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saturate a litre of water with the gas (water at 15° C. dissolves 450 times its bulk of the gas).
428. How is hydrochloric acid prepared on the large scale? Sketch the plant required.
429. What impurities are usually present in commercial hydrochloric acid, and how is their presence accounted for ?
430. At 12° C. and 760 m.m. pressure i gramme water absorbs 0°762 gramme hydrochloric acid. Find the quantity of salt and sulphuric acid required to yield a ton of hydrochloric acid at the same temperature and pressure.
431. What important fact was ascertained by Roscoe and Dittmar on distilling aqueous solutions of hydrochloric acid at different pressures ? How may this property be applied to the preparation of standard solutions of the acid ?
432. What occurs when a current of hydrochloric acid is passed over (a) sodium, (6) manganese dioxide, (c) iron ?
433. How is iodine chloride prepared, and what are its properties?
434. If a current of chlorine be led into solution of potassium iodide mixed with starch, the liquid at first becomes blue, but by the continued passage of the gas it becomes colourless. Explain this.
535. Give the names and formulæ of the oxides of chlorine, and state how each is prepared.
436. What occurs when a red-hot wire is placed in a tube filled with chlorine tetroxide ?
437. Give several illustrations of the powerful oxidiz. ing action of chlorine tetroxide ?
438. What is euchlorine, and how is it prepared ?
439. Write the names and formulæ of the compounds containing chlorine, hydrogen, and oxygen.
440. Give three distinct methods for the preparation of hypochlorous acid. What are the properties of the substance ?
441. Compare the bleaching action of chlorine with that of hypochlorous acid, and explain each by equations.
442. What happens when lime is thrown into a cylinder containing chlorine ? What is the common name of the substance produced, and how is it obtained on the large scale ?
443. Express by equations the action on bleaching powder of (a) sulphuric acid, (6) nitric acid, (c) hydrochloric acid.
444. What occurs when a stream of chlorine is passed through (a) a hot solution of potash, (6) a cold . solution of potash ? Express each reaction by an equation.
445. How is potassium chlorate prepared on the large scale ? How would you react on calcium chlorate so as to obtain potassium chlorate ?
446. How is potassium chlorate separated from potassium chloride when both are present in a solution ? By what tests could you distinguish the two salts ?
447. How is potassium perchlorate obtained from the chlorate? Give an equation.
448. A certain weight of potassium chlorate is heated for the preparation of perchlorate ; 10 litres of oxygen at N.T.P. are obtained. Find the weight of chlorate used and of perchlorate obtained.
449. How did Roscoe obtain pure perchloric acid, and what are its properties?
450. What compound does perchloric acid form with water, and how is it obtained ? How is its formation explained?
451. What occurs when perchloric acid is added to (a) water, (6) charcoal ?
452. Calculate the composition of potassium perchlorate from the following experimental data obtained by Roscoe. oʻ9915 gramme of the pure salt lost on heating 0-4570 gramme, the residue required 0'7683 gramme of silver for complete precipitation. Also, 0 3165 gramme of the salt when treated with sulphuric acid yielded o‘201 gramme potassium sulphate.
453. How could you distinguish (a) a solution of chlorine from one of hypochlorous acid, (6) a solution of potassium chlorate from one of potassium perchlorate?
454. What quantities respectively of potassium chlorate and potassium perchlorate would be needed to furnish when heated a litre of oxygen at N.T.P. ?
455. Starting with potassium chlorate, how could you obtain the chlorates of sodium and barium ?
COMPOUNDS OF BROMINE.
456. Describe different methods for combining bromine directly with hydrogen.
457. What weight of bromine and of hydrogen does a litre of hydrobromic acid gas at N.T.P. contain ?
458. What happens when potassium bromide is dropped into (a) sulphuric acid, (6) phosphoric acid ?
459. Express by equations the action of hydrobromic acid on sulphuric acid, and of bromine water on sulphuretted hydrogen.
460. If a hydrogen flame be surrounded with bromine vapour what occurs ? If coal-gas be substituted for hydrogen what occurs ?
461. What is the action of phosphorus on chlorine, on bromine, and on iodine, and what is the action of water on each of the products ?
462. Describe fully how you would fill a cylinder with