Front matter
TO BE KEP'r FOR RBPKREMCE OKLY
THE ROYAL SOCIETY
FOR THE PROMOTION
Dedication
TO ^I’HE
RIGHT HON. LORD VISCOUNT PALMERSTON, M.P.,
SECRETAEY OF STATE FOR THE HOME DEPARTMENT.
Chapter I. Of The Principles On Which Boilers And Furnaces Have Been Constructed
1. The several Parts of a Boiler and their respective functions.
2. Absence of Provision for the Admission of Air.
3. Watts’ early patent on this head.
4. Misapplied Theory of Relative Proportions.
5. Dr. Lardner’s Rules examined.
Chapter II
OF THE FURNACE, AND THE RELATION WHICH ITS SEVERAL PARTS BEAR TO THE OPERATIONS CARRIED ON WITHIN IT.
6. Two distinct Processes carried on in the Furnace.
7. The Gaseous and Solid Portions of the Fuel occuj)y distinct
Parts.
8. The Heat required for the Generation of the Gas.
9. The Grate Bar Surface, and requisite Depth of Fuel.
10. Superficial Area of Bar Surface, and Sectional Area of Chamber.
11. Introduction of Air cannot be systematized until the Supply of
Fuel be regulated.
12. Houldsworth’s Pyrometer Diagram conclusive on that head.
13. Peclet on the Waste Heat caused by the Irregular Supply of Coal.
14. Quick and Slow Combustion — Thick and Thin Firing.
15. Error of Confounding the Economy of Fuel with the Non-
appearance of Smoke.
16. Error in the construction of the “ Flame-bed.’^
17. Error in the Construction of the Furnace Chamber.
18. Marine and Locomotives compared, in this respect.
CON^J'ENTH.
CHAPTER III. OF IXTUODUCI^rO THE AIR TO THE COKE, OR FIXED PORTION
OF THE COAL,
19. Inattention to the ratio of Air introduced and Oxygen taken up.
20. Prevailing Error on this head.
21. Volume of Air required, in cubic feet.
22. Distinction between the Use of Coal and Coke.
Chapter IV. Of Introducing The Air To The Gaseous Portion Of
THE COAL.
23. Quantity of Gas generated, and Air required.
24. Irregulaiity of the Supply of Air incident to the Mode of Sup-
plying the Fuel.
25. Watt on the Introduction of the Air.
26. Imperfect Knowledge of the Subject in his time.
27. Professor Daniell on the Quantity of Air required.
28. Error in estimating the Area of Admission for the Air.
29. Dr. Ure on the Theoretic and Practical Rates of the Current.
30. Table of Estimated Areas and Velocities of Air Entering a
Furnace.
31. Effect of the Air entering by a single one, or by numerous
Orifices.
32. Illustrated by Reference to Modern Boilers.
33. Experimental Proofs of the same.
34. Mode of Introducing the Air for the Combustion of Carbonic
Oxide, adopted in France.
Chapter V. Of Regulating The Supply Of Air By Self-acting
OR OTHER MECHANICAL APPARATUS.
36. Theory on which the Supply may be regulated.
36. Reports of Sir Robert Kane and Mr. Parkes on this head.
37. Coal Gas or Coke Gas (Carbonic Oxide) always Generated,
and always requiring a Supply of Air.
CONTENTS.
38. Water llegiilating Valve.
39. Erroneous Pj-inciple on which Self-acting Air Valves are based,
40. Table of the Quantities of Gas generated throughout each
Charge.
41. Regulating Supply of Gas by Means of Double Furnaces.
42. Mr, Houldsworth’s Illustration of the Constant Supply of Air
required.
Chapter VI. Of The Place Most Suitable For Introducing The Air To The Furnaces
43. Air to be introduced by a separate Channel.
44. Parkes’ Split-bridge, First Application of this Principle.
45. Its Use in Slow Combustion.
46. Inapplicable to Marine Boilers.
47. Principle of admitting the Air in a divided state,
48. Dr. Ure’s Description and Opinion on the same.
49. Primary Condition of Temperature with Reference to the Place. 60. Result of the Tubular System in Marine Boilers.
51. Introduction of Ah’ to the Chamber of the Furnace.
52. Experimental lUusti’ation of the same.
53. Causes which interrupt the Action of Air Distributors.
Chapter VII. Of Various Furnace Arrangements, With Obser.vations
THEREON.
