their corrosive effects on living tissue. For example, sulfuric acid (H2SO4) at a high concentration is also a strong dehydrating agent, capable of dehydrating carbohydrates and liberating extra heat. This results in secondary thermal burns in addition to the chemical burns and may speed up its decomposing reactions on the contact surface. Some corrosives, such as nitric acid and concentrated sulfuric acid, are strong oxidizing agents as well, which significantly contributes to the extra damage caused. Hydrofluoric acid does not necessarily cause noticeable damage upon contact, but produces tissue damage and toxicity after being painlessly absorbed. Zinc chloride solutions are capable of destroying cellulose and corroding through paper and silk since the zinc cations in the solutions specifically attack hydroxyl groups, acting as a Lewis acid. This effect is not restricted to acids; so strong a base as calcium oxide, which has a strong affinity for water (forming calcium hydroxide, itself a strong and corrosive base), also releases heat capable of contributing thermal burns as well as delivering the corrosive effects of a strong alkali to moist flesh.