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 Catalogue of Technical Books on request 
 
 
COAL 
 
 ITS COMPOSITION, ANALYSIS, UTILIZATION 
 AND VALUATION 
 
McGraw-Hill BookCompaiiy 
 
 Electrical World The Engineering and Mining Journal 
 Engineering Record Engineering News 
 
 Railway Age G azette American Machinist 
 
 Signal Engineer American Engneer 
 
 Electric Railway Journal Coal Age 
 
 Metallurgical and Chemical Engineering Power 
 
COAL 
 
 ITS COMPOSITION, ANALYSIS, 
 UTILIZATION AND VALUATION 
 
 BY 
 
 E. E. SOMEKMEIER 
 
 Professor of Metallurgy, Ohio State University 
 
 McGRAW-HILL BOOK COMPANY 
 
 239 WEST 39TH STREET, NEW YORK 
 
 6 BOUVERIE STREET, LONDON, E. C. 
 
 1912 
 
OF 
 
 fBANIS H . 
 
 D6PI. 
 
 COPYRIGHT, 1912, BY THE 
 MCGRAW-HILL BOOK COMPANY 
 
 THE SCIENTIFIC PRESS 
 
 ROBERT DRUMMONO AND COMPANY 
 
 BROOKLYN, N. Y. 
 
 37 
 
 t;.;;---j 
 
 DEPi 
 
PREFACE 
 
 THE data and descriptive matter given herein, are largely 
 based upon private notes and upon information and material 
 scattered through text-books, technical bulletins, and in original 
 papers in technical and scientific journals. Much of this data 
 is either inaccessible or in such a form as not to be readily 
 applied or interpreted arid hence i^ not likely to be utilized 
 by those who have the most active interest in coal. 
 
 In the preparation and arrangement of the material, three dis- 
 tinct classes of readers have been to a certain extent kept in mind : 
 
 (1) The mechanical and power plant engineer; 
 
 (2) The chemical engineer and chemist; 
 
 (3) The non-technically trained business man and operator 
 who has to do with the buying and selling of the coal. 
 
 In including data which might be of interest and value to 
 these different groups of readers a portion of the material is 
 necessarily elementary for some and a portion is correspondingly 
 technical for others. Good advice to each reader is to select 
 that which may be of interest and use, and to pass over any 
 discussion or data which may appear too elementary or too 
 technical for his needs. 
 
 To the technical man who is familiar with much of the data 
 and many of the formulas given, it may appear that many of 
 the simpler illustrations and details might perhaps just as well 
 have been omitted. However, it is the writer's experience that 
 specific formulas and specific data are not, as a rule, likely to be 
 given too much in detail to suit the occasional user, who may 
 have neither the time nor the inclination to elaborate the formula 
 or to check up the data. He wants each in a form easily under- 
 stood and readily applicable to his needs. 
 
 In the effort to meet this " want " some statements are 
 repeated, perhaps too often, some details enlarged upon a little 
 too much and a few assumptions made which are perhaps not 
 
 M127178 
 
vi PREFACE 
 
 strictly in accordance with facts. It is hoped, however, that 
 any errors in this direction are of little real consequence and 
 that the collection of material given herein may be a slight con- 
 tribution toward a more general appreciation of the properties 
 and a better utilization of one of the earth's most valuable assets 
 coal. 
 
 The author desires to express his appreciation to Professor 
 E. A. Hitchcock of the Department of Mechanical Engineering, 
 Ohio State University, and Professor D. J. Demorest of the 
 Department of Metallurgy, for advice and suggestions. 
 
 Especial acknowledgment is due to the late Professor N. W. 
 Lord, the able and inspiring teacher, to whom the author is 
 indebted for much of the material given herein. 
 
 E. E. SOMERMEIER. 
 October, 1912. 
 
INTRODUCTION 
 
 COAL is generally recognized as being a product of the more or 
 less complete decomposition of vegetable matter under varying 
 conditions of moisture, temperature and pressure. Depending 
 upon the varying conditions and upon the completeness of the 
 decomposition and upon the kind of vegetation from which it is 
 derived, the resultant product as it actually occurs is far from uni- 
 form, ranging from the initial stage of woody fibrous peat through 
 lignite (brown coal), bituminous coal high in oxygen, bituminous 
 coal low in oxygen, semi-bituminous coal, anthracite and the final 
 stage graphite. For similar conditions of moisture, temperature, 
 extent of decomposition and similar vegetable origin, the resultant 
 coal should be uniform in composition and properties. Usually, 
 however, other factors acting during the period of formation 
 modify and change the final product, so that coal from different 
 portions of the same bed or even different portions of the same 
 mine is far from uniform in some important properties, namely, 
 the content of sulphur and ash. 
 
 If coal contained only constituents which were present in the 
 original vegetable matter, it would be uniformly low in both 
 sulphur and ash, but during the early stages of its formation under- 
 neath the surface of swamps or lakes, streams or rivulets carried 
 silt and sediment over the decomposing bed of vegetation, which 
 sediment settled down and became an integral but varying con- 
 stituent of the coal. Sulphur in solution in the water, coming in 
 contact with salts of iron and reducing organic compounds resulted 
 in the formation and precipitation of pyrite, while other reactions 
 not clearly understood produced variable quantities of organic 
 compounds of sulphur as a constituent of the coal. 
 
 Other factors or agencies may also materially affect the coal 
 in certain portions of the seam or field. Faults and fractures in 
 the coal and surrounding rocks are often accompanied by local 
 variations in the nature of the coal. Weathering of the coal near 
 
 vii 
 
viii INTRODUCTION 
 
 the outcrop often causes that portion to differ in quality from the 
 more deeply covered and better protected portions. Still other 
 factors or agencies might be enumerated as causes for local or 
 wide-spread differences in the coal, but those already given suffice 
 to show why variations in properties and constituents are to be 
 expected rather than the occurrence of a material of uniformity in 
 properties and exactness in composition. 
 
CONTENTS 
 
 PAGE 
 
 PREFACE v 
 
 INTRODUCTION vii 
 
 CHAPTER I 
 
 COMPOSITION AND HEATING VALUE 
 
 Moisture Ash Sulphur Total heating value Heat produc- 
 ing constituents Calculation of heating value from the chemical 
 composition Practically available heating value Determination 
 of heat lost during combustion Calculation of heating value of 
 Hocking or Ohio No. 6 coal Printed forms for heat balance 
 Thermal capacity table for heat balance calculation Comparison 
 of heat values on coal as fired with the A.I.M.E. code Variation 
 in available heating power Commercial value of coal Residual 
 coal Calculation of heating value from proximate analysis and 
 from H. 
 
 CHAPTER II 
 
 CHEMICAL ANALYSIS OF COAL 43 
 
 Proximate analysis- Proximate analysis of different coals Dis- 
 cussion of and constituents of proximate analysis Ultimate analysis 
 Calculation of ultimate analysis. 
 
 CHAPTER III 
 
 SAMPLING 57 
 
 Mine sampling Car sampling and sampling coal as used Reduc- 
 tion of large samples Effects of slate and pyrite on sample Effects 
 of clean coal on sample Relation of car sample to number of samples 
 Treatment of the sample in the chemical laboratory Special 
 notes on sampling. 
 
 ix 
 
x CONTENTS 
 
 CHAPTER IV 
 
 PAGE 
 
 METHODS OF ANALYSIS 79 
 
 Moisture Ash Volatile matter Fixed carbon Sulphur 
 Ultimate analysis Nitrogen Phosphorus Oxygen . 
 
 CHAPTER V 
 
 DETERMINING THE CALORIFIC VALUE 91 
 
 Description of the determination Special notes on the deter- 
 mination Complete combustion of the sample Valve leakage 
 Water used Temperature conditions Acidity corrections Correc- 
 tion for nitric acid Correction for sulphuric acid Ignition of wire 
 Cutting down voltage by means of a resistance coil Heat devel- 
 oped with closed circuit Effect of the coil on the heat developed 
 Water equivalent of the calorimeter Heat of combustion of standard 
 substances Errors in graduation of thermometers Determination 
 of graduation errors by divided threads Determination of gradua- 
 tion errors by comparison with a standard thermometer Determina- 
 tion of graduation errors by experimental determinations at different 
 temperatures with materials of known heating value Stem tem- 
 perature correction Use of tables in determination of steam tem- 
 perature correction Correction for variations in the specific heat 
 of water Effect of hydrogen in the sample on the observed calorific 
 value Use of a cover on the calorimeter Oxygen impurities. 
 
 CHAPTER VI 
 SUMMARY OF CHEMICAL DETERMINATIONS OR RECORDS 119 
 
 CHAPTER VII 
 
 IMPROVEMENT OF COAL BY WASHING 122 
 
 Method of operation Typical results. 
 
 CHAPTER VIII 
 
 PURCHASE OF COAL UNDER SPECIFICATIONS 126 
 
 Total heating value an index of the commercial value Other 
 factors affecting the commercial value Advantages of purchase 
 of coal under specifications Drawing up specifications Points to 
 be considered Reports from cities purchasing coal under specifi- 
 cations. 
 
CONTENTS xi 
 
 CHAPTER IX 
 
 PAGE 
 
 FLUE GAS ANALYSIS 132 
 
 Composition of flue gas Analysis of the gas Sampling the gas 
 Aspiration of the gas Apparatus for making the analysis Opera- 
 tion of the Orsat apparatus Reagents used and preparation 
 Filling the Orsat apparatus Absorbing power of reagents Care of 
 apparatus Discussion and interpretation of Orsat results Errors 
 in the Orsat determination Alternation of samples on standing 
 Leakage Chemical alteration Alteration of samples by absorp- 
 tion in water Effect of a water seal upon samples. 
 
 CHAPTER X 
 
 ANALYTICAL TABLES 158 
 
 Composition of different fuels Composition and heating value 
 of coals of the United States arranged alphabetically by states. 
 
 INDEX.. . 169 
 
COAL 
 
 CHAPTER I 
 COMPOSITION AND HEATING VALUE 
 
 CONSIDERED from a practical point of view, coal may be 
 described by discussing some of the more or less common terms 
 used in connection with its composition, analysis and utilization, 
 some of which are as follows: 
 
 (a) Moisture. 
 
 (6) Ash. 
 
 (c) Sulphur. 
 
 (d) Heating value, total and practically available. 
 
 (e) "Residual coal/' that is, coal free from the variable factors 
 moisture, ash and sulphur. 
 
 (/) Proximate analysis, in which the composition is expressed 
 as percentage of moisture, volatile matter, fixed carbon and ash 
 present. 
 
 (g) Ultimate analysis, in which the composition is given in 
 percentage of carbon, hydrogen, oxygen, nitrogen, sulphur and 
 ash. 
 
 MOISTURE 
 
 The term moisture includes only the more or less loosely held 
 water which is driven off by heating the finely powdered coal 
 slightly above the boiling-point of water, about 105 C. or 
 220 F. The residual coal substance or the mineral matter 
 present in the ash may hold additional water which is given 
 up on heating to higher temperatures, while still more water is 
 produced upon the actual combustion of the coal. But in the 
 ordinary use of the term " moisture," this more closely held water 
 
 1 
 
2 NOTES ON COAL 
 
 or the water produced by burning of the fuel is never included, 
 and if the closely held water is given at all in an analysis it is 
 designated " combined water " or " water of combination. " 
 
 The amount of moisture in coal is variable, depending upon 
 the nature of the coal, upon its physical condition (degree of 
 fineness) and upon weather conditions. As mined, Ohio coals 
 contain from 4 to 10 per cent of moisture. If allowed to air dry 
 a large portion of this moisture is expelled and well air-dried 
 samples of Ohio coals crushed to J inch and finer usually contain 
 less than 3 per cent of moisture. On the other hand, the 
 amount of loosely held moisture retained by fine coal (slack) may 
 be quite large. A car of slack which has been rained upon may 
 contain as much as 15 to 20 per cent of moisture, a large part of 
 this, as much as 10 to 15 per cent, being what may be termed 
 " surface " moisture or the moisture which gives the wet appear- 
 ance to the slack. On the other hand, lump coal containing 
 little or no slack retains a comparatively small amount of surface 
 moisture. Egg and lump coal from a washer, if allowed to drain 
 thoroughly, does not hold over 2 or 3 per cent of moisture as 
 superficial or surface moisture. 
 
 However, apparently dry lump coal often contains a con- 
 siderable amount of moisture. Lump coal gives up moisture 
 very slowly to air, and it is probable that most shipments of 
 lump coal from Ohio mines contain 4 or 5 per cent of moisture 
 upon delivery even in dry summer weather, while in winter the 
 amount in the lump coal as delivered is practically the same as 
 when mined, which in some Ohio coals is as high as 8 or 10 per 
 cent. Shipments of slack made in dry summer weather lose 
 considerable moisture in transit and may contain several per 
 cent less moisture on arrival at the point of destination than 
 when shipped from the mine, while in wet weather the reverse 
 is likely to be true, the shipment containing more moisture than 
 when loaded at the mine. 
 
 The statement regarding moisture in Ohio coals applies in 
 general to coals of intermediate moisture content. Under similar 
 conditions, for many West Virginia coals the values are lower; 
 for Illinois, Indiana and Iowa coals, the values are somewhat higher 
 than those given for the Ohio coals, while in the case of lignites 
 the moisture is very much higher, 40 per cent and over as mined, 
 and 10 to 15 per cent in the air-dried lignite. 
 
COMPOSITION AND HEATING VALUE 3 
 
 Unless special precautions are taken to prevent moisture loss 
 during handling, the percentage of moisture in the sample analyzed 
 may be considerably lower than in the coal as mined or shipped, 
 and the specimen analyses exhibited by the operator giving the 
 analysis of his coal are in many cases lower in moisture than the 
 average of the coal which is received by the consumer. 
 
 ASH 
 
 The term " Ash/' as commonly used, means the ignited mineral 
 residue left after complete combustion or burning of the coal. This 
 residue consists essentially of the mineral matter inherent in the 
 coal and varying quantities of slate and clay from the roof or floor 
 of the mine or from partings in the seam itself, also oxide of iron 
 from the combustion of pyrite which may be present in the coal. 
 If the ash contains little iron it is light colored, usually highly 
 silicious and gives little trouble on the grate bars. If it contains 
 much iron it is reddish and may give trouble from clinkering. 
 As ordinarily reported the ash represents the actual weight of 
 mineral residue after the coal is entirely burned. 
 
 Corrected ash. Some chemists report " corrected ash," 
 which correction is based on the following points and reasoning: 
 Iron as it occurs in coal is usually present as pyrite, a combination 
 of iron and sulphur of which more will be said under the head of 
 " Sulphur." In burning the coal the iron unites with oxygen from 
 the air and remains in the ash as oxide of iron and weighs more 
 than the iron present in the original coal. One gram of iron when 
 oxidized to ferric oxide weighs 1.43 grams. This one gram of iron 
 if present as pyrite is combined with 1.14 grams of sulphur, and 
 as the chemist does not as a rule determine the iron, but does de- 
 termine the sulphur in making the corrected ash reports, he bases 
 the amount of the correction upon the amount of sulphur present 
 and deducts three-eights of the amount of sulphur from the 
 weight of ash as actually weighed. A correction made on this 
 basis is always too large and in some cases may be decidedly too 
 high as some of the sulphur, sometimes as much as 2 per cent, is 
 present as organic sulphur and hence has no iron combined with 
 it. Again some of the iron may be actually present in an oxidized 
 form and hence need no correction. Furthermore, the mineral 
 matter in the coal present as slate or clay upon ignition lores 
 
COAL 
 
 approximately 15 per cent of combined water, hence the weight of 
 ash derived from this source is lower than the amount of mineral 
 matter originally present, the amount being about 0.17 of one 
 per cent 4 for each per cent of ash derived from clay and shale. 
 Hence if the object of a " corrected ash " is to obtain a correct 
 combustible residue, the correction should also include this cor- 
 rection due to changes in weight in clay and shale, which is directly 
 opposite in its effect upon ash to the corrections made for oxida- 
 tion of iron. The loss in weight from the ignition of about 2 \ per 
 cent of clay equals the increase in the weight of ash due to the 
 oxidation of thejron equivalent to 1 per cent of sulphur present 
 as pyrite. The amounts of clay and slate present are often two or 
 three times as high as the amount of iron present as pyrite. Car- 
 bonate and sulphate of calcium are sometimes present as a part 
 of the mineral constituents of the coal, and upon ignition both of 
 these materials lose weight, and the weight of the ignited residue 
 from these materials is less than the weight of the materials as they 
 occur in the coal. A corrected ash which only partially corrects 
 cannot be regarded as very satisfactory and in reporting a proxi- 
 mate analysis the common method of reporting the " ignited 
 mineral residue " as the ash is certainly to be preferred to uncer- 
 tain and possibly misleading " corrected ash " reports. 
 
 Fusibility of the ash. The fusibility of the coal ash is depen- 
 dent upon the chemical composition and physical condition of 
 the minerals present. The ash from most coals is highly silicious 
 but the variation in the nature and amounts of the different con- 
 stituents is so great that no typical composition can be given. The 
 following analyses of ash from different coals taken from Groves 
 and Thorpe 1 serve to illustrate this point: 
 
 
 No. 1. 
 
 No. 2. 
 
 No. 3. 
 
 No. 4. 
 
 No. 5. 
 
 No. 6. 
 
 SiO 2 
 
 64 21 
 
 45 13 
 
 '31 30 
 
 15.48 
 
 3 12 
 
 1 70 
 
 A1 2 3 
 Fe 2 O 3 
 CaO 
 MgO 
 K 2 O 
 
 28.78 
 2.27 
 1.34 
 1.12 
 
 2.28 
 
 22.47 
 
 25.83 
 2.80 
 0.52 
 0.60 
 
 8.31 
 54.47 
 3.44 
 1.60 
 0.07 
 
 5.28 
 74.04 
 2.26 
 0.26 
 0.53 
 
 29.50 
 32.78 
 20.56 
 2.16 
 0.99 
 
 2.12 
 60.79 
 19.20 
 5.03 
 0.35 
 
 Na 2 O . 
 
 
 0.28 
 
 0.29 
 
 
 1.72 
 
 0.08 
 
 CaSO 4 
 
 
 2 37 
 
 52 
 
 2 17 
 
 9 17 
 
 10 71 
 
 
 
 
 
 
 
 
 Chemical Technology. 
 
COMPOSITION AND HEATING VALUE 5 
 
 The fusibility of the ignited and well-mixed ash is dependent 
 Upon the ratio of the silica to the bases present, upon the parties 
 lar bases and upon the percentage of alumina present. Mixtures, 
 extremely high in silica, or extremely high in bases are not readily 
 fusible. As a rule the most readily fusible mixtures are those ap- 
 proximating a uni-silicate, but many silicates up to the bi-silicate 
 or even tri-silicate composition are fusible at temperatures be- 
 tween 1000 and 1200 C. (1800 to 2200 F.). 
 
 According to Hofman 1 , the temperature of formation of some 
 pure ferrous silicates are as follows: 
 
 4FeO, SiO 2 =82.8% FeO, 17.2% SiO 2 = 1280 C. 
 
 3FeO, 2SiO 2 = 64.3% FeO, 35.7% SiO 2 = 1140 C. 
 
 FeO, Si0 2 =54.55% FeO, 45.45% Si0 2 = 1110 C. 
 
 The fusion temperature after the silicate is once formed is 
 considerably lower than the temperature of formation. 
 
