The chemical makeup of this substance is potassium aluminum sulfate, and it is a form of salt. It is off-white or yellowish and is highly soluble in water and alcohol. It does not emit any odors, but it does have a strong, salty/sweet taste. It is stable in air and usually non-toxic to humans.
Alum can be found in both industrial and consumer applications, with the latter requiring the substance to be labeled “food-grade.” As an additive, it helps add a crispy texture to certain foods, such as pickles or fruit. It can also be used to purify and soften water from heavy metals and other minerals.
In concentrated doses, alum can be harmful to humans, irritating the eyes and skin, as well as sickness if ingested. As such, gloves and eye protection should be worn when handling the substance, both to avoid irritation as well as contamination.