Water gas is a kind of fuel gas, a mixture of carbon monoxide and hydrogen. It is produced by "alternately hot blowing a fuel layer [coke] with air and gasifying it with steam". The caloric yield of this is about 10% of a modern syngas plant. Further making this technology unattractive, its precursor coke is expensive, whereas syngas uses cheaper precursor, mainly methane from natural gas. Production Synthesis gas is made by passing steam over a red-hot carbon fuel such as coke: (ΔH = +131 kJ/mol) The reaction is endothermic, so the fuel must be continually re-heated to maintain the reaction. To do this, an air stream, which alternates with the vapor stream, is introduced to combust some of the carbon: (ΔH = -393 kJ/mol) Theoretically, to make 6 L of water gas, 5 L of air is required. Alternatively, to prevent contamination with nitrogen, energy can be provided by using pure oxygen to burn carbon into carbon monoxide. (ΔH = -221 kJ/mol) In this case, 1 L of oxygen will create 5.3 L of pure water gas. History The water-gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. Water gas was made in England from 1828 by blowing steam through white-hot coke. Hydrocarbonate (gas) Hydrocarbonate is an archaic term for water gas composed of carbon monoxide and hydrogen generated by passing steam through glowing coke. Hydrocarbonate was classified as a factitious air and explored for therapeutic properties by eighteenth-century physicians including: Thomas Beddoes and James Watt. The term hydrocarbonate was coined by Thomas Beddoes in 1794. It should not be confused with the modern name "hydrogen carbonate" for bicarbonate ion. Between 1794 and 1802, physicians such as Tiberius Cavallo and Davies Gilbert experimented with hydrocarbonate as an analgesic and anesthetic. Humphry Davy infamously inhaled three quarts of hydrocarbonate at the Pneumatic Institution and nearly died upon "sinking into annihilation"; Davy recovered two days later and concluded inhalation of more hydrocarbonate could have "destroyed life immediately without producing any painful sensations". Carbon monoxide is recognized to have a narcotic effect, therefore the scientists were likely experiencing carbon monoxide poisioning. Diseases treated by hydrocarbonate included: tuberculosis, inflammation, asthma, expectoration, hemoptysis, pneumonia, hydrothorax, spasm and other indications. Many of the diseases treated with hydrocarbonate, whose active ingredient was carbon monoxide, are now being investigated using modern biomedical research methods to determine the therapeutic potential of carbon monoxide. For example,