Hydrogen sulfide is a pollutant gas produced by many industrial processes, such as oil drilling. The National Oceanic and Atmospheric Administration says that inhaling large quantities can bring about rapid unconsciousness and death, and exposure to even small quantities can result in death or injury. Concentrations too faint to be harmful still give off a foul, rotten-egg stench. This is unpleasantly noticeable in quantities as little as 2 parts per billion, which Creighton University describes as less than 1 milliliter of gas in a 100-seat lecture hall. Researchers developed methods for industry to neutralize hydrogen sulfide with sodium bicarbonate---baking soda---in the 1970s.
Dissolve the sodium bicarbonate in water. Other salts such as ammonium bicarbonate, potassium bicarbonate and magnesium bicarbonate will work, but sodium bicarbonate is a good choice because it's stable and highly soluble in water. The Patent Storm website says a solution having from .01 grams to .25 grams of dissolved sodium bicarbonate per mole of water is ideal.
Bring a gas containing carbon dioxide and hydrogen sulfide—industrial operations commonly produce such a mix—into contact with the baking soda-laden water. This can be done by spraying the water/sodium bicarbonate mix over a container of gas or sending the gas bubbling through a vessel holding the water.
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Allow the carbon dioxide to ionize the baking soda in the water. This creates a solution that will absorb the hydrogen sulfide and neutralize it.
When dealing with a hydrogen sulfide gas leak, the National Oceanic and Atmospheric Administration recommends using water to spray down the gas, then adding sodium bicarbonate to neutralize it.