54. Of the Argand Principle applied to Land Boilers.
55. Numerous Imitations of Parke’s Split Bridge.
66. Fallacy of the Principle of Heated Air in Furnaces.
57. Erroneous construction of Marine Boiler Furnaces.
58. Brunton’s, Juke’s, and Stanley’s Mechanical Feeders.
59. Exemplification of the right, and the wrong, way of Feeding
Furnaces.
60. Locomotives using Coal — Dcwrance’s Patent.
CONTENTS.
Chapter VIII. Of Providing Internal Surface For Transmitting The
HEAT TO THE WATER.
61. Calculation of gi*oss superficies insuflficient.
62. Increased quantity of steam requiring enlarged boilers.
63. Length of flame indicative of the required length of run.
64. Increased aggregate surface no compensation for diminished length
of run.
65. Tabular view of the length of flame.
66. Consequences of short run and short time in tubular boilers.
67. Injudicious application of the tubular principle.
68. Insufficiency of heat in tubes.
69. Cornish boilers and their peculiarities.
70. Surface provided by the flue system.
71. Velocity of current ; its effect in the same.
72. Consequences of requiring small boilers to do the work of large
ones.
73. Inffuence of subdivision on flame.
Chapter IX
OF FLAME AND THE TEMPERATURE REQUIRED FOR ITS PRODUC- TION AND CONTINUANCE.
74. Sir Humphry Davy on Flame.
75. High Temperature required for its production.
76. Effect of Cooling Influences.
77. How Cooling Agencies are produced.
78. Heat of Flame dependent on its Mass.
79. Effect of tlie Tubular Pi-inciple in reducing the Temperature of
Flame.
86. Necessity for Large Areas in Flues.
contents.
Chapter X
OP THE CIRCULATION OP THE WATER, IN REPERENCE TO ITS INTESTINAL CURRENTS.
81. Of Ascending and Descending Currents.
82. Bationale of Intestinal Motion.
83. Conduction of Heat in Solids and Fluids.
84. Difference in Cun’ents, before and after Ebullition.
85. Direction of tlie Currents in Water examined.
86. Currents produced by Ebullition, hitherto unexammed.
87. Ascentional energy of Steam under Ebullition.
88. Necessity of Space for Descending Currents.
89. Intermittent Action of Steam, where Space is insufficient.
90. Causes of explosions.
Chapter XI
OP THE CIRCULATION OP THE WATER IN RELATION TO EVAPO- RATION AND THE TRANSMISSION OF HEAT.
91. Direction of the Colder Currents in Water, in reference to Absorb-
ing Heat.
92. Supposed Direction of Descending Currents erroneous.
93. Vaporization not depending on the Heat applied to the Plates.
94. Effect of Heat applied to the Sides, and Crown Plates of
Furnaces.
95. Causes of Crown Plates bulging.
96. Construction of Waggon and Marine Boilers.
97. Its Effect on the Circulation.
98. On the Power of Convection and Absorption of Heat.
99. Transmission and Absorption of Heat confounded in Practice.
100. Alleged difference in Temperature between the two Surfaces of
the Plates.
101. Water always assumed to be in contact with the Plate.
102. Relative Heat Absorbing Power of Steam and Water.
103. Mechanical Structure of Steam and Water.
CONTENTS.
Chapter XII
OP THE CIRCULATION OP THE WATER IN RELATION TO THE DURABILITY OP THE PLATE.
104. Constriietiou of the Flues of the First Marine Boilei*s.
105. Liability to Injury attributed to Neglect.
106. Disproved in the Case of the Liverpool Steam Ship.
107. Difficulty of the Steam to Escape and the Water to obtain nccess
to the Plate.
