Morning journal and courier., 1881-03-04
shefie1d Scientific school.

sen Lamp and Heating by Cas-" The lec turer very lucidly treated his subject. Ex tracts from his valuable lecture are given be- low The lecture was finely illustrated upon the screen, and the audience was both enter tained and instructed.
 The word gas, which properly signifies any aeriform fluid, has come in the language of common life to have more restricted mean ing, and to be chiefly applied aside from it's fgurative use to the mixture of certain in- fammable gases and vapors in varying pro portions, which is supplied to us for purposes of illumination.
 This gas, as you all know, is prepared by heating soft coals, wood or some similar substance in closed retorts and consists of various compounds of carbon Cor charcoaD with hydrogen, some of which yield lu- minous flame, while others emit but very lit tie light in burning.
 The proportion of these various ingredi- ents of illuminating gas varies more or less in gas from the same works and still more in that from different works, so that the words !" Illuminating gas by no means designate a definite or unvarying substance. At the Sam6 render it suitable object with which to illus trate the phenomena of flame.
 The great convenience of gas as an llu-
 ninating agent is due to it's cleanliness and its immediate availability in any desired quantity soon led to its use as fuel, and to- day we have apparatus of all degrees of size and complexity, from the simple burner over which you may make your cup of tea or coffee to the gas stove on which you may cook the meals of large family, or the gas furnace capable of melting iron or satisfying the demands of the gold and silver assayer, all using gas as fuel; not to speak of the various appliances for heating, used in the chemical laboratory or of the nu- merous applications of the waste gases from blast..furnaces and. the like, or of the Siemen's gas furnace, using gas made especially for it, and in which the degree of heat that can be attained is practically limited only by the capacity of the furnace itself to withstand it.
 in ali or nearly all, the applications of it. luminating gas to heating purposes, however, practical difficulty has to be overcome. The gas made for Illuminating purposes and therefore burning with bright flame which deposits layer of lamp-black, 8 soot, on everything brought into contact with it. Evi- dently this difficulty must be overcome be- fore any extensive use could be made of gas as fuel particularly for those domestic pur- poses to which it finds one of it's chief apph- ances For practical purposes one of two methods is adopted. Doe of tkese is to cause the gas to burn from number of small openings in metal pipe, as in the lamp be- fore you.
 Two effects are thus produced. The large mass of metal in the. tubes which abstracts heat from the fame and as a result the latter burns mostly blue and produces little smoke or soot; and, secondly, the distribution of the gas into several small flames allows us to place the article to be heated high enough over the flame to avoid the soot, and yet near enough to get good heating effect. A sec ond and more common method of preventing the deposition of soot is by the use of some form of the Bunsen lamp. (Here ilustra- tions of l, glass lamp; ? metal lamp; 3, figure, came
 Nearly all the common gas stoves and other arrangements for heating by gas are essen tially Bunsen lamps, more or less modified to suit particular purposes. have thus dwelt at some length on the nature of ordi- nary gas flames, because an understanding of how their light is produced is necessary to clear comprehension of the ways in which such flame may be converted into the al- most non luminous flame of the Bunsen lamp We have learned that the light of a. 
 small particles of carbon, which are separa- ted from the gas on the interior of the flame, are heated white hot while floating through the flame, and themselves finally burn.
 We are now prepared to study the ways in which such Q flame may be converted into what is frequently called 8 nonluminous flame; by which is meant not flame that gives out no light, for no such flame exists, but one which emits only the faint light of incandescent gases Having now con- sidered the three causes which may convert the 'sluminous'' flame of our common street gas into a faint and so called ''non lumi- nous' flame, we are prepared to trace the operation of these causes in the Bunsen lamp These three causes, you will recollect, are: First, cooling, by which the tempera- ture of the flame is reduced below the point at which 8 separation of carbon takes place; second, d1ution, mixture of Illuminating gas with some gas which burns with mon luminous flame requiring higher tempera- ture to cause separation of carbon than does the Illuminating gas alone and third, too abundant supply of oxygen, by which the carbon of the flame is burned before it can serve to give luminosity to the flame.
 All the various forms of the Bunsen lamp burn mixture of gas and air. Now the air, as you know is itself mixture of four parts of nitrogen with one part of oxygen. The nitrogen of the air takes no part in the pro- cess of combustion, but simply passes un- changed through the flame. It is plain that the nitrogen must act on the flame in two ways: First, it must cool it, just as any cold substance passing through the flame would cool it,-iust as carbonic acid cools the flame when mixed with the gas, as have already shown you. Second, the nitrogen dlutes the Illuminating gas. Now the tendency Of both cooling and dilution, as we have seen, is to make flame t'non-luminous. If the air now entering this burner were replaced by pure nitrogen the flame would still remain non-luminous as 1t is at present.
 But one-ffth of the air is oxygen, and this also has an effect on the flame. It has two effects, as we have seen- It makes the flame smaller and hotter, and it also tends to burn up the carbon of the Illuminating gas at once, before it can make the flame luminous
 All these causes, cooling, dilution and oxy- dation, are operative at once, in the Bunsen lamp, and the effect that we see is the re- sultant of all these forces. Probably the most important of them are cooling and di- lution by the nitrogen, for if I heat the burn CT through which the gases issue, the flame becomes luminous again, just as in the case of mixture of gas and carbonic acid gas.
 You will perhaps notice also that less heat is required to make the flame of the Bunsen lamp luminous than was needed to make the flame of the mixture of gas and carbonic acid. This is because the oxygen of the air so in- creases the heat of the flame that only little more heat suffices to overcome the effects of cooling and dilution by the nitrogen.
 The Bunsen lamp takes various forms, &C., cording to the purpose for which it is to be used. I have here few examples of this. I Exhibit. In some of these you will observe that the gas burns on the top oT a piece of | fine wire gauge after becoming mixed with l air below it. This form of burner is very common one It differs in appearance from l the usual form of Bunsen lamp, but is essen- tially the same in principle; that is, it burns I a mixture of gas and air, and gives 'tnon- l luminous flame for the same reason that the l ordinary Bunsen lamp does.
 These reasons have endeavored to pre- sent to you experimentally this evening. Our | study of the subject has led us to notice some | curious and interesting facts, which have | been brought to light by no little thought | and experimentation.
 As result df this thought and experiment tation we know, not indeed all, but much | about the laws which govern the phenomena exhibited by flame. The value of the facts Il which we have observed does not, however, | lie in their curiosity, and shall be sorry to | have you remember my lecture as you would a jugglers exhibition, by the number and the strangeness of the tricks performed.
 RHz .I----