The Thermo-Allotropic Modifications of Sulfur CLYDE Q. SAEELY Mississippi State College, State College, Missiesippi
SUZFUR, the element that migh? well be called "The Typical Element," is one of the oldest, cheapest,
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THETAERMO-ALLOTROPIC MODIFICATIONS OP SuLam (TEECHEMICAL Su~auaDERRICK)
and doubtless the third most essential elementary sub-
stance. Its occurrence and erystal formations appeal to the geologists, many of its approximately one hundred physical properties demand attention from the physicists, its unique method of manufacture in this country stimulates professional pride in the student of chemical engineering, and the numerous fungicidal and germicidal preparations containing sulfur and its compounds prove indispensable to the biologists. The chemist can properly claim a sharing interest in all scientific attainments involving this illustrative element, since chemistry is a science which deals with the properties of matter as tliey are changed by conditions. Sulfur, carbon, oxygen, phosphorus, arsenic, selenium, tin, antimony, tellurium, and boron are conspicuously allotropic; most of the heavy metals (with the exception of mercury) show some evidence of allotropy. Allotropy is the isomerism of a chemical element which may occur in different interchangeable amorphous and crystalline forms, yet having identical chemical properties. Isotopy, a term often confused with allotropy (by the beginning chemistry student), is the existence of very nearly allied but chemically nonseparable forms of some elements, the general chemical properties being identical but exhibiting variations in their atomic weights or masses; i. e., 32, 33, 34 for sulfur. The thermal conditions necessary for the interchanging of the seven thermo-allotropic modifications of sulfur may be expressed diagrammatically by the chemical sulfur derrick, showing simultaneously many other pedagogically digestible facts about this versatile element. The systematic and logical correlation of facts is of primary concern to an alert teacher of a science so general and voluminous as chemistry, so that he may present a long, intricate story in a vivid manner.