108. On the Construction of the Boilers of the Liverpool.
109. Construction of the Boilers of the Great Britain.
110. Obstruction to Circnlation unexplained.
111. Erroneous Opinion as to the Cause of Plates being Overheated.
112. Alleged difference of Temperature between the two Sides of the
Plates.
11.3. The Plates cannot be Injured so long as the Water is in contact with them.
114. Practical Illustration of the same.
115. Confirmed on the Authority of Dr. Ure.
116. Relative Heat Absorbing Powers of Steam, Water, and Air.
117. Durability of the Plates in reference to the Rapidity of the Cur-
rent of Heat through them.
Chapter XIII. Op The Draught
118. Cause of Draught.
119. Defect of Draught and Injudicious Arrangement of the Flues.
120. Practical Researches by M. Peclet.
121. Cause of Deficiency of Draught in Wing Thirnaces of Marine
Boilers illustrated.
122. The Action of the Flues interfering with each other.
123. Numerous Practical Illustrations by M. Peclet.
124. Examination of the Boilers of the Great Britain.
125. The Boilers of the Liverpool in reference to the Collision of Cur-
rents in the Flues.
126. Steam generated almost exclusively from the Furnaces.
127. Split Draughts in Flues illustrated.
CONTENTS.
Chapter XIV. Of The Tubular System In Marine, Land, And Locomotive
BOILERS.
128. Marine and Locomotive Tubular Boilers compared.
129. Obstruction to the Ascent of the Steam, and Descent of the
Water.
130. Disadvantages of Short Boilers.
131. Deficiency in length of the run incompatible with perfect
Combustion.
132. Effect on the Temperature.
133. Recapitulation of the Defects of the Tubular System.
Chapter XV. Of The Use Of Heated Air And Its Supposed Value
134. Plausible Theories of the Hot Air System.
135. No Sensible Increase of Heat Produced.
136. Disproportion between the Gas and the Air — as to bulk.
137. Practical Inconvenience of increasing the Volume of the Air.
138. Sir H. Davy on Condensing the Air.
Chapter XVI
ON THE INFLUENCE OF THE WATER GENERATED IN FURNACES FROM THE COMBUSTION OF COAL GAS.
139. Water is the largest Product of Combustion.
140. Unobserved in the ordinary Use of Gas.
141. Of the Quantity of Water Generated from each Ton weight of
Coal.
142. May be rendered Visible and Collected.
143. Difficulty of Disposing of the great Mass of Steam.
CONTENTS.
Chapter XVII. Of Increasing The Heat-transmitting Poaver Of The Plate
SURFACE.
144. Heat-Transmitting Power, illustrated experimentally.
145. Effect in Counteracting the Waste of Heat.
146. Rapid Current of Heated Products across the Surface of the
Plate.
147. Heat Transmitted Longitudinally, made available.
148. Use of Conduction Bars.
149. M. Peclet’s Suggestions on this head.
150. Dr. Ure on the Use of CoiTugated Plates.
151. Practical application in Marine Boilers.
Chapter XVIII. On Smoke
152. Its Constituents.
153. Incombustibility of Smoke.
153*. Professor Brande on the same.
154. Separate States of Gas, Flame, and Smoke.
^ 155. Experimentally proved.
156. Absurdity of Expedients for “Smoke Burning,” or “Smoke Consuming.”
Appendix
Remarks by Professor Brande, Dr. Ure, Dr, Brett, and Sir Pohert Kane.
PREFACE.
Being much interested in the improvement of steam vessels, from my connection with several steam navigation companies, and having had a longer and more extended experience in the details of their building and equipping than, perhaps, any individual director of a steam company in the kingdom, my attention has been uninterruptedly given to the subject since the year 1823, when I first established a steam company, and undertook to have the first steam-vessel constructed capable of maintaining a commercial intercourse across the Irish Channel, during the winter months, and which, till then, had been considered impracticable.
The result of this long experience is the finding, that, notwithstanding the improved state to which the construction and appointments of the hull and general machinery of steam-vessels have arrived, great uncertainty and risk of failure still prevail in the use of fuel and the generation of steam.
