662 CREATIVE CHEMISTRY Ammonia is frequently combined with phosphoric acid to produce important fertiHzers that supply the phosphorus that the soil needs in Ammonia is also combined with sulfuric acid addition to the nitrogen. Sulfuric acid in this case acts as an inex- to form ammonium sulfate. pensive carrier for the ammonia. Ammonia gas may be readily liquefied; in this form it is used extensively as a refrigerant in the manufacture of ice. Ammonia will react with nitric acid to produce ammonium nitrate, NH4NO3, used as a fertilizer and in making certain types of blasting agents. The E. I. du Pont de Nemours Company has recently developed a practical process on a commercial scale for the production of sulfamic acid, HSO3NH2, which has many interesting uses based upon its unique properties. The ammonium salt of sulfamic acid is now used Keep your eye on this as a weed-killer and as a flameproofing agent. product; it is sure to go places. The Air Contains Rare Elements Which Are More Inert Than Nitrogen. The rare gases, helium, argon, neon, krypton, and xenon, are sometimes referred to as the old maids and bachelors of chemistry because their chemical inactivity is their chief property. So inactive are these elements that they do not combine to form diatomic molecules as most gases do; their molecules consist of one atom only. Helium is next to the lightest gas known, having a lifting power 92 per cent of that of hydrogen, but unlike hydrogen in that it is not inflammable. The main source of helium is the natural-gas wells of western United States. It is used for airships and for the prevention and treatment of "bends," the disease of deep-sea divers and highaltitude aviators. A mixture of helium and oxygen is used in treating severe respiratory diseases such as acute asthma. Neon and argon are used in gas-filled glow lamps. Argon is also used in filling electric-light bulbs, thus reducing the tendency of the hot filaments to vaporize. Argon and neon are obtained along with nitrogen and oxygen in the fractional distillation of liquid air. Argon is present in air to the extent of 0.94 per cent by volume. One part in 65,000 parts of air is neon, while the other gases are present in such small proportions that they are too rare to have important uses. STUDY QUESTIONS 1. Discuss catalysis as to (a) definition, (b) the types of catalysts, (c) examples of six different catalytic processes, and (d) the nature of catalysis. 2. Discuss physiological catalysts.
AIR AND WATER AS RAW MATERIALS 663 3. Give an example of negative catalysis. 4. What is meant by nitrogen fixation? 5. Why is nitrogen fixation of importance? 6. Discuss the various types of nitrogen fixation. 7. Show how nitrogen fixation was an important problem in the World War of 1914-1918. 8. Discuss the preparation and uses of nitric acid. 9. How was dynamite discovered? 10. From what raw materials are the important explosives prepared? 11. Discuss the preparation and uses of ammonia. 12. What is the outstanding property of the rare gases? 13. Where is helium obtained, and for what is it used? 14. Give the uses of argon and neon. 15. Starting with air and water, show how the important chemicals, ammonia and nitric acid, can be prepared. 16. It was found that such plants as cereals increase in growth in proportion to the concentration of nitrates in the soil, but that in the case of legumes, no such regularity was observed. Chemical analysis showed that these legumes contained more nitrogen than the soil could supply. In some cases, however, it was observed that legumes failed to thrive in soil containing nitrogen fertilizer. The hypothesis was suggested that bacteria in the root nodules of legumes were responsible for these differences between cereals and legumes. Work out detailed suggestions for experiments by which this hypothesis could be tested. 17. What are the uses of ammonium sulfamate?