fi4 



THE CIVIL ?:XGINEER AND ARCHITECTS JOURNAL. 



[FeBRU AEY, 



the idea tliat the application of he;it to coal expels the bituniinousanci 

 volatizable part by a distillatory process, and in corroboration of this 

 opinion I find Dr. Ure says, " the first operation which coal undergoes 

 on being heated in a common furnace, is, distillation." 



I accompany the present with Dr. Ure's letter, from wliich I have 

 raa<le the above quotations. 



And am, your obedient servant, 



C. W. Williams. 



Reworks by yimlreji' I're, M.D., F.It.S., on Mr. }f'illiam.i' s Treatise on the 

 Combvstion of Coal. 



To C. W. Williams, Esa. 



Having now carefully perused your treatise " On the Combustion of Coals 

 and the Prevention of Smoke, Chemically and Practically considered," I can- 

 not help congratulating you nn the profound nj-inner in which you have 

 studied the phenomena of a furnace — phenoniena which, like those of the 

 freezing and boiling of water, had been for ages exhibited to the eyes of the 

 philosopher and the engineer, without receiving from the one a scientitic 

 analysis, or leading the other to any radical improvement. You have fully 

 demonstrated the defectiveness and fallacy of the ideas generally entertained 

 concerning the operation of fuel in furnaces, anil the errors, consequently, 

 committed in tlicir construction. Nothing places in a clearer light the heed- 

 lessness of mankind to the most instructive lessons than their neglecting to 

 perceive the difficulty of duly intermingling air with inflammable vapours, 

 for the purjiose of their combustion, as exliibited in the every day occurrence 

 of the flame of a tallow candle, or common oil lamp ; for, though this flame 

 be in contact, externally, with a current of air created by itself, yet a large 

 portion of the tallow and oil passes oft' unconsumcd, with a great loss of the 

 light and heat wliich they are capable of producing. Your quotations and 

 remarks upon this subject must convince every unprejudiced mind of the just- 

 ness of your views as to the imperfect combustion of the inflammable gases 

 given out by coals on the furnace grate. 



By experiments with Dr. Wollaston's Differential Barometer, made in 

 several factories, where both high and low pressure steam was employed, I 

 found, that the ai-rial products of combustion from the boiler furnaces tiew 

 off with a velocity of fully 3G feet per second ; * a rate so rapid as to pre- 

 clude the possibihty of the hydrogenated gases from the ignited coals be- 

 coming so duly blended with the atmospheric oxygen as to be burned. It is 

 well known, that elastic fluids of difl'erent densities, such as air and carhu- 

 retted hydrogen, intermingle e'Pry 4/o«'/y; but, when the air becomes con- 

 bonated, as it does in passing through the grate, and, consequently, heavier, 

 it will not incorporate at all with the lighter combustible gases above it, in 

 the short interval of the ai-rial transit through the furnace and flues. Thus 

 there can be no more combustion amidst these gases and vapours than in the 

 axis of a tallow candle flame. 



Your atomic representations are quite correct, and will please all those 

 who delight in tracing the workings of nature into her formerly mysterious 

 and inaccessible sanctuary. 



You will remember that when, about ten months ago, you laid before me 

 the first draught of the specification of your patent furnace, with what delight 

 I hailed your invention as the harbinger of a brighter day for steam navi- 

 gation, where economy of fuel has become the sine qvS non in regard to long 

 vogages. I rejoice that, with the ample means placed at your command, you 

 have since prosecuted the subject, through all its ambiguities, to a clear and 

 conclusive demonstration of tlie efficacy of your plan for calling forth from 

 pit-coal all its dormant fire, and ditfusing it most efficaciously over the sur- 

 faces of boilers and along the flues. I am more jiarticularly pleased with 

 your analysis of the combustion of the gases and vapours given out by hy- 

 drogenous coal, commonly, though incorrectly, called bituminous, for it con- 

 tains no ready-formed bitumen, but merely its elements, carbon, hydrogen, 

 and oxygen. 



Having been much engaged, during the two preceduig years, in experi- 

 mental researches upon the calorific powers of dift'crent species of fuel, t 

 I became aware that the hydrogenous constituents of coal underwent a most 

 imperfect combustion, and fo\ind I had been misled for some time to the false 

 conclusion, that the caking Newcastle coals afl"ordcd less heat than the non- 

 hydrogenous anthracite of Wales. When 1 improved my method of burning 

 the gaseous products first disengaged from coals, I obtained a greater quan- 

 tity of heat from the so-called bituminous sjiecies ; a result qinte in accord- 

 ance with long estabhshed chemical data. The immortal Lavoisier and La- 

 place ascertained, that one pound of hydrogen, when burned in their cele- 

 hrated calorimeter, melieil 295-6 lb. of ice, while one pound of charcoal 

 melted only 9.J-6 Hi., quantities very nearly in the ratio of .■? to 1 ; Despretz 

 gives the ratio of 315 to 104 ; thus pronng beyond a doubt, that hydrogen 

 can disengage, in its combustion, three times more heat than the same weight 

 of charcoal. It deserves to be remarked, that this ratio is exactly the inverse 

 of that in which hydrogen and carbon unite with oxygen ; for 1 part of hy- 



T An account of these experiments w as laid before the meeting of the Bri- 

 tish Association, at Birmingli;im. and printed in the Athen<nm of September 

 14. 1839. 



