Some sorcerers have the secret of reducing their bodies to this powdered salt.
Some who use this knowledge are wicked sorts who have sacrificed their humanity for immortality, for the salts can be mixed with appropriate ingredients, such as purified blood, and if done correctly a new body will be formed with the memories of the sorcerer.
By contrast, others have sought a more complete death in this wise. Fearing their body might be the subject of some fell magic (for sorcerers are ever the prey of seekers after revenge or knowledge) or perhaps fearing some future resurrection, they seek to reduce their body to a fine powder which can be cast to the wind.
If these salts are mixed in their entirity with water, mayhap by one who mistakes them for dehydrated water, they will likely produce a malevolent water spirit. The effect of combining them with water elementals is not known.