Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. WAter gas is a synthesis gas, containing carbon monoxide and hydrogen. IT is a useful product but requires careful handling because of the risk of carbon monoxide poisoning. THe gas is made by passing steam over red-hot coke: C + H2O CO + H2. THe reaction is endothermic so the coke must be continually re-heated to keep the reaction going. THis was usually done by alternating the steam stream with an air stream.