Correspondence "I
A QUESTION OF PROCEDURE Under this title, Mr. Charles H. Stone,' a clever teacher of chemistry in the English High School of Boston, recommends that the time-honored procedure for computing the smallest possible molecular weight of a compound from its percentage composition be changed. Instead of first finding out how many gram atoms of an element are present in one hundred grams of the original substance and in that way finding the ratio existing between the atoms in a given weight of substance, Mr. Stone first finds the molecular weight on the basis that one atom of some element, chosen a t random, is present in the molecule. Thus if a sub23 X 100 = 53 stance contains 43.4% of sodium, the molecular weight is 43.4 if only one atom of sodium is present in the molecule. According to the conventional method the first step in the reasoning is to say that since 43.4 grams of sodium are present in 100 grams of substance there must 43.4 be - = 1.89 gram atoms of sodium in 100 grams of material. 2.1 -.
Mr. Stone comes in contact with boys who are not as a rule going to study chemistry after he is through with them and it is quite natural with such pupils to attempt to draw analogies between chemical problems and interest problems but there seems to be little choice between the two methods of reasoning and the inference which one draws on reading Mr. Stone's paper, that his method is a more logical one, does not seem to correspond to the facts. It starts with an assumption that is not true in many cases whereas the older method starts with an assumption that is always true.
FURTHER QUESTION In a recent publication of the JOURNAL OF CHEMICAL EDUCATION appeared an article which advocated the teaching of an ingenious, yet circuitous, method for the calculation of empirical formulas in preference 'THISJOURNAL, 5, 465 (Apr., 1928).
