Perchloroethylene

The perchloroethylene or tetrachloroethylene is a chemical compound of Cl₂C=CCl₂ formula. It is sometimes called simply perchlo. This Solvant is used for the dry Nettoyage fabric and for to degrease metals.

Properties

With room temperature, it is a non flammable and non-explosible liquid. It evaporates easily in the air and has a bitter odor. The majority of people can feel perchloroethylene in the air starting from a concentration of 1 ppm (left per million). Certain people can feel it with a concentration even lower.

The perchloroethylene is almost insoluble in the Eau but miscible in the majority of the Solvant S organics. It is Lipophile (attracted by grease) and dissolves substances such as greases, Huile S or resins.

Its temperature of fusion is of -22°C and its temperature of boiling of 121°C.

It can react violently with alkaline or alkaline-earth metals, the Alcali S (Soude and Potasse) and the Aluminum.

History

The perchloroethylene was synthesized for the first time in 1821 by Michael Faraday. It heated Hexachloroéthane until it breaks up into perchloroethylene and Chlore.

Production

The majority of perchloroethylene are produced starting from the ethylene while passing by 1,2-dichloroethane. When 1,2-dichloroethane (ClCH₂-CH₂Cl) is heated with 400°C with Chlore (Cl₂), perchloroethylene is obtained according to the following reaction:

ClCH₂-CH₂Cl + 3Cl₂ --> Cl₂C=CCl₂ + 4HCl

This reaction can be catalyzed by a mixture of Chlorure of potassium and Chlorure of aluminum, or by Activated carbon. The Trichloroéthylène is the principal by-product of this reaction. The perchloroethylene and the Trichloroéthylène, which is also a marketed solvent, are collected together then separated by Distillation.

There exists another process of obtaining less running starting from Hydrocarbure S light partially chlorinated, chemical by-products of process. When these compounds are heated in the presence of chlorine in excess, they give a mixture of perchloroethylene, of Carbon tetrachloride and Chlorure of hydrogen.

Use

In general, the perchloroethylene is used like Solvant. The majority of made up the Organique S dissolve in perchloroethylene. The perchloroethylene is the solvent most usually used for the dry Nettoyage. It is also used to degrease the lic parts Métal in industries Automobile and metallurgical. One also finds it in some consumables like solvents for painting or to remove the spots.

Before their prohibition, the perchloroethylene was used with manufacture as cooling agents to the Fréon.

Effects on health

The perchloroethylene is absorbed by inhalation, oral way and the skin (when it is in liquid form). It is toxic for the nervous system and the kidney. The exposure to tetrachloroethylene can cause an irritation of the respiratory tracts and eyes, giddinesses, nauseas, headaches and losses of memory, a somnolence and that can go until the loss of consciousness and death.

The perchloroethylene is probably carcinogenic for the man. Countries like the Denmark or certain American states in particular the California limit its use drastiquement. This one set up a strict regulation which goes until the total ban of its use from here 2020.

At the time of the opening of the port-hole of a machine of dry cleaning, the vapors of perchloroethylene escape from the machine. The people working or living with the top of a steam pressing are exposed to these vapors.

It is recommended to air well the textiles which were cleaned dry. In the event of contact of perchlorethylene with the Skin or the eyes, to rinse with large water and to consult a doctor.

Effects on the environment

The perchloroethylene is dangerous for the environment. Rejected in water or the air, it is degraded very slowly. The machines of dry cleaning let escape from the perchlorethylene vapors in the air and produce muds charged with perchlorethylene which can be recycled but often leave in the sewers. Rejected in water, perchlorethylene disturbs the operation of the purification plants and is Toxique for the watery organizations.

This solvent belongs to the made up organics volatile (COV): it intervenes in the production of ozone to lower atmosphere.

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