ILLUMINATION. 



523 



takes advantage of this circumstance, cooling 

 the gas before passing it through the naphtha, 

 so that it may take up only the hydrocarbons 

 of such high volatility as not to be likely to re- 

 condense even at low temperatures. The gas 

 is cooled by causing it to flow through a long, 

 labyrinthine passage, formed by placing one 

 within another a series of cylinders between 

 which annular spaces are left. Some naphtha is 

 placed in the lower part of this cooler, and the 

 gas finally escaping from it and partly charged 

 ascends into a second vessel or tube filled with 

 a porous material, which, being by capillary 

 attraction kept saturated with naphtha, ex- 

 poses this liquid in the most effectual manner 

 to the gas rising through it. For this use, the 

 inventor prefers the material known as porous 

 carbon, and sometimes employed for filters. 

 A valve is so placed between the two vessels, 

 that the opening it allows for the gas shall be 

 inversely proportional in area to the pressure 

 and velocity of the current, thus serving to 

 equalize the delivery of the gas ; and another 

 valve, nearly closing when the supply of naphtha 

 in the apparatus diminishes to a certain extent, 

 interrupts in this manner the flow of gas, and 

 reduces the light, thus giving notice of the 

 necessity of replenishing with the carburetting 

 liquid. 



Illuminating Gases from Petroleum, or Coal 

 Oil, or from their Derivatives. Petroleum and 

 coal oil are alike mixtures of a variety of hydro- 

 carbons, liquid (at common temperatures), or 

 dissolved; and these components are to such 

 an extent identical or closely allied in the 

 two compound oils, that the latter may be 

 taken as for many purposes, very nearly equiv- 

 alents, the one of the other. Both of them 

 offer in quite concentrated and convenient form 

 the elements necessary to the production of 

 illuminating gases. This is in yet higher degree 

 true of certain derivatives or products separable 

 from the rock or coal oils, as naphtha, benzole, 

 kerosene, &c. ; and in case of these latter, an 

 additional advantage is, that the gas directly as 

 produced is certain to be very much more pure 

 than any coal gas can be, even after the best 



Sractical system of washing and purifying, 

 esides, the rock and coal oils are now to be 

 had, the one in nature, the other as resulting 

 in the manufacture of coal gas, &c., in very 

 great abundance ; so that, in some situations 

 actually worthless or of merely nominal value, 

 they are generally cheap in all places in which 

 an actual demand for them conld exist. In 

 view of these facts, as would be expected, 

 numerous methods and processes have been at- 

 tempted, or are now in course of trial, for pro- 

 ducing from the crude oils or their derivatives 

 the desideratum of an illuminating gas, at once 

 more convenient and certain in its manufacture, 

 as well as more pure and also more economical 

 in price, than the coal gas so generally in use. 

 Of course, the gas so sought mnst be a perma- 

 nent one, capable of being stored in gasometers 

 and delivered without condensation through 



pipes in the coldest weather ; while it is further 

 quite certain that, if an illuminating gas can be 

 economically produced from these oils or their 

 products, one element of its economy will be 

 in the superior brilliancy of its light, due to 

 the taking up of a larger percentage of the car- 

 bon so abundant in them. 



In fact, these oils and their several compo- 

 nents alike contain an excess of carbon over 

 the hydrogen present, as compared with the 

 proportions of these two elements required to 

 produce even the heaty, and much more the 

 light carburetted hydrogen, or the mixture of 

 both, as usual in coal gas. If, now, in attempts 

 at obtaining a gas from these oils, the effect 

 of the process employed is merely to produce 

 in whole or hi part a vapor, in lieu of a per- 

 manent gas, that is, if the molecules of the 

 vapors of the oils be not made by heat or by 

 some other cause to assume a new arrangement 

 and combination (so that the oil can be said to 

 be destructively distilled), then, so far as a mere 

 vapor is the product, this is quite certain to 

 prove worthless and positively troublesome by 

 recondensing at low temperatures. If, on the 

 other hand, destructive distillation of the oils 

 does take place, with generation of permanent 

 gases, these are quite certain to be chiefly the 

 light and the heavy carburetted hydrogen (C a 

 H 4 and C 4 Hi) in mixture, and the latter, in view 

 of the*abundant carbon of the oils, in larger 

 relative proportion than occurs in case of coal 

 gas. But, further, the percentage of hydro- 

 gen in the oils being fixed by the composition 

 of each of them, and always at a small limit, 

 it follows that this fact will limit also the 

 amount of the gases that can be generated, and 

 that in attempting to convert the oils alone into 

 gas. a considerable residue of carbon which 

 could not be taken up in the formation of the 

 gases must present itself after the process. So 

 far as the making of gas is concerned, this is a 

 waste of the material employed ; and as a mat- 

 ter of fact, the destructive distillation of any 

 one of the oils referred to shows such waste in 

 the copious residue of carbon, in form of soot, 

 or coke, &c. By the introduction, however, 

 during gasification of the oil vapors, of the re- 

 quisite addition of hydrogen from some extra- 

 neous source, the conditions of the moment 

 favoring chemical union, it is safe to presume 

 that a greatly increased proportion of the car- 

 bon will be taken up ; indeed, it appears, from 

 certain trials, that the whole of the carbon is 

 taken up in gaseous form, if the supply of hy- 

 drogen be sufficient. In such case, while a 

 pure and highly illuminating ga\s is produced, 

 there is no loss of the material which can enter 

 into its composition. Thus have been indicated 

 the various aspects and conditions of the prob- 

 lem under consideration ; that, namely, of the 

 economical production of an illuminating pas 

 from the oils already named. Some of the 

 methods recently tried or now being developed 

 with a view to such manufacture will now be 

 described, the reader being left to judge how 