 Replacing a portion of the ferrous oxide by calcium oxide, 
 magnesium oxide, potassium oxide, etc., gives compounds having 
 a- lower formation temperature than the pure ferrous silicates. 
 Replacing a part of the silica by alumina gives compounds 
 having a somewhat higher temperature of formation. Ash which 
 is low in iron is usually so highly silicious that it is not readily 
 fusible. Ash from coals high in pyrite is necessarily high in iron 
 and the ratio between the bases and silica is often such that easily 
 f-usible compounds may be formed. 
 
 The values given for the temperature of formation of the 
 ferrous silicates are of interest as showing the possible fusibility 
 of the ash, but fusibility of well-mixed ignited ash and fusibility 
 of the ash in the coal during combustion of the coal are two 
 entirely different things. The first is dependent upon the constitu- 
 tion of the ash as a whole; the second is dependent upon the 
 nature and distribution of the different minerals in the coal acting 
 separately or only partially mixed. An ash may form clinker 
 during burning of the coal on account of the fusibility of a portion 
 of the mineral matter when the chemical composition of the ash 
 taken as a whole indicates that clinker should not form. Also 
 some ashes may not clinker during burning of the coal when the 
 chemical composition indicates them to be more fusible than 
 other ashes which do clinker. 
 
 1 Trans. A.I.M.E., Vol. 29. 
 
6 COAL 
 
 In the coal the different minerals constituting the ash do not 
 always occur mixed intimately, but lumps of minerals of different 
 composition may be scattered irregularly through the coal. Some 
 of these lumps in themselves may be fusible or form fusible com- 
 pounds during the burning of the coal. The effect of lumps of 
 pyrite on the clinkering of coal is discussed under " Sulphur." 
 
 On account of this irregular distribution of mineral constitu- 
 ents in the coal any effort to establish a close relation of the clinker- 
 ing properties of the coal ash and the composition of the entire 
 ash will always be more or less unsatisfactory and uncertain. 
 The composition of the ash as a whole tells nothing at all as to the 
 regularity or irregularity of distribution of the different mineral 
 constituents in the coal. 
 
 Amount of ash in coal. The quantity of ash is so variable 
 that no definite statement as to the percentage can be given. 
 Clean lumps of some coals occasionally contain as low as 1 per cent 
 of ash while dirty slack may contain as high as 25 per cent. Selected 
 lumps of coal from Ohio seams may be as low as 2 per cent in ash, 
 but no mine can average that figure on its actual output. The 
 best shipments are nearer 6 per cent in ash while much of it may 
 be 9 to 10 per cent. In shipments of slack, the ash may be as 
 high as 14 or 15 per cent or even more. The same statement as 
 to specimen analyses which was given under " moisture " is also 
 applicable in regard to ash, namely, that the content of ash in 
 picked lumps or clean coal is likely to be much lower than the 
 average ash content of the shipment received by the consumer. 
 
 SULPHUR 
 
 Forms in which it occurs. One of the most prominent forms 
 in which it occurs is iron pyrite (FeS2) . In some cases the pyrite 
 is scattered in large masses or in partings and is readily recognized 
 as such. In other cases it occurs in a very finely divided form, the 
 separate particles being too small to be readily recognized. An- 
 other important form in which sulphur occurs is what is known 
 as organic sulphur, or sulphur combined with carbon or carbon 
 and hydrogen. Some Ohio coals show as much as 2 per cent of 
 organic sulphur. Occasionally sulphur occurs in coal in the form 
 of free sulphur but the amount of such is usually quite small. In 
 weathered coal, such as coal near the outcrop of the seam, or the 
 
COMPOSITION AND HEATING VALUE 7 
 
 coal in the face of an old entry or room, or in piles of slack which 
 have been standing for some time exposed to air and moisture, 
 some of the sulphur is present as sulphate of iron, lime and alumina, 
 some forms of pyrite oxidizing very readily upon exposure to air. 
 
 Heating value of sulphur. The unoxidized form of sulphur on 
 combustion of the coal is burned to sulphur dioxide, which burning 
 is accompanied by the liberation of heat. Where it occurs as 
 ferrous sulphate or calcium sulphate it has no heating value and 
 during the combustion of the coal the decomposition of these 
 sulphates absorbs heat. The amount of oxidized sulphur in 
 unweathered coal is, however, too small to be of practical import- 
 ance and for freshly mined coal sulphur may be credited with a 
 heating value of from approximately 2250 to 2950 calories (4050 
 to 5300 British thermal units), the different values depending 
 upon whether it is present as organic sulphur or as pyrite 
 (FeS2). If present as pyrite, the heat of its combustion which 
 results in the formation of sulphur dioxide (862) and ferric oxide 
 (Fe 2 O 3 ) is approximately 700 calories (1250 British thermal 
 units) higher than the combustion of sulphur in organic form 
 to sulphur dioxide. 
 
 Sulphur in weathered coal. In weathered coal the 
 presence of sulphates may very decidedly affect the heating value 
 per unit of coal, as may be shown by the following: One per cent 
 of sulphur as pyrite in coal has a heating value of about 29| 
 calories. During combustion of the coal the decomposition of the 
 ferrous sulphate (FeSO4 TH^O) corresponding to 1 per cent of 
 sulphur absorbs about 21 J calories of heat, which is a net loss in 
 heating value of about 51 calories or about three-fourths of one 
 per cent of the heating value of the coal. If this were the only 
 effect it would not be so important as the amount of sulphur 
 present as sulphate does not often exceed 1 per cent. However, 
 1 per cent of sulphur as pyrite, on oxidation, absorbs 2 per cent by 
 weight of oxygen and absorbs and combines with about 4 per cent 
 of water which is not given up on air drying so that the appar- 
 ently air dry coal may be 6 per cent heavier on account of this 
 oxidation of 1 per cent of sulphur, and the calorific value per unit 
 of coal instead of being only three-fourths per cent lower, may be 
 actually nearly 7 per cent lower in heating value. 
 
 Action of sulphur dioxide. Upon the cooling of the flue gases 
 the sulphur dioxide formed during the combustion of the coal 
 
8 COAL 
 
 unites with water and forms sulphurous acid, which as such 
 or upon further oxidation to sulphuric acid has a corrosive 
 effect upon metallic structures. This corrosive action takes place 
 after cooling and the popular idea that sulphur in coal causes cor- 
 rosion of boiler tubes, etc., by action of sulphur dioxide is largely 
 without real foundation. 
 
 Relation of sulphur to clinkering of the ash. When the sul- 
 phur occurs in the coal as pyrite, as it usually does, it is objection- 
 able for two reasons : 
 
 First, the oxide of iron produced during combustion may unite 
 with other constituents of the ash and produce a fusible compound 
 or clinker. Oxide of iron by itself produces no clinker, but as has 
 been stated under " ash," the other mineral constituents of the 
 coal are usually highly silicious and oxide of iron in contact with 
 silica or silicates at a high temperature is very liable to result 
 in the production of easily fusible silicates (or clinkers). The 
 higher the temperature the more readily this fusion occurs and the 
 operation of -a furnace so as to keep the grate bars and the lower 
 portion of the fuel bed at a relatively low temperature may result 
 in a clean ash, when the same coal with hot grate bars and a hot 
 bed of ash may clinker badly. 
 
 Second, pyrite (FeS2) on being heated gives off approximately 
 one-half of its sulphur, and a compound approximating the formula 
 (FeS) remains. This ferrous sulphide is fusible at a red heat and 
 in the combustion of coals containing pyrite in pieces of consider- 
 able size, lumps of this ferrous sulphide may fuse before they have 
 had an opportunity to burn, and may be starting points for the 
 formation of a clinker which may render it difficult to satisfactorily 
 burn the coal. Finely disseminated pyrite will not produce this 
 kind of trouble, but finely disseminated pyrite and a uniform dis- 
 tribution of highly silicious ash is a condition very favorable for 
 the formation of clinker. Organic sulphur has no tendency to 
 form clinker, hence high sulphur in coal is by itself not a certain 
 index of the clinkering qualities of the ash. As a general rule, the 
 higher the sulphur the greater the probability that the ash will 
 clinker, but with frequent exceptions due to the presence of the 
 sulphur in an organic form or due to the fact that the other mineral 
 constituents of the coal are not present in forms or quantities 
 favorable to the production of clinker. 
 
COMPOSITION AND HEATING VALUE 
 
 TOTAL HEATING VALUE OF COAL 
 
 This is the total number of calories or British thermal units 
 developed when a unit weight of the coal is burned. Expressed in 
 a general way, it is the number of unit quantities of water which 
 are raised one degree by the total heat from the combustion of a 
 unit weight of coal. Expressed in calories it is the number of grams 
 of water which can be raised one degree Centigrade by the heat 
 from the combustion of one gram of coal. Expressed in British 
 thermal units, it is the number of pounds of water which can be 
 raised one degree Fahrenheit by the heat from the combustion of 
 one pound of coal. 
 
 The specific heat of water is not uniform at different tempera- 
 tures and an exact definition requires the defining of the particular 
 temperature through which the water is raised. The temperature 
 most usually taken is from 15 to 16 C. or 62 to 63 F. With this 
 restriction the definition of the calorific value of a coal is the 
 number of grams of water which can be raised from 15 to 16 C. 
 by the heat from the combustion of one gram of coal. 
 
 Relation of British thermal value to calorific value. In any 
 given coal the relation between the heating value in calories and in 
 British thermal units is as follows : 
 
 Let the calorific value = a, and 
 the B.t.u. value =6. 
 
 then the combustion of 1 gram of coal raises a grams of water 
 1 C. and the combustion of one pound of coal raises 6 pounds 
 of water 1 F. Evidently as far as amounts of coal and water arc 
 concerned a and b will be numerically equal and the only thing 
 in the two expressions which will cause them to be unequal is 
 the difference in the unit of temperature. 
 
 1 C. = | F. or 1 F. = J C. 
 
 In expressing the value in British thermal units the unit of 
 water is raised only | as far as it is in expressing the value in calor- 
 ies, hence 1 as many units can be raised, or numerically, 
 
 b = 5 a and conversely a = I b. 
 
10 COAL 
 
 or in general, 
 
 The heating value in B.t.u. = f the heating value in calories. 
 The heating value in calories = f the heating value in B.t.u. 
 
 If it is desired to express the amount of heat in a given weight 
 of coal in British thermal units and in calories the relation between 
 one pound and one gram must be considered. One pound avoir- 
 dupois= 453.6 grams. Since a British thermal unit is the heat 
 necessary to raise one pound of water one degree Fahrenheit, to 
 express this value in calories the equivalent in grams and degrees 
 Centigrade must be substituted, or one B.t.u. =453. 6 grams of 
 water raised I of one degree Centigrade, from which 1 B.t.u. = 
 252 small calories. Expressing calories in B.t.u., one small calorie 
 
 .t.u. = 0.003967 B.t.u. 
 
 Heat producing constituents of coal. The heat of combus- 
 tion of coal is due essentially to the heat produced by*the oxida- 
 tion of the carbon plus the heat produced by the oxidation of the 
 hydrogen not combined with oxygen plus the oxidation of 
 unoxidized forms of sulphur and iron. The amount of heat pro- 
 duced by the combustion of these elements in combination is not 
 always exactly the same as that produced by the combustion of 
 the free elements separately. However, the difference is not so 
 great but that the heat can be calculated with a fair degree of 
 accuracy from the amounts of these elements present. 
 
 Calculation of heating value from chemical composition. 
 Many different formulas have been and are used in calculating 
 the heating value from the chemical analysis. One of the best 
 known and most generally used is Dulong's formula, which is 
 commonly stated as follows: 
 
 The heating value = (8080 X the carbon) + [34460 X (the hydro- 
 gen i the oxygen) ]+ (2250 X the sulphur). The results for heat- 
 ing values obtained by the use of this formula are usually within 
 less than 1 1 per cent of the actual value as determined in the calo- 
 rimeter. About 150 analyses of Ohio coals given in Bulletin No. 9 
 of the Ohio Geological Survey, show that the values by Dulong's 
 formula range from about 30 to about 100 calories lower than the 
 value as determined in the calorimeter. Inspection of the deter- 
 mined and calculated values of the coals given in Chapter X 
 
COMPOSITION AND HEATING VALUE 11 
 
 shows a very fair agreement between the calculated and determined 
 values. 
 
 High oxygen coals show a calculated value considerably lower 
 than the determined value, and the calculated values, as a whole, 
 are lower than the determined values. Two factors may help to 
 account for the greater part of this difference: (1) The latest value 
 given for the heat of combustion of carbon is about 8100 instead 
 of 8080 as used in Dulong's formula. If this higher value for car- 
 bon be used, the calculated calorific values will be raised from 10 
 to 15 calories on each sample. (2) The determined calorific values 
 given were in all cases based upon the heating value of naphthalene 
 as 9692. Later values by Atwater, Fischer and Wrede and the 
 U. S. Bureau of Standards are considerably lower than this. If 
 the value for naphthalene be taken as low as 9628 Atwater's 
 value this will lower the determined calorific values given by 
 about 50 calories. The effect of these two causes if applied to the 
 values given brings the calculated and determined values much 
 nearer together with the calculated value still somewhat lower 
 than the determined value. 
 
 Some of the differences between the calculated and determined 
 values are very probably due to errors in the determination, while 
 others probably correspond to actual differences in the heat 
 developed by the combustion of the different elements in the com- 
 binations in which they exist in the coal. Some organic compounds, 
 such as carbon bisulphide, have a decidedly higher calorific value 
 than the calorific value of equivalent amounts of the elements 
 present. In other words, the decomposition of the carbon bisul- 
 phide into its elements liberates heat. Such compounds are known 
 as endothermic compounds. The low results obtained by Dulong's 
 formula on some coals indicate the presence of endothermic 
 compounds in the coal. 
 
 Distribution of oxygen in coal and modification of Dulong's 
 formula. A small portion of the oxygen (in some high volatile 
 and high moisture coals, a considerable portion) is present in coal 
 in combination with the carbon or at least it escapes in com- 
 bination with the carbon as carbon dioxide (CO2) and as carbon 
 monoxide (CO) instead of in combination with the hydrogen as 
 water (H^O), when the coal is decomposed and the volatile 
 matter is given off. Hence Dulong's formula should be con- 
 sidered merely as a means of estimating heating value rather 
 
12 COAL 
 
 than that the composition of the coal is in exact agreement with 
 the formula. Any oxygen combined with carbon has a smaller 
 effect in reducing the heating value than if it is combined with 
 hydrogen, and some calculated heating values agree more closely 
 with the determined ones on the assumption that carbon and 
 oxygen are combined rather than the oxygen and the hydrogen. 
 On this assumption, Dulong's formula would be modified to read 
 as follows: 
 
 (C-fO) 8080+H(34460) +8(2250). 
 
 In certain compounds the estimation of the heating value by 
 this formula is closer to the determined value than the estimation 
 by Dulong's formula unmodified. For example, cane sugar 
 (Ci2H220n) contains 42.1 per cent carbon; 6.43 hydrogen and 
 51.47 oxygen. 
 
 The determined calorific value of cane sugar is 3958 calories. 
 The calculation of the heating value by Dulong's formula is 3402 
 calories. By the modified formula, assuming the oxygen with the 
 carbon = 4058 calories. Neither calculated value agrees with the 
 determined value. The value calculated by Dulong's formula is 
 556 calories too low and the value calculated by the modification is 
 200 calories too high. For this particular material a composite 
 formula, assigning a portion of the oxygen to the carbon and a 
 portion to the hydrogen, is necessary to obtain a calculated result 
 in agreement with the determined value. Many high oxygen 
 coals give better calculated values with a slightly modified formula 
 instead of the regular Dulong formula. However, each class 
 of coal requires a particular modification and often the ultimate 
 analyses themselves may be inaccurate so that special modifica- 
 tions to fit particular samples are to be accepted with caution. 
 
 Heat calculation formulas and actual chemical composition. 
 The actual heating value of a fuel is the final heat evolved by 
 complete combustion and may be and usually is the net result 
 of a number of intermediate reactions. In such a complex sub- 
 stance as coal little is known as to the exact nature of the material 
 and of these intermediate reactions and the agreement or non- 
 agreement of the actual and calculated heating values proves 
 nothing as to the exact chemical composition. On account of 
 this lack of knowledge as to exactness of composition and as to 
 the nature of the intermediate decomposition reactions it is not 
 
COMPOSITION AND HEATING VALUE 13 
 
 possible to give an exact general formula for the heating value 
 of coal based on its chemical composition and any and all formulas 
 must be regarded merely as more or less exact approximations. 
 These approximations are in general of practical value only in 
 so far as they accord with actual determinations. However, 
 to the chemist the calculated calorific value has a special appli- 
 cation in that it serves as a check on the laboratory work. For 
 any given set of samples of the same kind of coal with accurate 
 calorimeter and ultimate determinations, the agreement or dis- 
 agreement between the calculated and the determined calorific 
 values should show considerable uniformity and any considerable 
 error in a particular calorimeter or ultimate determination will 
 usually be discovered upon comparing the calculated and deter- 
 mined calorific values. 
 
 In the past much importance and stress have been placed on 
 calculated values but at present bomb calorimeters are in such 
 general use that calculated values are apt to be more of special 
 interest to the chemist than of practical importance to the con- 
 sumer and discussions as to just what formulas are the most 
 applicable are of no great practical interest to the average coal 
 user or producer. 
 
 PRACTICALLY AVAILABLE HEATING VALUE OF A COAL 
 
 This is the amount that can be utilized, or is the total heating 
 value less the losses necessary or incident to combustion. For a 
 steam boiler, the losses are as follows: 
 
 (1) The latent heat in evaporating the water in the coal, in- 
 cluding moisture, combined water and water formed during com- 
 bustion. 
 
 ' (2) The heat carried up the stack as sensible heat by the prod- 
 ucts of combustion. 
 
 (3) The heat carried up the stack by the excess air used in 
 burning the coal. 
 
 (4) The heat lost by incomplete combustion, as formation of 
 carbon monoxide (CO) instead of carbon dioxide (CO2). 
 
 (5) Heat not realized from the unburned coal in the ash pit. 
 (7) Radiation and other losses. 
 
 The relative amounts of these losses expressed in percentages 
 range about as follows: Latent heat, 3 to 5 per cent; sensible 
 
14 COAL 
 
 heat, 8 to 14 per cent; excess air, 8 to 25 per cent; carbon 
 monoxide (CO), to 5 per cent; unburned coal, 1 to 10 per cent; 
 radiation and other losses, 3 to 15 per cent. The sum of all the 
 losses is usually between 25 and 50 per cent, leaving an available 
 value of 50 to 75 per cent. The actually available value varies 
 with the kind of coal, the type of stoker and boiler used and the 
 completeness of the combustion. The best boiler tests give an 
 available heating value for the best coals as high as 75 per cent, 
 while poor practice and inferior coals may give an available heat- 
 ing value as low as 50 per cent. Losses Nos. 2, 3, 4, 5 and 7 are, 
 within limits, under control of the boiler crew and up to 15 per 
 cent of the total heat may be saved or lost depending upon how 
 the fire is operated. This means as high as 20 per cent of the 
 available value and when fuel bills amount to thousands of 
 dollars, an increase in efficiency by having at least an occasional 
 expert inspection and test run ought to be money well spent. 
 
