CORRESPONDENCE BALANCING EQUATIONS tions, we find a = "4, x = '/*, y = I/. and w = a/,; or,clearing To the Edibr of frsctions, a =. 3.6 = 4, w = 3, x = 2, and y = 2. Substituting DEARSIR: these numerical values now for the literal ones above given, we The inquiry of A. W. S. Endslow [J. CHEM.EDUC., have the correct equation: 8,2453 (Dec., 1931)] about an algebraic method for bal3Sn 4HNOa = 3Sn01 2Nn01 2Hn0 ancing equations, and the numerous responses to it, [ibid., 9,35843, 560, 7514, 944-5, 1124-6, 1299-1301 I have not been able to learn when the f i s t edition of (1932), and 10, 250 (1933)l leads me at this late date to this book was published or if it contained this procedure. While Professor of Chemistry in George Washington call your attention to a paragraph on page 70 in "A Textbook of Elementary Chemistry, Theoretical and University, Dr. Munroe gave this method to his classes Inorganic" by George F. Barker, M.D., second edition, from 1892 to 1918. Since then I have continued the revised and enlarged, 1891, in which the "algebraic practice though emphasizing the knowledge of chemmethod of simultaneous linear equations" is mentioned istry that will enable the pupil to write the products of a reaction rather than to balance precisely a complex and illustrated by means of an example. The statement from Barker's "Chemistry" is as equation, which result may be more misleading than useful in the matter of showing the true course, or follows: I n some cases, however, where the reaction is a complex one, courses, of the reaction. In these later years when new ideas of valence, it is convenient t o be able t o calculate the number of molecules. This may readily be done by the use of the algebraic method of oxidation-reduction, and ion transfer have unduly simultaneous linear equations, which may be illustrated as fol- magnified the business of balancing intricate chemical lows:' Suppose i t be required t o write the reaction where tin reactions, my pupils take with avidity to this method acts on nitric acid, the products being stannic oxide, nitrogen dioxide, and water. Using letters t o indicate the number of which is given once only and after the other methods have been thoroughly exemplified, and they often tell molecules, we have the equation: me that they prefer it to any other method that has aSn + 6HNOs = wSnO2 xN10a yH*O Since the number of atoms of each element must be the same on been presented. the two sides of the equation, we have for the tin, a = w; for the Very truly yours, hydrogen, b = 2y; for the nitrogen, b = 2r; and for the oxygen, H. C. McNEn 36 = 2w + 22 + y. Assuming b = 1, and salving these equaGEORGE WASHINOTON UNIVERSITY WASRINGT~N, D. C . * As suggested by C. E. Munroe.
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