Chapter 6 Ions: Charged Particles in Solution 95 extra H+ ions they can contribute. Bases easily accept protons and are therefore called proton acceptors. Bases have a negative charge and will readily accept H+ ions. These facts about the nature of acids and bases are summarized in the Bronsted-Lowry theory. This theory states that acids are proton donors and bases are proton acceptors. This scientific explanation also states that, whenever possible, acids and bases natu- rally react with their opposites to achieve a neutral charge. The Bronsted-Lowry theory defines acids and bases in terms of proton needs that will achieve this balance. The Bronsted-Lowry theory is the most compre- hensive theory about the nature of acids and bases. Even so, it does not explain the reaction of carbon dioxide (CO2) in water-based mixtures like soft drinks and egg whites. Carbon dioxide is the source of carbonation for soft drinks. However, it does not have a hydrogen ion or proton to donate. Another discovery about acids and bases was made in 1923 by an American chemist named Gilbert Newton Lewis. Lewis discovered that acid/base reactions could be described in terms of the move- ment of electrons. In acids and bases where there is no hydrogen involved, ions are looking to donate or accept electrons. Substances that donate electrons are bases, and substances that accept electrons are acids. Carbon dioxide increases the acidity of a mixture because, in the presence of water, it is an electron acceptor. Identifying Acids and Bases You can identify acids and bases in two common ways. One way is through sensory evaluation. You can also identify acids and bases with the use of organic dyes. Sensory Evaluation of Acids and Bases A simple way to identify many acids and bases is by sensory evaluation, such as taste testing. You must use caution, however, because not all acids and bases are safe to taste. Poisoning and burning can result from tasting certain acids and bases. In those cases where testing can be done safely, you would find that acids taste sour. Lemons, grapefruit, cranberries, vinegar, and yogurt contain acids that are safe to taste, 6-3. Bases have a bitter flavor. Quinine water, milk of magnesia, and baking soda are examples of bases that are safe to taste. Another type of sensory evaluation that can help you identify bases is to touch them with your fingers. Again, you must use caution. Some bases can cause problem that may be tied to excess sodium intake is stomach cancer. Sodium appears to irritate the lining of the stomach, which increases the chances of cancer cells developing. Excess sodium has an additional risk for athletes. Too much salt causes dehydration of cells and increases potassium loss, which leads to chronic fatigue. To reduce your risk of these health concerns, registered dietitians recommend that you avoid high- sodium foods. Foods highest in sodium are processed foods, especially mixes, frozen entrees, and canned foods. Read labels, cook from scratch, limit “instant” products, and select low-sodium and no-salt options. Try flavoring foods with pepper, fresh herbs, onion, garlic, and spices that are all low in sodium and high in flavor. Taste before reaching for the salt shaker. Keep in mind that it may take about four to six weeks to become used to foods with less salt. Nutrition News Salt in the Diet The 2015 Dietary Guidelines for Americans recommend a maximum sodium intake of 2,300 mg for most people. The average American 19 to 51 years of age consumes around 3,400 mg of sodium per day. Higher levels of sodium may be needed by athletes after high-intensity activity and by those who sweat excessively. People with high blood pressure, diabetes, or chronic kidney disease may need to keep salt consumption below 1,500 mg per day. There is some evidence that salt preference is established through exposure between the ages of one and three. Limiting sodium in the diets of young children may help them control their salt intake when they grow older. Research has linked excess sodium in the diet to a number of health problems. For some people, excess sodium can increase the risk of high blood pressure. Sodium also speeds calcium loss from bones. For each teaspoon of salt you consume in a day, you will lose 23 mg of calcium from your bones. This equals 10% of your total bone mass over each 10-year period. Bone loss is associated with fractures and related complications, especially in later life. A third health Copyright Goodheart-Willcox Co., Inc.