104 



GAS-LIGHTING 



the Rev. Dr John Clayton, Dean of Kildare, ad- 

 dressed a letter to the Hon. Robert Boyle, in which 

 he described experiments on the production and 

 storage of inflammable gas distilled from coal ; and 

 this Tetter was published in the Royal Society's 

 Transactions for 1789. In 1787 Lord Dundonald 

 made some domestic experiments on lighting by 

 coal-gas. In 1792 William Murdoch lit up his 

 house and office atRedruth in Cornwall ; in 1798 he 

 lit up a part of Boulton & Watt's manufactory at 

 Soho, Birmingham ; and in 1805, with 1000 burners, 

 the mills of Messrs Philips and Lee at Salford. In 



1801 Le Bon lit his house with coal-gas, and in 



1802 he proposed to light a part of the city of Paris. 

 In 1803 Wintzer or Winsor lectured in London upon 

 the new light ; he was a sanguine projector, holding 

 forth fantastic hopes, but was instrumental in found- 

 ing the Chartered Gas Company which obtained its 

 Act of Parliament in 1810. In 1813 he was replaced 

 by Mr Samuel Clegg, who had been managing 

 Boulton and Watt's gas-lighting since 1805 in suc- 

 cession to Mr Murdoch, and who was the inventor 

 of the hydraulic main, the wet meter, and the wet- 

 lime purifier. In 1813 Westminster Bridge was 

 lighted by gas, and immediately thereafter the 

 new method of lighting made very rapid pro- 

 gress in Great Britain and other countries ; and in 

 the contest for supremacy between coal-gas and oil, 

 wood, and peat-gas, which were at one time some- 

 what extensively tried, coal-gas took the lead. 



II. Oil-gas is prepared from heavy mineral oils 

 (sp. gr. =0'9) or paraffins, from their residues, 

 and sometimes from spent grease, suint, waste 

 mutton fat (in Australia), &c. One hundred Ib. 

 of oil yields from 722 to 1092 cubic feet of gas, of 

 which one cubic foot per hour yields a light of 10 

 to 12 candles. The oil is made to flow in a thin 

 steady stream into cast-iron retorts, heated to 

 between 900 and 1000 C. : these retorts are hori- 

 zontal or vertical, or are in some cases so arranged 

 that gas formed in one retort or section of a retort 

 is further heated in another retort or in another 

 section of the same retort. The condensation 

 requires special attention ; oil-gas has a tend- 

 ency to carry non-permanent vapours with it, 

 and these must be removed. The purification 

 necessitates the use of scrubbers, purifiers, and so 

 on as in coal - gas. Even in refined paraffin 

 and petroleum oils there is sulphur present 

 often far in excess of that contained in an 

 equivalent quantity of coal-gas. Oil-gas must be 

 burned at a low pressure and in small burners ; the 

 standard burner is No. 1 ( 1 cubic foot per hour). 

 Oil-gas is used for lighting railway carriages ; the 

 gas, carefully purified, is compressed at 10 atmo- 

 spheres' pressure ; it is then transferred to the reser- 

 voirs borne by the railway carriage, each of which 

 carries, at 6 atmospheres' pressure, enough gas for 

 33 to 40 hours' lighting ; a regulator governs the 

 pressure at the burners, and each burner, con- 

 suming 0*777 cubic feet per hour, gives 7 candle- 

 light. Compressed oil-gas has also been applied to 

 the lighting of buoys, and to some extent to steam- 

 ship lighting. In the Young & Bell process, oil 

 is made to trickle from cooler to hotter regions, but 

 at no point is the temperature relatively very high ; 

 as the oil descends, any given constituent of it 

 meets a temperature competent partly to decompose 

 it into lighter and heavier hydrocaroon gases and 

 vapours : the gaseous and vaporous mixture pro- 

 duced travels upwards and meets the down -flowing 

 stream ; this stream dissolves everything except 

 the lightest gases and vapours, which pass off as 

 oil-gas, without being subjected to any excessive 

 temperature, while the materials dissolved find 

 their way back towards the retort, and are again 

 subjected to heat and further decomposition. The 

 only by-product is a very pure form of coke. This 



gas has an enrichment value of about 90, and may 

 be applied to the enrichment either of ordinary 

 coal-gas or to that of poor gas or water-gas. Mi 

 Tatham mixes oil-gas with about 15 per cent, of 

 oxygen, and thereby enables the gas to be burned 

 directly in greater volume with ordinary small 

 burners, so that a lighting-power is attained equi- 

 valent to 100 candles per 5 cubic feet. The light is 

 brilliantly white, and the flames are not so small 

 that they are chilled by the burner itself. 



