Prep. Made by rubbing a quarter of an ounce of plaster of Paris (sulphate of lime, dried), in a porcelain mortar with two fluid ounces of distilled water, and then adding the milky fluid to eighteen fluid ounces of water, and after allowing the undissolved sulphate to subside, decanting off the clear solution for use.

Use. This solution gives rise to a precipitate (oxalate of lime) when treated with oxalic acid or a soluble oxalate; it is used under Acidum Tartaricum to ascertain the absence of oxalic acid.