 When two plants operating on practically the same equipment 
 and using the same grade of coal vary greatly in the efficiency ob- 
 tained one or both of the plants need inspection. Equipment for 
 flue-temperature measurements and adequate apparatus for mak- 
 ing flue-gas analyses are usually profitable investments. The 
 determinations which should be made on the flue gases are the de- 
 termination of the amounts of carbon dioxide (CO2), oxygen (62) 
 and carbon monoxide (CO) present. The determination of carbon 
 dioxide alone by mechanical devices or other means may give 
 fairly satisfactory control if checked by properly taken Orsat 
 determinations. Mechanical or automatic devices left to take 
 care of themselves may be worse than useless. For details and 
 discussion of flue gas sampling and analysis, see Chapter XL 
 
 DETERMINATION OF THE HEAT LOSSES; 
 
 An illustration of the values and methods of obtaining these 
 losses is as follows: 
 
 (1) Latent heat. The amount of this loss is dependent upon 
 the coal used and is not subject to control by the firemen operating 
 the furnace unless the coal is wet down intentionally by the fire- 
 men, in which case the latent heat loss is greater than the amount 
 calculated from the analysis. The amount of hydrogen in the coal 
 as determined by analysis multiplied by 9 equals the amount 
 
COMPOSITION AND HEATING VALUE 15 
 
 of water present in the coal together with that formed during 
 combustion. This amount of water multiplied by 539.1+0.52 
 (100 f) equals the calories of heat lost. Where 539 . 1 is the latent 
 heat in evaporating the water at 100 C.; t is the boiler room 
 temperature in degrees Centigrade and 0.52 (100 equals the 
 difference between the specific heat of water and the specific heat 
 of water vapor for the range 100 t degrees. The other portion 
 0.48 (100 t) is taken care of under sensible heat carried off by the 
 products of combustion where it is assumed that the water is 
 evaporated at the boiler room temperature and the sensible heat 
 of water vapor calculated from that temperature. The above 
 value for latent heat of water at 212 F. is that given by Marks 
 and Davis 1 and is based upon the work of Joly and Henning. The 
 above formula for British thermal units is, 
 
 B.t.u. =970. 4+0. 52(212-0, 
 
 with = boiler room temperature in degrees Fahrenheit. 
 
 (2) Products of combustion. The products of complete combus- 
 tion are carbon dioxide, water vapor, sulphur dioxide, nitrogen 
 and ash. The amounts of these obtained from the unit weight of 
 coal are 3f times the carbon for the carbon dioxide; nine times the 
 hydrogen for the water vapor; two times the sulphur for the sul- 
 phur dioxide, and the ash and nitrogen as shown by the analysis. 
 The water equivalent of the products of combustion is obtained 
 by multiplying each of these items by its specific heat and adding 
 the products. 
 
 The weight of the nitrogen in the air used for combustion is 
 equal to very nearly 3.33 times the weight of the oxygen required 
 for combustion. This oxygen is equal to 2f times the carbon, plus 
 eight times the hydrogen, plus the sulphur minus the oxygen con- 
 tained in the coal. The nitrogen thus obtained multiplied by the 
 specific heat of nitrogen gives the water equivalent of the nitro- 
 gen from the air. Similarly the amount of ash multiplied by its 
 specific heat gives the water equivalent of this item. 
 
 The sum of all the water equivalents obtained as above mul- 
 tiplied by the difference between the temperature at which the 
 products escape and the temperature of the air supplied for com- 
 
 1 Tables and Diagrams of Thermal Properties of Saturated and Super- 
 saturated Steam. 
 
16 COAL 
 
 bustion gives the heat carried off in the' products of combus- 
 tion. 
 
 (3) Excess air. The excess air present is equal to the amount 
 of air required for combustion multiplied by the ratio of the 
 excess air to that required. The weight of air required for 
 combustion is 4.33 times the oxygen required for combustion, 
 or 4.33 times the sum of I of the carbon, plus 8 times the hydro- 
 gen plus the sulphur minus the oxygen in the coal. The ratio 
 of the excess air present to that used for combustion is obtained 
 from the analysis of the gases passing out of the chimney. If 
 the small amount of nitrogen present in coal be neglected the 
 ratio of the air present in the chimney gases to the air used in 
 combustion is equal to 
 
 Oxygen 
 
 0.3 Nitrogen Oxygen' 
 
 in which the oxygen and nitrogen are percentages by weight of 
 the gases. Where the percentages are given by volume the for- 
 mula becomes: 
 
 Oxygen 
 
 Nitrogen 
 -- -Oxygen 
 
 Calculation of the excess air. The derivation of the above 
 formula for excess air is as follows: 
 
 ,~ , . ,, . the excess air 
 
 The ratio of the excess air 
 
 the air required for combustion 
 
 In the flue gas the oxygen present is that which is in the excess 
 air. The nitrogen present is the nitrogen from the air required 
 plus the nitrogen in the excess air. The required air equals the 
 total air minus the excess air. By volume, air is composed of 
 20.8 parts oxygen and 79.2 parts nitrogen or for every 4.8 parts 
 of air there are 3.8 parts of nitrogen and one part of oxygen. 
 The excess air is found from the amount of oxygen present and is 
 equal to 4.8 times the oxygen present. The total air is determined 
 
 1 Q 
 
 from the total nitrogen present and is equal to ^ ^ times the total 
 
 o.o 
 
 nitrogen. Subtracting the excess air (4.8 times the oxygen) from 
 
COMPOSITION AND HEATING VALUE 17 
 
 the total air ( - 5 times the nitrogen ) gives the air required for 
 \d.o / 
 
 combustion as 
 
 - nitrogen 4.8 oxygen, 
 o.o 
 
 Substituting these values for the excess air and the required air, 
 the ratio of the excess air equals 
 
 4.8 Oxygen 
 
 4 8 
 
 ^-r Nitrogen 4.8 Qxygen 
 
 o.o 
 
 and dividing by 4.8 gives the formula in the form as given above: 
 
 Oxygen 
 
 Nitrogen 
 
 TQ-f Oxygen 
 
 o.o 
 
 The formula by weight is obtained in a similar manner. 
 
 As an illustration, when the flue gas by volume analyzes as 
 follows : 
 
 CO 2 9. 2 per cent 
 
 O 2 10.9 per cent 
 
 CO 0.0 per cent 
 
 N 2 79 . 9 per cent 
 
 Total 100.0 per cent 
 
 the excess air, by substituting these values in the formula, is 
 
 ^^ =1.08 
 
 or 108 per cent of the air required for combustion. 
 
 These formulas are applicable only where the amount of 
 nitrogen in the fuel is so small as to be neglected as in the case 
 of coals. If, however, the fuel contains nitrogen in considerable 
 quantity, which is the case with some gaseous fuels, the formula 
 
18 
 
 COAL 
 
 is modified to allow for the nitrogen present in the fuel. The 
 formula where the percentages are given by volume becomes 
 
 Oxygen 
 
 Nitrogen 
 
 V'E 
 
 3.8 
 
 Oxygen 
 
 where V is the volume of gaseous carbon in 100 volumes of flue 
 gas and V the volume of gaseous carbon in 100 volumes of fuel 
 gas and E is the percentage by volume of nitrogen in the fuel gas. 
 The derivation, of this modified formula is as follows: For 
 convenience in calculation, the molecule of carbon in a gaseous 
 state is usually considered as composed of two atoms. As all 
 the carbon in the fuel is present in the products of combustion 
 the relation of the volume of the fuel gas to the volume of the 
 flue gas is obtained by comparison of the ratio of the volumes 
 of the carbon present in the two gases, from which the volume 
 of nitrogen in the fuel gas can be determined in terms of the 
 volume of the flue gas. This is 
 
 V'E 
 V 
 
 The nitrogen in the total air required for combustion is accord- 
 ingly the total nitrogen in the flue gas minus the nitrogen in the 
 fuel gas or 
 
 V'E 
 Nitrogen =-. 
 
 To make this clearer by a special example, suppose the fuel 
 gas and the flue gas by volume to have the following composition: 
 
 
 Fuel Gas. 
 
 Flue Gas. 
 
 Carbon dioxide (CO2) 
 
 4 5 
 
 14 5 
 
 Oxygen (O 2 ) 
 Ethylene (C 2 H 4 ) 
 
 0.5 
 1 
 
 2.9 
 
 Carbon monoxide (CO) . . . 
 
 22 
 
 
 Hydrogen (H2) 
 
 9.5 
 
 
 Methane (CH 4 ) 
 
 3 5 
 
 
 Nitrogen (N 2 ) . 
 
 59.0 
 
 82 6 
 
 
 
 
 
 100.0 
 
 100.0 
 
COMPOSITION AND HEATING VALUE 19 
 
 The volume of carbon molecules in the fuel gas is as follows: 
 
 iXCO 2 = 2.25 
 1XC 2 H 4 = 1.00 
 iXCO =11.00 
 iXCH 4 = 1.75 
 
 Total =16.00 
 
 In the flue gas the volume of the carbon molecules equals J the 
 C02 = 7.25. Substituting these values in the formula, it becomes: 
 
 (59) 
 
 16 -2.9 
 
 3.8 
 
 or 24 per cent of the air required for combustion. 
 
 These calculations may be made if desired on the assumption 
 of one atom in the gaseous carbon molecule in which case the 
 volume of the carbon molecules in each gas will be twice as great, 
 but they will have the same ratio to each other and the same 
 numerical result is obtained. 
 
 (4) Incomplete combustion. The heat lost by incomplete 
 combustion or formation of CO instead of CO 2 is determined 
 as follows: One gram of carbon burned to 002 = 8080 calories. 
 One gram of carbon burned to 'CO = 2430 calories, or the heat 
 loss due to the formation of CO instead of CO 2 is 8080 2430 
 = 5650 calories. The amount of carbon which is burned to CO 
 instead of C0 2 is determined from the flue gas analysis and the 
 amount of carbon present in a unit of coal. Since equal volumes 
 of CO and CO 2 contain equal amounts of carbon, the ratio of 
 carbon burned to CO instead of CO 2 is equal to the 
 
 CO by volume 
 
 C0 2 by volume + CO by volume' 
 
 Multiplying the percentage of carbon present in the coal by this 
 ratio gives the actual amount of carbon burned to CO per unit 
 of coal fired. This multiplied by 5650, equals the calories of 
 heat lost. 
 
20 COAL 
 
 (5) Unburned coal. The heat not realized from unburned 
 coal in the ash pit is also a large loss in many cases. The total 
 calories of heat lost is the amount of unburned coal times the 
 calorific value of the coal. 
 
 Calculation of amount of unburned coal. The amount of 
 unburned coal is determined from the analysis of the refuse taken 
 from the ash pit and the analysis of the coal as fired. 
 
 Let the ash in the coal by analysis = a. Then the total 
 volatile and combustible matter including moisture and fixed 
 carbon in the coal by analysis = 1 a. 
 
 Let the volatile and combustible matter or ignition loss in 
 the refuse c. 
 
 Let the incombustible matter in the refuse = r, all of these 
 values being decimals. 
 
 The unburned coal in the refuse expressed in terms of the 
 
 refuse = . 
 1 a 
 
 The ash in this unburned coal in the refuse expressed in terms 
 of the refuse is 
 
 / \ 
 
 ca 
 
 l-aj 1-ctj 
 
 The ash in the unburned coal : total ash : : the unburned coal : 
 total coal. Substituting the above values, this proportion 
 becomes : 
 
 ca 
 
 - : r::x : 1, 
 1 a 
 
 where x is the unburned coal, from which 
 
 As a particular example suppose the ash in the coal= 10 
 per cent. The refuse by analysis = volatile and combustible 
 30 per cent, incombustible 70 per cent. Substituting these 
 values, 
 
 ca 0.3(0.10) 0.03 
 
 (l-a)r (0.9) (0.7) 0.63 
 
COMPOSITION AND HEATING VALUE 21 
 
 In which case the loss due to unhurried coal equals the calorific 
 value of the coal times 0.049. 
 
 (7) Radiation. The radiation and other losses. The sum 
 of 1, 2, 3, 4 and 5 plus the heat in the water evaporated sub- 
 tracted from the total calorific value of the coal gives the radia- 
 tion and other unaccounted for losses. 
 
 Unaccounted losses. Some of the unaccounted losses are 
 as follows: 
 
 (a) Traces of hydrogen and hydrocarbons in the flue gas. 
 
 (6) Unburned carbon in soot and smoke. 
 
 (c) Latent and sensible heat due to water used to wet down 
 the coal or added to the ash pit. 
 
 (d) Sensible heat in flue gas due to the moisture in the air. 
 The heat losses due to the presence of traces of unburned 
 
 hydrogen or methane or ethylene in the flue gas are usually con- 
 sidered as small. Certainly no large amounts of these gases 
 are found in the escaping flue gas but the presence of undeter- 
 mined traces of any of these gases may help to account for some 
 of the unaccounted-for losses. As an example, in the combus- 
 tion of No. 6 coal with 100 per cent excess air and a flue-gas analysis 
 of CO 2 , 9.3; O 2 , 10.6; CO, 0.0 and N 2 80.1 per cent, the presence 
 of TOO per cent of hydrogen (H2) or of methane (CH4) or of 
 ethylene (C 2 H4) would represent a heating loss approximately 
 as follows: On the assumption that practically all of the 0.66 
 gram of carbon in one gram of coal fired is contained in the 9.3 
 per cent of CO 2 in the flue gas, a molecular volume 22.4 liters 
 of CO 2 = 44 grams of C0 2 = 12 grams of carbon. A molec- 
 ular volume of hydrogen = 2 grams of hydrogen, from which 1 
 cubic centimeter of hydrogen contains by weight one-sixth as 
 much hydrogen as the weight of the carbon in 1 cubic centi- 
 meter of C0 2 . The relative volumes of hydrogen and CO 2 
 in the gas on the assumption of j-J-j per cent of hydrogen present 
 is as 1 : 930. Hence the weight jf aydrogen in the gas correspond- 
 ing to 1 gram of coal tired is J -X ^iuX 0.66 = -g-Fo T gram. The 
 calorific value of -O^-Q of a gram of hydrogen is -gV<nr of 34460 = 4 
 calories. 
 
 One cubic centimeter of methane (CEU) has approximately 
 3 times the heating value of 1 cubic centimeter of hydrogen = 12 
 calories. One cubic centimeter of ethylene (C 2 H4) has approxi- 
 mately 5 times the heating value of 1 cubic centimeter of hydro- 
 
22 COAL 
 
 gen = 20 calories. Hence for this condition of 100 per cent excess 
 air the losses expressed in percentage of the total calorific value 
 of a fuel are as follows: 
 
 T J T per cent of hydrogen in the flue gas = ^\ per cent loss. 
 TOO per cent of methane in the flue gas = J per cent loss. 
 per cent of ethylene in the flue gas = f per cent loss. 
 
 The determination of hydrogen, methane and ethylene in the 
 flue gas to -TOT per cent is not at all easy, and the unaccounted- 
 for losses due to traces of these gases in some cases might have 
 appreciable effects on the heat balances without the chemist in 
 charge being able to determine with certainty the quantities of 
 these gases present. 
 
 The heat loss due to the unburned coal in the soot and smoke 
 usually does not exceed a few tenths of one per cent, and any 
 serious effect due to this cause must be due to poor absorption 
 of heat by the boilers as a result of deposition of soot on or in the 
 tubes, or on the heating surfaces. 
 
 Water added to dry dusty coal to wet it down just previous 
 to firing may, by securing more favorable conditions of firing, 
 increase the available heating value more than enough to counter- 
 act the heat lost by the evaporation of this water and the sensible 
 heat in the water vapor. However, the addition of any water 
 after the coal is actually weighed, in so far as the heat balance is 
 concerned, simply contributes so much more heat as latent and 
 sensible heat to the unaccounted for heat losses. Likewise water 
 added to the ash pit may by its cooling action on the grate bars 
 and lower part of the fuel bed tend to improve the combustion 
 of the coal and make it more efficient. In so far as the heat bal- 
 ance is concerned this sensible and latent heat is also included in 
 the unaccounted-for losses. 
 
 The sensible heat carried off by the moisture in the air used 
 varies with the excess air and with the temperature and humidity 
 of the air ranging from less than 0.1 per cent in cold dry weather 
 to upwards of 1 per cent of the total heating value of the coal in 
 warm rainy weather. For example, 1 gram of Ohio No. 6 coal 
 (assuming 100 per cent excess of air) requires: 
 
 4}X[ (0.6903X1) + (0.0543X8) + (0.0330 XI) -0.1362] = 9.41 
 
COMPOSITION AND HEATING VALUE 23 
 
 grams or allowing the 100 per cent excess air = approximately 19 
 grams of air per gram of coal fired. 
 
 19 grams of dry air -14.7 liters of moist air at C. (32 F) 
 760 mm. or = 17.0 liters of moist air at 30 C. (86 F) 760 mm. 
 
 One liter of saturated air at C. contains 4.8 mg. of water vapor. 
 One liter of saturated air at 30 C. contains 30 mg. of water vapor. 
 
 14.7 liters at C. contains 70 mg. of water vapor 
 and 
 
 17.0 liters at 30 C. contains 510 mg. of water vapor. 
 
 The sensible heat of the water vapor at 300 C. (572 F.) for 
 the two conditions is, 
 
 0.070X0.48X300 = 10 calories 
 0.510X0.48X270 = 66 calories 
 
 a loss from about 0.14 per cent to about 1 per cent, from which 
 it is apparent that in cold or dry w r eather the loss is quite small, 
 but that in warm rainy weather it may be very appreciable. 
 
 Specific heat of products of combustion. The exactness of 
 the above formulas for determining the available heat depends 
 upon the exactness of the values for the specific heats. The 
 specific heats of the gases were formerly regarded as being 
 practically constant for all temperatures, but more recent re- 
 searches have shown that changes in the temperatures of the 
 gases are accompanied by changes in the specific heats. 
 
 The mean specific heats in small calories per gram molecular 
 volume of gases under constant pressure from Centigrade to 
 temperature (t) based upon the results of Le Chatelier and 
 Mallard are given by Damour 1 substantially as follows: 
 
 Diatomic gases (0 2 , N 2 , H 2 and CO) =6.83+0.0006 t. 
 Water vapor (H 2 O) =8.08+0.0029 t. 
 Carbon dioxide (CO 2 ) =8.52+0.0037 t. 
 Methane (CH 4 ) =9.78+0.006 t. 
 
 The values in small calories per gram of gas or in kilograms 
 calculated per kilogram of gas under constant pressure as given 
 by Richards 2 and as figured from the formulas given above are 
 as follows: 
 
 1 Industrial Furnaces. 2 Metallurgical Calculations, Vol. I. 
 
24 
 
 COAL 
 
 RICHARDS. 
 
 DAMOUR. 
 
 Nitrogen 
 Oxygen 
 Water vapor 
 Carbon dioxide 
 Sulphur dioxide 
 Carbon monoxide 
 Hydrogen 
 Methane 
 
 = 0. 2405+0. 0000214* 
 = 0.2104+0.0000187* 
 = 0.42 +0.000185* 
 = 0.19 +0.00011* 
 '0.125 +0.0001* 
 = 0. 2405 +0.0000214* 
 = 3.37 +0.0003* 
 
 0.2438+0.0000214* 
 0.2135+0.0000187* 
 0.447 +0.000162* 
 0.194 +0.000084* 
 
 0.2438+0.0000214* 
 3.412 +0.000300* 
 0.611 +0.000375* 
 
 The most recent values for specific heats of the common gases 
 are given by Lewis and Randall 1 and are based mainly upon the 
 work of Holborn and Austin, Holborn and Henning and of Pier. 
 The values for specific heats in small calories per gram molecular 
 volume of gas under constant pressure, for absolute temperatures 
 are as follows: 
 
 Nitrogen = 6.50+0.0010T; 
 
 Oxygen =6.50+0.00107 1 ; 
 
 Carbon monoxide = 6 . 50 +0 . 00107 7 ; 
 
 Hydrogen =6.50+0.0009^; 
 
 Water vapor =8.81 - 0. 00 19T+0. 00000222 T 72 ; 
 
 Carbon dioxide =7.0+0.00717 1 -0.00000186T 2 ; 
 
 Sulphur dioxide = 7.0+0.0071T-0.00000186T 2 . 
 
