Q. I am concerned about the amount of sugar in cereal. Labels on the boxes commonly provide information on how much sugar a serving contains, but the figure is given in grams. How much does a teaspoon of sugar weigh?

A. A teaspoon of sugar weighs four grams. Thus, if a serving of cereal contains 13 grams of sugar, that's the equivalent of just over three teaspoonfuls. The catch lies in the definition of serving.

Your question prompted us to visit a supermarket cereal aisle to check how much sugar is being used these days. The findings? Sugar content ranged from none to 13 grams per serving. But once again, remember that serving sizes are defined by the manufacturer.

Portion sizes were found to vary from just 1/4 cup in a granola-type cereal (considerably less than most people would eat), to over a cup. The amount of sugar in a granola-type cereal with a serving size of 1/4 cup was seven grams, but it's easily possible that someone would eat twice that much or more.

Another variation on granola also had seven grams of sugar per serving. But in this case the serving size was 1/2 cup. A third popular cereal provided 13 grams, but the serving size was one cup. Unfortunately for consumers, the range is limitless.

As for calories, the most heavily sugared granola had 130 calories in the 1/4 cup serving. So, too, did 1/2 cup of the less heavily sugared variety. The cereal that contained 13 grams of sugar in one cup had 110 calories. If you're watching your calories closely, the differences are not very great -- that is, as long as you carefully adhere to the serving sizes.

Better still, stick to the unsugared varieties and depend for sweetness on some sliced fresh fruit.

Q. Are carbonated beverages an American phenomenon?

A. The idea for carbonating water originally dates back to Joseph Priestley, an 18th-century British chemist, but he did not explore its vast potential. It was left to Benjamin Silliman, a professor of chemistry at Yale, to make the first efforts in that direction. In 1807, he marketed carbonated, bottled water for the first time. By the 1830s, more entrepreneurial types had seized upon the concept and, aided by aggressive advertising slogans, were vigorously selling unflavored soda water.

What wizard thought of adding flavor is not known for sure, but credit generally goes to the one of two Frenchmen, both living in Philadelphia in the 1830s. It had thus taken more than 60 years to get from Priestley's idea to the instantly successful notion of flavoring it. By 1849, there were 64 soda plants in the United States. Ten years later, that number had nearly doubled, producing over $1 million worth of mineral waters and flavored soda.

By the turn of the century, more than 2,700 bottling plants were doing $25 million worth of business. And the beat goes on, as our unfortunate thirst for carbonated beverages seems to know no limit. In 1987 Americans drank, on average, 30 gallons of carbonated beverages each, four gallons more than the amount of milk they consumed.

1990, Washington Post Writers Group