Salt (しお, Shio) is an item in the first Suikoden. It can be obtained in Kirov but its only use is to trade it for Soy Sauce as part of the fetch quest to recruit Sarah.
Suikoden
When Tir attempted to recruit Sarah in Kirov by getting her some Soap, he had to complete a series of trades in order to obtain it. After obtaining the Salt by trading a Yardstick for it, he went to trade this in the city for some Soy Sauce.