 According to these different authorities the mean specific 
 heats from to 300 Centigrade (572 Fahrenheit) and from 
 to 1000 Centigrade (1832 Fahrenheit) for these different gases 
 are as follows : 
 
 
 Richards 
 
 Damour 
 
 Lewis and Randall 
 
 to 300 
 
 to 1000 
 
 to 300 
 
 to 1000 
 
 to 300 
 
 to 1000 
 
 Nitrogen 
 
 0.247 
 0.216 
 0.223 
 0.476 
 0.247 
 0.240 
 0.155 
 
 0.262 
 0.229 
 0.300 
 0.605 
 0.262 
 0.257 
 0.225 
 
 0.250 
 
 0.219 
 0.219 
 0.497 
 0.250 
 0.243 
 
 0.265 
 0.232 
 0.278 
 0.610 
 0.265 
 0.258 
 
 0.247 
 0.216 
 0.219 
 0.469 
 0.247 
 0.240 
 0.150 
 3.41 
 
 0.259 
 0.227 
 0.248 
 0.512 
 0.260 
 0.252 
 0.170 
 3.57 
 
 Oxvffcn 
 
 Carbon dioxide 
 
 Water vapor 
 
 Carbon monoxide 
 
 Air 
 
 Sulphur dioxide 
 
 Hydrogen 
 
 3.460 
 
 3.670 
 
 3.502 
 0.723 
 
 3.712 
 0.986 
 
 Methane 
 
 
 
 
 The specific heat of ash may be taken as about 0.16. 
 1 Jr. Am. Chem. Soc. Vol. XXXIV, page 1128, Sept. 1912. 
 
COMPOSITION AND HEATING VALUE 25 
 
 Calculation of the available heating power of Hocking or 
 Ohio No. 6 coal. As an illustration of the foregoing calculations, 
 the available calorific value of this coal based on the average 
 analysis of the seam and under conditions corresponding to the use 
 of the coal in a steam boiler of the best type working under the best 
 conditions is calculated as follows: The excess of air under the 
 conditions assumed is taken at 50 per cent, flue temperature 
 at 300 C., temperature of the air at zero and the temperature 
 at which the ash is withdrawn from the furnace the same as the 
 temperature of the air. The composition and the calorific value 
 of the coal are : 
 
 Carbon . 6903 
 
 Hydrogen 0.0543 
 
 Nitrogen . 0126 
 
 Oxygen . 1362 
 
 Sulphur 0.0330 
 
 Ash . 0.0736 
 
 Calorific value 6980 Calories 
 
 The latent heat equals 9 X 0.0543 X (539. 1+0.52(100)) =288.7 
 The water equivalent of the products of combustion exclusive 
 of the nitrogen in the air equals : 
 
 Carbon dioxide = 0. 6903 xxO. 223 = 0.5644 
 Water = 0.0543X 9X0.476=0.2326 
 
 Sulphur dioxide =0.0330X2 XO. 155 =0.0102 
 Nitrogen =0.0126X 0.247=0.0031 
 
 0.8103 
 The oxygen in the air used in combustion equals: 
 
 For carbon =|X0.6903 = 1.8408 
 For hydrogen =8X0. 0543 = . 4344 
 For sulphur =0.0330 
 
 2.3082 
 Deducting the oxygen in the fuel . 1362 
 
 2.1720 
 
 The water equivalent of the nitrogen in the air corresponding 
 to the oxygen equals 3.33X0.247X2.1720 = 1.7865. 
 
 The water equivalent of the products of combustion, 0.8103, 
 plus the water equivalent of the nitrogen from the air, 1.7865, 
 
26 COAL 
 
 equals 2.5968, which multiplied by 300, the flue temperature- 
 equals 779.0, the sensible heat carried off in the products of com, 
 bustion. 
 
 The excess air equals the oxygen (2.1720) multiplied by 4.33 
 and by 0.5 (the ratio of excess air), or 2.1720X4.33X0.5 = 4.7024. 
 The heat carried off in the excess air equals: 
 
 4.7024X0.24X300 = 338.6 heat units. 
 
 Writing these various values together and adding them, gives 
 the following: 
 
 Latent heat = 288.7 
 
 Heat lost in products of combustion (including nitrogen from 
 
 air used) = 779 . 
 
 Heat lost in excess air in flue gas = 338 . 6 
 
 Total. . =1406.3 
 
 Deducting the sum (1406.3) from the calorific value of the 
 fuel '(6980) leaves 5573.7 as the heat theoretically available per 
 unit of fuel and under the conditions assumed. This is equal 
 to about 80 per cent of the total calorific value. 
 
 This value is higher than the actual available value as any 
 heat loss due to unburned coal in the ash pit or the formation 
 of CO instead of C02 and the radiation losses are included in the 
 80 per cent. Also the assumed value of 50 per cent for the 
 excess air is much lower than is usually found, 100 per cent excess 
 being a closer approximation to common practice. With 100 
 per cent excess air and the same flue temperature, 300 C., 
 (572 F.) the heat loss due to excess air is 338.6 calories higher 
 or approximately 4.8 per cent of the total heating value. Assum- 
 ing 5 per cent for unburned coal remaining in the ash pit, or 
 that the coal actually burned equals 95 per cent of the coal 
 fired then the heat lost in the excess air and in the products 
 of combustion with 100 per cent excess air is 0.95 of (1406.3 + 
 338.6) = 1657.6 calories or 23.8 per cent of the total heating 
 value. To this add 5 per cent, the heat in the unburned coal, = 
 23.8+5 = 28.8 per cent. Then 100-28.8 = 71.2 per cent for 
 evaporation of water and radiation and unaccounted-for losses. 
 If the radiation and unaccounted for losses be taken as 10 per 
 cent the remainder available for actual evaporation of water = 
 
COMPOSITION AND HEATING VALUE 27 
 
 61.2 per cent of the total heating value. 61.2 per cent of 6980 
 calories = 4272 calories. Dividing this number by 539.1, the 
 latent heat of evaporation of water into steam at 100 C., gives 
 7.92 as the number of grams of water that can be evaporated 
 by one gram of coal, or expressed in pounds as the number of 
 pounds of water that can be evaporated by one pound of coal. 
 
 Printed forms for calculating the heat balance. The calcu- 
 lation of the heat balance can be shortened and made much easier 
 by the use of a printed form for entering the various values as 
 determined or as calculated. Such a form using logarithms 
 with the logarithms of the constants printed on the form saves 
 much labor in multiplying and dividing and once familiar with 
 the routine the calculation is comparatively simple. 
 
 On pages 28-29 are given the calculation of the Ohio No. 6 
 coal together with data on the flue-gas and refuse and assuming 
 that the refuse is removed from the ash pit at 300 C. The 
 values for the specific heats corresponding to the logarithms used 
 are as follows: Nitrogen, 0.246; oxygen, 0.215; water vapor, 0.48; 
 carbon dioxide, 0.217; carbon monoxide, 0.220; air, 0.238; sulphur 
 dioxide, 0.15; ash, 0.16. 
 
 THE USE OF THERMAL CAPACITY TABLES FOR HEAT 
 CALCULATIONS 
 
 The use of thermal capacity tables to determine the sensible 
 heat carried off in the flue gas considerably shortens heat balance 
 calculations. 
 
 By thermal capacity of a gas is meant the heat necessary 
 to raise a definite quantity of the gas from C. to the tem- 
 perature (). The tables may be figured on any basis desired, 
 as the thermal capacity per liter, per molecular volume or per 
 cubic foot, or the thermal capacity per kilogram, gram or 
 pound, or as in the table given the thermal capacity of the gas 
 corresponding to a gram of one of the elementary constituents 
 of the gas, as the thermal capacity of carbon dioxide per gram 
 of carbon, from which the carbon dioxide is derived. The 
 table which follows is on the basis of the thermal capacity of the 
 several gases, produced during combustion, corresponding to 
 one gram of the elements carbon hydrogen sulphur and 
 nitrogen in the coal. The value for air is per gram of air. 
 
28 
 
 GOAL 
 
 HEAT BALANCE FOR BOILER TEST WITH COAL 
 
 Analysis of Coal 
 
 Vloisture .... 5.56 
 Vol. Combusti- 
 ble 38 11 
 
 C' = Carbon in coal burned 
 H' = Hydrogen in coal burned 
 O' = Oxygen in coal burned 
 S' = Sulphur in coal burned 
 N' = Nitrogen in coal burned 
 
 C" = Carbon burned to CO 
 C"' = Carbon burned to CO 2 
 
 C'=C"+C'" 
 
 Unburned Coal=D 
 
 ac 
 r(l-a) 
 
 a =Ash in coal by analy- 
 sis 
 c =Combustib'e in refuse 
 r = Incombustible in ref- 
 use 
 
 (All decimals) 
 Log. a =2.8669 
 Log. c =1 .6010 
 
 Log. ac =2 .4679 
 
 Carbon as CO 
 
 Log. C' 
 Log. Q 
 
 Fixed Carbon . 48.96 
 Ash 7.36 
 
 Log C" =.. 
 
 
 C" 
 
 Total. . . . 100. 00 
 
 Hydrogen (H) 5.43 
 Carbon (C) 69.03 
 Nitrogen (N) 1.26 
 Oxygen (O) 13.63 
 Sulphur (S) 3.30 
 Ash (a) 7.36 
 
 Total ... 100.00 
 
 Log. C" 
 Log.? =0.3680 
 
 O" =Oxvgen in CO 
 O'"= Oxygen in CO 2 
 O'v = Oxygen in H 2 O 
 Qv = Oxygen in SO 2 
 
 2O=O"+O'"+0'v+Ov 
 
 SO O' =Oxygen from air 
 used 
 31 ( 230 -0')=N"= Nitrogen 
 from air used 
 
 Log. CO = 
 
 T ntr PO 
 
 Log. r =7 . 775-9 
 Log. (1-a) =1.9668 
 
 Log. Sp. ht.=T-3424 
 
 S Log. = 
 
 Calorific Value 
 
 Calories .... 6980 
 B.T.U 12564 
 
 Log. r(l-a) =7.7457 
 
 W. E. CO = 
 
 Log. ac =~2.4679 
 (-)Log. r(l-a) 
 = 1.7457 
 
 Heat Loss Due to 
 Formation of CO 
 
 Log. C" 
 Log. 5650 =3.7520 
 2 Log. 
 
 Log. D =8.7222 
 
 Analysis of Refuse 
 
 Combustible (c) 39.9 
 Refuse (r) 60 . 1 
 
 Total 100.0 
 
 Fvr, - Air (by V L > 
 
 D =0.0527 
 ID 9473 
 
 o- 
 
 3-8- *'- OS 
 O= 10.60 
 
 3 V = 10.48 
 
 Log. (1-D) =1.9765 
 
 No. Calories 
 
 
 Loss Due to Unburned 
 Coal 
 
 Log. D =2.7222 
 Log. cal. value =3.8439 
 
 Oxygen in CO 
 
 Log. C" 
 Log =0.1249 
 
 Analysis of Flue Gas 
 
 By Vol. 
 CO 2 .... 0.4 
 O 2 , 10.6 
 
 2 Log 2 5661 
 
 Log. O =.7.02.53 
 (-)Log- (j^g-o) =1.0204 
 
 No. Calories = ?.68 
 
 Log. O" = 
 
 CO 0.0 
 N 2 80.1 
 
 0" 
 
 Total . . . 100.0 
 
 Ash 
 
 Ash(l-D) =0.0697 
 D =0.0527 
 
 Log. Xs Air =0.0040 
 
 Carbon as CO 2 
 
 C'"=C'-C" 
 
 Log. C'" =1.8155 
 Log. y =0.5643 
 Log. Sp. ht. =1.3365 
 
 Temperature 
 
 Flue Gases (f) = 300 
 
 Log. CO (Vol.) 
 
 Ash(l-D)+D = 0^122_4 
 
 Log. Ash(l -D) +D 
 = / . 0575 
 Log. Sp. ht. =1.2041 
 
 
 
 S Log. =1.7163 
 
 
 Log. Q = 
 
 22 Log 2 ^919 
 
 W. E. CO 2 =0.524 
 
 Water Evaporated 
 per Ib. coal =7 .96 
 
 
 Water Evaporated =W =7.96 
 
 Log. W =0.9009 
 Log. 539.1 =2.7317 
 
 W. E. Ash =0.0197 
 
 Oxygen in CO 2 
 
 Log. C'" = 1.8 155 
 Log. =0.4259 
 
 Carbon 
 
 CO (by vol.) 
 
 S Log. =8.6304 
 
 Lo?. (1-D) =1.9765 
 
 Log. O"' =0.^4/4 
 
 No. Calories = 4270 
 
 Log. C' =7.5/55 
 
 0'" =1.744 
 
 C0+C0(hy vol.) 
 
 Note. Where the amount of CO present in the flue gas is small, the calculation of the sensible 
 heat carried off by CO may be omitted, and in calculating the heat carried oft as COa, C' taken as =C"'. 
 
COMPOSITION AND HEATING VALUE 
 
 29 
 
 TEST No. 
 
 DATE. 
 
 COAL 'Oiiio No. 6" 
 
 Hydrogen 
 Log. II =.7348 
 Log. (1-D) =1.9766 
 
 Oxygen 
 
 Log. O =7.1341 
 
 Water Equivalent of Products of Combustion 
 
 W. E. CO 2 . . =0.6X4 
 WP PO ^ /"">'> 
 
 Log. H' =~8J_!1. 
 
 
 Log. O' =1 .1106 
 
 W. E. H 2 O 
 
 = 0.222 
 
 Log. H' =2.7113 
 Log. 9 =0.9542 
 Log. Sp. h. =1.6812 
 
 O' =0.1290 
 
 W. E. N 2 
 W. E. SO 2 
 W. E. Ash 
 
 v 
 
 Log. S 
 Log. (t'-t) 
 
 S Log. ....... 
 
 . -1.690 
 = 0.009 
 . =0.020 
 
 . =2.465 
 
 s Log. =L-A4^7- 
 
 O" 
 
 O'" =1.7440 
 O'v =0.4116 
 Ov =0.0312 
 
 =0.3918 
 
 . =2.4771 
 
 . =2.8689 
 
 W. E. H 2 O =0.222 
 
 Oxygen in H 2 O 
 
 Log. H' =2.7113 
 Log. 8 =0.9031 
 
 SO =2.1868 
 
 Log. O'v -~L^1JA 
 
 2O -O' =2.0578 
 
 
 . = 740 
 
 O'v =0.4116 
 
 31(20-0') =N" 
 Log.( 2O-OO =0.3134 
 Log. 31 =0.5229 
 
 
 Latent Heat 
 Log. HaO =1.6655 
 Log.(691.1-0.62t)=2.7717 
 
 Log. N" =0.8363 
 
 Heat Balance 
 
 Calories; % 
 
 S Log. =*L4?Zf 
 
 N" =0.50 
 
 Latent Heat = #?'-4 
 
 Heat in Excess Air 
 
 Log. ( 2O-O') =0.3134 
 Log. 41 =0.6368 
 
 Sulphur 
 
 Log. S =2.5185 
 Log. (1-D) =1.9765 
 
 Log. S' =~2.4950 
 
 Latent Heat .... i 
 Products of combustion 
 Excess Air < 
 
 174 3.9 
 ?40 10.6 
 144 9 . 3 
 0.0 
 168 5.3 
 >70 61.2 
 84 9.7 
 
 Log. Air =0.9502 
 
 Log. S' =2.4950 
 Log. 2 =0.3010 
 Log. Sp. ht. =1.1761 
 
 Log. Air =0.9502 
 Log. Xs Air =0.0049 
 Log. Sp. ht. = 1 . 3766 
 
 Log. (t'-t) =18.4771 
 
 CO 
 
 Unburned coal ... t 
 Water evaporated . . 4- 
 Loss i 
 
 SLog. =3.9721 
 
 Total , 1 6i 
 
 W6~ 100.0 
 
 W. E. SO 2 =0.0094 
 Ov =S' =0.0312 
 
 
 S Log. =2.8038 
 
 No. Calories = 0^4 
 
 Nitrogen 
 Log. N =2.1004 
 Log. (1-D) =1.9766 
 
 Total heat carried off by H 2 O in gases = 
 
 f (100 t) =the heat required to raise water to 100 C. 
 1 539. 1 =the latent heat of vaporization at 100 C. 
 [0.48(f 100) the sensible heat in water vapor from 100 to t'. 
 
 This may.be written 
 
 0.52(100 -t) +0.48(100 -t) +639.1 +0.48 (f -100) =\539.1 +0.52(100 -t)] 
 +0.48(t' -t) =691 . 1 -0.52t(the latent heat) +0.48(t' -t) the sensible 
 heat in water vapor from t up to t'. 
 
 Log. N' =~2.0769 
 
 N' =0.0119 
 N" *=0.*0 
 
 S =6.872 
 
 Log. S =0.8371 
 Log. Sp. ht. = 1 . 3909 
 
 S Log. =0_._2280 
 
 W. E. N 2 =7.55 
 
 If 0.01 of the carbon burns to CO and is calculated to CO 2 instead, the error introduced in sensible 
 heat is about 5.6 cal. where flue gas is 200 C. above boiler-room temperature. 
 
30 
 
 COAL 
 
 THERMAL CAPACITY FROM C. TO TEMPERATURE (t) 
 
 VALUES IN SMALL CALORIES 
 
 
 
 
 d 
 
 d 
 
 . 
 
 
 
 
 
 d 
 
 
 d 
 
 c 
 
 d 
 
 
 ,d 
 
 "o 
 
 
 
 
 o 
 
 "8 d 
 
 
 "8 c 
 
 
 
 *8 3 
 
 
 
 d M 
 
 
 UH 
 
 
 
 
 si* 
 
 i 
 
 m 
 
 a 
 
 
 V 
 
 ft 
 
 111 
 
 a 
 
 
 i 
 
 
 a 
 
 
 25 
 
 *O<! 
 