It is true, the engineer, who undertakes the construction of the engines, also undertakes that the boilers shall provide a sufificiency of steam to work them ; but what that sufficiency means, has not been decided ; and, in too many instances, the absence of some fixed data on the subject leaving the evils of a deficiency of steam or a great expenditure of fuel unabated.
So long as the operations of steam-vessels were confined to coasting or short voyages, the consequences of these defects in boilers, as regards the quantity of fuel, were a mere question of pounds, shillings, and pence. When, however, those operations came to be extended to long sea voyages, these consequences
took a more comprehensive range, and involved the more im-
l
II portant question, whether such voyages locre practicable or profitable.
From being so deeply interested in the improvement of this department of steam navigation, I have watched, with no small anxiety, the efforts of the engineers to arrive at some degree of certainty in what was admitted, on all hands, to be the most serious drawback to the successful application of steam-vessels to long sea voyages. I perceived the absence of any wellfounded principle in the construction of the boiler; — that the part on which most depended appeared least understood, and least attended to, namely, the furnace; and that this was too often left to the skill (or want of it) of working boiler-makers or bricklayers. I saw that, although the great operations of combustion carried on in the furnace, with all that belongs to the introduction and employment of atmospheric air, were among the most difficult processes within the range of chemistry, the absence of sound scientific principles still continued to prevail; yet on these must depend the extent or perfection of the combustion in our furnaces.
Years were still passing away, and while every other department was fast approaching to perfection, all that belonged to the combustion of fuel — the production of smoke — and the wear and tear of the furnace part of the boiler, remained in the same status quo of uncertainty and insufficiency; and even that boilers and their furnaces, constructed within the last few years, exhibit greater violations of chemical truths, and a greater departure from the principles on which nature proceeds, than any preceding ones which have come under my observation.
In the proper place I will shew, that, of late years, as much uncertainty as to the success of a new boiler has prevailed as when I first began operations, thirty years ago; and that few boilers, for land or marine engines, exhibit more in the way of effecting perfect combustion or economy of fuel than those of any former period since the days of Watt.
I here observe, that I do not affect to give any new view of the nature of combustion, much less do I make any claim to discovery. What I take credit for is, the practical application.
Ill on the large scale of the furnace y of those chemical truths which are so well known in every laboratory. I also take credit for bringing together the scattered facts and illustrations of such authorities as bear on the subject before us, and so applying them as to enable practical men to understand that part which chemistry has to act in the construction, arrangements, and working of our boilers and furnaces.
The first part of this Treatise, in which the chemistry of combustion is considered, first published in 1840, is here now republished in a condensed form, in connexion with the second part, involving the practical application of the subject.
It is here unnecessary to say any thing on the causes which have led to so long an interval. It may, however, be observed, that the postponement of the second or practical part, has had this advantage, that it has afforded the means of introducing the recent changes that have been made in boilers; and particularly of that important one, the introduction of the tubular principle into steam navigation.
C. W. WILLIAMS.
Liverpool,
9*9 i *ti. »
V* j •
*1 ^ - ■•' ' *'
I3S
- —
Chapter I. Of The Constituents Of Coal, And The Gene- Ration Of Coal Gas
In the following treatise I do not undertake to shew how the smoke from coals can be burned; but I do undertake to shew how coals may be burned wihout smoke; and this distinction involves the main question of economy of fuel.
When smoke is once produced in a furnace or flue, it is as impossible to burn it or convert it to heating purposes, as it would be to convert the smoke issuing from the flame of a candle to the purposes of heat or light.
When we see smoke issuing from the flame of an ill- adjusted common lamp, we also find the flame itself dull and murky, and the heat and light diminished in quantity. Do we then attempt to burn that smoke? No; it would be impossible. Again, when we see a well-adjusted Argand lamp burn wthout producing any smoke, we also see the flame white and clear, and the quantity of heat and light increased. In this case, do we say the lamp burns its smoke? No; we say the lamp burns without smoke. This is the fact, and it remains to be shewn why the same language may not be applied to the combustion of the same coal and the same gas, in the furnace, as in the lamp.
