Technical Chemistry, 279 



M abundant supply of gas and air is given ; when the glass is made, and 

 the condition has to be reduced to working-temperature, the quantity of 

 fuel and air is reduced. If the combustion in the furnace is required to 

 be gradual from end to end, the inlets of air and gas are placed more or 

 less apart the one from the other. The gas is lighter than the air ; and 

 if a rapid evolution of heat is required, as in a short puddling-furnace, 

 the mouth of the gas inlet is placed below that of the air inlet ; if the re- 

 " "' ' ' ... . , ,. « ., ^ contrary ar- 



enaraeiler's fun 

 ) greater 

 3 goods, being put i 



long muffle, it is requisite that the heat be greater at the door end c 



ithdrawn first, 

 course, for a shorter time in the heat at that end ; and though the fuel 



necessary difference of temperature is preserved by the adjustment of the 

 apertures at those ends. 



Not merely can the supply of gas and air to the furnace be governed 

 by valves in the passages, but the very manufacture of the gas fuel itself 

 can be diminished, or even stopped, by cutting off the supply of air to 

 tfie grate of the gas-producer; and this is important, inasmuch as there 

 18 no gasometer to receive and preserve the aeriform fuel, for it proceeds 

 at once to the furnaces. 



Some of the furnaces have their contents open to the fuel and com- 

 Distion, as in the puddling and metal-melting arrangements ; others are 

 enclosed, as in the muffle furnaces and the flint-glass-furnaces. Because 

 Jfthe great cleanliness of the fuel, some of the glass-furnaces, which be- 

 fore had closed pots, now have them open, with great advantage to the 

 Working, and no detriment to the color. 

 . The economv in ths fiipl is esteemed practically as one-half, even when 



P'oyed, sucli 

 ^«l at a dis 



ic, which can be converted into a clean gaseous 



^^ .,^,^, .he' place of the furnace, so many advantages seem 



^present themselves in this part of the arrangement. 

 . « will be seen that the system depends, in a great measure, upon the 

 intermediate production of carbonic oxyd from coal, instead of the direct 

 Foduction of carbonic acid. Now carbonic oxyd is poisonous, and, in- 

 ?e^, both these gases are very deleterious. Carbonic acid must at last go 

 '"to the atmosphere; but the carbonic oxyd cea-ses to exist at the^fur- 

 J^ce, its time is short, and whilst existing it is co.ifined on its way from 

 tfie gas-producer to the furnace, where it becomes carbonic a'lid. No 

 ^f«8 of harm from it have occurred, although its application has been 

 Oiade in thirty furnaces or more. , . 



ibe following are some numbers that were used to convey general im- 

 Preasions to the audience. Carbon, burnt perfectly into carbonic acid m 

 Jgas-producer, would evolve about 4000° of heat, but if burnt into car- 

 Jonic oxyd it would evolve only 1200°. The carbonic oxyd, m its fuel 

 '°[0i, carries on with it the 2800° in chemical force, which it evolves 

 ^'len burning in the real furnace with a sufficient supply of air. 1 he re- 

 «»a»ning 1200° are employed in the gas-producer in distilling hydrocar- 



