Disulfuric acid

• Pyrosulfuric
• Oleum

Colorless, hygroscopic crystals

Fixed

1.9 g · cm -3

35 ° C.

With water violent reaction

Risk

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Disulphuric (also pyrosulfuric ) is an oxoacid of sulfur and one of the inorganic acids. It is derived from the sulfuric acid and can be represented formally as a common storage of two sulfuric acid molecules with elimination of water. Disulphuric is highly hygroscopic and highly reactive, especially with water and organic materials, there is very strong reactions. The salts of the disulphuric be called pyrosulfates or disulfates. They can be obtained by heating bisulfates with elimination of water.

Disulphuric is often equated with oleum, this is formally owned but only for 45 % oleum properly. In oleum (also known as fuming sulfuric acid ) is a solution of sulfur trioxide (SO3) in sulfuric acid ( H2SO4) with varying proportions of sulfur trioxide, which are present as a mixture of sulfuric acid and disulphuric depending on the concentration in the concentration range up to 45 %. The concentrations given for oleum are each the proportion of "free " SO3 based on the amount of oleum.

However Oleum provides in various concentrations represent the commercially dominant form of disulphuric, so will be discussed in this article on this mixture.

Production and representation

Industrially disulfuric falls in the form of oleum in the production of sulfuric acid by the contact process. To remove the intermediate sulfur trioxide according to the law of mass action from the reaction equilibrium in which Oleumproduktion this intermediate absorption is carried out in two stages. In the first stage a portion of the SO3 in the oleum is absorbed, which is diluted with concentrated sulfuric acid to the required concentration of oleum. In the second stage of the intermediate absorption residual SO3 is absorbed in concentrated sulfuric acid. This one utilizes the property of SO3, well to dissolve in concentrated sulfuric acid.

The product is a colorless oily (actually heavy, viscous ) fluid present in the sulfuric acid, as well as disulphuric Trischwefelsäuremoleküle. The ratio of components (SO3 and H2SO4) determines the molecular composition and the physico- chemical properties:

Properties

Chemical Properties

Disulphuric is highly hygroscopic and decomposes in the presence of water very quickly and generates considerable heat to sulfuric acid (hydrolysis) and reacts as such strongly acidic. It already comes to this reaction with the existing water in the air, creating a dense fog forms of sulfuric acid droplets. This is for example in the case of oleum, which is why this also called " fuming sulfuric acid " carries.

Safety

Disulphuric and oleum are very dangerous. They are corrosive and react violently with most organic materials. For example, it comes in contact with skin or clothing to severe dehydration, even with cleavage of molecules such as carbohydrates. Thus, the affected area is colored yellow to black. Due to the excessive heat in the incoming hydrolysis to organic material can ignite easily and may even lead to an explosion. Oleum reacts so violently with water that it can only be diluted by slowly pouring it on ice. In addition, it is able, unlike sulfuric acid to destroy even plastic vessels and neoprene gloves. An additional danger represent escaping Schwefeltrioxiddämpfe