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Describe experiments which show its lightness and rapid diffusion.

53. Sketch the apparatus you would use to demonstrate that hydrogen may be syphoned.

54. A burning jet of hydrogen is placed successively in air, in oxygen, in hydrogen, and in chlorine. State exactly what occurs in each case.

55. By what methods have Pictet and Cailletet liquefied hydrogen? Give a short account of previous unsuccessful attempts to effect this result.

56. The captive balloon at Paris in 1878 was 36 metres in diameter and spherical. What volume of gas at N.T.P. is required to fill it? What weight of hydrogen would be required ?

57. What impurities are generally found in hydrogen prepared by the action of acids on zinc, and how may they be completely removed ?

58. What impurity is always present in hydrogen which has been dried by passing the gas over strong sulphuric acid ? Explain its presence.

59. If you were provided with magnesium, sulphuric acid, water, and a graduated cylinder, how could you ascertain the combining weight of hydrogen ?

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HYDROGENIUM (ALLOTROPIC HYDROGEN).

60. Give a short account of the substance called by Graham “hydrogenium," and state how it is prepared.

61. Explain the terms “occlusion," "diffusion," " effusion," and "transpiration” of gases. Give examples of each.

62. How has the density of hydrogenium been ascertained ? In what respects does hydrogenium resemble a metal ?

63. Contrast the chemical properties of hydrogen with those of hydrogenium.

64. Give an example of a reaction in which hydrogen acts like a metal. What property, characteristic of metals and their compounds, is possessed by hydrogenium?

CHLORINE,

65. By whom and in what year was chlorine gas discovered ? By whom and when was it shown to be an element ?

66. Name several commonly occurring compounds which contain chlorine.

67. Give three distinct inethods for obtaining chlorine from hydrochloric acid.

68. What is the action of hydrochloric acid on sodium hypochlorite, on potassium chlorate, and on nitric acid ?

69. One hundred grammes of manganese dioxide are treated with excess of hydrochloric acid. How much chlorine is evolved? If treated with the proper quantities of sodium chloride and sulphuric acid how much more would be obtained ?

70. Seven litres of hydrochloric acid gas at N.T.P. are passed over heated manganese dioxide. Give the weight and volume of chlorine produced.

71. How much chlorine gas should be obtained by heating with excess of hydrochloric acid, 129 grammes of pyrolusite containing 4:7 per cent. of impurities ?

72. What occurs when an electric current is passed through a strong solution of hydrochloric acid ? Describe exactly how the experiment should be made.

73. By the electrolysis of a certain quantity of hydrochloric acid, 224 C.C. of chlorine at N.T.P. were obtained. Find the weight and volume of hydrogen obtained at the same time and the weight of acid decomposed.

74. How is chlorine prepared (a) by Deacon's process, (6) by Weldon's process ? Discuss the advantages of each method.

75. One hundred c.c. of manganese liquor contain 27'3 grammes manganese chloride. How much chlorine should be obtained from 1,000,000 gallons of such liquor, treated by Weldon's process ?

76. Thirteen cwts. of common salt containing 2*7 per cent. impurity are decomposed by sulphuric acid, and the evolved gas is treated by Deacon's process. How much chlorine should be obtained ?

77. What impurities are likely to be contained in chlorine gas as ordinarily prepared, and how may they be removed ?

78. At what temperature would a litre of chlorine weigh the same as a litre of hydrogen ?

79. Name any chlorides which evolve chlorine on heating. Give equations.

80. If chlorine be passed into ice-cold water, what occurs? What happens when the dried product is gently heated in a sealed tube ?

81. Describe some experiments to show the tendency of chlorine to unite with other elements. Name the metalloids with which it does not directly combine.

82. Chlorine unites readily with free hydrogen. How may this be shown experimentally?

83. Describe several experiments which show the union of chlorine with combined hydrogen.

84. State fully what occurs when a lighted taper is placed in chlorine gas.

85. What occurs when the following bodies are separately brought in contact with chlorine gas ? (a) phosphorus, (6) turpentine, (c) indigo, (d) antimony, (e) olefiant gas, (f) mercury.

86. How does chlorine act as a bleaching agent? Explain why the presence of water is necessary.

87. How does freshly prepared chlorine water differ from the same substance after exposure to light?

88. What occurs when a mixture of chlorine and steam is passed through a red-hot porcelain tube?

89. Fourteen grammes of iron are dissolved in hydrochloric acid. How much hydrogen (at N.T.P.) is evolved, and what volume of chlorine is needed to convert the ferrous into ferric chloride ?

90. Give several examples of chlorine acting as an oxidizing agent. 91. What occurs when perfectly dry chlorine is passed

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