Imágenes de páginas


952. Give a short account of the natural occurrence and distribution of gold.

953. How is the quantity of gold in auriferous minerals, and in gold bullion ascertained ?

954. Describe how gold is extracted (a) by placer mining, (6) by vein mining, (c) by hydraulic mining.

955. Give a short account of Plattner's chlorination process for the extraction of gold.

956. How is gold separated from silver and copper by “parting”?

957. How may gold be refined by means of chlorine ?

958. How may a solution of gold be obtained ? Name any reagents which precipitate metallic gold from the chloride.

959. What are the properties of gold ? State the action of acids and alkalies on it, and how the oxides of gold are obtained.



960. From what ore is tin invariably prepared ? Describe the various processes employed in its extraction.

961. How is tin-plate made? What is the composition of the following alloys of tin ? (a) pewter, (6) solder, (c) gun-metal, (d) bronze, (e) speculum metal, Britannia metal.

962. Express by equations the action of nitric, hydrochloric and sulphuric acids on tin.

963. How are each of the chlorides of tin prepared ? Why does stannous chloride solution become turbid after exposure to air, and how may this be prevented ?

964. What occurs when zinc is added to an acid solution of stannous chloride ? What is the action of stannous chloride on mercuric chloride and on ferric chloride?

965. What is the constitution of stannic and of metastannic acids, and how is sodium stannate prepared ?


966. Name some of the most abundant minerals containing aluminium, and give the composition of cryolite, orthoclase, and wavellite.

967. By whom and when was the metal aluminium first prepared ? What are its properties ?

968. How is aluminium prepared on the large scale, and what is it chiefly used for ?

969. Find the quantity of sodium which is theoretically required to decompose 197 pounds of the double chloride of aluminium and sodium. How much potassium would be required for the same purpose ?

970. What is the composition of the ruby, and how may it be prepared artificially?

971. What is the action of the common acids and alkalies on aluminium ? Starting with metallic aluminium, how would you prepare potash alum?

972. How are aluminium chloride and the double chloride of aluminium and sodium prepared ?

973. How are aluminium sulphate, aluin cake, and common alum respectively obtained ?

974. What is the constitution of the alums? Give the formulæ for each of the following-ammonia alum, chrome alum, and silver alum.

975. How much ammonia alum contains 156 grammes of aluminium ? How much aluminium sulphate and ammonium sulphate must be used to obtain 1,897 grammes of the alum?

976. What is a “mordant”? Explain how alum is used as a mordant.

977. What occurs when aluminium acetate solution is boiled ? How is the substavce used in calicoprinting ?

978. Give a short description of the manufacture of glass and of pottery.


979. What is pyrolusite, and how may manganese be prepared from it? What is the action of manganese on water?

980. Give a short account of each of the oxides of manganese, and state how they may be obtained from the dioxide.

981. Which oxide of manganese loses, when heated till constant, 3-37 per cent. of oxygen ?

982. How much pure manganese dioxide is required when heated in a current of hydrogen to yield 798 grammes of water ?

983. Express by equations the action of hydrochloric and sulphuric acids on each of the oxides of manganese.

984. What evidence is there for supposing the existence of a tetrachloride of manganese ?

985. How are manganate and permanganate of potassium prepared, and what are their properties ?

986. What is the action of each of the following bodies on solution of potassium permanganate? (a) hydrogen, (1) ammonia, (c) stibine, (d) ferrous sulphate,

« AnteriorContinuar »