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859. How is thallium found in nature, and from what substance is it most conveniently obtained ? Describe the methods of preparation.
860. Discuss the position of thallium among the metals, and point out its analogies to the alkali metals, and to lead.
861. How did Crookes determine the combining weight of thallium?
862. How could you separate thallium from a mixture containing the chlorides of lead, thallium and potassium ?
863. Find the percentage of thallium in a sample of thallium chlorate, of which 0·223 gramme yielded oʻ3138 gramme double chloride of platinum and thallium. To what formula do these results correspond ?
864. Give the formulæ for the oxides, chlorides, and hydrate of thallium, and state how each is obtained. What is the action of the hydrate on solutions of iron and aluminium ?
865. How is thallium detected and estimated ?
866. What is the composition of the following minerals containing calcium? (a) aragonite, (6) fluorspar, (c) gypsum, (d) calcite, (e) dolomite, () anhydrite, (8) Iceland spar, (h) selenite, (i) apatite, and (7) marble.
867. How is the metal calcium prepared, and what are its properties ?
868. How much lime should be obtained by heating to redness 2*726 kilogrammes of calc-spar, and how much calcium hydrate should be obtained on slaking the product ?
869. How is lime prepared on the large scale? How are hydraulic mortars obtained ?
870. Enumerate the chief uses of lime, and state the causes of the hardening of mortar.
871. Starting with a piece of marble, how would you prepare (a) lime-water, (b) milk of lime, (c) calcium chloride, (d) quick-lime ?
872. Represent by equations the reactions which occur when chlorine is led into cold and into hot milk of lime.
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 o‘047 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 ?