Specification of the Patent Granted to George Hudson, of the City of Edinburgh, North Britain, Ash-Manufacturer; for a Method of Separating the Alkaline Salt from the Acid, as It Exists in the following Substances; Viz. Kelp, Black Ashes, Soapers' Salts, Spent Leys, Soda Natron, Rock Salt, Common Salt, Brine, Sea Water, Caput Mortuum of Aquafortis, Caput Mortuum of Oil of Vitriol, and Caput Mortuum of Salt Used by Bleachers