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321. How would you analyse the air from a crowded theatre, and what ingredients would you expect to find in large quantity ?

322. One hundred and twenty-nine c.c. of air at 15° C. and under a pressure of 753 m.m. mercury were contained in a cylinder standing over water. How much nitric oxide at the same temperature and pressure would be needed to combine with the oxygen ?

323. During fogs in Manchester, Dr. Angus Smith found 679 volumes carbon dioxide in 10,000 volumes of air. How much calcium carbonate would be formed on shaking up a litre of such air with lime-water?

324. It has been found that air containing 250 volumes of carbon dioxide in 10,000 volumes will not support combustion. What is the percentage amount of oxygen, nitrogen, and carbon dioxide in such air?

325. A man inhales 18 cubic feet of air per hour. What weight of oxygen does he consume in 24 hours ?

326. A man exhales 1,122 cubic inches of carbon dioxide

per hour. How many men at the same rate would


be required to produce a ton of carbon dioxide in 24 hours ?

327. In a well ventilated room the amount of carbon dioxide ought not to exceed 6 volumes in 10,000 of air. What weight does this correspond to per litre of air, and how much calcium carbonate would it precipitate from lime-water?

328. Give a short account of what is known about the solid matters, organic and inorganic, found floating in air? What impurities does rain-water extract from the air ?

329. How did Pasteur prove that atmospheric dust contains particles capable of germination ?

330. Mention various circumstances in which a putrescible liquid might be left in contact with air without giving rise to germination.

231. How may it be shown that air has weight? What is the weight of a litre of dry air at N.T.P.?

332. What is meant by the pressure of the atmosphere?

333. What is a barometer? Describe the simplest form of the instrument. What is the principle of the aneroid barometer ?

334. What is meant by the “Torricellian vacuum ?”


335. Why does the mercury in a barometer fall on ascending a mountain, and rise on descending ?

336. Describe several experiments which prove that the atmosphere exerts a certain pressure.

337. Describe the construction and action of an ordinary air-pump, and of the instrument called Sprengel's pump.





338. Describe the various kinds of naturally occurring water. Arrange them in order from the purest to the

least pure.

339. Why is river-water more impure than rain-water? What does the latter contain ?

340. Of what is pure water composed ? Who discovered the composition of water? How and when was the discovery made ?

341. Sketch the apparatus you would use to show the decomposition of water by the galvanic current.

342. Give all the ways you know for obtaining (a) hydrogen and (6) oxygen from water.

343. Cavendish exploded a mixture of 19,500 measures of oxygen with 37,000 of hydrogen. Which gas would remain after the explosion, and how much of it ?

344. How could you show that water is produced by burning hydrogen in air or oxygen? Water is also produced when a candle or a gas-jet burns in air. How do you explain this ?

345. What weight of hydrogen and of oxygen is contained in 100 lbs. of water ?

346. A gas-holder contains 74 litres of hydrogen at N.T.P., what volume of oxygen is required for its combustion, and what weight of water would result ?

347. A strong glass flask containing 200° C.c. hydrogen and 100 c.c. oxygen weighs 417 grammes. An electric spark is passed through the mixed gases. What is the weight of the flask when cold?

348. How is the composition of water ascertained by means of the eudiometer ? Give the details of the process.

349. After exploding a mixture of hydrogen and oxygen, o‘017 gramme water was obtained, and 11'5 CC. hydrogen remained. The temperature was 15° C. and the pressure 760 m.m. Find the volume of the mixed gases.

350. What volume of steam is obtained by exploding a mixture of two volumes of hydrogen with one of oxygen ?

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