Dichloromethane or methylene chloride is a chemical compound widely used as a solvent for organic materials, with the chemical formula of CH₂Cl₂. It is a colorless, volatile liquid with a moderately strong aroma, which is sweet in some sense but which makes some people feel very uncomfortable.

Methylene chloride was first prepared in 1840 by the French chemist Henri Victor Regnault, who isolated it from a mixture of chloromethane and chlorine that had been exposed to sunlight.

Production

Industrially, methylene chloride is produced by reacting either methyl chloride or methane with chlorine gas at 400-500Â°C. At these temperatures, both methane and methyl chloride undergo a series of reactions producing progressively more chlorinated products.

CH₄ + Cl₂ â†' CH₃Cl + HCl:CH₃Cl + Cl₂ â†' CH₂Cl₂ + HCl:CH₂Cl₂ + Cl₂ â†' CHCl₃ + HCl:CHCl₃ + Cl₂ â†' CCl₄ + HCl

The output of these processes is a mixture of methyl chloride, methylene choride, chloroform, and carbon tetrachloride. These compounds are then separated by distillation.

Uses

Methylene chloride's volatility and ability to dissolve a wide range of organic compounds makes it an ideal solvent for many chemical processes. It is mainly used as a paint stripper and a degreaser. In the food industry, it is used to decaffeinate coffee and to prepare extracts of hops and other flavorings.The chemical has many other uses aswell, as it is used to chemically weld certain plastics (for example, a factory that produces electric meters uses this chemical to seal the casing of the meter). Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams. It is also used as a fumigant pesticide for stored strawberries and grains. It is also the most common "active" component in Drinking Birds. However, concerns about its health effects have led to a search for alternatives to it in many of these applications.

It is used in Christmas lights called bubble lights, in a sealed vial which bubbles when the incandescent light bulb below it is lit. Wurlitzer also used it in their 1940's "bubbler" style jukeboxes. The bubble tubes were up to 30 inches long and used resistors to provide the heat to boil the liquid in a small constricted chamber that had bits of rock and a special glass valve to concentrate the small bubbles into larger ones. It is still used today in their reproduction machines.

Safety

Methylene chloride is the least toxic of the simple chlorohydrocarbons, but it is not without its health risks. Chronic exposure to methylene chloride may be carcinogenic, as it has been linked to cancer of the lungs, liver, and pancreas in laboratory animals. It is a mutagen and teratogen, causing birth defects if women are exposed to it during pregnancy. Prolonged skin contact can result in the methylene chloride dissolving some of the fatty tissues in skin, resulting in skin irritation or chemical burns.

In many countries, products containing methylene chloride must carry labels warning of its health risks.

External links

* National Pollutant Inventory - Dichloromethane Fact Sheet

Dichloromethane: Encyclopedia BETA

Contents

Dichloromethane

Production

Uses

Safety

External links