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The compound sulphuric acid (H2S04) was discovered in about the eighth century, and was first used in the tenth century. The process for producing sulphuric is called the contact process. The contact process was patented by an English vinegar company in 1831, and replaced the chamber process for producing sulphuric acid, as the contact process was an economically and efficiently superior process. After the process was patented in 1831, there was a lack of incentive to produce sulphuric acid via this method on an industrial scale until about 1881. Improvements in technology have led to advancements in the contact process. The earliest contact plants in the late nineteenth century used platinum as a catalyst and required gas cleaning systems in order to reduce poisoning of the catalyst. These Contact plants produced approximately 20 tonnes of Sulphuric acid per day. In modern day, with the invention of the pressurised sulphur furnace (in 1927 by company ‘chemico’), and the use of vanadium as a catalyst, modern contact plants have been allowed to produce 4000-5000 tonnes of sulphuric acid per day. Le Chatelier’s Principle states if a dynamic chemical equilibrium process is forced or placed out of balance due to a change in volume, temperature, pressure or concentration, the position of the equilibrium shifts in either the left or right direction in order to oppose the change, balance the equation and form a new equilibrium. The purpose of Le Chatelier’s principle is to predict the effect of a change in conditions in a chemical system at equilibrium. The equilibrium reaction involved in the contact process is: This equilibrium is the conversion of sulphur dioxide to sulphur trioxide. Le Chatelier’s principle applies to this equilibrium because the desired product from this reaction is sulphur trioxide (2S03), therefore the equilibrium needs to be shifted to the right as much as possible, in order to produce as much sulphur trioxide as possible.
 * __ The contact process __**
 * __ History: __**
 * __ Le Chatelier’s Principle: __**

By decreasing the temperature of the reaction, according to Le Chatelier’s principle, the equilibrium will shift to the right in order to compensate for the loss of heat in the reaction. A new equilibrium is formed and therefore a higher amount of sulphur trioxide is produced.

Another way to increase the amount of sulphur trioxide produced in the equilibrium is to increase the pressure. Le Chatelier’s principle tells us that if you increase the pressure of a system in equilibrium, the equilibrium will shift in favour of the side with the least amount of molecules, therefore the result of increasing the pressure of the Reaction the equilibrium will shift to the right as desired, because there are two molecules on the right hand side and three molecules on the left hand side.

Another disadvantage of this process is that the sulphuric acid is limited to low concentrations. The concentration of sulfuric acid obtain from this process cannot exceed roughly 35%. This is due to the fact that at high concentrations the nitrosylsulfuric precipitates and forms crystals on the lead walls, stopping further oxidation in the chamber. In this day and age, this process does not have any advantages over the contact process because it is relatively inefficient compared to the contact process, and it produces sulphuric acid at low concentrations compared to the contact process.
 * __ Similar Processes: __** Two similar processes that are similar to the contact process are the lead chamber process and the wet sulphuric acid process
 * __ Lead chamber process: __** The lead chamber process was introduced in 1746 by John Roebuck. The process involves sulphur dioxide, nitrogen oxides and steam being pushed through a chamber lined with lead walls, where the nitrogen oxides and the sulphur dioxide undergo a period of dissolving for thirty minutes. Sulphuric acid is formed due to the oxidation of sulphur dioxide. In this process nitric oxides react with oxygen in order to form nitrogen dioxide. Nitric acid and [|__nitrosylsulfuric acid__] (formed due to reactions between liquor at the bottom of the chamber and nitric oxides) concentrate the sulfuric acid at the bottom of the chamber.
 * __ Wet sulphuric acid process: __**



The wet sulphuric acid is a four stage process. These stages are as followed: Combustion- H2S is mixed with 02 (hot air) to form sulphur dioxide (S02) Oxidation- sulphur dioxide is combed with oxygen (oxidised) in order to form sulphur trioxide. Hydration- Sulphur trioxide (S03) is mixed with water (H­20) to form sulphuric acid in gas form Condensation- With the use of water cooling, the acid is condensed from gas form to liquid form The advantages of the wet sulphuric acid process (WSA), is high efficiency. 99% of the sulphur used in the process comes out as commercial grade sulphuric acid and the process is simple to operate.

The contact process produces gases such as sulphur dioxide (S02). Such gases can cause harm or health problems for people such as breathing problems, and problems for asthmatics. Short term exposure to sulphur dioxide can result in wheezing chest tightness and shortness of breath. Longer term health effects of sulphur dioxide include cardiovascular disease, increased levels of soot in the lungs, and all sorts of respiratory illnesses. Though there are possible health impacts sulphur dioxide can create, the likelihood of being affect by them are minimal as the production of sulphuric acid via the contact process occurs in industry with machines and high standards of safety
 * __ Environmental impact of the contact process __**

Sulphur dioxide can cause environmental issues such as acid rain which has the ability to speed up rates of corrosion, and to increase the acid content in lakes, rivers and soil.

Sulphur is a substance that can be oxidised to produce sulphur dioxide or hydrogen sulphide. There must be care taken with these substances as they are strong air pollutants at low concentrations.

Sulphuric acid, the product of the contact process can cause environmental issues such as acid rain, it causes damage to plants, it causes damage to aquatic life, and can lead to the deterioration of limestone structures.

The contact process causes neither more or less harm to the environment than any other process that produces sulphuric acid. This is because most of the other processes involve similar reactions of sulphur just achieved in a slightly different way. The risks of pollution or harm to the atmosphere are roughly equal due to the fact that the processes take place in industrial environments.

Though the contact process has the possibility of causing harm to the environment, overall I consider the contact process to be relatively safe and that it only has very minimal impact on the environment. This is because the production of sulphuric acid takes place industrial environments with high standards of safety, therefore there is minimal chance that the acid or sulphur dioxide will escape into the environment and cause harm or pollution.

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