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And while many metals must be refined using harsh chemicals and processes that generate air and water pollution, crystals are often just washed with water or oxalic acid.

These animals showed lowered levels of a compound called oxalic acid, which indicates sleep deprivation.

Instead, the researchers measured levels of oxalic acid, a metabolite associated with sleep loss, for some of the animals before, during and after the breeding season.

"There have been many attempts to explain the peculiar brown film. In 1851, German chemist, Justus von Liebig, performed the first actual scientific investigation and determined that the brown film contained oxalates -- salts of oxalic acid. This has been confirmed by later analyses, but the origin of the oxalates has remained a mystery," says Professor emeritus Kaare Lund Rasmussen, an expert in chemical analyses of historical and archaeological artifacts, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark.

The chestnut blight secretes a searing chemical, oxalic acid, into the tree bark, eventually causing cankers and death.