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311. How may the composition of air be ascertained by means of the eudiometer?

312. In an analysis by Dumas and Boussingault's method the copper employed gained in weight 14904 gramme. Find the number of grains of air used and of nitrogen obtained.

313. Dr. Angus Smith found in 100 volumes of air, at the sea-shore in Scotland, 20'999 volumes of oxygen and in Manchester 20 960 volumes. How much sulphur would be required to unite with all the oxygen in one litre of each specimen?

314. How much air by volume is required for the complete combustion of 11234 grammes of charcoal containing 85.89 per cent. carbon and 241 per cent. hydrogen?

315. Give two distinct physical processes for separating oxygen from air.

316. Lavoisier heated some mercury for several days in contact with 50 cubic inches of air at a temperature of 19° C. and under a pressure of 28 inches of mercury. At the close of the experiment, 42 cubic inches of gas remained unabsorbed, and 45 grains of mercuric oxide were obtained, which when heated yielded 41 grains of

mercury and 7 cubic inches of oxygen.

results agree with modern determinations?

How do these

317. Find the volume of nitrogen and oxygen present in air from the following results obtained by Bunsen in an analysis of the air at Marburg :

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318. What is the action on air of (a) phosphorus, (b) potassium pyrogallate, at the ordinary temperature? How may the latter substance be used for the analysis of air?

319. Find the volume of air at 13° C. and 755 m.m. pressure required to burn a litre of carbon monoxide at the same temperature and pressure.

320. Find the composition of air from the following results obtained by Bunsen by absorption with potassium pyrogallate:

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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 6.79 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?"

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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.

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