lionth of a millionth of a meter. This is the micromicron. The milli mu or mp, is a thousandth of a millionth of a meter. It is often incorrectly designated mu mu or pp, which is a thousandth of a milli mu. In short, it is much simpler and much more easily understood if these small units are defined in terms of the meter using milli- for thousandth and mu for millionth. S. FRANCIS HOWARD
The can had slowly corroded and within the past year or so, during wbich time I recall no use of its contents, small leaks had developed along the bottom seam and apparently the ether had slowly worked through and reacted with oxygen of the air t o produce, near the bottom of the can, a coating of white solid material, portions of which were tinged yellowish brown with admixed iron rust. The first knowledge of this condition arose when the writer stepped between the shelves to get a bottle of some other material, and a bruising explosion occurred on the inside of the left foot. The detonation was similar to that resulting when a half Cleaning Benches gram or so of nitrogen iodide is set off. Except for momentary numbness there was no serious injury, To the Editor: I don't know whether the following procedure is possibly due to the fact that contact was made only a t used or not in other labs but it has helped me a great the edge of the shoe. A section of the leather sole was deal in ours. In cleaning the tops of the chemical broken through and a crater four centimeters in diamebenches a t Portland Technology we use a window ter and eight-tenths centimeter deep in the center was squeegee instead of sponges. After a bench has been made in the hard pine Aoor. Examination revealed washed clean of the residues and stains which collect solid crustlike material, some of which had sloughed during the day we dry it with the rubber squeegee, off the can of isopropyl ether and become scattered out pushing the excess water into the sink. This cleans on the floor. Portions of this material detonated loudly and dries the bench in one motion, giving it a clean when struck by a hammer or when heated. Possibly it will be wise to keep this ether in brown appearance in contrast to the sponge-cleaned bench, wbich usually dries spotty. Also, the time is more than glass bottles, with traces of water or some alcohol cut in half, since the squeegee does not have to be added, since sunlight and absence of moisture are said to be conducive to peroxide formation. squeezed out. J. B. CULBERTSON WALTERA. BECKER,Janitor CORNELL COLLEGE P O R T TECHNOLOGY L~ MOUNT VERNON. IOWA PORTLAND, MAINE Double Decomposition of Salts
More Written Work?
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To the Editor: ' To the Editor: In the August number of the JOURNAL OF CHEMICAL The situation discussed in the letter from G. WakeEDUCATION in an article entitled "Some Illustrations ham of the University of Colorado in the October issue of Reactions between Solids," by H. S. van Klooster, is admitted true by most of us who are teaching freshthe statement is made, "There are-some examples of man chemistry. I t appears to me that one very large contributing double decomposition of salts . . . " which statement is followed by some half dozen or so examfles. The im- factor in this regrettable circumstance is the almost plication seems to be that such examples are not numer- complete elimination of written work from high-school ous. We feel that for the sake of completing the bib- science courses. The "more modern" educators seem liography given with the paper attention should be to hold that the writing of reports and other assigncalled to a detailed study of sixty such reactions recently ments tends to disinterest the student. In addition to reported in the Journal of the American Chemical this, it must be admitted that the teachers in the past few years have had rather heavy teaching loads, and Society, 60, 2320 (1938), and 62, 766 (1940). even those who have been willing have been handiLYMAN J. WOOD capped by lack of time. Consequently, there has been SCHOOL O F MEDICINE SAINTLOUIS UNIVERSITY SAINT LOUIS, MISSOURI an almost complete adoption of short form tests which do not fulfil completely the desired ends. Rather recently, I ittended a meeting a t which the Danger of Peroxide Formation head of the department of education of a prominent To the Editor: state institution gave science teachers a talk upon You have had previous correspondence concerning "newer tests" in science. The "newer tests" were peroxide formation in ethers. A recent experience in nothing more or less than true and false and other our laboratory may be of added significance in this short form examinations. The speaker contended that connection. these were definitely superior t o the "describe, discuss, A gallon can of isopropyl ether had been stored on a and explain" questions, and held that matters of that floor shelf of our storeroom for about four years. Ap- sort belong entirely t o the English department, and are proximately one-half of its contents had been use*. not the responsibility of the science teachers. Surely,
