![]() ![]() It is a cylindrical iron chamber fitted with iron pipes. These are then introduced in the contact chamber. (4) Contact chamber or converter : The pure gases are then, heated to about 723-823 K in a pre-heater. In case the gases are impure, they are passed through the purifying unit again. If some impurities are present, they will scatter light and the path will become visible. (3) Testing box : The gases coming out of purification unit are tested in this box with the help of a strong beam of light. The impurities of arsenic oxide present in the gases are absorbed by ferric hydroxide. (v)Arsenic purifier: This is a small chamber fitted with shelves containing gelatinous ferric hydroxide Fe(OH) 3. (iii) Scrubber: Gases are introduced into a washing tower (packed with quartz) also known as scrubber which dissolves mist and any other soluble impurities. (ii) Coolers: The hot gases are cooled to about 373 K by passing them though cooling pipes. (i) Dust chamber: Steam is introduced to remove dust particles. (2) Purification Unit : The gaseous mixture coming out of sulphur burners is generally impure. (1) Sulphur burners : Sulphur or iron pyrites are burnt in excess of air to form sulphur dioxide. ![]() (iv) Purity of gases: The gases must be purified before subjecting them to oxidation in the presence of catalyst. It is comparatively cheap and is not poisoned by the impurities. But it is easily poisoned by the impurities present in the gases and therefore, has now been replaced by vanadium pentoxide (V 2O 5). Platinised asbestos was used as catalyst. (iii) Use of catalyst: A catalyst increases the speed of reaction. Therefore, a pressure of 2 to 3 bar is sufficient for the oxidation. But a very high pressure may cause the corrosion of the vessel in which oxidation is carried. (ii) High pressure: Since the volume of the gaseous products is less than that of the gaseous reactants, high pressure should favour the oxidation of sulphur dioxide. However, it is essential to have minimum temperature of 720 K, called optimum temperature, to get the maximum yield of the product. (i) Low temperature: The forward reaction is exothermic and therefore low temperature favours the oxidation of sulphur dioxide. The key step in the manufacture of sulphuric acid is the catalytic oxidation of SO 2 with O 2 to give SO 3. The conditions for the maximum yield of sulphur trioxide are derived by using Le Chatelier’s principle as follows: Oleum is then diluted with required quantity of water to get sulphuric acid of any desired concentration.Ĭonditions favouring the maximum yield of sulphur trioxide ![]() Sulphur trioxide is absorbed in about 98% H 2SO 4 to form oleum or fuming sulphuric acid. ![]()
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