316
JOURNAL OF CHEMICAL EDUCATION
FEBRUARY, 1932
(Plate 14.) If the rods used in forming these rings are made such a length that the distance between centers of the carbon atoms is 15 cm. they serve as a suggestive multiple of the 1.5 Angstrom units. With one ring structure of carbon atoms in hexagonal planar form (Plate 20) the instructor can, by adding springs and lead wires, demonstrate the traditional benzene ring forms of Claus, Ladenburg, Armstrong, Thiele, Keknl6. and modern conceptions as well. Benzene space molecular models to show the principles of Baeyer, Vaubel, Sachse, and Kekul6 can be made by using small tetrahedra cut from sheet tin to represent the various space conditions. (Plate 21.) The tetrahedra are arranged around the frames according to the particular theory under consideration. The resourceful instructor will find many other opportunities for the use of models in teaching. If their use stimulates the learning process and simplifies the task of teaching, they are valuable to the teacher. If their use clarifies the theory and promotes mental skill in the subject, they are valuable to the student. Experience indicates that this is one valuable visual aid in teaching. Chinese to make acids. China has awakened t o the fact that she is largely depeno.f chloride. Since dent upon foreign countries for sulfuric and nitric acids and sulfate . these three commodities are essential for the operation of arsenals, besides being important in the industrial life of the nation, China has suddenly realized that she would he helpless if Japan and the other powers were t o stop shipments. At the suggestion of the government, a group of Chinese capitalis& in Shanghai has organized the Kaicheng Acid Mfg. Works and has begun the building of a plant which, in its initial stages, will have an output of 18 tons of sulfuric acid a day. If the enterprise thrives, the manufacture of niaic acid and sulfate o j chloride will he engaged in.-New York Times via I d . Eng. Chern., N m s Ed.,9,316 (Oct. 20, 1931).