 M 
 
 ss 
 
 IM 
 
 n'OO 
 
 IM 
 
 OO 
 
 M-j 
 
 Ooo 
 
 <*j 
 
 K osW 
 
 *^ 
 
 
 H 
 
 < 
 
 Q 
 
 52 
 
 Q 
 
 O 
 
 Q 
 
 
 
 Q 
 
 
 
 Q 
 
 o 
 
 Q 
 
 32 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 50 
 ' 68 
 86 
 104 
 122 
 140 
 158 
 176 
 194 
 212 
 230 
 248 
 266 
 284 
 302 
 320 
 338 
 356 
 374 
 392 
 410 
 428 
 446 
 464 
 482 
 500 
 518 
 536 
 554 
 572 
 590 
 608 
 626 
 644 
 662 
 680 
 
 10 
 20 
 30 
 40 
 50 
 60 
 70 
 80 
 90 
 100 
 110 
 120 
 130 
 140 
 150 
 160 
 170 
 180 
 190 
 200 
 210 
 220 
 230 
 240 
 250 
 260 
 270 
 280 
 290 
 300 
 310 
 320 
 330 
 340 
 350 
 360 
 
 2.37 
 4.74 
 7.12 
 9.50 
 11.89 
 14.28 
 16.67 
 19.07 
 21.48 
 23.88 
 26.30 
 28.71 
 31.13 
 33.56 
 35.98 
 38.42 
 40.85 
 43.29 
 45.73 
 48.19 
 50.64 
 53.09 
 55.55 
 58.02 
 60.49 
 62.97 
 65.44 
 67.92 
 70.41 
 72.90 
 75.40 
 77.89 
 80.39 
 82.90 
 85.42 
 87.93 
 
 0.237 
 0.238 
 0.238 
 0,239 
 0.239 
 0.239 
 0.240 
 0.241 
 0.241 
 0.242 
 0.242 
 0.242 
 0.243 
 0.243 
 0.244 
 0.244 
 0.244 
 0.244 
 0.245 
 0.245 
 0.245 
 0.246 
 0.247 
 0.247 
 0.248 
 0.248 
 0.248 
 0.249 
 0.249 
 0.250 
 0.250 
 0.250 
 0.251 
 0.251 
 0.251 
 
 2.44 
 4.88 
 7.33 
 9.78 
 12.24 
 14.70 
 17.17 
 19.64 
 22.11 
 24.59 
 27.07 
 29 . 56 
 32.05 
 34.55 
 37.05 
 39.55 
 42.06 
 44.57 
 47.08 
 49.61 
 52.13 
 54.66 
 57.20 
 59.74 
 62.28 
 64.83 
 67.37 
 69.93 
 72.48 
 75.05 
 77.62 
 80.19 
 82.77 
 85.35 
 87.94 
 90.53 
 
 0.244 
 0.245 
 0.245 
 0.246 
 0.246 
 0.247 
 0.247 
 0.247 
 0.248 
 0.248 
 0.249 
 0.249 
 0.250 
 0.250 
 0.250 
 0.251 
 0.251 
 0.251 
 0.252 
 0.252 
 0.253 
 0.254 
 0.254 
 0.254 
 0.255 
 0.255 
 0.256 
 0.256 
 0.257 
 0.257 
 0.257 
 0.258 
 0.258 
 0.259 
 0.259 
 
 7.1 
 14.3 
 21.6 
 28.9 
 36.3 
 43.7 
 51.2 
 58.8 
 66.4 
 74.1 
 81.8 
 89.6 
 97.5 
 105.4 
 113.4 
 121.5 
 129.6 
 137.8 
 146.0 
 154.3 
 162.7 
 171.1 
 179.6 
 188.1 
 196.9 
 205.6 
 214.2 
 222.9 
 231.8 
 240.7 
 249.7 
 258.8 
 267.9 
 277.0 
 286.3 
 295.5 
 
 0.72 
 0.73 
 0.73 
 0.74 
 0.74 
 0.75 
 0.76 
 0.76 
 0.77 
 0.77 
 0.78 
 0.79 
 0.79 
 0.80 
 0.81 
 0.81 
 0.82 
 0.82 
 0.83 
 0.84 
 0.84 
 0.85 
 0.85 
 0.87 
 0.87 
 0.87 
 0.87 
 0.89 
 0.89 
 0.90 
 0.91 
 0.91 
 0.91 
 0.92 
 0.92 
 
 5.7 
 11.6 
 17.1 
 22.9 
 28.6 
 34.3 
 40.1 
 45.9 
 51.6 
 57.4 
 63.2 
 69.0 
 74.8 
 80.6 
 86.5 
 92.4 
 98.2 
 104.1 
 110.0 
 115.8 
 121.7 
 127.6 
 133.6 
 139.5 
 145.4 
 151.4 
 157.3 
 163.3 
 169.3 
 175.3 
 181.3 
 187.3 
 193.3 
 199.3 
 205.3 
 211.4 
 
 0.55 
 0.55 
 0.56 
 0.57 
 0.57 
 0.58 
 0.58 
 0.58 
 0.58 
 0.58 
 0.58 
 0.58 
 0.58 
 .59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.59 
 0.60 
 0.60 
 0.60 
 0.60 
 0.60 
 0.60 
 0.60 
 0.60 
 0.60 
 0.60 
 0.61 
 
 2.5 
 5.1 
 7.7 
 10.4 
 13.1 
 15.8 
 18.6 
 21.5 
 24.4 
 27.3 
 30.2 
 33.2 
 36.3 
 39.4 
 42.5 
 45.6 
 48.8 
 52.1 
 55.4 
 58.7 
 62.1 
 65.5 
 69.0 
 72.6 
 76.0 
 79.6 
 83.2 
 86.9 
 90.6 
 94.4 
 98.2 
 102.0 
 105.9 
 109.8 
 113.8 
 117.8 
 
 0.26 
 0.26 
 0.27 
 0.27 
 0.27 
 0.28 
 0.29 
 0.29 
 0.29 
 0.29 
 0.30 
 0.31 
 0.31 
 0.31 
 0.31 
 0.32 
 0.33 
 0.33 
 0.33 
 0.34 
 0.34 
 0.35 
 0.35 
 0.35 
 0.36 
 0.36 
 0.37 
 0.37 
 0.38 
 0.38 
 0.38 
 0.39 
 0.39 
 0.40 
 0.40 
 
 40.6 
 81.4 
 122.5 
 163.9 
 205.6 
 247.6 
 289.9 
 332.5 
 375.3 
 418.5 
 462.0 
 505.6 
 549.7 
 594.0 
 638.6 
 683.8 
 728.7 
 774.1 
 819.9 
 866.0 
 912.3 
 958.9 
 1005.9 
 1053.1 
 1100.6 
 1148.4 
 1196.5 
 1244.9 
 1293.5 
 1342.5 
 1391.7 
 1441.2 
 1491.1 
 1541.2 
 1591.6 
 1642.3 
 
 4.08 
 4.11 
 4.14 
 4.17 
 4.20 
 4.23 
 4.26 
 4.28 
 4.32 
 4.35 
 4.36 
 4.41 
 4.43 
 4.46 
 4.49 
 4.52 
 4.54 
 4.58 
 4.61 
 4.63 
 4.66 
 4.70 
 4.72 
 4.75 
 4.78 
 4.81 
 4.84 
 4.86 
 4.90 
 4.92 
 4.95 
 4.99 
 5.01 
 5.04 
 5.07 
 
 1 F. =5 C. ( C. Xs)+32= F. 
 
 1 C. =j}F. ( F-32) X= C. 
 
 To determine the heat necessary to raise a gas from temper- 
 ature t to t' by means of a thermal capacity table, the thermal 
 capacity of the gas at t is subtracted from the thermal capacity 
 of the gas at t'. For example, the heat required to raise 1 gram 
 of air from 20 C. to 320 C. is the difference between the thermal 
 capacity at 320 C. and the thermal capacity at 20 C. = 77.89 
 -4.74 = 73.15 calories. In ordinary boiler test calculations 
 his value can be obtained with sufficient accuracy by simply 
 
COMPOSITION AND HEATING VALUE 
 
 31 
 
 taking the thermal capacity of the gas corresponding to the 
 difference in temperature. 320 C. minus 20 C. = 300 C., 
 and the thermal capacity of the gas at 300 C. by the table is 
 72.90 as against the more exact figure 73.15, an agreement suf- 
 ficiently close to warrant the use of the abbreviated method 
 in most calculations. 
 
 The calculation of No. 6 coal using the data on the logarithmic 
 form and the thermal values using the table of thermal capac- 
 ities is as follows: 
 
 The unburned coal is 0.0527 from which ld = 0.9473. 
 The values of the different constituents in the coal burned for a 
 unit of coal as fired are as follows; 
 
 Carbon . 6903 
 
 Hydrogen 0.0543 
 
 Nitrogen 0.0126 
 
 Oxygen . 1362 
 
 Sulphur 0.3330 
 
 Ash. . . 0.0736 
 
 X(l-d) or 0.9473 = 
 
 C'= 0.6539 
 H'=0.0514 
 N'=0.0119 
 O' =0.1290 
 S' =0.0312 
 A' =0.0697 
 
 The latent heat = 9 X0.0514X (539.1 +0.52 (100)) =274. 
 The sensible heat of the products of combustion using the 
 thermal capacity values of the gases for 300 equals: 
 
 For carbon dioxide = . 6539 X 240 .7 =157.0 
 
 For carbon monoxide = . 0000 X 
 
 For water =0.0514X1342 = 69.0 
 
 For sulphur dioxide =0.0312X94.4 = 3.0 
 
 For nitrogen =0.0119. (See below) 
 
 The sum =229.0. 
 
 The oxygen required for carbon dioxide = 0.6539Xf =1.7437 
 The oxygen required for water =0.0514X8=0.4112 
 
 The oxygen required for sulphur dioxide =0.0312 XI =0.0312 
 
 Total 
 
 Deducting the oxygen in the fuel 
 The oxygen from the air required 
 
 = 2.1861 
 
 0.1290 
 
 ' 2. 0571 
 
 The nitrogen corresponding to the oxygen = 3. 33X2.057 = 6. 85. 
 To this add the nitrogen in the coal, 0.0119 = 6.862. The 
 
32 
 
 COAL 
 
 sensible heat in the nitrogen using the thermal value for 300 
 = 6.862X75.05 = 515.0. 
 
 The excess air = 4. 33 X oxygen required (2.057)X1.01, the 
 ratio of the excess air = 8.996. 
 
 The sensible heat in the excess air = 8. 996 X thermal capacity 
 of air for 300 = 8.996X72.90 = 656. 
 
 The sensible heat of the refuse = [the ash (0.0697) +the 
 unburned coal (0.0527)] X0.16 (the specific heat)X300 = 5.9 
 
 The heat lost due to the formation of 
 
 CO = C'X 
 
 CO 
 
 CO+CO 2 
 
 X 5650 = 000.0 
 
 The heat lost in unburned coal = 0.0527X6980 = 368.0. 
 The heat of the water evaporated = 7.92X539. 1=4270.0 
 The summary of the heat balance is as follows: 
 
 
 Calories. 
 
 Per Cent. 
 
 Latent heat 
 
 274 
 
 3 9 
 
 Products of combustion (including refuse) 
 Excess air 
 
 747 
 656 
 
 10.7 
 9 4 
 
 Carbon monoxide 
 
 000 
 
 
 
 Unburned coal 
 
 368 
 
 5 3 
 
 \Vatp7 evaporated 
 
 4270 
 
 61 2 
 
 Radiation etc 
 
 665 
 
 9 5 
 
 
 
 
 Total 
 
 6980 
 
 100 
 
 
 
 
 The values obtained for the losses in the products of com- 
 bustion and in the excess air are 7 and 12 calories higher than 
 those obtained by use of the logarithmic form. A portion of 
 this difference is due to the use of the log tables but the greater 
 portion is due to the differences in the values taken for specific 
 heats, the values used on the logarithmic form differing some- 
 what from Damour's values which are used in the thermal 
 capacity table. The differences are not large, but are sufficient to 
 call attention to the fact that the actual results obtained depend 
 upon the particular constants used. 
 
 To change calories into B.t.u., it is only necessary to multiply 
 each item in calories by | to obtain the equivalent value in 
 B.t.u. The percentage relations are unchanged. 
 
COMPOSITION AND HEATING VALUE 33 
 
 Balance on basis of coaL fired. The heat balance as given 
 is based on the amount of coal actually fired under the boiler. 
 From this balance the calculation to any basis desired is com- 
 paratively easy. 
 
 (I)' Per pound of dry coal fired. To obtain the values per 
 pound of dry coal fired, divide the values per pound of coal 
 fired by (1 the moisture in the coal). 
 
 (2) Per pound of combustible fired. (Combustible by the 
 Mechanical Engineering Code definition = l (moisture + ash)). 
 To obtain the values per pound of combustible fired, divide the 
 values per pound of coal fired by 1 (moisture + ash). 
 
 (3) Per pound of coal burned. To obtain the values per pound 
 of coal burned omit the item of unburned coal and divide the 
 remaining items per pound of coal fired by (1 the unburned 
 coal). Reduce to a basis of 100 per cent. 
 
 (4) Per pound of dry coal burned. Omit the item of unburned 
 coal and divide the remaining items per pound of coal fired by 
 [(1 the moisture) X(l the unburned coal)]. Reduce to a basis 
 of 100 per cent. 
 
 (5) Per pound of combustible burned. Omit the item of 
 unburned coal and divide the other values per pound of coal 
 fired by [[1 (moisture + ash)] X (1 the unburned coal)]. Reduce 
 to a basis of 100 per cent. 
 
 For purposes of comparing different values, or compar- 
 ing boiler efficiency, some of these modified forms are desirable, 
 but there appears no valid reason for not making the i: coal 
 as fired " the primary basis. Certainly the consumer testing 
 out two coals needs this basis as he pays for the coal in the ash 
 pit just the same as for that which is burned and a report of a 
 balance omitting the item of unburned coal is hardly to be con- 
 sidered as complete. 
 
 The foregoing heat balance in its essential details has 
 been used in the Departments of Metallurgy and Mechan- 
 ical Engineering at the Ohio State University for the past 
 fifteen years and graduates of these departments who conduct 
 boiler tests are consistently using heat balance forms based 
 on these principles. The mechanical engineering profession, in 
 general, has not given this basis of calculation the considera- 
 tion that it deserves, but has continued to use the older code 
 form. 
 
34 COAL 
 
 The Code balance recommended by the American Society 
 of Mechanical Engineers is based on the combustible actually 
 burned. The distribution of the items is as follows: 
 
 HEAT BALANCE OR DISTRIBUTION OF THE HEATING VALUE OF THE 
 COMBUSTIBLE 
 
 Total Heat Value of 1 Pound of Combustible B.t.u. Per Cent. 
 
 1. Heat absorbed by the boiler = evaporation from and at 
 
 212 per pound of combustible X 965. 7 
 
 2. Loss due to moisture in coal = per cent of moisture re- 
 
 ferred to combustible divided by 100 X [ (2 12 -t +966 + 
 0.48(T-212)] (t= temperature of air in the boiler 
 room, T = that of the flue gases.) 
 
 3. Loss due to moisture formed by the burning of hydrogen 
 
 = per cent of hydrogen to combustible divided by 
 100X9X[(212-0+966+0.48(T-212)] * 
 
 4. Loss due to heat carried away in the dry chimney gases = 
 
 weight of gas per pound of combustible X0.24(T ) 
 
 5. Loss due to incomplete combustion of carbon = 
 
 CO ..per cent C in combustible 
 
 co 2 +co x ~loo~~ 
 
 6. Loss due to unconsumed hydrogen and hydrocarbons, to 
 
 heating the moisture in the air, to radiation, and un- 
 accounted for 
 
 Totals 100.00 
 
 A comparison of the items given in the heat balance of the 
 coal as fired with the items of the Code balance is as follows: 
 
 Item. Balance Coal as Fired. Code Balance. 
 
 No. 1. Latent heat corresponds to Nos. 2 and 3 
 
 No. 2. Sensible heat in products of combustion corresponds to part of Nos. 2, 
 
 3, and 4 
 No. 3. Heat in the excess air corresponds to remainder of 
 
 No. 4 
 
 No. 4. Heat lost due to CO corresponds to No. 5 
 
 No. 5. Loss due to unburned coal not included 
 
 No. 6. Heat in the water evaporated corresponds to No. 1 
 
 No. 7. Radiation and other losses corresponds to part of No. 6 
 
 A balance to be satisfactory should show where all the heat 
 goes and should separate the variable heat losses into separate 
 items in order that the magnitude of each can be readily appre- 
 ciated. In this respect the enumeration of the heat lost in 
 the unburned coal and the heat lost in the excess air as separate 
 
COMPOSITION AND HEATING VALUE 
 
 35 
 
 items is a decided improvement over the code form. The 
 separation of relatively fixed losses from the more variable ones 
 is certainly desirable in order to more clearly appreciate the 
 magnitude of the variable losses, as loss due to too much air 
 compared to the loss from formation of CO due to too little air 
 or the losses in sensible heat for different temperatures of the 
 flue gases and different percentages of excess air. For example, 
 what are the losses in burning Ohio No. 6 (Hocking) Coal with 50 
 per cent excess air and 0.2 per cent of CO in the flue gas and a 
 flue temperature of 350 C.; or with 150 per cent excess air and 
 no CO in the flue gas at temperatures of 200 and 300 compared 
 with the given conditions of 100 per cent excess air, no CO and 
 a temperature of 300 C? These conditions as to excess air 
 correspond to flue gas analyses as follows: 
 
 ANALYSIS OF FLUE GASES WITH VARYING EXCESS AIR 
 
 
 50 Per Cent. 
 
 100 Per Cent. 
 
 150 Per Cent. 
 
 CO 2 
 2 
 CO 
 
 12.7 
 7.0 
 0.2 
 
 9.5 
 10.4 
 0.0 
 
 7.4 
 12.5 
 0.0 
 
 N 2 
 
 80 1 
 
 80 1 
 
 80 1 
 
 
 
 
 
 
 100.0 
 
 100.0 
 
 100.0 
 
 The carbon burned to CO with 50 per cent excess air is 
 CO 2 
 
 == ^"^' ^'^ ^ ^-6538 (the car ^ on burned per 
 
 unit of coal fired) =0.01 gram per gram of coal fired. 
 
 The calculated losses with the different conditions are as 
 follows : 
 
 100 per cent excess air, 300 C., per cent CO 
 
 Products of combustion = /as already calculatedX 740 
 Excess air ............. = I in the heat balance. I 644 
 
 CO .................. = \See log sheet. / 
 
 Total. 
 
 1384 
 
36 COAL 
 
 50 per cent excess air, 350 C., 0.2 per cent CO 
 
 350 
 
 Products of combustion = 740 X - = 863 
 
 oOO 
 
 350 
 
 Excess air = 644X^X^- =376 
 
 oOO 
 
 CO.. .=0.01X0.5650= 57 
 
 Total 1296 
 
 150 per cent excess air, 200 C., per cent CO 
 
 Products of combustion = 740 X =493 
 
 oUU 
 
 200 
 
 Excess air = 644Xf X-- =644 
 
 oOO 
 
 CO.. 
 
 Total 1147 
 
 150 per cent excess air, 300. C., per cent CO 
 
 300 
 
 Products of combustion = 740 X =740 
 
 oUU 
 
 Excess air =644Xf = = 966 
 
 oOO 
 
 CO.. 
 
 Total 1706 
 
 These widely divergent values serve to show the importance 
 of a proper relation of excess air to flue temperature and the 
 importance of having the heat balance stated in such a form as 
 to admit of a ready comparison of these losses. 
 
 Variation of available heating power. The available heating 
 power of a coal as used under a boiler is greatly modified by the 
 adaptability of the coal to burn on the particular grate and in 
 the particular furnace used. Coals differ in the percentage of 
 the excess of air required for their complete combustion and it 
 is well known that experience in the use of any coal is necessary 
 to use it to the best advantage. Coals which contain, or furnish 
 on burning, large percentages of water will show low percentages 
 
COMPOSITION AND HEATING VALUE 37 
 
 of available heat calculated on their total calorific value on 
 account of the large amount of the latent heat and the large 
 quantity of sensible heat carried off by the water vapor in the 
 products of combustion. As has just been shown, the amount 
 of sensible heat carried off in the products of combustion increases 
 directly with the temperature of the escaping gas and the best 
 results for available heating power are usually not secured where 
 the flue temperature is excessive. This is especially true where 
 the amount of moisture in the coal is large. The amount of 
 ash present in the coal has an important effect on the available 
 heating power realizable as complete combustion and low excess 
 air are hard to obtain with high ash or where the ash clinkers 
 badly. Aside from its effect on the excess air and complete 
 combustion, large amounts of ash involve extra expense in 
 handling and on this account have a negative heating value. 
 The loss of heat due to formation of smoke and soot varies with 
 the coal used and also with the type of furnace, but the actual 
 loss from this cause is in no case very large and coals which 
 have a tendency to form large amounts of smoke and soot are 
 objectionable, more on account of being a nuisance and a menace 
 to public health, or because the deposition of soot on the heat 
 absorbing surfaces of the boiler prevents the ready absorption 
 of heat by the boiler rather than on account of the loss of heat 
 due to failure of the smoke and soot to burn, 
 
 COMMERCIAL VALUE OF COAL 
 
 For most purposes the relative commercial value of a coal is 
 dependent upon the amount of heat or power which can be obtained 
 from a given amount of the coal, or in other words is dependent 
 upon the available heating value of the coal. In most cases the 
 available heating value varies directly with the total heating 
 value, and, other things being equal, the value of a coal is 
 dependent upon the total number of heat units it contains. This 
 is however not always the case. A number of factors, some 
 of which have already been mentioned, as clinkering of ash, 
 adaptability of one coal rather than another to the furnace and 
 stokers in use, etc., may cause the total value, if considered alone, 
 to be somewhat misleading and some coals having a lower total 
 calorific value may under certain conditions of practice give 
 
38 COAL 
 
 a higher actual available value than other coals showing a 
 greater total value. 
 
