558 GAS, COAL 



illuminating value of each grain of naphtha burnt with the gag. The naphtha thus 

 added to gas does not burn with a rod flamo, which gives off much Binoko, as it does 

 when burnt alone, but it gives a bright, white, smokeless flamo. This result is duo 

 to the non-illuminating but heat-producing compounds of the gas. The naphtha 

 contains so much carbou and so little heat-producing hydrogen, that when it is set on 

 fire alone the carbon is not heated sufficiently to burn and still less to render it 

 highly luminous ; wherefore its light is feeble, and much of the carbon is deposited 

 as soot. But when it is burnt with gas the heat-producers in the gas raise the carbon 

 of the naphtha to a sufficient temperature to enable it to give off a brilliant light, and 

 to burn without smoke. Thus, the heat-producers are rendered directly useful. They 

 raise the carbon to the temperature required for illumination and combustion. The 

 naphtha, on the other hand, remedies the want of luminosity in the gas by adding to 

 it much carbon, in which it is deficient, and but little hydrogen, in which the gas itself 

 abounds. 



1 But for the teaching of experiment we should expect that if a given quantity of 

 naphtha added to a given quantity of gas raised it in illuminating value (a) candles, 

 then double the quantity of naphtha added to the same quantity of gas would raise it 

 (2 a) candles, three times the quantity (3 a) candles, and so on. In other words, we 

 should expect the illuminating value of a grain of naphtha to be the same however 

 it was burnt with gas. Experience shows this to be a mistake, and proves that the 

 illuminating value of a grain of naphtha depends upon the relation which it bears 

 to the bulk of gas with which it is burnt, and that within certain limits its illuminat- 

 ing value varies greatly. Dr. Letheby investigated the increase of illuminating 

 power obtained by naphthalising, and his results are published in the " Chemical 

 News," vol. vi. pp. 283-292. It is there stated that four grains of naphtha added 

 to a foot of gas gave 25 per cent, increased light, whereas 8 grains per foot gave 

 60 per cent, increased light, instead of 50 per cent., which would have been the in- 

 crease if each grain of carburetting material had a constant illuminating value 

 irrespective of its relation to the bulk of gas with which it is consumed. The in- 

 vestigation had reference to the use of naphtha in the public lamps of the city of 

 London, and therefore the results must have been obtained in flat-flame burners, bat's- 

 wing or fish-tail. The average illuminating value of a foot of common gas burnt in a 

 flat-flame burner, is 1*6 candle, and the weight of a foot of such gas is about 224 

 grains. When the relation between the weight of the gas and the naphtha burned with 

 it is as 224 to 4, the illuminating value of the naphtha is -^ of the illuminating value 

 of the gas ; but when the relation is altered to 224 to 8, then the illuminating value of 

 the naphtha is ^, instead of 50, as it would have been if its illuminating value were 

 constant instead of variable, and depending much upon the quantity of gas consumed 

 with it.' 



Another condition is the attainment of the highest possible temperature within the 

 flame. The first of these conditions has been more or less perfectly obtained in the 

 different gas burners now in use. The second has been hitherto almost entirely neg- 

 lected ; the means by which it may be attained will be discussed after the burners 

 at present in general use have been described. 



GAS BUHNER. The chief burners now in use are the bat's-.wing, fish-tail, argand, 

 bude argand, Winfield's argand, Guise's argand, Leslie's argand. 



1012 ^ e bafs-wing consists of a fine slit cut in an iron nipple, 



giving a flat fan-like flame. 



The fish-tail consists of a similar nipple perforated by two 

 holes, drilled so that the jets of gas are inclined towards each 

 other at an angle of about 60. A flat film of flame is thus 

 produced, somewhat resembling the tail of a fish. This form 

 of burner is especially adapted for the consumption of cannel 

 and other highly illuminating gases. 



The argand consists of a hollow nnnulus (see fig. 1012), from 

 the upper surface of which the gas issues through a number of 

 small apertures, which are made to vary in diameter from J^nd 

 of an inch to ^th of an inch, according to the richness of the 

 gas ; the most highly illuminating gases requiring the smallest 

 apertures. The distances of the orifices for coal-gas should bo 

 16 to -18 inch, and for rich cannel-gas '13 inch. If the argand 

 ring has 10 orifices, the diameter of the central opening should 

 ]>'j = -j*jths of an inch ; if 25 orifices, it should bo one inch for 

 coal-gas; but for oil-gas, with 10 orifices, the central opening 

 should have a diameter of an inch, and for 20 orificet", 1 inch. 

 The pin holes should bo of equal size, otherwise the larger ones will cause smoke, as 

 in an argand flamo with an uneven wick. 



