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872. Represent by equations the reactions which occur when chlorine is led into cold and into hot milk of
873. A litre of water at 10° C. when saturated with carbon dioxide, dissolves o 88 gramme calcium carbonate. What volume of such water contains 100 tons of calcium carbonate ?
874. Explain the formation of stalactites, stalagmites, and petrifactions.
875. What is the cause of temporary, and of permanent hardness in water? How may each kind of hardness be removed or modified ?
876. How is Clark's soap test applied to determine the hardness of water? How can it be used to ascertain both the temporary and permanent hardness ?
877. What is plaster of Paris and how is it made ? What loss of weight should one pound of pure selenite suffer when heated to 200° C. ?
878. Sea-water contains 1'33 gramme calcium sulphate, and oʻ047 gramme calcium carbonate in 1,000 grammes. Find what weight of the water treated with ammonium oxalate should yield 3-24 grammes calcium oxalate.
879. By whom was strontium discovered, and why was the name given to the metal ? Who first obtained the metal and in what year ?
880. How could you obtain strontium nitrate (a) from strontianite, (6) from celestine ?
881. Give the formulæ of the hydrates of strontium and state how each is obtained.
882. How could you obtain sulphur from strontium sulphate ?
883. A litre of water at the ordinary temperature dissolves oʻ145 gramme strontium sulphate. Find how much of this solution would be required exactly to precipitate one gramme of barium chloride.
884. How are strontium salts distinguished from those of calcium?
885. Name the common minerals which contain barium, and state how the metal is best obtained.
886. What is baryta, and how is it prepared ? What is the action of water on it?
887. Describe Pettenkofer's method for determining the amount of carbonic acid in air by means of baryta.
888. What occurs when barium monoxide is heated in a current of air or oxygen ? What occurs on heating the product strongly?
889. How are chloride and nitrate of barium prepared on the large scale, and what are their chief uses ?
890. How could you obtain oxygen from barium sulphate ?
891. How may barium sulphate be distinguished from the sulphates of lead and strontium ?
892. What occurs when barium sulphate is fused with sodium carbonate ? Represent the reaction by an equation.
893. What substances when heated in a non-luminous flame tinge it green? How are they distinguished ?
894. What is the composition of the following naturally occurring magnesium compounds, and which are used as sources of magnesium salts ? (a) talc, (6) carnallite, (c) meerschaum, (d) magnesite, (e) asbestos, (f) serpentine, (g) dolomite, (h) kieserite, (i) spinelle.
895. Describe fully the preparation of magnesium (a) on the small scale by Bunsen's method, (b) on the large scale by Deville and Caron's process.
896. How is the crude metal purified and made in the form of wire and ribbon? What is magnesium chiefly used for?
897. What occurs when magnesium is (a) burned in air, (5) placed in boiling water, (c) heated in contact with ammonia or nitrogen, (d) heated in a covered Hessian crucible in an ordinary coal-fire, (e) heated with boron trioxide ?
898. What occurs when solution of magnesium chloride is evaporated to dryness? How is anhydrous magnesium chloride obtained ?
899. How is magnesium sulphate obtained from kieserite and from dolomite?
900. What is the composition of the precipitate produced by adding a soluble phosphate to a solution of a magnesium salt containing ammonia and ammonium chloride ? What occurs on heating this precipitate ? Give an equation.
901. How are the following magnesium compounds obtained, and what is the composition of each ? (a) calcined magnesia, (6) fluid magnesia, (c) magnesia alba.
902. Give an account of Black's experiments magnesia by which he clearly proved the nature of the difference between carbonated and caustic alkalies.