Testing a novel method to identify salt production pottery via release and detection of chloride ions

A recently published analytical technique to detect chloride ions in ceramic vessels that were used to produce salt is replicated (Horiuchi et al., 2011). The method involves releasing bound chloride ions permanently retained by the vessel via a chemical exchange reaction with ammonium fluoride, following the removal of all unbound salt with water. The chloride concentration is measured in solution and used to quantify the amount of salt that was bound to the ceramic matrix. Our data suggest that this method is not a viable way to consistently discriminate salt-making pottery, as the detected chloride may not be derived from salt production activities, but from the ceramic material of the pot itself. We employ experimental vessels in which salt-making was simulated, in addition to analyzing excavated sherds from two Chinese and one North American site known to have been involved in salt production. The method proposed by Horiuchi et al. is not able to distinguish salt-making and non-salt-making vessels from one another.