0.05 purslane 1.31 radish 0.48 rhubarb leaves 0.52 rutabaga 0.03 spinach 0.97 (ranges from 0.65% to 1.3%on fresh weight basis) squash 0.02 sweet potato 0.24 swiss chard, green 0.96 tomato 0.05 turnip 0.21 turnip greens 0.05 watercress 0.31 toxicity oxalic acid has an oral ldlo (lowest published lethal dose) of 600 mg/kg. it has been reported that the lethal oral dose is 15 to 30 grams. the toxicity of oxalic acid is due to kidney failure caused by precipitation of solid calcium oxalate. oxalate is known to cause mitochondrial dysfunction. ingestion of ethylene glycol results in oxalic acid as a metabolite which can also cause acute kidney failure. kidney stones most kidney stones, 76%, are composed of calcium oxalate. notes ^a unless otherwise cited, all measurements are based on raw vegetable weights with original moisture content.