Let's Put an End to Textbook Nonsense

It took half a century to get NH4OH out of our high school and college chemistry textbooks. Arrhenius hypothesized its existence around the turn of the century because ammonia dissolves in water to form a basic solution, and his definition of a base required it to contain an OH group. Diligent research in the 1920s and 1930s failed to provide evidence for it, Lewis structures suggested it was impossible, but it was in our textbooks up to the late 1970s. That’s not the only error in chemistry textbooks. A 0.5M solution of MgCl2 does not contain 0.5M Mg2+. Using published equilibrium constants (Smith RM Martell AE, Critical Stability Constants, vol. 1-4, Plenum, 1975-1982), 36 percent of the Mg exists as MgCl+. Yet introductory high school and college texts encourage students to believe that metal salts are totally ionized in solution! CdCl2 in 1.4M solution exists as 34 percent unionized CdCl2 63 percent CdCl+ and only 3 percent Cd2+. A recent article in the Journal of Chemical Education (vol. 64, 1987, pp. 124-127) suggests another error in the most commonly used chemistry texts. The article shows that the bonds of H20 are formed from unhybridized p-orbitals rather than the sp3 orbitals described in standard texts. Because I am much less comfortable with molecular orbital theory than with ionic equilibria, I cannot decide for myself which is correct. This example illustrates two aspects of the perpetuation of nonsense in textbooks. First, it is safer for publishers to go along with received wisdom than adopt a new viewpoint that carries with it the risk of making one appear foolish, especially if such an appearance reduces sales. We can expect apparent errors like this one to continue. But more importantly, there is no reason to expose students to the concept at all. If we can tell students an untruth for decades (as I apparently have in this case) and get away with it, then the subject obviously is unimportant. Students who take only one year of chemistry will be unable to apply the concept of hybrid orbitals to anything of the slightest interest to them, and should not be required to waste their time on it. It is nearly 20 years since Mason and Evans explained in the Journal of Chemical Education (vol. 46, 1969, p. 358, 423) that Graham’s Law of Diffusion is inapplicable to any situation that any of us is ever likely to meet. Graham’s Law is popular with teachers because it can be derived from the kinetic theory in a way that brighter students can appreciate. Still, it is malpractice to teach a law, however intellectually elegant, that produces wrong answers in any realistic situation. Occasionally, textbook authors omit it, presumably realizing its pointlessness, but they do so at the risk of reduced sales. These are just two examples of textbook errors. What really frightens me is the thought that I probably am teaching even more nonsense that I confidently believe to be correct. If this is true in chemistry, it’s probably true for other disciplines, too. Can scientists do anything about these errors? Yes, we can. First the errors need to be identified. Professional societies should appoint committees to examine the received wisdom, encourage complaints about common errors, and sort the real errors from the hobby-horses of the trivial-minded and the misinformed. These committees must then publish their results. History shows that this is not nearly enough. The “Textbook Errors” column of the Journal of Chemical Education has listed and explained such errors for decades, but many of them remain uncorrected in the texts. Some clout is necessary The committees must examine new texts, and list the errors in each of them inappropriate journals that are read by primary and secondary science teachers and in professional journals that are read by high school and college teachers. Above all, they must persuade the authors of national exams not to include questions that involve the regurgitation of nonsense. Teachers normally teach what they themselves were taught and continue to do so for decades. high school chemistry teacher ~in 1944 acknowledged that there were people who believed that salts were ionized in solution, but clearly implied that such people were the lunatic fringe. Teachers continue to teagh the Bohr theory of the atom and the Arrehenius concept of acid/base behavior although both are obsolete confusing and deceptive. Obsolete concepts are difficult to eliminate, but there can be few more important projects in education than to protect the young from having to learn obsolete and deceptive ideas. The new Committee on Introductory Chemistry of the American Chemical Society can be relied upon to question what subjects our students should study, but will it address the question of textbook errors? Let us hope so, and let us further hope that other professional bodies follow its example. Hawkes is professor of chemistry at Oregon State University, Corvallis, OR 97331-4003.

Let's Put an End to Textbook Nonsense

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