Methyl mercaptan Guide, Meaning , Facts, Information and Description
Methyl mercaptan is a colorless gas with a smell like rotten cabbage. It is a natural substance found in the blood, brain, and other tissues of people and animals. It is released from animal feces. It occurs naturally in certain foods, such as some nutss and cheese. The chemical formula for methyl mercapatan is CH3SH.Methyl mercaptan is released from decaying organic matter in marshes and is present in the natural gas of certain regions in the United States, in coal tar, and in some crude oils.
The United States material safety data sheet (MSDS) lists methyl mercaptan as a colorless, flammable, gas with an extremely strong and repulsive smell. At very high concentrations it is highly toxic and affects the central nervous system. Its penetrating odor provides warning at dangerous concentrations.
Methyl mercaptan is primarily used as an odorant to add warning properties to propane and natural gas used as fuel. Propane by itself is odorless, as are many sources of natural gas. Methyl mercaptan is added for safety reasons so that gas leaks are readily noted by anyone present due to the odor. Mercaptan vaporizes readily and is odiforous enough that only small quantities need be used.
For propane, methyl mercaptan liquid is mixed with liquid propane by the refinery. The mercaptan remains in solution in the desired concentration as the propane is piped and trucked through the distribution system until it is stored in the tank from which it will be used. Propane tanks are usually configured to withdraw vapor rather than liquid, and since the boiling point of methy mercaptan is somewhat higher than that of propane (and since its vapor pressure is lower), mercaptan becomes more concentrated in the tank as vapor is withdrawn. For this reason, even minute leaks in a piping system connected to a nearly-empty tank produce the characteristic odor, especially if much of the propane was withdrawn at low temperatures.
In natural gas systems, methyl mercaptan is injected into the distribution piping, usually within several miles or less of the point of use. Injection equipment and a tank of methyl mercaptan can be seen at the master meter point outside many cities. Mercaptan tanks are similar in construction to tanks used for propane and anhydrous ammonia.
Because of its reactivity, mercaptan can be removed from the gas before it reaches the point of use, or after leaking out of piping. It can react with or be adsorbed by metallic pipe materials, particularly when corroded, and will bind to soil particles. Explosions have occurred where underground gas leaks went unnoticed because the mercaptan was filtered out by the soil.
Methyl mercaptan is also manufactured for use in the plastics industry, as a precursor in the manufacture of pesticides, and as a jet fuel additive. It is also released as a decay product of wood in pulp mills.Uses