{Oxalic acid} (Chem.), a dibasic acid, existing combined in
oxalis as an acid potassium oxalate, and in many plant
tissues as the calcium oxalate. It is prepared on a large
scale, by the action of fused caustic soda or potash on
sawdust, as a white crystalline substance, which has a
strong acid taste, and is poisonous in large doses. It is
used in dyeing, calico printing, bleaching flax and straw,
the preparation of formic acid, and in salts of lemon for
removing ink stains, mold, etc.