In a treatise purporting to describe the means of obtaining the largest quantity of heat from coal, the first step is an inquiry into the varieties of that combustible and its respective constituents.
The classification of the various kinds of coal, the details of an elaborate analysis, made by Mr. Thomas Richardson, with the aid of Professor Liebig are as follows : —
Species of Coal.
Locality.
Carbon.
Hydrogen.
Azote and Oxygen.
Ashes.
Splint . .
Wylani . .
74-823
6-180
5-085
13-912
Glasgow
82-924
5-491
10-457
1-128
Cannel . .
Lancashire .
83-753
5-660
8-039
2-548
Edinburgh .
67-597
5-405
12-432
14-566
Cherry . .
Newcastle .
84-846
5-048
8-430
1-676
Glasgow
81-204
5-452
11-923
1-421
Caking . .
Newcastle .
87-952
5-239
5-416
1-393
Durham
83-274
5-171
9-036
2-519
The most important feature in reference to this analysis, is the proportion of hydrogen which all bituminous coal contains, and which may be estimated at 5^ per cent — hydrogen being the main element in the evolved gas, and by the combustion of which flame is produced.
The theory of combustion is now well understood by scientific men ; but, as a 'practical art, it still remains at a very low ebb.
We know, scientifically, that carburetted hydrogen and the other compounds of carbon require given quantities of atmospheric air to eflect their combustion ; yet we adopt no means, practically, of ascertaining what quantities are supplied, and treat them as though no such proportions were necessary. We know, scientifically, the relative proportions in which the constituents of atmospheric air are combined; yet, practically, we appear wholly indifferent to the distinct nature of these constituents, or their effects in combustion. We know, scientifically, that the inflammable gases are combustible only in proportion to the degree of mixture which is effected between them and the oxygen of the air ; yet, practically, we never trouble our heads as to whether we have effected such mixture or not. These and many similar illustrations exhibit a reprehensible degree of carelessness, which can only be corrected by a sounder and more scientific knowledge of the subject; and this can only be attained through the aid of chemistry.
The main constituents of all coal, as we see in the preceding table, are carbon and hydrogen.
In the natural state of coal, the hydrogen and carbon arc imited and solid. Their respective characters and modes of entering into combustion are, however, essentially different ; and to our neglect of this primary distinction is referable much of the difficulty and complication which attend the use of coal on the large scale of our furnaces.
The first leading distinction is, that the bituminous portion is convertible to the purposes of heat in the gaseous state alone ; while the carbonaceous portion, on the contrary, is combustible onlg in the solid state; and, what is essential to be borne in mind, neither can he consumed while they remain united.
The use of the term ‘‘fuel^^ as applied to the combustion of coal dming its several processes in the furnace, without reference to any particular constituent, whether gaseous or solid, is sufficiently indicative of the inattention to the chemical conditions of combustion.*
The general impression is, that coal, spoken of under the objectionable term of “fuel,” enters into combustion at once, on the application of heat, and that, during such combustion, it evolves the gaseous matter which it contains. This, however, is neither correct nor scientific, and evades an important feature in the use of coal, namely, the order in which the gaseous and solid portions come into use as heat-giving media.
When heat is first applied to bituminous coal, the question naturally arises, What becomes of it? or, What is its effect?
A charge of fresh coal thrown on a furnace in an active state, so far from augmenting the general temperature, becomes at
* Many instances of inattention might here he given. The following will suffice. In a popular treatise on the steam-engine, by Dr. Lardner, speaking of Brunton’s revolving grate, he observes, “ The coals are let down from the hopper on the grate, and as they descend in very small quantities at a time, they are almost immediately ignited.’’ Here the coal is represented as being ignited, or converted into flame, which is incorrect. Coal-gas may be converted into flame, and coke may be ignited, but coal can neither be ignited nor converted into flame.
