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67. Give three distinct methods 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 297 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.

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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 scparately brought in contact with chlorine gas? (a) phosphorus, (6) turpentine, (c) indigo, (d) antimony; (e) olefiant gas, (f) mercury.

86. How does chlorire 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

over (a) fused sodium, (6) heated quicklime, (c) slaked lime, (d) heated diamond ?

G2. How could you obtain chlorine from common salt without using manganese dioxide ?

BROMINE.

93. By whom and when was bromine discovered ? Name the naturally occurring compounds which contain it.

94. What is kelp, and how is bromine obtained from it?

95. How mayo the presence of bromine in a mineral water be detected ?

96. What occurs when bromine is added to (a) ether, (6) potash, (c) antimony ?

97. Chlorine water is dropped into solution of potassium bromide, and bromine water is dropped into solution of potassium iodide. What occurs in each case ?

98. Give two distinct methods for the preparation of bromine from potassium bromide.

99. A sample of sea-water contained o‘36 parts magnesium bromide in 1,000. How much of it would be required to yield one litre of bromine ? S. G. = 3*187.

100. Contrast the properties of chlorine with those of bromine and point out the differences between them.

101. How may bromine be made to combine with (a) free hydrogen, (6) hydrogen in compounds ?

102. What occurs when bromine water is treated (a) with sulphuretted hydrogen, (6) with sulphurous acid ?

103. A piece of antiinony was completely converted into tribromide by the absorption of 187 c.c. bromine vapour at N.T.P. Find the weight of the antimony.

IODINE.

104. Give a short account of the history and occurrence of iodine.

105. How is kelp prepared, and by what other names is it known? Name all the products which are practically obtained from it.

106. A sample of water contains four parts calcium iodide in 1,000,000. What volume of chlorine at N.T.P. would exactly liberate the iodine from a kilogramme of the water ?

107. Describe fully the preparation of iodine from kelp and state how the crude product is purified.

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