RE: Hydrogen????11 May 2021 10:28
Yes it was hydrogen typically over 50%, CH4 over 25%, CO over 5%, less other hydrocarbons: even less some gases CO2, nitrogen, which would exit unburnt. While these latter would reduce calorific yield, hydrogen is so light that the yield per volume (rather than mass; it was sold per cu.ft.) must be less.
Like petroleum "natural" gas the composition was variable, but there were no valuable byproducts to justify refining coal gas, unlike the other alkanes in "natural" gas.
The proportion of hydrogen made the gas so buoyant, that schoolboys could inflate condoms (not so-named then) and they would stick firmly to a school hall ceiling. With the new gas they were much less buoyant, and would sometimes drift down during assemblies, an improvement in our view.