VOL.9, No. 2
CORRESPONDENCE
361
solution) makes it almost impossible for practical use. It surely would be a very good hobby for any one interested in chemistry to keep in mind. Very respectfully yours, ARTHURR. CLARK FRANKLIN AND MARSAALL COLLEGE LANCASTER, PENNA. DEAREDITOR: The algebraic method of balancing chemical equations set forth in the recent communication of A. W. S. Endslow U. CHEM.EDUC.,8,2453 (Dec., 1931)l requires the solution of as many simultaneous linear equations as there are substances symbolized in a given chemical equation. It follows that there must be a t least (n- 1) different elements involved in a chemical equation of n substances, since one algebraic equation is formulated for each element, and in addition, a is set equal to one. This requirement is met by many, but not by all, chemical equations. For example, cannot be balanced by this method, since i t is possible to formulate only six independent linear equations, whereas seven are necessary. Very truly yours, NICHOLAS DIETZ,JR. TnE UNIVERSITY OF PITTSBURGH P I T T ~ B ~PENNS~VANIA GH, T DEAREDITOR: From time to time I see in the JOURNAL OF CHEMICAL EDUCATION and other magazines articles on methods of balancing equations. The one occurring in the correspondence section of the December, 1931, issue of THIS JOURNAL (p. 2453) caused me to submit the method I have used in my general chemistry classes for a number of years. This method seems simple to me, though my description may appear involved. My students have had very little trouble using it on even the most difficult equations. It might be helpful to others. I classify reactions in three groups as follows: Case No. 1. Reactions that are non-oxidation-reduction or simple oxidation-reduction. Case No. 2. Oxidation-reduction rextions in which one element is oxidized and one reduced. Case No. 3. Oxidation-reduction reactions in which two different elements are oxidized or reduced and, in rmjunction, one or two reduced or oxidized.
