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over (a) fused sodium, (b) heated quicklime, (c) slaked lime, (d) heated diamond?
92. How could you obtain chlorine from common salt without using manganese dioxide ?
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 may the presence of bromine in a mineral water be detected?
96. What occurs when bromine is added to (a) ether, (b) 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.
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, (b) with sulphurous acid?
103. A piece of antimony was completely converted into tribromide by the absorption of 187 c.c. bromine vapour at N.T.P. Find the weight of the antimony.
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.
108. What is the weight of one litre of iodine vapour at N.T.P.? Give the volume of hydrogen and of air which would weigh the same as the iodine.
109. How much sulphuric acid and manganese dioxide would be needed to liberate all the iodine from 379 grammes of potassium iodide?
110. Four thousand three hundred and twenty-one c.c. of chlorine at N.T.P. were required to liberate all the iodine from a solution of potassium iodide. How much of this salt was present?
III. How is iodine tested for when in the free state? How is it detected when in combination?
112. Name the impurities usually present in commercial iodine and state how it may be obtained chemically pure. 113. To an aqueous solution of potassium iodide and starch, chlorine water is added drop by drop. What occurs? On adding excess of chlorine water what takes place? Explain both reactions.
114. Chlorine, bromine, and iodine are separately added to solutions of (a) potassium iodide, (b) potassium bromide (c) potassium chloride. What occurs in each case?
115. 0*5205 gramme of an oxide of manganese was treated with hydrochloric acid and the evolved chlorine
was led into solution of potassium iodide. The liberated iodine required 165 ̊4 c.c. of a standard solution of sodium thiosulphate, of which I c.c. was equal to o'005 gramme iodine. Find percentage of manganese dioxide in the oxide.
116. One hundred and nineteen grammes of iodine are suspended in water. What volume of chlorine at N.T.P. will be required to convert all the iodine into iodic acid?
117. Seventy-three c.c. of a solution of iodine (containing 127 grammes per litre) were added to a mixture of sulphuretted hydrogen and starch before a permanent blue coloration was obtained. Find the amount of sulphuretted hydrogen present.
118. Give the names and formulæ of the chief minerals containing fluorine, and name substances in which it is always found in minute quantity.
119. Describe the various attempts which have been made to isolate fluorine.
120. What is the action of flucrine on (a) hydrogen, (6) water, (c) platinum, (d) silica?
121. Find the percentage of fluorine in fluor spar and
122. How may the presence of fluorine in a compound be ascertained?
123. Give the formulæ of the fluorides of (a) hydrogen, (b) silver, (c) silicon, (d) boron, (e) calcium, (ƒ) potassium.
124. Berzelius found that when 100 parts of calcium fluoride were heated with sulphuric acid till completely decomposed, 175 parts calcium sulphate were obtained. Calculate the atomic weight of fluorine from these data. Later experiments gave 1745 parts calcium sulphate. Calculate the atomic weight from this result.
125. 3'2617 grammes of calcium fluoride when treated with strong sulphuric acid, yielded 5'6867 grammes of calcium sulphate. From these data calculate the atornic
weight of fluorine.