• Experimental Inquiry into the Modes of M'.'irming and Ventilating Apart- 

 ments, in reforem-e to tlie Health of their Inmates. By Andrew Ure, M.D., 

 V.R.S. Read belove the Uovnl Society, 16th June. 1836. 



drogen, by weight, condjines with 8 of oxygen to form water; and 3 pails of 

 carbon combine with 8 of oxygen to form carbonic acid gas, which is the 

 product of the complete combustion of charcoal. From these and similar 

 researches, chemists have been led to conclude, that the heat aflfbrded by 

 different bodies in the act of their combustion is proportional to the (piantity 

 of oxygen which they consume ; a conclusion which accords, also, with the 

 prineijile, that the intensity of heat is proportional to the intensity of chemical 

 action, as measured by the proportion of oxygen which enters into com- 

 bination. 



For the first accurate analysis of pit-coals, we arc indebted to Mr. Thomas 

 Richardson of Newcastle,* who pubUshed, a few years ago, in the eleventh 

 volume of Erdniann's Joxrnal fiir Chcmie, the results of an excellent series 

 of researches on coals, made in Professor Liebig's laboratory^. He used the 

 fused chromate of lead to oxygenate the carbon and hydrogen of the coals, 

 with Liebig's new apparatus ; and his results deserve entire confidence. In 

 the earlier analyses of coals, made by Dr. Thomson, myself, and others, the 

 peroxide of cop])er, which was employed to oxygenate the combustible mat- 

 ter, always left some of the carbon unconsumcd, and thus occasioned una- 

 voidable errors. 



1. Rich caking coal, from Garesfield, near Newcastle, of sp. grav. 1-2S0, 

 was found to contain as follows : 



Carbon 87-952 



Hydrogen 5-239 



Azote and oxygen 5-416 



Ashes .' 1-393 



lou- 



2. Caking coal, of excellent quality, from South Hetton, in the county of 

 Durham, of sp. grav. 1-274, afforded. 



Carbon 83274 



Hydrogen 5171 



Azote and oxygen 9-036 



Ashes ." 2-519 



100- 



3. The parrot coal of Edinbmgh afl'orded. 



Carbon 67-597 



Hydrogen 5-405 



Azote and oxvgen 1 2.432 



Ashes .' 1 4-566 



100- 



100 parts of these several kinds of coal take for perfect combustion (sub- 

 tracting the oxygen contained in the coal) as follows : 



1st. 266-7 parts of oxvgen: giving out heat as the number 122-56 

 2nd. 250-2 „ " „ „ 114-98 



3rd. 217-6 „ „ „ 100-00 



The quantity of heat is here presumed to be proportional to the quantity 

 of oxygen consimied. M. Regnault pubUshed, in Erdmann's Journal, vol. 

 xiii., p. 69, the following statement of his analysis of coals, which is regarded 

 by Professor Liiwig as very correct :* 



Newcastle coal, of sp. grav. 1-280, affording a much inflated coke, (quite 

 akin to the Garesfield coal, if not the same,) was found to consist of carbon. 

 87-95 ; hydrogen, 5-24 ; azote and oxygen, 5-41. 



k Lancashire coal, of sp. grav. 1-317, which afli'orded an inflated coke, was 

 found composed of carbon, 83-75 ; hydrogen, 5-66; azote and oxygen, 8-04. 

 The quantity of azote is not given separately by either Jlr. Richardson or M. 

 Regnault ; but it is known to be inconsiderable. The deficit to 100 in his 

 analyses represents the amount of ashes per cent. Mr. R. says : " With the 

 present means of analysis at our disposal, it is impossible to determine the 

 tnie amount," (of azote,) " but the coal cannot contain more than two per 

 cent." In the Edinburgh coal he found, by an experiment made on purpose 

 to determine this point, 0-38 per cent, of azote. This uncertainty introduces 

 a proportional ambigtuty into the calculation of the quantity of heat evolved, 

 from the quantity of atmospherical oxygen consumed. The less the propor- 

 tion of azote, in the above analysis, the greater will be that of the oxygen 

 directly combined with the coals, and the less atmospherical oxygen, of course, 

 will be consumed, which is the only source of the heat disengaged. 



Since it is the proportion of hydrogen in coal that determines the propor- 

 tion of volatile products, a tolerable approximation upon this point is aftbrded 

 by the proportional loss of weight which different coals sufter from ignition 

 in retorts or covered crucibles. I found that 100 pirts of the Felling-main 

 coal used by some of the Lonilon Gas Companies, when strongly ignited in a 

 covered crucible, well-luted, lost 37-5 per cent., leaving 62-5 of a porous coke. 

 The Llangennock coals from Caermarthenshire, of sp. grav. 1-337, lose by 

 ignition only 15-5, and leave 84-5 of a rather dense coke, which contains 3 of 

 ashes. In furnaces of the common construction about London this coal 

 affords much heat with Uttle smoke, and is, therefore, greatly in request, and 

 fetches a high price. 100 parts of the Tanfield Moor coal, of sp. grav. 1-269, 



* An account of these experiments has been since presented, ly Mr. 



Richardson, to the Natural History .Society ol Ne»castle-upon-Tync. and is 

 printed in their Transactions, vol. ii., p. iOl, and in the London and Kdin- 

 ourgh Philos. Magazine, vul. xiii., p. 121, fi>r August, 1338. 

 T Chemie der Organischen Verbindungen, vol, ii., p. 88. 



