1895.] in the Flames of Hydrocarbon Gases. 459 



FIG. 1. 



subject, dilution with hydrogen and carbon monoxide acts regularly, 

 and decreases the value of the illuminant in a direct ratio down to 

 about 50 per cent., whilst when the degree of dilution exceeds 60 per- 

 cent, a rapid falling away in the luminosity takes place, a fact which 

 I think points clearly to a regular pro rata rise of temperature being 

 needed for increase in dilution up to between 50 and 60 per cent., 

 whilst higher degrees of dilution need a far greater rise of tempera- 

 ture ID order to bring about decomposition. 



Moreover it would be manifestly incorrect to look upon the per- 

 centage of acetylene present in the gas issuing from the burner as 

 being any guide to the degree of dilution existing at the point at 

 which luminosity commences. As the two small streams of gas issuing 

 from the holes in the union jet meet and splay themselves out into 

 the flat flame, they draw in with them a considerable proportion of 

 air, the quantity being governed by the pressure of the gas at the 

 burner. 



This can be clearly seen by the fact that a high value gas which 

 burns from a union jet burner of a given size with a smoky flame, 

 under a gas pressure of half an inch of water, will burn with a 

 bright, smokeless, and rigid flame of greatly increased illuminating 

 value when the pressure is raised to 2 in., whilst an ordinary coal 

 gas of 16-candle value must be burnt from a flat flame burner at a 

 pressure of about 0'75 in. if the best results are to be obtained, the 

 increase in air drawn in, if the pressure rises to a much higher degree, 

 diminishing the illuminating value. 



Then, again, the area of non-luminous combustion in a mixture of 

 gases like coal gas means that some at least of the hydrocarbons are 

 consumed before the required temperature for their decomposition is 



