632 CREATIVE CHEMISTRY A gel is formed Na4Si04 + sodium silicate
OXYGEN AND SULFUR, CARBON AND SILICON 633 A new, fireproof, transparent film was produced in 1938 by drying a jelly made by mixing bentonite clay with water. These films are made transparent by the application of pressure. They are flexible, electrically insulating, and resistant to chemicals. Undoubtedly bentonite films will find many useful applications in industry and commerce. Feldspars such as NaAlSisOs consist of three-dimensional networks of oxygen and silicon atoms. STUDY QUESTIONS 1. Sulfur is a very poor conductor of heat and electricity, resists wetting by water, may be readily melted, and is fairly strong. Can you suggest any possible uses which take advantage of the above properties of sulfur? 2. In what respects does sulfur resemble oxygen? 3. In what respects does silicon resemble carbon? 4. Account for the large number and the complexity of the compounds of silicon. 5. Why is oxygen called "the breath of industry"? 6. Considering how active oxygen is, how would you account for so much free oxygen in the atmosphere? 7. How is industrial oxygen prepared? 8. What are allotropic forms? Give examples of the two elements discussed in this Section which occur as allotropic forms. 9. What is the outstanding property of the diamond? 10. Account for the large beds of sulfur. 11. Describe the Frasch process of mining sulfur. 12. Discuss the occurrence, preparation, and uses of the different forms of carboa 13. Discuss the preparation, properties, and uses of sulfuric acid. 14. How do you account for the presence of sulfur in coal? 15. Discuss the properties and uses of graphite. 16. Account for the different varieties of coal. 17. Why has coal production decreased during the past decade? 18. What important materials may be obtained from coke? 19. What is meant by destructive distillation? Illustrate with an example. 20. How is silica gel prepared, and for what purposes is it used? 21. How is water glass prepared, and for what is it used?