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sulphur acids which decolorize iodine solution. Give the reactions in each case.

745. How was sulphuric acid originally prepared ? What is Nordhausen sulphuric acid, and how is it prepared ?

746. How much sulphuric anhydride when dissolved in water will yield 1298 grammes of sulphuric acid ?

747. In this country 850,000 tons of sulphuric acid are made annually. What weight of sulphur is contained in this quantity ?

748. Name the materials necessary for the manufacture of sulphuric acid, and state how each is used.

749. How may the process for preparing sulphuric acid be illustrated on the small scale? Sketch the apparatus.

750. Explain fully the theory of the formation of sulphuric acid in the leaden chambers. Give equations to represent the reactions supposed to occur.

751. What is the composition of the crystalline compound often found in the leaden chambers ? What is the action of water on it?

752. How is sulphuric acid made on the large scale ? Sketch the plant required.

753. Represent by equations the reactions which occur when iron pyrites is heated (a) in a limited quantity of air, (6) with excess of air,

754. What occurs when nitrous fumes are left in contact with sulphuric acid, and what occurs on the addition of water to such acid ?

755. What is the use in the manufacture of sulphuric acid of the towers called (a) Glover's, (6) “Gay Lussac's ? "

756. Describe different methods for concentrating the dilute acid obtained in the leaden chambers, and state how 6 rectified vitriol” is obtained.

757. How much sulphuric acid should theoretically be obtained from 100 tons of sulphur, and how much from 100 tons of iron pyrites containing 49*2 per cent. of sulphur?

758. What impurities are usually contained in coinmercial sulphuric acid ? How do you account for the presence of each, and how may they be completely removed ?

759. If 136.3 tons of sulphuric acid were practically obtained from 100 tons iron pyrites, find the percentage of sulphur in that ore.

occurs

760. How much sulphuric acid should be theoretically obtained from 197 tons of iron pyrites, if the burnt ore contained 2.74 per cent. of sulphur? 761. What

when sulphuric acid vapour is heated ?

762. What occurs when sulphuric acid is left exposed to the air ?

763. What is the action of sulphuric acid on lead ? What is the composition of the precipitate which forms when commercial sulphuric acid is diluted with water?

764. How would you detect the presence of arsenic in sulphuric acid, and how do you account for its presence ?

765. How much sulphuric acid is contained in a litre of a liquid, of which ico c.c. require 1'97 gramme barium chloride for complete precipitation ?

766. How much sulphuric acid is required exactly to decompose 2.345 grammes of sodium carbonate ?

767. How would you prepare a solution of sulphuric acid, such that each cubic centimetre should contain 0'098 gramme H,S04?

768. What is the action of strong sulphuric acid on each of the following bodies ? (a) sodium nitrate, (6) oxalic acid, (c) lead, (d) zinc, (e) potassium chloride, (f) manganese dioxide. Give equations.

769. What is the action of sulphuric acid on organic matter such as sugar ?

COMPOUNDS OF SELENIUM.

770. How is seleniuretted hydrogen usually obtain Compare its properties with those of sulphuret hydrogen.

771. What oxide is formed by burning selenium oxygen ? What is the action of water on it?

772. Give the names and formulæ of the oxychlori and chlorides of selenium which have been obtained.

773. Give a short account of the acids of seleniu and point out their analogies with the acids of sulphur.

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