Oxalic acid and oxalates can be oxidized by permanganate in an autocatalytic reaction. In contrast, mineralized calcium secretions in cacti are composed of calcium oxalates. Calcium oxalates are a major constituent of human kidney stones. Bacteria produce oxalates from oxidation of carbohydrates. Gadolinium oxide can be formed by thermal decomposition of the hydroxide, nitrate, carbonate, or oxalates. Finally, calcium oxalates serve as a reserve of carbon dioxide. The oxalates are decomposed to oxides by heating. Cooking the leaves with baking soda can make them more poisonous by producing soluble oxalates. The oxalates are converted to oxides by annealing. Iron, nickel, uranium, and beryllium submicrometre powders are obtained by reducing metallic oxalates and formates. These oxalates can form larger kidney stones that can obstruct the kidney tubules. The largest such group is the oxalates, which combine with cations. Many tropical plants contain oxalates in varying amounts. Mean lethal dose by ingestion of oxalates is 10-15 grams/kilogram of body weight (per MSDS). Oxalates also decolourise KMnO and give a white precipitate with CaCl.