March 04, 2019
Are you worried that I contaminate your decaf coffee? Don’t be.
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March is MOTW Solvent Month! This is the first of four articles about key solvents — Ed.

Dichloromethane, commonly called methylene chloride, is a solvent that is widely used in chemical research and manufacturing. It is a highly volatile liquid (see fast facts table), but it is neither flammable nor explosive in air.

Dichloromethane is commonly produced by chlorinating methane. The process also produces the other three C1 chlorohydrocarbons—chloromethane, trichloromethane (chloroform), and tetrachloromethane (carbon tetrachloride). The four are separated via distillation.

Although dichloromethane is the least toxic C1 chlorohydrocarbon, it does present hazards. Inhaling it can produce symptoms ranging from drowsiness to respiratory tract irritation and even death. It also may be carcinogenic, but not enough studies have been done to establish the degree of exposure that causes cancer.

Despite its health risks, dichloromethane is one of the main solvents used to decaffeinate coffee beans. After the caffeine is removed, the solvent’s volatility makes it easy to remove residual solvent. Any remaining dichloromethane is well below the 10-ppm concentration allowed by the US Food and Drug Administration.

Dichloromethane hazard information

GHS classification*: skin irritation, category 2
H315—Causes skin irritation Chemical Safety Warning
GHS classification: serious eye irritation, category 2A
H319—Causes serious eye irritation Chemical Safety Warning
GHS classification: specific target organ toxicity, single exposure, narcotic effects, category 3
H336—May cause drowsiness or dizziness Chemical Safety Warning
GHS classification: carcinogenicity, category 2
H351—Suspected of causing cancer Chemical Safety Warning
GHS classification: hazardous to the aquatic environment, acute hazard, category 3
H402—Harmful to aquatic life

*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.

Dichloromethane fast facts

CAS Reg. No. 75-09-2
Empirical formula CH2Cl2
Molar mass 84.93 g/mol
Appearance Colorless liquid
Boiling point 40 ºC
Water solubility 13 g/L

MOTW update: 
April 01, 2019

Dichloromethane (aka methylene chloride) has been a useful sovlent for decades; but its significant hazards have caused it to be used in a declining number of applications. In mid-March, the US Environmental Protection Agency finalized a ban on dichloromethane as an ingredient in paint and coating removers used by consumers, effective at the end of 2019. Environmental and health activists say that the ban, originally promulgated during the Obama administration for consumer and industrial use, does not go far enough.

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