Again, “ But, until their ignition is complete,” a smoke wiU arise, which, passing to the flue over the burning coal, will he ignited.” Here it is the gas which is ignited — the term smoke being improperly used instead of gas. This, also, is incorrect, as smoke, properly speaking, being once formed, cannot be ignited or inflamed in the same furnace.
once an absorbent of it and tlie source of the volatilizalion of the bituminous portion of the coal ; in a word, of the generation of the gas. Now, volatilization is the most cooling process of nature, by reason of the quantity of heat which is directly converted from the sensible to the latent state. So long as any of the bituminous constituents remain to be evolved from any atom or division of the coal, its solid, or carbonaceous part remains black, at a comparatively low temperature, and utterly inoperative as a heating body. In other words, the carbonaceous part has to wait its turn for that heat Avhich is essential to its own combustion, and in its own peculiar way, as will be explained hereafter.
We also see, that if this bituminous part be not consumed and turned to account, it would have been better had it not existed in the coal ; as such heat would, in that case, have been saved and become available for the business of the furnace. To this circumstance may be attributed the alleged comparatively greater heating properties of coke, or anthracite, over bituminous coal.
The point next under consideration will be the processes incident to the combustion of the gaseous “portion of the coal, as distinct from the carbonaceous or solid portion.
Chapter II
OF GASEOUS COMBINATIONS, AND PARTICULARLY OF THE UNION OF COAL GAS AND AIR.
Having pointed out the leading characteristic in the use of coal, arising out of its elementary divisions, bituminous and carbonaceous, our next step is, its union with atmospheric air. This part of the subject will require the more attention, as the practicable economy in the use of coal will be found connected with the combustion of the gases. The mechanical engineer may ask. What has this to do with boiler-making and furnacebuilding? Nevertheless, it involves the whole question of right or wrong, so long as a furnace is to be part of a boiler, and that coal is to be consumed in that furnace.
On the application of heat to bituminous coal, the first result, as already mentioned, is its absorption by the coal, and the disengagement of gas, from which flame is exclusively derivable.
The constituents of this gas are, hydrogen and carbon: and the unions which alone concern us here are, carburetted hydrogen, and bi-carburetted hydrogen, commonly called olefiant gas.
Combustibility is not a quality of the combustible, taken by itself. It is, in the case now before us, the union of the combustible with oxygen, and which, for this reason, is called the “ supporter neither of which, however, when taken alone, can be consumed.*
* “ In ordinary language, a body is said to burn when its elements unite with the oxygen of the air, and form new products. One of the bodies, as hydrogen, is termed the burning or combustible body, and the oxygen is said to be the supporter of combustion ; but this language, although convenient for common use, is incorrect as a scientific expression, for oxygen may be
To effect combustion, then, we must have a comhustihle and a supporter of combustion. Strictly speaking, combustion means union ; but it means chemical union.
Let us bear in mind, that coal gas, whether generated in a retort or a furnace, is essentially the same. Again, that, strictly speaking, it is not inflammable; as, by itself, it can neither produce flame nor permit the continuance of flame in other bodies; a lighted taper introduced into a jar of carburetted hydrogen, (coal gas,) so far from inflaming the gas, is itself instantly extinguished. Effective combustion, for practical purposes, is, in truth, a question more as regards the air than the gas. Besides we have no control over the gas, as to quantity, after having thrown the coal on the furnace, though we can exercise a control over that of the air, in all the essentials to perfect combustion. It is this which has done so much for the perfection of the lamp, and may be made equally available for the furnace; yet, strange to say, in an age, when chemical science is so advanced, and in a matter so purely chemical, this is precisely what is least attended to in practice. The how, and the when, and the where this controlling influence over the admission and action of the air is to be exercised, are points demanding the most serious consideration, and can only be decided on strict chemical principles.
burned in a vessel of hydrogen, as well as hydrogen in a vessel of oxygen, the one and the other being equally active in the process, and being related to each other in every way alike,” — Elements of Chemistry, by Itobert Kane, M.D. Part I., p. 285. 1840.
Chapter III. Of The Constituents Of Coal Gas And Air, And
THE RELATIVE QUANTITIES REQUIRED FOR COM- BUSTION.