 In general, however, the coal having higher total healing value 
 is the better coal and the seller of the coal having the lower heating 
 value should show under what special conditions an inherently 
 inferior coal may actually be the superior coal in production of 
 heat or power, or if not actually superior, show that it actually is 
 the more desirable coal under the conditions where it is to be used. 
 
 Actual testing under average working conditions is sometimes 
 necessary to prove or disprove the claim of any certain coal. A 
 comparison of the results of a boiler test made by experts under the 
 best obtainable conditions with the every-day results of the ordi- 
 nary boiler crew is not the way to prove or disprove it, but only 
 shows that the average conditions may be far from satisfactory. 
 The boiler tests if taken as a guide should be made on both coals 
 and under similar working conditions. The average results for a 
 considerable period of time on one coal compared with the average 
 results on another coal for the same length of time, if conditions 
 of firing, weather conditions, etc., are similar ought, to be con- 
 clusive as to which coal is better under the same conditions. This 
 does not necessarily show how much better either coal might be 
 if the firing and regulations were as good as they should be. 
 Boiler tests with expert handling should show what maybe done; 
 how nearly every-day results can come to this is largely depen- 
 dent upon the efficiency of the boiler crew. 
 
 RESIDUAL COAL 
 
 If the variable factors of coal, moisture, ash and sulphur, 
 be removed the remainder may be considered as consisting of a 
 practically uniform residual coal substance which while complex 
 in its nature is fairly uniform in composition and heating value. 
 The value of the coal actually bought and sold is largely depen- 
 dent upon the actual percentage of residual coal present. In any 
 given seam the heating value of a unit amount of the residual 
 coal is fairly constant and different samples of coal from the 
 same bench or seam will differ from one another in heating value 
 according as they differ in the amounts of moisture, ash and sul- 
 phur present, or stated in another way, as they differ in the 
 amount of actual " residual coal " present in a unit amount of each. 
 
COMPOSITION AND HEATING VALUE 39 
 
 Heating value of residual coal, H. The heating value of a 
 unit weight of the residual coal was designated by the late Pro- 
 fessor N. W. Lord as H and is found as follows: 
 
 From the total heating value of the sample subtract that 
 due to the sulphur present which equals the amount of sulphur 
 times 2250 calories or times 4050 British thermal units. Divide 
 the remainder by 1 minus the sum of the amount of moisture, 
 ash and sulphur present. The product is the heating value per 
 unit of residual coal, or 
 
 _ calorific value 2250 (sulphur) 
 1 (moisture + ash + sulphur) 
 
 The average of 65 samples of Ohio No. 6 coal as given in 
 Bulletin No. 9 of the Ohio Geological Survey is as follows: 
 
 Moisture ............................. 0.0556 
 
 Ash ................................. 0.0736 
 
 Sulphur .......... . ................... 0.0330 
 
 Calorific value ........................ 6980 calories 
 
 from which, 
 
 6980-0.0330X2250 
 
 or expressed in British thermal units, 
 
 8243X1 = 14837. 
 
 Calculation of heating value from proximate analysis and 
 from H. Since the heating value of the coal is due to the residual 
 coal and sulphur present, the heating value of one sample may 
 be calculated from the determined heating value of another sample 
 if the moisture, ash and sulphur in both samples are known. For 
 example, to calculate the heating value of a sample of Ohio No. 
 6 coal, Sample No. 115 of Bulletin No. 9 of the Ohio Geological 
 Survey contains, 
 
 Moisture ............................. . 0472 
 
 Ash ................................. 0.0547 
 
 Sulphur .............................. . 0405 
 
 The amount of residual coal 
 
 = 1 - (0.0472+0.0547+0.0405) =0.8576. 
 
40 COAL 
 
 Multiplying the value of H above 8243 by this value 
 = 8243X0.8576 = 7069 whfich is the heat of the residual coal. 
 To this add the heat due to the sulphur = 0.0405X2250 = 91 
 calories. The total heating value = 7069 +91 = 7160. The calo- 
 rific value as actually determined was 7199 or a difference of 39 
 calories. 
 
 Accuracy of calculated heating value. Where the samples 
 from which H is determined are from the same portion of the 
 seam as the sample, the heating value of which is to be determined, 
 and where the variations in moisture, ash and sulphur are not too 
 large the calculated results agree fairly well with actual determin- 
 ations. 
 
 Results for heating value calculated on oxidized and weathered 
 samples are likely to be much too high, and it is unsafe to apply 
 this calculation to such samples. 
 
 Results on widely different samples. As it is difficult or 
 impossible to determine the exact relation of the ash obtained to 
 the amount of mineral matter as it occurs in the coal where the 
 variations in ash and sulphur are large, the results by this formula 
 may be considerably in error. 
 
 Effect of changes in ash on accuracy of calculation. As pre- 
 viously stated under the subject of " Ash," the ash as actually 
 weighed is too high by f of 1 per cent for each per cent of sul- 
 phur in the coal as pyrite, and too low by about 0.17 of 1 per cent 
 for each per cent of ash originally present in the coal as clay or 
 shale. Where the differences in ash and sulphur in the different 
 samples are due to differences in amounts of clay and pyrite, 
 application of this formula in a modified form, using a " corrected 
 ash " for the difference in ash in the two samples, gives more con- 
 cordant results. Designating the amounts of ash and sulphur 
 in the samples from which H has been determined as A and S 
 and the amounts of ash and sulphur in the samples the calorific 
 value of which is to be determined by A' and S f , then the ash 
 corrected or A' (corrected) = 
 
 from which the corrected ash in Sample No. 115 corresponding to 
 0.0547 = 0.0547 - f (0.0405 -0.0330) + .17(0.0547 - 0.0736 - f (0.0405 
 
COMPOSITION AND HEATING VALUE 
 
 41 
 
 -0.0330)] =0.0482 or 0.0065 less ash than the amount as actually 
 weighed up. Using this corrected value gives, 
 
 1- (0.0472+0.0482+0.0405) =0.8641 
 
 as the amount of residual coal as against 0.8576 by the first 
 calculation. The calorific value of the sample is therefore, 
 
 0.8641X8243+0.0405X2250 = 7214 calories 
 
 as against 7160 calories with the uncorrected ash and 7199 calories 
 as actually determined in a bomb calorimeter. The calculated 
 value with the uncorrected ash is 39 calories lower than the value 
 determined in the calorimeter while the calculated value with 
 the corrected ash is 15 calories higher or a difference of 24 calories 
 in favor of the result by the corrected ash. 
 
 As further illustration, samples of Ohio No. 6 coal, samples 
 Nos. 92 and 93 in Bulletin No. 9 of the Ohio Geological Survey 
 contain nearly the same amount of ash but differ in sulphur by 
 1.53 per cent. The moisture, ash and sulphur and determined 
 calorific values are as follows: 
 
 
 Sample No. 92. 
 
 Sample No. 93. 
 
 Moisture 
 Ash 
 
 5.25 
 
 9 86 
 
 5.90 
 10 10 
 
 Sulphur 
 Determined calorific value 
 
 3.43 
 6773 
 
 4.96 
 6686 
 
 The value obtained for H in sample No. 92 is 8220. The 
 calculated calorific value of Sample No. 93, using this value for H 
 and making no corrections for the ash is 6609. Assuming that the 
 difference in sulphur is due to a difference in the amount of pyrite 
 present, and correcting the ash by subtracting f of this sulphur 
 difference and using this corrected ash, the calculated value ob- 
 tained is 6656. With the uncorrected ash the calculated value is 
 77 calories lower than the actually determined value. With the 
 corrected ash it is only 30 calories lower for this sample, a differ- 
 ence of 47 calories in favor of a corrected ash. 
 
 Comparison of samples with the same sulphur content. Two 
 other samples of Ohio No. 6 coal, Samples Nos. 99 and 104, in 
 
42 
 
 COAL 
 
 Bulletin No. 9 of the Ohio Geological Survey, have essentially 
 the same sulphur content but differ in ash. The moisture, ash, 
 sulphur and determined calorific value of the samples are as 
 follows : 
 
 
 Sample No. 99. 
 
 Sample No. 104. 
 
 Moisture 
 
 5.44 
 
 5 55 
 
 Ash 
 
 9 28 
 
 5 23 
 
 Sulphur 
 
 3 77 
 
 3 63 
 
 Calorific value 
 
 6822 
 
 7191 
 
 
 
 
 The value obtained for H in Sample No. 99 is 8265. Cal- 
 culating the calorific value of 104 from this value for H and 
 making no correction for the ash gives 7156 as the calorific value. 
 Assuming that the difference in ash is due to differences in amount 
 of slate or clay in the sample, and correcting the ash and calcu- 
 lating the calorific value with corrected ash, the value obtained 
 is 7213 as against 7191 as actually determined in a calorimeter. 
 The uncorrected ash result is 35 calories too low, the corrected 
 ash is 22 calories too high or a difference of 13 calories in favor of 
 the corrected ash. 
 
 The use of this " corrected ash " should be restricted to com- 
 parisons of the ash in the two samples, which is practically limit- 
 ing it to the ash difference. It cannot be used in the formula for 
 obtaining the value for H, as much of the sulphur present in the 
 sample may be present as organic sulphur, also a portion of the 
 ash is present in other forms, as clay and shale. A failure to cor- 
 rect for the amounts of clay and pyrite means that the actual 
 value for H is too low or too high. This is however of little im- 
 portance as in obtaining the calculated calorific value of another 
 sample, approximately the same error is present as in the sample 
 from which H is derived and in the calculation one error practically 
 eliminates the other and only the difference in amounts of clay 
 and pyrite need be allowed for. Since in most samples of the same 
 coal the difference in ash and sulphur is largely due to differences 
 in amount of clay and pyrite present, this corrected formula 
 should in most cases give somewhat more accurate results. 
 
CHAPTER II 
 
 CHEMICAL ANALYSIS OF COAL 
 PROXIMATE ANALYSIS 
 
 THIS analysis gives the composition of the coal under four 
 headings as follows: moisture, volatile matter, fixed carbon, 
 and ash. 
 
 The results obtained are more or less dependent upon the exact 
 process used and small variations in working out the details of the 
 process may make a considerable difference in the results actually 
 obtained, while a distinctly different process gives radically 
 different values for some of the determinations. Hence the re- 
 sults are relative and not absolute and should be so regarded by 
 both the chemist and the user of the coal. The efforts of some 
 chemists to find a method of determining the " true moisture " 
 in coal might better be spent in trying to simplify and im- 
 prove the method already in use for obtaining the comparative 
 value. 
 
 Moisture. As has already been stated, the term moisture 
 includes only the more or less loosely held water which is driven 
 off by heating 1 gram of the finely ground sample for 1 hour 
 at 105 C. A finely ground sample of coal during the operation 
 undergoes changes due to oxidation and escape of gases, hence 
 the actual value obtained for moisture is the amount of water 
 driven off plus or minus any oxidation changes. In most 
 coals if not ground excessively fine these oxidation changes are 
 of minor importance compared to the moisture loss so that the 
 reporting of this net loss as moisture does not lead to any serious 
 errors although it practically never represents the exact amount 
 of water expelled. A sample of coal which has been heated for 
 1 hour at 105 will give off more moisture and undergo further 
 oxidation changes if heated to a still higher temperature, the 
 
 43 
 
44 COAL 
 
 amount of moisture given off depending upon the kind of coal and 
 upon the increase in temperature. The extent of the oxidation 
 also increases with the temperature and varies with the kind of 
 coal and fineness of the sample. While it is true that the results 
 for moisture obtained by heating the sample to 105 have no 
 absolute value but merely a relative one, it is equally true when 
 two samples of approximately the same kind of coal are treated 
 in the same way for moisture by heating to 105, the difference 
 in the results obtained show very closely the difference in the 
 amount of loosely held moisture in the coal. Usually this is what 
 the user of the coal wishes to know and on this account the mois- 
 ture determination has importance and value. 
 
 Volatile matter. The determination of volatile matter is an 
 arbitrary one and the results are obtained by following a certain 
 prescribed procedure, which is essentially to heat 1 gram of the 
 finely ground sample in a covered platinum crucible over the full 
 flame of a Bunsen burner for seven minutes. The loss in weight 
 represents moisture plus volatile matter. Subtracting the value 
 for moisture from this result gives the amount of volatile matter 
 in the coal. This determination cannot be regarded as entirely 
 satisfactory as the result obtained is to a considerable degree 
 dependent upon the particular conditions under which the sample 
 was run and two different chemists in two different laboratories 
 both trying to follow out the same method of procedure may 
 easily obtain results for volatile matter upon the same sample of 
 coal which may differ by 2 or 3 per cent. Furthermore, some high 
 moisture coals suffer mechanical losses during the heating to 
 drive off the volatile matter. Such samples require special treat- 
 ment to insure results of even approximate accuracy. On 
 account of such possible differences and errors this determina- 
 tion cannot be regarded as very exact. It is, however, true 
 that the same chemist working in the same way with the same 
 crucibles, the same height of gas flame, the same Bunsen burner, 
 etc., can obtain results which will duplicate within a few tenths 
 of 1 per cent, and in control work the same chemist's results on 
 approximately the same coals ought to be comparable among 
 themselves to within less than 1 per cent. The amount of vola- 
 tile matter in itself gives very little idea of the coal, as two coals 
 with approximately the same amount of volatile matter may 
 differ very greatly in heating value, physical properties, etc., 
 
CHEMICAL ANALYSIS OF COAL 45 
 
 and any significance which the determination of volatile 
 matter actually has is largely a relative one which may be of 
 value when the same or similar coals are compared with one 
 another. 
 
 The volatile matter consists essentially of any combined 
 water in the coal plus a portion of the sulphur, on an average 
 probably about one-half of the total sulphur present in the coal, 
 plus the nitrogen in the coal, plus hydrocarbons of unknown 
 and varying composition. The nitrogen and combined water 
 in the volatile matter have no heating value and, if present 
 large amounts, the heating value of the combustible will be 
 correspondingly lower. 
 
 Fixed carbon. Fixed carbon represents the difference obtained 
 by subtracting the percentage of moisture, volatile matter and 
 ash from 100. The fixed carbon as its name indicates is mostly 
 carbon. Approximately one-half the sulphur in the coal present 
 in the form of pyrite and a variable portion of that present as 
 organic sulphur remains with the fixed carbon and the heating 
 value of the fixed carbon is, on this account, somewhat lower 
 than that of pure carbon. On the other hand, small amounts 
 of hydrogen may be retained in the fixed carbon which would 
 slightly increase its heating value. In most coals the heating 
 value per unit of the fixed carbon is not far from that of car- 
 bon 8080 and this value may be used in estimating heat values 
 without any great error. With high sulphur coals, a somewhat 
 lower value, approximately 30 calories lower for each per cent of 
 sulphur in the coal, is probably more nearly a correct value. 
 This is based on the assumption that one-half of the sulphur 
 remains with the fixed carbon and that not more than traces of 
 hydrogen are retained in the fixed carbon. 
 
 Ash. As ordinarily reported this is the weight of ignited 
 mineral matter in the coal. The relation of this ignited 
 mineral matter to the mineral matter in the coal has already 
 been discussed in detail and no especial points need repeating 
 here. 
 
 Comparison of proximate analyses of certain coals. As illus- 
 trations of the proximate analyses of widely different coals the 
 following determinations including sulphur and calorific value 
 are taken from Professional Paper No. 48 and Bulletin No. 290 
 of the U. S. Geological Survey: 
 
46 
 
 COAL 
 
 
 North D. 
 No. 1. 
 
 Wyo. 
 No. 1. 
 
 Colorado 
 No. 1. 
 
 Mon. 
 No. 1. 
 
 Illinois 
 No, 4. 
 
 Indiana 
 No. 1. 
 
 Ohio 
 No. 8. 
 
 Moisture 
 
 35 38 
 
 22 63 
 
 18 68 
 
 11 05 
 
 12 91 
 
 11 40 
 
 7 55 
 
 Volatile matter. 
 Fixed carbon. . 
 Ash 
 
 29.59 
 25.68 
 9.35 
 
 35.68 
 37.19 
 4 50 
 
 34.88 
 40.45 
 5 99 
 
 35.90 
 
 42.08 
 10 97 
 
 31.90 
 43.55 
 11 64 
 
 33.81 
 41.39 
 13 40 
 
 38.00 
 46.08 
 8 37 
 
 
 
 
 
 
 
 
 
 Sulphur 
 
 100.00 
 1.55 
 
 100.00 
 0.59 
 
 100.00 
 0.55 
 
 100.00 
 1 73 
 
 100.00 
 1 32 
 
 100.00 
 2 50 
 
 100.00 
 
 2 84 
 
 Calories 
 
 3846 
 
 5408 
 
 5635 
 
 5855 
 
 6002 
 
 6145 
 
 6738 
 
 
 
 
 
 
 
 
 
 
 
 (N 
 
 
 
 
 
 o 
 
 (N 
 
 
 
 6 
 
 
 
 
 
 
 
 
 <N 
 
 55 
 
 rH* 
 
 r ~ l 
 
 6 
 
 
 
 
 
 6 
 
 
 C 
 
 >> 
 
 6 
 
 ^6 
 
 ^ 
 
 6 
 
 55 
 
 55 
 
 
 55 
 
 
 
 55 
 
 << 
 
 2 
 
 55 
 
 rt 
 
 2 
 
 
 03 
 
 
 
 >j 
 
 S 
 
 03 
 
 '5 
 
 '3 
 
 
 1 
 
 fc 
 
 I 
 
 o 
 
 '? 
 
 S 
 
 "S 
 
 'S 
 
 
 1 
 
 H 
 
 03 
 
 3 
 
 a 
 
 > 
 
 1 
 
 
 
 
 
 c 
 
 
 0) 
 
 
 
 
 
 
 **^ 
 
 c3 
 
 < 
 
 
 0) 
 
 <jj 
 
 OT 
 
 S 
 
 
 
 -9 
 a 
 
 
 
 ^ 
 
 
 ^ 
 
 OJ 
 
 Moisture 
 
 3.36 
 
 4.45 
 
 2.34 
 
 3.10 
 
 1.75 
 
 2.36 
 
 1.75 
 
 1.72 
 
 Volatile matter. . 
 
 32.88 
 
 36.15 
 
 31.84 
 
 36.12 
 
 36.77 
 
 12.68 
 
 18.59 
 
 17.85 
 
 Fixed carbon . . . 
 
