- July 14th, 2010
Though most people have never seen sodium metal, it is almost impossible that they do not see many compounds of sodium every day. Ordinary table salt, baking soda, baking powder, household lye, soaps and detergents, aspirin and other drugs, and countless other consumer products are sodium products. Sodium is a member of the alkali metals family. The members of the alkali metals family are among the most active elements.
Sodium carbonate, or soda (Na2CO3), was probably the sodium compound best known to ancient peoples. It is the most common ore of sodium found in nature. This explains why glass was one of the first chemical products made by humans. Glass is made by heating sodium carbonate and calcium oxide (lime) together. When the mixture cools, it forms the hard, clear, transparent material called glass. Glass was being manufactured on a large scale in Egypt as early as 1370 B.C. The Egyptians called soda natron. Much later, the Romans used a similar name for the compound, natrium. These names explain the chemical symbol used for sodium, Na.
The name sodium probably originated from an Arabic word suda, meaning “headache.” Soda was sometimes used as a cure for headaches among early peoples. The word suda also carried over into Latin to become sodanum, which also means “headache remedy.” In the early 1800s, Davy found a way to extract a number of active elements from their compounds. Sodium was one of these elements. Davy’s method involved melting a compound of the active element, then passing an electric current through the molten (melted) compound. Davy used sodium hydroxide (NaOH) to make sodium.
Though oil and vinegar don’t mix, sodium and water really don’t mix. Sodium reacts violently with water. The effect is fascinating. When sodium metal is first placed into water, it floats. But it immediately begins to react with water, releasing hydrogen gas. A great deal of energy is released in this reaction. It is enough to set fire to the hydrogen gas. The sodium metal reacts with water. So much heat is released that the sodium melts. It turns into a tiny ball of liquid sodium. At the same time, the sodium releases hydrogen from water. The hydrogen gas catches fire and causes the ball of sodium to go sizzling across the surface of the water. Sodium reacts violently with water.
Sodium chloride can also be obtained from seawater and brine. Brine is similar to seawater, but it contains more dissolved salt. Removing sodium chloride from seawater or brine is easy. Sodium stored in oil to prevent its reaction with the surrounding air. All that is needed is to let the water evaporate. The sodium chloride is left behind. It only needs to be separated from other chemicals that were also dissolved in the water.
There is only one naturally occurring isotope of sodium, sodium-23. Six radioactive isotopes of sodium are also known. Two radioactive isotopes of sodium—sodium-22 and sodium-24—are used in medicine and other applications. They can be used as tracers to follow sodium in a person’s body. Sodium-24 also has non-medical applications. For example, it is used to test for leaks in oil pipe lines. These pipe lines are usually buried underground. It may be difficult to tell when a pipe begins to leak. One way to locate a leak is to add some sodium-24 to the oil. If oil leaks out of the pipe, so does the sodium-24. The leaking oil may not be visible, but the leaking sodium-24 is easily detected. It is located by instruments that are designed to detect radiation.
The combination of an electric current and sodium vapor produces a yellowish glow in street lamps. Sodium is frequently used in making light bulbs. Sodium is first converted to a vapor (gas) and injected into a glass bulb. An electric current is passed through a wire or filament in the gas-filled bulb. The electric current causes the sodium vapor to give off a yellowish glow. Many street lamps today are sodium vapor lamps. Their advantage is that they do not produce as much glare as do ordinary lights.
Almost all sodium compounds dissolve in water. When it rains, sodium compounds dissolve and are carried into the ground. Eventually, the compounds flow into rivers and then into the oceans. The ocean is salty partly because sodium compounds have been dissolved for many centuries. But that means that finding sodium compounds on land is somewhat unusual. They tend to be more common in desert areas because deserts experience low rainfall. So sodium compounds are less likely to be washed away. Huge beds of salt and sodium carbonate are sometimes found in desert areas.
Dozens of sodium compounds are used today in all fields. Some of the most important of these compounds are mentioned as under:
Sodium chloride (NaCl): The most familiar use of sodium chloride is as a flavor enhancer in food. It is best known as table salt. Large amounts of sodium chloride are also added to prepared foods, such as canned, bottled, frozen, and dried foods. One purpose of adding sodium chloride to these foods is to improve their flavors. But another purpose is to prevent them from decaying. Sodium chloride kills bacteria in foods. It has been used for hundreds of years as a food preservative. The “pickling” or “salting” of a food, for example, means the adding of salt to that food to keep it from spoiling.
This process is one reason people eat so much salt in their foods today. Most people eat a lot of prepared foods. Those prepared foods contain a lot of salt. People are often not aware of all the salt they take in when they eat such foods. Sodium chloride is also the starting point for making other sodium compounds. In fact, this application is probably the number one use for sodium chloride. Almost all sodium compounds dissolve in water. They tend to be more common in desert areas because deserts experience low rainfall.
Sodium carbonate (Na2CO3): Sodium carbonate is also known by other names, such as soda, soda ash, sal soda, and washing soda. It is also used as the starting point in making other sodium compounds. A growing use is in water purification and sewage treatment systems. The sodium carbonate is mixed with other chemicals that react to form a thick, gooey solid. The solid sinks to the bottom of a tank, carrying impurities present in water or waste water. Sodium carbonate is also used to make a very large number of commercial products, such as glass, pulp and paper, soaps and detergents, and textiles.
Sodium bicarbonate (NaHCO3): When sodium bicarbonate is dissolved in water, it produces a fizzing reaction. That reaction can be used in many household situations. For example, the fizzy gas can help bread batter rise. The “rising” of the batter is caused by bubbles released when sodium bicarbonate (baking soda) is added to milk in the batter. Certain kinds of medications, such as Alka-Seltzer, also include sodium bicarbonate. The fizzing is one of the effects of taking Alka-Seltzer that helps settle the stomach. Sodium bicarbonate is also used in mouthwashes, cleaning solutions, wool and silk cleaning systems, fire extinguishers, and mold preventatives in the timber industry.
A common compound of sodium, sodium bicarbonate, produces a fizzing reaction. It is an ingredient in such medications as Alka-Seltzer.
This high level of sodium intake troubles many health experts. Too much sodium can affect the body’s ability to digest fats, for example. The most serious problem, however, may be hypertension. Hypertension is another name for “high blood pressure.” A person with high blood pressure may be at risk for stroke, heart attack, or other serious health problems. Sodium is also involved in sending nerve messages to and from cells. These impulses control the way muscles move. Again, an excess or lack of sodium can result in abnormal nerve and muscle behavior. Sodium is also needed to control the digestion of foods in the stomach and intestines.