Alum

Alum is a scientific term that applies to both a class of compounds and to the individual members of that class. Some alums occur naturally and are mined, while others are created chemically. They form when a chemical, such as potassium hydroxide or sulfuric acid, acts on a trivalent metal. A trivalent metal is a metal with a valence of three, meaning each of its atoms has the power to combine with three other atoms. Alums are double sulfates that can form from a number of metals but are most commonly made with aluminum. They have many diverse uses for water purification and the production of paper, leather, and dyed cloth. The most widely known and used alum is potassium aluminum sulfate, which is a common ingredient in food and pharmaceuticals.

Background

Alums are most often seen and used in the form of white or colorless crystals. These crystals dissolve in water and can be turned into a liquid by heating them. If the heating process is continued, the alum will turn into a powder. Most alums are non-combustible.

Alum is commonly used in food. Alum has been used for many years to help pickled foods remain firm. It is also an ingredient in some baking powders and in other food additives such as colorings and preservatives.

Alums have astringent properties and cause body tissue to shrink. They also help liquids to coagulate, or come together in a firm or semi-firm state. As a result, alums have been used for centuries for wound care to help control bleeding. In modern times, alum is a common ingredient in styptic pencils used to stop bleeding from shaving nicks. It is also used as an aftershave and in some cosmetics. Alums are added to some medicines and vaccines to extend the life of the active ingredients or to make them more effective.

Some alums have antimicrobial properties, making them useful in deodorants. People seeking a natural way to control body odor sometimes use larger alum crystals from mines in place of commercially produced deodorants. This is common in Asian and Pacific cultures.

Treated alums will coagulate with particles in water, causing them to drop to the bottom of the water source or to form clumps of particulates that can be removed by filtering. This makes alums useful for the treatment of both potable (drinkable) water and for wastewater treatment.

Alums are used in photography during the developing process for fixing images and cleaning the final negatives. They are used in textile manufacturing as a mordant, or a dye-fixing agent. Alums are used by papermakers to help the fibers combine, and taxidermists use alum during the skin-tanning process.

Overview

A number of different alums exist. These include sodium alum (sodium aluminum sulfate), ammonia alum (ammonium aluminum sulfate), and papermakers' alum (aluminum sulfate). However, the term alum is most commonly used to refer to potassium aluminum sulfate.

Sometimes called potassium alum, this form can be created synthetically but also occurs naturally. It is mined in quarries in Tennessee and Arizona in the United States and in several areas of the Andes Mountains in South America, including Bolivia, Chile, Colombia, Argentina, and Venezuela. Mined potassium alum is found as an encrustation on other rocks and is a white crystal. Larger crystals of alum are often sought by mineral collectors.

Potassium alum is the form most often used for food, pharmaceutical, and cosmetic preparation. It is widely available for purchase in the spice section of grocery stores and is used in home canning and for baking. Alum is also a part of many processed foods and beverages, including baked goods and wines.

Despite its many and diverse applications, the use of alum in food, cosmetic, and pharmaceutical products is not without controversy. Some of the controversy stems from an incident in England in 1988, when a truck driver accidentally dumped twenty tons of aluminum sulfate—a type of alum—into the drinking water supply for Camelford in Cornwall. The water had a foul taste, and many residents reported short-term health repercussions such as digestive problems, skin problems, joint pain, and fatigue. Others complained of memory loss and premature aging. After an autopsy on a fifty-eight-year-old woman who died of an uncommon and aggressive form of Alzheimer's disease revealed large amounts of aluminum in her brain, concerns were raised about the health risks of ingesting aluminum and its related products, including alum.

Aluminum is known to be toxic in high quantities but it was long thought that the amount ingested under normal circumstances was safe. While each individual source may be safe, people are often unknowingly exposed to aluminum or its derivatives in many sources, including the alum that appears naturally in some foods, such as tea; the alum used as an additive in foods, cosmetics, and pharmaceuticals; and the alum used to treat water. Some experts began to question whether it was safe for people to consume so much of so many forms of aluminum and what the long-term health consequences might be.

One of the largest areas of concern includes vaccines, especially those given to children. Potassium alum is used as an adjuvant in many, but not all, vaccines. An adjuvant increases the potency of the vaccine and allows for the use of smaller amounts of the active ingredient, which is sometimes a live version of the disease-causing organism. Most physicians' groups recommend that children be vaccinated against as many as fourteen diseases, some requiring multiple doses, by the time the child reaches fourteen years of age. Although government agencies such as the US Food & Drug Administration have approved these vaccines for use and say the level of alum present is safe, some have raised concerns. They cite the small size of the children who receive these vaccines, the amount of development their brains and bodies are undergoing at the time, and the cumulative exposure from the frequent vaccines received during this time as increasing the risk to current and future health. As a result, some parents decline to have their children immunized.

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