 51.33 
 
 48.40 
 
 53.28 
 
 56 . 39 
 
 55.14 
 
 72.88 
 
 75.08 
 
 73.56 
 
 Ash 
 
 12.43 
 
 11.00 
 
 12.54 
 
 4.39 
 
 6.34 
 
 12.08 
 
 4.58 
 
 6.87 
 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 Sulphur 
 
 1.01 
 
 1 . 52 
 
 0.72 
 
 1.22 
 
 0.90 
 
 1.99 
 
 0.56 
 
 0.68 
 
 Calories 
 
 6861 
 
 7004 
 
 7142 
 
 7860 
 
 7837 
 
 7366 
 
 8346 
 
 8095 
 
 
 
 
 
 
 
 
 
 
 This series of samples was selected not as representing the 
 coals of these regions but to show the wide variation in moisture 
 and volatile matter and fixed carbon in different coals and the 
 variable heating value of the volatile matter. The variable 
 heating value of the volatile matter can be most strikingly 
 seen by comparing the different values for H in these differ- 
 ent coals. H, as has already been explained, is the heating 
 value per unit of " residual coal " and is obtained by dividing 
 the total calorific value less the calorific value of the sulphur 
 present by one minus the sum of the moisture, ash and sul- 
 phur. The values for H for the different samples are as 
 follows: 
 
CHEMICAL ANALYSIS OF COAL 
 
 47 
 
 VALUE FOR // 
 
 
 Calorics. 
 
 Nitrogen, 
 Per Cent. 
 
 North Dakota, No. 1 
 
 7094 
 
 0.54 
 
 Wyoming No 1 . .... 
 
 7464 
 
 1 02 
 
 Colorado, No. 1 
 
 7519 
 
 1.15 
 
 JMontana No 1 
 
 7627 
 
 1 33 
 
 Illinois, No. 4 
 
 8056 
 
 1 15 
 
 Indiana No 1 
 
 8375 
 
 1 18 
 
 Ohio, No. 8 
 
 8216 
 
 1 29 
 
 Alabama No 2 
 
 8219 
 
 1 54 
 
 Indian Territory, No. 2 
 
 8395 
 
 1 67 
 
 Alabama, No. 1 
 
 8443 
 
 65 
 
 Kentucky, No. 1 
 
 8580 
 
 83 
 
 West Virginia, No. 1 
 
 8589 
 
 54 
 
 Arkansas, No 5 
 
 8760 
 
 37 
 
 West Virginia, No. 10 
 West Virginia, No. 12 
 
 8950 
 8905 
 
 .06 
 33 
 
 
 
 
 The value ranges from about 7100 to over 8900, an extreme 
 difference of nearly 1900 calories. As the moisture and ash in 
 the samples have no heating value and the value of the fixed 
 carbon is approximately the same per unit of fixed carbon in all 
 the samples^the great difference in the value of H is due to the 
 variable composition of .this volatile matter. The inert con- 
 stituents of the volatile matter are nitrogen and combined water. 
 The amount of nitrogen in the different samples is given in 
 the foregoing table. 
 
 The extreme difference is less than 1J per cent and the effect 
 of nitrogen on the value for H is of minor importance. 
 
 As has been mentioned in connection with Dulong's formula 
 and its modifications, a greater part but not all of the oxygen in 
 the coal appears in the form of water. The exact relation between 
 the small amount properly belonging with carbon and that 
 present as water varies with each coal, but for purposes of com- 
 parison all of it can be assumed as present as water without 
 serious error, bearing in mind however, that the values for 
 combined water on this assumption are all somewhat high. On 
 this assumption the combined water in the samples is as 
 follows : 
 
48 
 
 COAL 
 
 
 Oxygen. 
 
 Total 
 Water. 
 
 Moisture. 
 
 Combined 
 Water. 
 
 North Dakota, No. 1 
 
 41 72 
 
 46 93 
 
 35 38 
 
 11 55 
 
 Wyoming, No. 1 
 
 32 59 
 
 36 66 
 
 22 63 
 
 14 03 
 
 Colorado, No. 1 
 
 28 78 
 
 32 38 
 
 18 68 
 
 13 70 
 
 Montana, No. 1 
 
 21 52 
 
 24 21 
 
 11 05 
 
 13 16 
 
 Illinois No 4 
 
 19 72 
 
 22 18 
 
 12 91 
 
 9 27 
 
 Indiana, No. 1 
 Ohio No 8 
 
 17.21 
 15 00 
 
 19.36 
 16 87 
 
 11.40 
 
 7 55 
 
 7.96 
 9 32 
 
 Alabama, No. 2 
 
 11 49 
 
 12 93 
 
 3 36 
 
 9 57 
 
 Indian Territory, No. 2 
 
 11 15 
 
 12 54 
 
 4 45 
 
 8 09 
 
 Alabama No 1 
 
 8 50 
 
 9 56 
 
 2 34 
 
 7 22 
 
 Kentucky, No. 1 
 
 9 76 
 
 10 98 
 
 3 10 
 
 7 88 
 
 West Virginia, No. 1 
 
 7 94 
 
 8 93 
 
 1 75 
 
 7 18 
 
 Arkansas, No. 5 
 
 4 30 
 
 4 84 
 
 2 36 
 
 2 48 
 
 West Virginia, No. 10 
 
 4 18 
 
 4 70 
 
 1 75 
 
 2 95 
 
 West Virginia, No. 12 
 
 3 98 
 
 4 48 
 
 1 72 
 
 2 76 
 
 
 
 
 
 
 An inspection of the values for combined water shows a 
 variation of from 14 per cent in the highest to 2J per cent in 
 the lowest, or a variation of about 12 per cent. The highest 
 combined water however is not found in the sample having the 
 lowest value for H so that the variable composition of the volatile 
 hydrocarbons must be compared in order to more completely 
 explain the variation in H . The total hydrogen in these samples 
 as shown by the ultimate analysis and the available hydrogen 
 which is the amount left after subtracting that as combined 
 water are as follows: 
 
 
 Total 
 Hydrogen. 
 
 Available 
 Hydrogen. 
 
 North Dakota No 1 
 
 6 61 
 
 1 40 
 
 Wyoming No 1 .... 
 
 6 39 
 
 2 32 
 
 Colorado, No. 1 
 
 6 07 
 
 2 47 
 
 IVtontana No 1 
 
 5 37 
 
 2 68 
 
 Illinois No 4 
 
 5 43 
 
 2 97 
 
 Indiana, No. 1 
 
 5 37 
 
 3 22 
 
 Ohio No 8 
 
 5 48 
 
 3 60 
 
 Alabama No 2 
 
 4 84 
 
 3 40 
 
 Indian Territory No 2 
 
 5 17 
 
 3 78 
 
 Alabama No 1 
 
 5 01 
 
 3 95 
 
 Kentucky No. 1 
 
 5 43 
 
 4 21 
 
 \Vest Virginia No 1 
 
 5 28 
 
 4 29 
 
 Arkansas No 5 
 
 3 82 
 
 3 28 
 
 West Virginia, No. 10 
 
 4 65 
 
 4 13 
 
 West Virginia No 12 
 
 4 43 
 
 3 93 
 
 
 
 
CHEMICAL ANALYSIS OF COAL 
 
 49 
 
 Listing the volatile constituents under the following head- 
 ings: combined water, nitrogen, sulphur, available hydrogen 
 and carbon, the following values are obtained for the different 
 samples: 
 
 
 Total 
 Volatile. 
 
 Com- 
 bined 
 Water. 
 
 Nitrogen. 
 
 Sulphur. 
 
 Avail- 
 able 
 Hydro- 
 gen. 
 
 Carbon. 
 
 North Dakota, No. 1 
 Wyoming, No. 1 
 
 29.59 
 35 58 
 
 11.55 
 14 03 
 
 0.54 
 1 02 
 
 0.78 
 0.30 
 
 1.40 
 2 32 
 
 15.32 
 17 91 
 
 Colorado, No 1 
 
 Montana, No. 1 
 
 34.88 
 35 90 
 
 13.70 
 13 16 
 
 1.15 
 1 33 
 
 0.28 
 86 
 
 2.47 
 2 68 
 
 17.28 
 17 87 
 
 Illinois, No. 4 
 Indiana, No. 1 
 
 31.90 
 33.81 
 
 9.27 
 7.96 
 
 1.15 
 1.18 
 
 0.66 
 1.25 
 
 2.97 
 3.22 
 
 17.85 
 20.20 
 
 Ohio No. 8 
 
 38 00 
 
 9 32 
 
 1 29 
 
 1 90 
 
 3 60 
 
 21.89 
 
 Alabama, No. 2 
 Indian Territory, No. 2 . . 
 Alabama, No. 1 
 
 32.88 
 36.15 
 31.84 
 
 9.57 
 8.09 
 
 7 22 
 
 1.54 
 1.67 
 1 65 
 
 0.50 
 0.51 
 36 
 
 3.40 
 3.78 
 3.95 
 
 17.87 
 22.10 
 18.66 
 
 Kentucky, No. 1 
 
 36.12 
 
 7.88 
 
 1.83 
 
 0.72 
 
 4.21 
 
 21.48 
 
 West Virginia, No. 1 
 Arkansas, No. 5 
 West Virginia, No. 10 
 West Virginia, No. 12. ... 
 
 36.77 
 12.68 
 18.59 
 17.85 
 
 7.18 
 2.48 
 2.95 
 2.76 
 
 1.54 
 1.37 
 1.06 
 1.33 
 
 0.30 
 1.00 
 0.19 
 0.28 
 
 4.29 
 3.28 
 4.13 
 3.93 
 
 23.46 
 4.55 
 10.26 
 9.55 
 
 The amount of sulphur in the volatile matter varies with the 
 nature of the occurrence of the sulphur from as low as f 
 to as high as f of the total sulphur present. On the follow- 
 ing samples the amount of sulphur in the volatile matter 
 is calculated from the results on the coke tests given in 
 Professional Paper No. 48 and in Bulletin No. 290 of the 
 U. S. Geological Survey. The approximate percentages of the 
 total sulphur in the coke and in the volatile matter are as 
 follows : 
 
 
 Coke. 
 
 Volatile Matter. 
 
 Indian Territory No 2 
 
 Per Cent. 
 
 67 
 
 Per Cent. 
 33 
 
 Kentucky, No. 1 
 
 40 
 
 60 
 
 Ohio, No. 8 ... ... 
 
 33 
 
 67 
 
 West Virginia, No. 1 
 West Virginia, No. 10 
 
 67 
 67 
 
 33 
 33 
 
 West Virginia, No. 12 
 
 60 
 
 40 
 
 
 
 
50 COAL 
 
 On the remaining samples on which no coke tests were 
 made, the amount of sulphur in the volatile matter is esti- 
 mated as 50 per cent of the total amount present. This is of 
 course an assumption but the error introduced by it can in ho 
 case be very large, not large enough to materially change the 
 final findings as to the nature and heating value of the volatile 
 matter. 
 
 The carbon values are obtained by subtracting the sum of 
 the combined water plus the nitrogen plus the sulphur plus the 
 available hydrogen from the total volatile matter. The heat 
 per unit of volatile matter may be calculated by Dulong's 
 formula and is equal to: 
 
 (8080 XCarbon) + (34460 X available Hydrogen) + (2250 XSulphur) 
 
 Volatile matter 
 
 The results for each of the samples are as follows: 
 
 North Dakota, No. 1 5874 
 
 Wyoming, No. 1 6332 
 
 Colorado, No. 1 6459 
 
 Montana, No. 1 6649 
 
 Illinois, No. 4 7774 
 
 Indiana, No. 1 , 8193 
 
 Ohio, No. 8 8034 
 
 Alabama, No. 2 7989 
 
 Indian Territory, No. 2 8575 
 
 Alabama, No. 1 9036 
 
 Kentucky, No. 1 8868 
 
 West Virginia, No. 1 9195 
 
 Arkansas, No. 5 11995 
 
 West Virginia, No. 10 12135 
 
 W T est Virginia, No. 12 11944 
 
 These results show a range for the heating value of the volatile 
 matter of from about 5900 to over 12,000 calories or a difference 
 of over 100 per cent in heating value per unit of volatile matter. 
 The highest heating value is found in those coals which are rela- 
 tively high in available hydrogen, and at the same time are low 
 in combined water. West Virginia No. 10 with a value of 8950 
 for H has over 4 per cent of available hydrogen and less than 3 
 per cent of combined water, while North Dakota No. 1 has only 
 1.4 per cent available hydrogen and 11.55 per cent of combined 
 
CHEMICAL ANALYSIS OF COAL 51 
 
 water. These values make clear that in order to determine 
 anything very definite about the actual heating value of the coal, 
 something more than the proximate analysis is required. The 
 value of this determination is merely a relative one and should 
 be restricted to a comparison of different samples of the same 
 bed, or at most to different coals known to be somewhat similar 
 in the relative amounts of oxygen and available hydrogen which 
 are contained in a unit amount of the " residual coal." This 
 term " residual coal/' from what has been given above, is less 
 misleading than the more commonly used term " combustible," 
 since in many of the samples a large part of the volatile matter 
 is non-combustible. 
 
 ULTIMATE ANALYSIS 
 
 This analysis gives the composition of the coal under the 
 following headings: percentages of carbon, hydrogen, nitrogen, 
 sulphur, oxygen and ash. The percentage of oxygen is ob- 
 tained by subtracting the sum of the other percentages from 
 100. Hence the algebraic sum of all the errors in the other 
 determinations appears in the value obtained for oxygen which 
 makes the accuracy of the obtained value for oxygen somewhat 
 uncertain. Corrections in the ash may improve the oxygen value 
 somewhat, but as has been discussed under " Ash " this correc- 
 tion is not entirely satisfactory. As the errors in the oxygen are 
 dependent upon the errors in the other determinations the approx- 
 imate limits of the accuracy of these determinations must be 
 considered in order to obtain an idea of the probable accuracy 
 of the oxygen determination. 
 
 The determination of the carbon and hydrogen requires a 
 high degree of skill and care in order to secure satisfactory results. 
 The results of determinations made by poor manipulators or 
 under unfavorable conditions may easily be 1 or 2 per cent in 
 error for carbon and 0.4 or 0.5 of 1 per cent in error for hydrogen. 
 With careful manipulation and proper conditions the carbon and 
 hydrogen results in most samples should be accurate to within 0.2 
 of 1 per cent for carbon and within about 0.05 or 0.06 of 1 per cent 
 for hydrogen, provided that the laboratory sample of coal has been 
 previously reduced to approximately an air dry condition. Unless 
 the latter has been done, the errors incident to weighing out small 
 
52 COAL 
 
 amounts of sample for ultimate analysis makes a high degree of 
 accuracy practically impossible. The question of air drying of 
 the samples is discussed in detail under the head of " Sampling." 
 The results for sulphur, nitrogen and ash should be accurate 
 within 0.05 of 1 per cent and the value obtained for oxygen 
 can be duplicated to within 0.25 of 1 per cent on coals which are 
 fairly low in oxygen. Whether it is within 0.25 of 1 per cent 
 for the oxygen as it actually occurs in the sample is not so cer- 
 tain, since in high ash coals the possible corrections to the ash 
 are several times this amount. The actual value obtained for 
 oxygen for small differences has a relative value rather than an 
 absolute one. Large differences, such as are shown in the list of 
 samples given, have an absolute value in indicating the nature of 
 the coal, the errors in the determination or corrections for the ash 
 being of minor importance compared to the total difference in the 
 oxygen value. 
 
 While the results for the ultimate analysis should be accurate 
 to within about the limits given for the sample as analyzed, it 
 does not necessarily follow that these results actually come this 
 near to representing the original coal, as this is dependent upon 
 whether the sample itself is representative of the coal. This is 
 another question in itself and is discussed in detail under the head 
 of " Sampling." 
 
 The complete ultimate analyses and the determined and 
 calculated heating values expressed in calories and British ther- 
 mal units on the different coals, the proximate analyses of which 
 have already been given are given on page 53, the calculated 
 values being based on Dulong's formula: 
 
 8080C+34460(H - JO) +2250S. 
 
 Some of the variations in the results are as follows: total 
 hydrogen 3.82 to 6.61; carbon 40.23 to 84.97; oxygen 3.98 to 
 41.72, and nitrogen 0.54 to 1.83. Such wide variations in the 
 ultimate composition make it easy to understand why the heating 
 values likewise have such a wide range, from 3767 to 8346 calories, 
 and help to make more clear the statement that "coal as it 
 actually occurs in nature differs widely in physical and chemical 
 properties." 
 
CHEMICAL ANALYSIS OF COAL 
 
 53 
 
 
 f O 
 
 03 
 O 
 
 03 
 
 Q 
 
 J3 
 
 6 
 
 M 
 
 a 
 
 a 
 
 o 
 
 
 
 Colorado No. 1. 
 
 Montana No. 1. 
 
 ^6 
 
 'o 
 
 Indiana No. 1. 
 
 GO 
 
 6 
 
 
 M 
 
 O 
 
 Alabama No. 2. 
 
 Hydrogen 
 
 6.61 
 40.23 
 0.54 
 41.72 
 1.55 
 9.35 
 
 6.39 
 54.91 
 1.02 
 32.59 
 0.59 
 4.50 
 
 6.07 
 57.46 
 1.15 
 28.78 
 0.55 
 5.99 
 
 5.37 
 59.08 
 1.33 
 21.52 
 1.73 
 10.97 
 
 5.43 
 60.74 
 1.15 
 19.72 
 1.32 
 11.64 
 
 5.37 
 60.34 
 1.18 
 17.21 
 2.50 
 13.40 
 
 5.48 
 67.02 
 1.29 
 15.00 
 
 2.84 
 8.37 
 
 4.84 
 68.69 
 1.54 
 11.49 
 1.01 
 12.43 
 
 Carbon 
 
 Nitrogen 
 
 Oxygen 
 Sulphur 
 
 Ash 
 
 Calories 
 B.t.u 
 
 100.00 
 
 3846 
 6923 
 
 3767 
 6781 
 
 100.00 
 
 5408 
 9734 
 
 5247 
 9445 
 
 100.00 
 Heatir 
 
 5635 
 10143 
 
 Heat 
 
 5508 
 9913 
 
 100.00 
 ig value 
 
 5855 
 10539 
 
 ng vak 
 
 5739 
 10330 
 
 100.00 
 5 detern 
 
 6002 
 10804 
 
 ic calcu 
 
 5959 
 10726 
 
 100.00 
 lined : 
 
 6145 
 11061 
 
 lated: 
 
 6044 
 10880 
 
 100.00 
 
 6738 
 12128 
 
 6718 
 12092 
 
 100.00 
 
 6861 
 12350 
 
 6745 
 12140 
 
 Calories 
 B.t.u 
 
 
 
 
 
 
 6 
 
 
 
 
 
 ^ 
 
 rH > 
 
 1-1 
 
 ft 
 
 10 
 
 
 
 
 ! 
 
 6 
 
 
 
 03 
 
 '3 
 
 6 
 ft 
 
 03 
 
 '3 
 
 'Sbo 
 
 03 
 
 '3 
 
 
 E-" 6 
 
 03 
 
 3 
 
 03 
 
 o 
 
 1 
 
 i 
 1 
 
 
 d 
 
 
 '3 
 
 | 
 
 g 
 
 o 
 
 
 m* 2 * 
 
 !^ 
 
 
 a 
 
 < 
 
 M 
 
 ^ 
 
 .3 
 
 ^ 
 
 
 
 Hydrogen 
 
 5.17 
 
 5.01 
 
 5 .43 
 
 5.28 
 
 3.82 
 
 4.65 
 
 4.43 
 
 Carbon . 
 
