"Our aim is to present as clearly as possible the underlying physical processes occurring in flames. We fully realise, of course, the need for quantitative measurements, but have avoided purely mathematical discussion; indeed we have little enthusiasm for abstract mathematical treatments of combustion, these usually involving many unknown and often unknowable parameters."
I remember being told in high school chemistry that the top of the inner flame is the hottest part of the Bunsen flame. The chart shows that propane and butane have a hotter flame than CO. It also shows that higher alkanes such as heptane and octane give an even hotter flame. However, these produce a flame with a higher degree of carbon zero, which gives a more luminous flame but leave a black solid residue. This is because the fuel to oxidant ratio for these hydrocarbons does not give an equal stoichiometric ratio. The lower alkanes are said to give a more clean burning flame as they produce only the oxidation product CO2; an odourless, colourless gas. Hence we have: Higher alkanes = hotter but dirtier flame.