FEBRUARY, 1891
is not essential in developing the topic of gases that is to culminate in the concept of gram-molecular volume. Any mnemonic device that will assist the beginning But it seems to me that without at leaet some mention student to correlate information on the gas laws is to he of it much of value is lost in the presentation of the welcomed, and I noted the chart proposed by Calvin kinetic-molecular theory of gases. With what experiP. Midgley with interest. The spelling of the name of mental evidence is the equation K.E. = '/a mv2 corGay-Lussac should be corrected. The omission of related? There is no doubt that the law is difficult to Graham's law was a surprise. Perhaps no appropriate teach; there is no question that students often fail to key word suggested itself. Why not the "A, B, C, D, solve even simple problems illustrating the law; but the and G's" of the Gas Laws7 The key word for Gre, fact that the rates of diffusion of gases vary inversely ham might be "Going." This would connote the as the square roots of their densities should be brought motion of gaseous molecules. to the attention of students because of its application It is more probable, however, that the author is in the problems of the pollution of the air in large infollowing the fashion of the day. I n certain of the text- dustrial and commercial cities today. Perhaps one of books in general chemistry published in the last few the authors who has omitted Graham's law from his years the name of Graham is not mentioned in the dis- textbook will discuss his reasons for doing so in the cussion of the diffusion of gases, and the formulation JOURNAL OF CHEMICAL EDUCATION. of the law is also often omitted (see 1950 editions of the CLARADEMILT textbooks by L. Pauling and H. I. Schlesinger). What NEWCOMB COLLEGE, TULANE UNIVERSITY is the explanation for this omission? Graham's law NEW ORLEANS,LOUISIANA
To the Editor:
