Coal gas
Coal gas coming directly from the bench was a noxious soup of chemicals, and removal of the most deleterious fractions was important, for improving the quality of the gas, for preventing damage to equipment or premises, and for recovering revenues from the sale of the extracted chemicals. Several offensive fractions being present in a distributed gas might lead to problems – Tar in the distributed gas might gum up the pipes (and could be sold for a good price), ammoniacal vapours in the gas might lead to corrosion problems (and the extracted ammonium sulfate was a decent fertilizer), naphthalene vapours in the gas might stop up the gas-mains, and even carbon dioxide in the gas was known to decrease illumination; thus various facilities within the gas-works were tasked with the removal of these deleterious effluents. But these do not compare to the most hazardous contaminant in the raw coal gas: the sulfuret of hydrogen (hydrogen sulfide, H2S). This was regarded as utterly unacceptable for several reasons: