301 



GAS-LIGHTING. 



GAS LIQUOR. 



803 



Intensity of the light emitted. The heat required to render matter 

 luminous in its three states of aggregation differs greatly. Thus, solids 

 are sometimes luminous at comparatively low temperatures, as 

 phosphorous and phosphoric acids. Usually, however, solids require a 

 temperature of 600 or 700 Fahr., to render them luminous in the 

 dark ; and must be heated to 1000 Fahr. before their luminosity 

 becomes visible in daylight. Liquids require about the same tem- 

 perature. But to render gases luminous, they must be exposed to an 

 immensely higher temperature ; even the intense heat generated by 

 the oxhydrogen blowpipe scarcely suffices to render the aqueous vapour 

 produced visibly luminous, although solids, such as lime, emit light of 

 the most dazzling splendour when they are heated in this flame. 

 Hence, those gases and vapours only can illuminate, which produce or 

 deposit solid or liquid matter during their combustion. This depen- 

 dence of light upon the production of solid matter is strikingly seen in 

 the case of phosphorus, which when burnt in chlorine produces a light 

 scarcely visible ; but, when consumed in the air or oxygen, emits light 

 of intense brilliancy ; in the former case, the vapour of chloride of 

 phosphorus is produced, in the latter inlid phosphoric acid. 



Several gases and vapours possess this property of depositing solid 

 matter during combustion, but a few of the combinations of carbon 

 and hydrogen are the only ones capable of practical application : these 

 latter compounds evolve during combustion, only the same products as 

 those generated in the respiratory process of animals, namely, carbonic 

 acid and water. The solid particles of carbon which they deposit in 

 the interior of the flame, and which are the source of light, are entirely 

 consumed on arriving at its outer boundary ; their use as sources of 

 artifnal light, under proper regulations, is therefore quite compatible 

 with the most stringent sanatory rules. 



The light emitted during the combustion of coal gas is due entirely 

 to the illuminating class of its constituents, which yield an amount of 

 light proportional to the quantity of carbon contained in a given 

 volume ; thus, propylene and butylene yield respectively 50 and 100 per 

 cent, more light than olefiant gas, because they contain respectively 50 

 and 100 per cent, more carbon in a given volume. 



It would not be desirable to employ a gas containing only lumini- 

 ferous ingredients, even if it were possible to manufacture such a gas, 

 because it is exceedingly difficult to consume these constituents with- 

 out the production of smoke attendant on imperfect combustion. An 

 inflammable diluting material is therefore necessary to give the flame 

 a sufficient volume, so as to separate the particles of carbon farther 

 asunder, and thus diminish the risk of their imperfect combustion. 



All the three diluents above mentioned perform this office equally 

 well ; but if we study their behaviour during combustion we shall find 

 that in a sanatory point of view hydrogen is greatly to be preferred. 



The two objections most frequently urged against the use of gas in 

 apartments are, first, the heat which it communicates to the atmos- 

 phere ; and, second, the deterioration of the air by the production of 

 carbonic acid. Now, in their action upon the atmosphere in which 

 they are consumed, the above three diluents present striking differ- 

 ences in these two respects. 



One cubic foot of light carburetted hydrogen, at 60 Fahr., and 30 

 inches barometrical pressure, consumes two cubic feet of oxygen during 

 ito combustion, and generates one cubic foot of carbonic acid, yielding 

 a quantity of heat capable of heating 5 Ibs. 14 oz. of water from 82 to 

 or causing a rise of temperature from 80 to 80'8 in a room 

 containing 2500 cubic feet of air. 



One cubic foot of carbonic oxide at the same temperature and 

 pressure, consumes during combustion half a cubic foot of oxygen, 

 generates one cubic foot of carbonic acid, and affords heat capable of 

 rawing the temperature of 1 Ib. 14 oz. of water from 82 to 212 or 

 that of 2500 cubic feet of air from 60 to 66-6. 



One cubic foot of hydrogen at the same temperature and pressure, 

 consumes half a cubic foot of oxygen, generates no carbonic acid, 

 and yields heat capable of raising the temperature of 1 Ib 13 oz 

 of water from 82* to 212; or that of 2600 cubic feet of air from 

 60 to 66-4. 



This comparison shows the great advantage which hydrogen possesses 

 10 other diluent*, especially over light carburetted hydrogen, 



nch is evidently a very objectionable constituent, and shows that a 

 normal gas for illuminating purposes should consist of illuminating 

 hydrocarbons diluted with pure hydrogen. 



As an illuminating agent gas is superior to all others in an economical 

 wint of view, as seen from the following table, showing the compara- 

 ve cost of light from various sources equal to 20 sperm candles, each 

 burning for 10 hours at the rate of 120 grains per hour : 



Wax . 



Spermaceti 

 Tallow . 

 Sperm oil (I 

 London gas 

 Manchester gas 

 Liverpool gas 



As regards the production of a minimum amount of carbonic acid 



heat, gas is also greatly superior to other light-giving agents, as 



een from the following comparison, showing the absolute 



amounts of carbonic acid and the relative quantities of heat generated 

 per hour, by various sources of light each equal to 20 sperm candles 

 burning at the rate of 120 grains per hour : 



Carbonic Acid. Heat. 



Tallow 10-1 cubic feet. 100 



\VnT } 



.'.'.'} 8 ' 3 " 82 



Spermaceti 



Sperm oil (Carcd's lamp) . . 6-4 

 London gas .... 5'0 

 Manchester gas . . . . 4-0 

 Liverpool gas . . . .3-0 



63 

 47 

 33 

 32 



Notwithstanding the great economy and convenience attending the 

 use of gas, and in a sanatory point of view, the high position which, 

 as an illuminating agent, coal gas of proper composition occupies, its' 

 use in dwelling-houses is still extensively objected to. The objections 

 are partly well founded and partly groundless. As is evident from the 

 foregoing table, even the worst London gases produce, for a given 

 amount of light, less carbonic acid and heat than either lamps or 

 candles ; but then, where gas is used, the consumer is never satisfied 

 with a light equal in brilliancy only to that of lamps or candles, and 

 consequently, when three or four times the amount of light is produced 

 from a gas of bad composition, the heat and atmospheric deterioration 

 greatly exceed the corresponding effects produced by the other means 

 of illumination : but by using a gas of high illuminating power, like 

 those of Liverpool or Manchester, it is evident that two or three times 

 the light may be employed with the production of no greater heat or 

 atmospheric deterioration than that caused by wax candles, or the best 

 constructed oil lamps. 



But there is nevertheless a real objection to the employment of gas- 

 light in apartments, founded upon the production of sulphurous acid 

 during its combustion ; this sulphurous acid is derived from bisulphide 

 of carbon, which has already been referred to as incapable of removal 

 from the gas by the present methods of purification. 



This impurity, which is more or less encountered in all coal-gas 

 now used, is the principal, if not the only, source of the unpleasant 

 symptoms experienced by many sensitive persons in rooms lighted with 

 p i It is also owing to the sulphurous acid generated during the 

 combustion of this impurity, that the use of gas is found to injure 

 the binding of books, and impair or destroy the delicate colours of 

 tapestry; therefore the production of gas free from this noxious 

 sulphur compound is at the present moment a problem of the highest 

 importance to the gas manufacturer, and one which demands his 

 earnest attention. 



As it is impossible for the consumer to procure gas free from this 

 objectionable compound, the only method of obviating its unplea- 

 sant and noxious effect*, is to remove entirely the products of com- 

 bustion from the apartments in which the gas is consumed, and thus 

 prevent them from mingling with the circumambient air. This sug- 

 gestion was first made by Faraday, who accomplished this object 

 by his very beautiful and effective ventilating burner. This appa- 

 ratus, which is used at Buckingham Palace, Windsor Castle, the 

 House of Peers, and in many public buildings, may be truly said to 

 have brought gas illumination to perfection ; for not only are all the 

 products of combustion conveyed at once into the open air, but nearly 

 the whole of the heat is in like manner prevented from communicating 

 itself to the atmosphere of the room. The only obstacles to the uni- 

 versal adoption of this description of .burner are its expense, and the 

 difficulty of conveying the ventilating tube safely into the nearest flue 

 without injuring the architectural appearance of the room. The public 

 at large will therefore still await the removal of the objectionable 

 compound in question, by the gas manufacturer, before they will uni- 

 versally adopt this othenvise delightful means of artificial illumination. 

 For the method of analysing gas, and for the chemical mode of deter- 

 mining its illuminating power, see GASOMETBIC ANALYSIS, Analutit of 

 Coal Gat. 



GAS LIQUOR. In the manufacture of gas for illuminating pur- 

 poses, by the destructive distillation of coal, certain liquid products 

 are always obtained. Evolved from the heated coal in the state of 

 vapour, they condense by the mere cooling of the gas, and then separate 

 into two portions, the one having an oily character and constituting 

 coal-tar [COAL-TAB] ; the other being water containing some matters in 

 solution, and known as gas-liquor, or the arnmoniacal liquor of the 

 gas-works. 



The substances contained in this solution are ammouiacal gas, and 

 the following compounds of ammonia with volatile acids : 



Carbonate of ammonia, 

 Sulphate of ammonia, 

 Sulphide of ammonium, 

 Chloride of ammonium, 

 Ferrocyanide of ammonium. 



On account of the immense demand for ammoniacal salts by metal- 

 lurgists, calico-printers, colour-makers, artificial manure manufacturers, 

 and others, gas-liquor, although a secondary product in gas-manufacture^ 

 is of considerable commercial value. The various methods that a 

 knowledge of chemistry would suggest for the extraction and working 

 of the ammonia contained in gas-liquor have consequently formed the 