III. Peat-gas and IV. Wood-gas are occasion- 

 ally used. Wood-gas is a by-product in the pre- 

 paration of pyroligneous (crude acetic) acid ; its 

 lighting-power is about 20 candles ; the yield is 546 

 to 642 cubic feet per 1000 Ib. of wood ; of the crude 

 gas 20 to 25 per cent, consists of carbonic acid. Peat 

 yields 320 to 500 cubic feet of gas per 100 Ib. ; light- 

 ing-power about 18 candles ; the carbonic acid in 

 the crude gas is about 30 per cent. 



V. Producer Gas. When a limited stream of air 

 is driven through glowing coke, the coke is first 

 burned to carbonic acid ; the carbonic acid, as it 

 travels through the remainder of the brightly glow- 

 ing coke, takes up carbon and, for the most part, 

 becomes carbonic oxide ; the resultant gaseous 

 mixture consists of carbonic oxide (about 26 per 

 cent.), the nitrogen of the air employed (about 70 

 per cent.), and some undecomposed carbonic acid 

 (about 4 percent.). This mixture is combustible 

 with a clean flame, and this kind of fuel is now 

 largely employed (generally with utilisation of the 

 waste heat to warm the incoming current of air, as 

 in the so-called regenerative furnaces) for heating 

 the retorts in coal-gas-making, in metallurgical 

 operations, in glass and pottery making, and in 

 boiler firing. The furnace hearth becomes a clear, 

 clean, deoxidising region of intense heat without 

 visible flame. The gas from the producer is very 

 hot ; if it be passed at once into the furnace, a large 

 proportion of the heat of the coke may be utilised ; 

 if it be allowed to cool, a considerable percentage is 

 lost. The usual yield of producer gas is from coal 

 (Siemens) about 160,000, from coke about 175,000 

 cubic feet per ton ; the heating values are, for cooled 

 gas, respectively 29,700 and 26,900 calories per 

 thousand cubic feet, or altogether 60 and 68 per 

 cent, of those of the respective materials employed. 



VI. Producer Water-gas. When mixed air and 

 steam are driven through glowing coke (or anthra- 

 cite, Dowson), the air keeps the coke glowing, and, 

 as in the previous case, produces carbonic oxide, 

 carbonic acid, and nitrogen ; the steam acts on the 

 glowing coke and produces hydrogen and carbonic 

 oxide ; the result is a mixture whose composition 

 varies according to the relative quantities of air 

 and steam, and according to the temperature in 

 the producer ; as an average it may be said to con- 

 sist of 9 per cent, of carbonic acid, 24 of carbonic 

 oxide, 13 of hydrogen, and 54 of nitrogen. If an 

 excess of steam be used, there is more hydrogen, 

 more carbonic acid, and less carbonic oxide. The 

 usual yield is about 168,000 cubic feet per ton of 

 material ; the heating value is about 33,500 calories 

 per 1000 cubic feet ; altogether about 80 per cent, 

 of that of the coke and anthracite employed. 



VII. Water-gas. In 1793 Lavoisier discovered 

 that when steam, unmixed with air, is passed 

 through glowing coke, the coke is oxidised ; car- 

 bonic oxide and hydrogen gas are produced, theo- 

 retically, pure and in equal volumes ; practically, 

 the product contains 3 to 8 per cent, of carbonic 

 acid, and 4 to 9 of nitrogen. The yield is from 

 coke (7,000,000 calories per ton) about 35,000 cubic 

 feet, with a heating value of about 75,000 calories 

 per 1000 cubic feet, or on the whole about 40 per 

 cent, of the heat-value of the coke ; from coal 

 (7,800,000 calories per ton) about 42,000 cubic feet, 

 at 95,000 calories, or about 49 per cent. In the 



