First, because the expression "molecular" has been given to equations in which all species are written indiscriminately as molecules regardless of their degree of ionic or covalent character, use of the term "ionic" for this type of equation advocated by Wruck as well as by numerous textbooks and laboratory manuals is often misleading to students. Indeed, examination of some students' efforts in this field seems to point to their apparent belief that the method involves writing everything as ionic. For this reason and because such equations are "principal", i. e., they show both reactants and products in the principal form (covalent or ionic) in which they exist, and "net", i. e., they omit extraneous, nonreacting species, my mentor and Doktorvater, the late John F. Baxter, Jr. (1), advocated the term "principal net reactions". Because a large proportion of beginning students experience considerable difficulty in writing such equations, a detailed discussion of and directions for consistent writing of principal net equations, along with specific examples (2), has proved to be of value to students and instructors alike.

Second, several chemists have pointed out that the principal species in aqueous ammonia is molecular NH₃ (3­6), even though Tuttle (7) reports that NH₄OH exists as a highly labile complex with an extremely short lifetime (10^-10 s). However, Wruck writes it as NH₄OH. Indeed, one of the reasons that John Baxter and I advocated the use of "Hydrated Cations in the General Chemistry Course" (8) was to avoid consistently the necessity of using NH₄OH or NH₃ + H₂O in equations for the hydrolysis of hydrated metal cations or the precipitation of gelatinous metal hydroxides by the action of aqueous ammonia on solutions containing hydrated metal cations such as Al(H₂O)₆³⁺, Cr(H₂O)₆³⁺, Mg(H₂O)₆²⁺, and Zn(H₂O)₄²⁺. Furthermore, the Brønsted­Lowry concept (9) permits hydrolysis to be viewed as a normal acid­base reaction.

Literature Cited

1. Kauffman, G. B. J. Chem. Educ. 1987, 64, 752.

2. Kauffman, G. B. J. Coll. Sci. Teaching 1979, 9, 83.

3. David. J. B. J. Chem. Educ. 1953, 30, 511.

4. Laing, M. Spectrum 1988, 26(4), 11.

5. Yoke, J. T. , J. Chem. Educ. 1989, 66, 310.

6. Kauffman, G. B. J. Chem. Educ. 1991, 68, 534.

7. Tuttle, Jr., T. R. J. Chem. Educ. 1991, 68, 553.

8. Kauffman, G. B.; Baxter, Jr., J. F. J. Chem. Educ. 1981, 58, 349.

9. Kauffman, G. B. J. Chem. Educ. 1988, 65, 28.