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RUBIDIUM AND CAESIUM.

841. Give a short account of Bunsen's discovery of rubidium and caesium, and give reasons for classing thein with the alkali metals.

842. How is rubidium chloride obtained from lepidolite ?

843 How is the metal rubidium prepared, and what are its properties?

844. Give the derivation of the names rubidium and caesium.

845. How may caesium and rubidium salts be separated?

846. What is the formula for caesium alum? How can pure caesium sulphate be obtained from it?

SILVER.

847. How is silver extracted from its ores (a) in Mexico, (6) in Freiberg ?

848. Describe the processes for the extraction of silver known as Ziervogel's, Augustin's, and Von Patera's. Explain the chemical reactions involved in each process.

849. What is the composition of English silver coin ? How is the assay of an alloy of silver performed by the dry and wet methods ?

850. How is silver extracted by the cupellation process? How is the “spitting” of silver in this process accounted for ?

851. What occurs (a) when silver is heated to redness in air, (6) when steam is passed over melted silver, (c) when hydrochloric acid gas is passed over hot finely divided silver, (d) when chlorine is passed over heated silver ?

852. How are the oxides, chloride and nitrate of silver prepared, and what are their properties?

853. Of what use are the silver salts in photography?

K

How is a negative taken, and how is a “print” obtained from it ? State in each case how the result is rendered permanent.

854. Give a short historical sketch of the discovery of photography, and state the improvements due to Wedgwood, Niépce, Daguerre, Fox Talbot, Herschell, and Archer.

855. How is silver nitrate used in the analysis of chlorides, and how would you determine the amount of silver in a coin ?

856. 2.971 grammes of a metallic chloride on precipitation with a silver salt yielded 4098 grammes silver chloride. Find the per cent of chlorine in the salt, and its formula.

857. What happens when pure hydrogen is left in contact with solution of silver nitrate ?

858. Russell found that 105'3 c.c. of hydrogen at N.T.P. precipitated 1'0089 gramme silver from a solution of silver nitrate. Calculate from this result the combining weight of silver.

THALLIUM.

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 mctals, 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 o‘223 gramme yielded o‘3138 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 ?

86;. How is thallium detected and estimated ?

DYADS.

CALCIUM.

866. What is the composition of the following minerals containing calcium ? (a) aragonite, (6) fluorspar, (c) gypsum, (d) calcite, (e) dolomite, (f) anhydrite, (9) Iceland spar, (h) selenite, (i) apatite, and (j) 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) calciuin Chloride, (d) quick-lime ?

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