May 2005

Ammonium chloride, NH4Cl, is a component of dry cell batteries, those little storehouses of energy that power so many of our electrical devices. Batteries are awfully convenient little inventions that permit us to use electricity when we are nowhere in sight of an electrical outlet. With battery power we can have music while we jog down the sidewalk, light while we camp on a moonless night, and the convenience and accuracy of a pocket calculator.

Found in nature and also produced industrially, ammonium chloride has other important uses too, including lowering the melting temperatures of certain metals for manufacturing processes, and as a fertilizer, anti-caking agent and ingredient in personal care products and pharmaceuticals.

Two Pathways to Ammonium Chloride

Photo copyright © Frank de Wit

Tiny, delicate crystals of ammonium chloride, the mineral "sal ammoniac," form around the fuming vents of active volcanoes. These crystals are products of the chemical reaction of volcanic gases containing hydrochloric acid (HCl) with nitrogen-rich, natural organic matter, such as vegetation found in soils and sediments around volcanoes. Water soluble, the beautiful crystals are short-lived because they dissolve in the very first rainwater that falls upon them.

Less dramatically, but quite efficiently, ammonium chloride may be produced industrially by more than one method. In one process, ammonia gas, the chemical compound NH3, is bubbled into water, forming NH4OH, ammonium hydroxide:

Ammonium hydroxide is then combined with hydrochloric acid, HCl, according to the following reaction:

Notice that water is a "co-product" of this reaction.

An atom: Everything you can touch is made of atoms.

Dry Cell Batteries: Delivering Electricity on Demand

Batteries convert chemical energy into electricity. Remember that all matter-everything you can touch--is made of atoms. Atoms consist of positively charged protons, neutral neutrons and negatively charged electrons (see the diagram to the right). Electricity may be thought of as the flow of electrons that are temporarily separated from atoms. Batteries are designed to take advantage of the movement of electrons that occurs during chemical reactions. Different types of batteries use different chemicals, and ammonium chloride is one of several chemical compounds that plays a role in generating portable electricity.

Battery Basics

There are three main components to every battery: a cathode (the raised top of your everyday AA battery, for example, from which electrons flow), an anode (the bottom of the AA battery, toward which electrons flow) and an electrolyte through which electrons and ions can move. When ammonium chloride is used as an electrolyte in a battery, it is made into a watery paste and placed between the cathode and anode.

Dry cell batteries can be used to power your portable CD player. Chemical reactions between the batteries' cathodes and anodes cause electrons to stream through the ammonium chloride paste, away from the cathode and toward the anode (see figure below). The electrons then stream through the metal contacts in your CD player's battery compartment and through the instrument to power it. 

For a list of previous "Chlorine Compound of the Month" features, click  here.


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