... :dimethyl oxalate2.Appearance:white slanting crystal3.Assay(GC). % (as dimethyl oxalate) : 99.554.Free acidity w/w,% (as oxalic acid) :0 ... in the presence of an alkali catalyst to form sodium oxalate, which should be converted to free oxalic acid when treated ... formic acid) is readily oxidized and combine with calcium, iron, sodium, magnesium, or potassium to form less soluble salts called oxalates ...