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481. What volume of hydriodic acid at N.T.P. contains i gramme of iodine, and how could it be extracted ?

482. Illustrate the action of hydriodic acid on organic compounds by explaining how it acts on tartaric acid and on glycerine.

483. Name six soluble and six insoluble iodides, and state what is the action of chlorine on each.

484. How could you detect each of the constituents in a mixture of potassium chloride, bromide, and iodide ?

485. Give a short account of the compounds of iodine with chlorine and with bromine,

486. Find the percentage composition and formulæ of the chlorides of iodine, from the following data :

(a) 0-521 gramme chloride contained o‘283 gramme

iodine and 0'238 gramme chlorine. (6) 0'732 gramme chloride contained 0-574 gramme

iodine and oʻ158 gramme chlorine. 487. What evidence is there for supposing the existence of hypoiodous acid ?

488. How is iodic acid obtained, and what occurs when it is heated ?

489. What is the action on iodine of (a) nitric acid, (6) caustic potash ?

490. What weight of iodic acid contains 1'567 gramme iodine, and by what reactions could it be obtained from it?

491. How are periodic acid and the periodates respectively prepared ?

492. Write the formulæ of all the known compounds of the halogens with (a) hydrogen, (6) oxygen, (c) hydrogen and oxygen.

493. Chlorine is passed into water containing 23 grammes iodine in suspension. What volume at N.T.P. is required to convert all the iodine into iodic acid ?

COMPOUNDS OF FLUORINE.

494. What is the action of sulphuric acid on calcium fluoride, and of heat on hydrogen potassium fluoride ? Give equations.

495. What is the difference between the action of anhydrous and dilute hydrofluoric acid on (a) glass, (69 gutta-percha ?

496. What is the action of hydrofluoric acid on silica and of the product on water? State also the action of the acid on glass. Give equations.

497. A weighed piece of glass is acted on by hydrofluoric acid. After the action it is found to have lost I'347 gramme, how much hydrofluoric acid is needed to produce this result ?

498. Gore heated 16'4 grains silver fluoride in contact with 6 cubic inches pure hydrogen and obtained 14.5 cubic inches hydrofluoric acid measured at 200° F. Find the volume of hydrogen which had combined

occurs.

with fluorine, and state what conclusions you draw as to the composition and density of hydrofluoric acid.

499. 4'387 grammes meerschaum (Si,01.H.Mg2) are heated with hydrofluoric acid till no further reaction

How much silicon tetrafluoride should be formed ?

500. How is hydrofluoric acid used in the preparation of eudiometers ?

501. How would you obtain the fluorides of silver, barium, and potassium ? Which of these salts dissolves in water ?

502. Give the formulæ of potassium borofluoride and of potassium silicofluoride, and state how each of these substances is obtained.

503. How is hydrofluosilicic acid prepared ? Sketch the apparatus required for its preparation, and give its action on solutions of potassium and barium salts.

COMPOUNDS OF BORON.

504. How is boron hydride prepared ? What are its properties, and what occurs when it burns in air ?

505. Compare the properties of boron hydride with those of the hydrides of silicon, phosphorus, and arsenic.

506. How may the composition of boron hydride be ascertained ?

507. How is the chloride of boron prepared, and what is its formula ? What is its action when heated with (a) 'sodium, (6) magnesium, (c) zinc ?

508. What occurs when boron trichloride is placed in water? Give an equation and name another chloride which reacts similarly on water.

509. A compound of boron trichloride with ammonia contains 14:68 per cent. of nitrogen, find its formula and state how it is obtained.

510. Give the formulæ and modes of preparation of the compounds of boron with bromine and fluorine.

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