The first step towards effecting tlie combustion of any gas, is the ascertaining the quantity of oxygen with which it will chemically combine, and the quantity of air required for supplying such quantity of oxygen. Here, then, we are called on for strict chemical proofs — these several quantities depending on the faculty of each in combining with certain definite proportions of the other — the supporter ; these respective proportions being termed equivalents^^ or combining volumes.
Now, the doctrine of equivalents,” that all-convincing proof of the truths of chemistry, reduces, to a mere matter of calculation, that which would otherwise be a complicated tissue of uncertainties.
Much of the apparent complexity which exists on this head arises from the disproportion between the relative volumes^ or bulk, of the constituent atoms of the several gases, as compared with their respective weights. For instance, an atom of hydrogen is double the bulk of an atom of carbon vapour; yet the latter is six times the weight of the former.
Again, an atom of hydrogen is double the bulk of an atom of oxygen ; yet the latter is eight times the weight of the former.
So of the constituents of atmospheric air — nitrogen and oxygen. An atom of the former is double the bulk of an atom of the latter ; yet, in weight, it is as fourteen to eight.
I have stated, that there are two descriptions of hydro-carbon gases in the combustion of which we are concerned ; both being generated in the furnace, and even at the same time, namely, the carburetted and hi-carburetled hydrogen gases, the proportion of the latter in coal gas being estimated at about ten per cent. For the sake of simplifying the explanation, I will confine myself to the first.
On analyzing this gas, we find it to consist of two volumes of hydrogen and one of carbon vapour ; the gross bulk of these three being condensed into the hidk of a single atom of hydrogen, that is, into two-fifths of their previous bulk, as shewn in the annexed figures. Let figure 1 represent an atom of coal gas — carburetted hydrogen — with its constituents, carbon and hydrogen ; the space enclosed by the lines representing the relative size or volume of each ; and the numbers representing their respective weights — hydrogen being taken as unity both for volume and weight.*
Carburetted Hydrogen.
Fig. 1.
Its constitueuts,
Bi-carburetted Hydrogen.
Fig. 2.
* Ce gaz (carburetted hydrogen) est compose de 75.17 parties (by weight) de Carbone, et 24*33 d’hydrogene; ou, d’un volume de carbone gazeux et quatre volumes de gaz hydrogeue, condenses a la moitie du volume de ce dernier, ou, aux 2/5 du volume total du gaz, de maniere que de cinq volumes simples, il n’en resulte pas plus de deux de la corabinaison.” — Berzelius Vol. I., 330.
Let us now, in the same analytical manner, examine an atom of atmospheric air, the other ingredient in combustion.
AtTnospheric air is composed of two atoms of nitrogen and one atom of oxygen ; each of the former being double the volume of an atom of the latter, while their relative weights are as fourteen to eight : the gross volume of the nitrogen, in air, being thus four times that of the oxygen ; and in weight, as twenty-eight to eight, as shewn in the annexed figure 3.
In the coal gas we found the constituents condensed into tivoffths of their gross bulk : this is not the case with air ; an atom of which is the same, both as to bulk and weight, as the sum of its constituents, as here shewn. Thus, we find, the oxygen bears a proportion in volume to that of the nitrogen, as one to five; there being but 20 per cent, of oxygen in atmospheric air, and 80 per cent, of nitrogen.
We now proceed to the ascertaining the separate quantity of oxygen required by each of the constituents (of the gas), so as to effect its perfect combustion.
With respect to this reciprocal saturation, the great natural law is, that bodies combine in certain fixed proportions only, both in volume and weight.^
The important bearings of this elementary principle cannot be more strikingly illustrated than in the combinations of which the elements of atmospheric air are susceptible.
For instance, oxygen unites chemically with nitrogen in five different proportions, forming five distinct bodies, each essentially different from the others, thus :
Atoms. Weight. Atoms. Weight. Gross Weight.
1 of Nitrogen 14 unites with 1 of Oxygen 8 forming Nitrous Oxide 22 1 .... 14 .... 2 .... 16 . , Nitric Oxide . 30
Or thus; Fi^. 4. ™
Or thus; Fi^. 4.
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