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The acid in pure form is highly corrosive towards other materials, as it is an oxidant and has a strong acidic nature. Additionally the pure acid is highly dehydrating, which means it will strip water away from many substances as it comes into contact with them. A notable exception is phosphorus pentoxide, which is capable of dehydrating sulfuric acid to sulfur trioxide. Sulfuric acid is also hygroscopic, readily absorbing water vapor from the air. Upon addition of sulfuric acid to water, a considerable amount of heat is released. For this reason, the reverse procedure of adding water to concentrated sulfuric acid solutions should not be performed. The heat released may boil the solution, spraying droplets of hot acid in the process. Upon contact with bodily tissue, pure sulfuric acid can cause severe chemical burns and even secondary thermal burns due to dehydration; even small amounts of the pure acid are dangerous. Dilute solutions of sulfuric acid in water are substantially less hazardous as the oxidative and dehydrating properties are only present in the concentrated acid. However, solutions of the acid in water are strongly acidic, and should therefore still be handled with care.