 69 49 
 
 71 58 
 
 77.37 
 
 78.00 
 
 76.44 
 
 84 97 
 
 82 71 
 
 Nitrogen 
 
 1 67 
 
 1.65 
 
 1.83 
 
 1.54 
 
 1.37 
 
 1.06 
 
 1 33 
 
 Oxvffen 
 
 11 15 
 
 8 50 
 
 9 76 
 
 7.94 
 
 4 30 
 
 4 18 
 
 3 98 
 
 Sulphur 
 
 1.52 
 
 0.72 
 
 1.22 
 
 0.90 
 
 1.99 
 
 0.56 
 
 0.68 
 
 Ash 
 
 11 00 
 
 12 54 
 
 4 39 
 
 6 34 
 
 12 08 
 
 4 58 
 
 6 87 
 
 
 
 
 
 
 
 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 100.00 
 
 
 Heating value determined: 
 
 Calorics 
 
 7004 | 7142 
 
 7860 
 
 7837 
 
 7366 
 
 8346 
 
 8095 
 
 B.t u. 
 
 19G07 12856 
 
 141 AS 
 
 1/1107 
 
 1 2950 
 
 15023 
 
 14751 
 
 
 Heating value calculated: 
 
 
 
 Calorics . . . 
 
 6952 
 
 7160 
 
 7729 
 
 7801 
 
 7353 
 
 8299 
 
 8054 
 
 B.t.u. 
 
 12514 
 
 12888 
 
 13912 
 
 14042 
 
 13235 
 
 14938 
 
 14498 
 
 
54 COAL 
 
 Calculating an ultimate analysis. From what has been 
 stated concerning the difficulties in the carbon and hydrogen 
 determinations, it may rightfully be inferred that the ultimate 
 analysis is a somewhat troublesome and expensive determination 
 and for most purposes where an ultimate analysis is required, 
 as in a boiler-test heat balance, a calculated ultimate analysis, 
 based on an actual ultimate analysis of a similar sample of the 
 same coal, is fairly satisfactory. If the percentage of moisture, 
 ash and sulphur in each sample be subtracted from 100 the 
 remainder is the per cent of residual coal in each sample and the 
 calculation of the derived ultimate, based on the assumption that 
 the residual coal in each sample has approximately the same 
 percentage composition, is as follows: The determined ultimate 
 analysis is given in per cent of carbon, hydrogen, nitrogen, oxygen, 
 sulphur and ash per unit of coal. Representing these percentages 
 by C, H, N, O, S, and A and the percentages of the derived samples 
 by C', H', N', 0', S', and A' and the moisture, ash and sulphur 
 in the two samples by M, A, and S and M', A', and S' respect- 
 ively, then the procedure is as follows: 
 
 Subtract the hydrogen, H, and oxygen, 0, corresponding to the 
 moisture, M, from the total hydrogen and oxygen as given in 
 the ultimate analysis. The remainder will be the hydrogen and 
 oxygen in the residual coal. Represent the residual coal (100 
 (M+A-f S),in the sample by R and the residual coal (100-(M'+ 
 A'+S'), in the sample to be calculated by R'. The carbon, 
 hydrogen, oxygen, and nitrogen in a unit of residual coal = 
 
 fc 
 O-SM livi(lcdb R - 
 
 N 
 
 Multiplying these values by R' gives the amount of carbon, 
 hydrogen, oxygen and nitrogen in the residual coal, R'. . To 
 get the ultimate composition of the coal corresponding to R', the 
 hydrogen and oxygen must be corrected by adding to these 
 obtained values the correction corresponding to the moisture, M'. 
 For hydrogen this correction = iM', for oxygen fM'. 
 
 IQO-CM'+A'+S') R' 
 
 If - or - be represented by K the ultimate 
 
 100 (M+A+S) R 
 
 analysis of the derived sample is as follows: 
 
CHEMICAL ANALYSIS OF COAL 
 
 55 
 
 ' = (H-iM)K+iM' 
 ' = (O-9M)K+|M' 
 
 A' = A' 
 
 Total 
 
 100 
 
 The agreement between the calculated and determined ulti- 
 mates is shown by determinations on samples Nos. 1061 and 
 and 1157, Professional Paper, No. 48, U. S. Geological Survey, 
 the moisture, ash and sulphur in which are as follows: 
 
 
 Sample No. 1157. 
 
 Sample No. 1061. 
 
 Moisture 
 
 2.56 
 
 2 03 
 
 Ash 
 
 13.92 
 
 13.46 
 
 Sulphur 
 
 78 
 
 5 39 
 
 
 
 
 Sample No. 1157 is a portion of Alabama No. 1 and Sample No. 
 1061 is a portion of Kansas No. 3 coal. The determined and 
 calculated values for carbon and hydrogen on these two samples 
 are as follows: 
 
 Sample No. 
 
 Determined 
 Hydrogen. 
 
 Calculated 
 Hydrogen. 
 
 Determined 
 Carbon. 
 
 Calculated 
 Carbon. 
 
 1157 
 
 4.82 
 
 4.94 
 
 70.00 
 
 70.19 
 
 1061 
 
 4.77 
 
 4.84 
 
 68.94 
 
 68.85 
 
 The proximate and ultimate analysis of the car samples from 
 which the ultimates are derived are given in the analytical tables 
 in Chapter X. 
 
 The derived results for carbon differ from the actually deter- 
 mined results by an amount within the limit of variation of 
 duplicate determinations of carbon. The variations between the 
 determined and derived hydrogen 0.07 and 0.12 are not much 
 greater than the errors in the actual hydrogen determinations and 
 a calculated ultimate based on a carefully run ultimate of a similar 
 
56 COAL 
 
 sample of coal is in the opinion of the author likely to be as reli- 
 able as an actual determination made by an average manipu- 
 lator under ordinary working conditions. Certainly the error 
 introduced is usually not large enough to have any great effect 
 upon the calculations which are affected by it. 
 
 Effect of errors in the ultimate analysis on the heat balance. 
 For illustration, assume a maximum error of 1 per cent in the cal- 
 culated value for carbon and 0.2 per cent in the calculated value 
 for hydrogen. Then 0.01 gram of carbon is equivalent to 0.0367 
 gram of CO2- The nitrogen equivalent to the oxygen from the 
 air required to produce this amount of CO2 = 0.10 gram; allowing 
 100 per cent excess air = 0.128 gram of air. On the boiler test 
 with the products of combustion escaping at 300 C. (572 F.) 
 the sensible hea't carried off in these products is about 19 calories. 
 0.2 per cent of hydrogen = 0.018 gram of H^O. The latent heat 
 of this amount of water equals 10.6 calories. The sensible heat, 
 assuming the gases escaping at 300 C., in this amount of water 
 is 2.7 calories. The nitrogen equivalent to the oxygen required to 
 combine with this amount of hydrogen equals 0.053 gram. Allow- 
 ing 100 per cent excess air, the amount of air required for the 
 excess is 0.069 gram. The sensible heat carried off at 300 C. by 
 this amount of air and nitrogen equals about 8 calories, making 
 the total heat carried off about 21 calories. If the errors in carbon 
 and hydrogen are both high or both low at the same time, the 
 total error in the distribution of the heat loss amounts to about 
 40 calories or about ^ per cent of the total heat produced; as 
 the radiation and unaccounted-for losses in a boiler test are fre- 
 quently 20 times this large, it is apparent that the error from the 
 use of a calculated ultimate of approximate accuracy has little 
 effect upon the actual results of the boiler test. 
 
CHAPTER III 
 SAMPLING 
 
 THE old saying that a chain is only as strong as its weakest 
 link may well be applied to the valuation of the results of chemical 
 tests and many times the weakest link is the sampling. This may 
 be due to one or more of several reasons: 
 
 (1) Failure to secure a representative sample due to the 
 faulty method of sampling, as for example the sampling of a car 
 of coal by merely taking several lumps or shovel fulls from the 
 top of the car. 
 
 (2) Difficulty in securing a representative sample due to the 
 occurrence and the irregular distribution of materials of different 
 composition, as the irregular distribution of pyrite in coal or the 
 irregular distribution of gold in gold ores. 
 
 (3) Alterations or changes in the sample during handling or 
 before it is analyzed, as changes due to gain or loss of moisture or 
 changes due to oxidation. 
 
 Failure to secure a representative sample due to any or all of 
 these causes may result in errors ten times as large as any of the 
 probable chemical errors and too much emphasis cannot be laid 
 on the importance of care and thoroughness in taking and hand- 
 ling the sample on which the chemical results are to be obtained. 
 If necessary as much or more time and money should be expended 
 in securing a sample as is expended in having it analyzed, as the 
 determinations of the chemist if properly made represent only the 
 sample as received and if made on improperly taken samples 
 they may be so far from representing the actual material as to be 
 worse than useless. The practice of entrusting sampling to 
 ignorant laborers or mere boys having little or no idea of what 
 they are doing deserves to be strongly condemned, as skill and 
 training are as essential in taking and handling a sample as in mak- 
 ing the chemical determinations. It is indeed true that an ordin- 
 ary laborer can be trained to the work and can take the samples 
 
 57 
 
58 COAL 
 
 properly but the training should be thorough as to details and 
 strict observance of details insisted upon if the results are to be 
 of value and too often the persons giving instructions in sampling 
 do not themselves appreciate the importance of some of the neces- 
 sary precautions. 
 
 In sampling coal the effect upon the sample of the three vari- 
 able factors, moisture, ash and sulphur, should be considered 
 separately and collectively. The amounts of these constituents 
 vary in the different materials composing the coal (i.e., in the 
 coal, slate, pyrite, etc.) and also in different parts of these 
 separate constituents, as in the lump and fine coal. Hence to 
 secure a representative sample, it is essential that the amount 
 of lump coal, fine coal, slate, clay and pyrite in the sample be 
 proportionate to that in the entire lot of coal sampled. The prob- 
 lem of the sampler therefore is to endeavor to get this propor- 
 tionate amount for each of the samples taken. 
 
 The details of handling and taking the sample are dependent 
 upon what it is desired that the sample shall represent. For 
 example, when sampling coal in the mine what the operator 
 often desires especially to find out are the variations in ash and 
 sulphur in order that the average ash and sulphur of the coal 
 shipped from the different parts of the mine may be estimated. 
 
 The moisture variations in the samples in this particular case 
 are of minor importance and the moisture content in such mine 
 samples when analyzed may differ by several per cent from the 
 amount of moisture that the coal actually contains in the mine. 
 However, this difference has very little effect upon the percent- 
 ages obtained for ash and sulphur. For illustration, suppose 
 that the sample taken in the mine analyzed as follows: Mois- 
 ture 5 per cent, ash 7 per cent and sulphur 2 per cent and that 
 the true moisture content of the coal in the mine is 10 per cent. 
 Then the analysis of this sample reduced to mine conditions is 
 moisture 10 per cent, ash 6.75 per cent and sulphur 1.90 per cent. 
 The effect of variation in' moisture on the ash percentage is as a 
 rule of minor importance to the operator. On the other hand, if 
 the sample is to represent the coal as fired under a boiler any failure 
 to secure the proper result in moisture is simply an error propor- 
 tionate to the amount of moisture gain or loss. In the illustration 
 just given the 5 per cent difference in moisture means a 5 per 
 cent difference in the heating value of the coal and approximately 
 
SAMPLING 59 
 
 a 5 per cent difference in the value of the coal in dollars and 
 cents. 
 
 The sampling of coal may be considered under two general 
 heads: Sampling of coal as it occurs in the mine and sampling 
 of lots of coal as bought and sold or as used. 
 
 Sampling coal in the mine. In sampling coal in the mine a 
 number of factors are to be considered, as the number of samples 
 to be taken, their location and the method of taking them. For 
 a mine shipping coal the directions of the Bureau of Mines specify 
 not less than 4 samples for a daily production of 200 tons or less, 
 with an additional sample for each additional 200 tons of coal 
 mined per day. The number should be greater from mines in 
 which the quality of the coal varies greatly. The location of the 
 samples taken should be such as to fairly represent the coal being 
 worked. Other samples in head entries or in the deepest portions 
 of the mine may be taken if desired in order to indicate the char- 
 acter of the future output. 
 
 In selecting the exact place to take a sample, care should be 
 taken to avoid exceptional features, such as faults or irregular 
 patches or partings or veins of pyrite. A freshly exposed face of 
 the coal should be selected and before taking the sample the face 
 should be freed or cleaned from any dirt or loose coal from roof 
 to floor for a width of 5 or 6 feet. This is done in order to pre- 
 vent fragments of foreign matter from falling off the face and 
 becoming mixed with the sample. For the same reason, insecure 
 portions of the roof should also be carefully taken down. The 
 face, where the sample is to be cut, should be squared up and an 
 inch or so of the surface cut away with the pick before actually 
 cutting the channel sample. In cutting the sample a uniform 
 cut should be made across the face of the seam including in the 
 sample all that portion that is included in the coal as mined and 
 rejecting any portions which would be rejected in good mining 
 practice. The amount of coal taken for a sample should be 
 sufficient to reasonably insure a fair representation. The sample 
 obtained from a channel 1 inch wide and 1 inch deep if strictly 
 uniform in width and depth is satisfactory but no sampler can 
 cut such a channel and a channel 4 to 8 inches wide by 2 to 4 
 inches deep should be cut, the errors in width and depth being 
 relatively much less with a wide and deep cut than with a narrow 
 and shallow one. 
 
60 COAL 
 
 In collecting the sample a large canvas or oil cloth about 7 
 ft. square should be spread on the floor, care being taken that 
 mud and dirt are not introduced into the sample from the boots 
 or shoes of the sampler. With a uniform depth and width of cut 
 the amount of the sample cut varies with the height of the seam. 
 The directions of the United States Government for sampling 
 are to take at least 6 pounds for each foot of thickness. This 
 amount corresponds approximately to a channel 2x6 or 3x4 inches. 
 After cutting the sample it should be either shipped entire or if 
 a sampling outfit is available it may be broken down till the 
 coarsest particles pass through a f-inch screen, especial care being 
 taken to crush all lumps of slate and pyrite quite fine. The 
 sample may then be reduced after thorough mixing by quarter- 
 ing and rejecting the opposite quarters, taking care to brush away 
 the entire part of the rejected portions. The two remaining 
 quarters may be again mixed and quartered until the final prod- 
 uct amounts to not less than 8 or 10 pounds. If a f-inch sieve 
 is available this 10-pound portion may be crushed until the 
 largest particles pass this sieve after which it may be quartered 
 down to 4 or 5 pounds. 
 
 A careful and painstaking sampler with a keen eye for slate 
 and pyrite may if all such particles are finely crushed quarter 
 this f-inch portion down to 2 or 3 pounds without introducing 
 any error of consequence since portions of clean coal f-inch in 
 size or larger have little influence on the ash and sulphur content. 
 This item is discussed more in detail under " Car sampling." 
 
 Working down the sample in the mine is however too often 
 done in a dim light and hurriedly, rather than under favorable 
 conditions and the author strongly favors a minimum division 
 of the sample in the mine rather than the division to the smaller 
 amounts. The 10-pound portion of the J-inch size or the 5- 
 pound portion of the f-inch size, or better still the entire sample 
 if not reduced should be sent to the chemical laboratory. If 
 the moisture result is unimportant the shipment may be made 
 in a closely woven canvas bag. If, however, the moisture is of 
 importance the shipment must be made in a closed metal or glass 
 container. A half gallon fruit jar suffices for the smaller sample 
 but a metal container is to be preferred as being less liable to 
 breakage, in which case a J-gallon galvanized or tin container 
 with a screw top for the small sample or a one- to four-gallon 
 
SAMPLING 61 
 
 container with screw top for the larger sample is satisfactory, 
 the screw top being sealed by means of adhesive tape to prevent 
 moisture loss. 
 
 The shipments of samples by the Ohio Geological Survey are 
 made in galvanized iron cans 10x10x10 inches, fitted with 3j-inch 
 screw caps or tops. One of these cans hold about 40 pounds of 
 sample and allows for the shipment either of all or of one-half of 
 the sample cut. Well-constructed wooden cases built to hold four 
 of these cans are used in shipping the samples to the laboratory. 
 
 If nothing better is at hand tall tin pails or cans with well- 
 fitting lids may be used, care being taken to tie the lids very 
 securely on to the pails or cans. If not well secured they may 
 loosen in transit and where several samples are shipped together 
 in the same box all may be spoiled by an accident of this kind. 
 In shipping glass cans or metal containers they should be well 
 packed with burlap, paper or excelsior in order to lessen danger 
 of breakage in transit. 
 
 Portable sampling outfit. Where much mine sampling is to 
 be done a portable sampling outfit is almost a necessity. The 
 essential articles comprising such an outfit are as follows: 
 
 Carrying bag or container, sampling cloth or canvas, mortar 
 and pestle, sieves, sampling scoop, brush or whisk broom, sam- 
 pling cans, adhesive tape, measuring tape. A pick and shovel 
 are a necessary part of the equipment but these can usually be 
 obtained at the mine and are not included as such as a part of 
 the portable outfit. 
 
 Carrying bag or container. Any container which will hold the 
 outfit will do and the simpler the better. An ordinary canvas sack 
 is very satisfactory and the outfit can be carried either in the hand 
 or thrown over the shoulder. 
 
 Sampling cloth. This should be of durable material and 
 impervious to -.water. Closely woven 16 to 20 oz. duck or heavy 
 enamelled buggy cloth is satisfactory. If the enamelled cloth is 
 used it should be used enamelled side down. The cloth must not 
 be too small. The author prefers a cloth about 7 feet square. 
 
 Portable mortar. The mortar at present used by the Depart- 
 ments of Metallurgy and Mining Engineering at the Ohio State 
 University is constructed as follows: The mortar block consists 
 of a Y^-inch steel plate 10 inches in diameter on which is mounted 
 a wooden block 1J inches thick and to this is attached the mortar 
 
62 
 
 COAL 
 
 plate proper of J-inch steel. Each plate is secured to the wooden 
 block by countersunk screws. The lower portion of the sides of 
 the mortar are formed by a heavy circular piece of sole leather 
 2f inches wide which is firmly secured by screws to the wooden 
 block. To prevent escape of coal the ends of the leather are 
 tapered, lapped and glued together with waterproof leather cement. 
 To the upper portion of the leather is attached a circular piece 
 of 16-ounce canvas, 7J inches wide, which forms the upper por- 
 tions of the sides of the mortar. The upper edge of the canvas 
 is attached to a flat steel ring, this ring being connected to the 
 mortar base by collapsible spring steel supports held in position 
 
 FIG. 1. Portable Sampling Outfit. 
 
 by set screws. When the set screws are loosened the supports 
 and canvas fold down out of the way, the loose ends of the spring 
 steel supports being secured by spring clips on the sides of the 
 mortar block. 
 
 Pestle. A common molder's tamping iron 3f inches in diameter 
 and fitted with a handle 12 inches long is used. 
 
 Sieve. This consists of a galvanized iron frame 11 inches in 
 diameter by 5 inches high, into which are fitted removable screens 
 of different sizes, as f, i, f and } inch. The J- and f-inch screens 
 are the two usually used. This sieve is large enough to hold the 
 mortar when the outfit is packed together. 
 
 Sampling scoop. This is merely a heavy piece of galvanized 
 iron resembling a small dustpan but having no handle. It is 
 
SAMPLING 63 
 
 used for quartering down and mixing and also for scooping up 
 the reserve portion of the sample. 
 
 Broom. A small 6-inch whisk broom is very satisfactory. 
 
 Sampling cans. The cans at present used by the Departments 
 of Metallurgy and Mining Engineering are 5 inches in diameter 
 by llf inches high and hold from 8 to 10 pounds of sample. They 
 are constructed of 22 gauge galvanized iron and the dimensions 
 are such that two cans fit end to end in an ordinary 24-inch trunk. 
 
 Adhesive tape. Ordinary electrical or bicycle tape is used for 
 sealing the lid after the sample has been put into the can. 
 
 Measuring tape. A 25-ft. metallic tape graduated to fractions 
 of an inch is useful in measuring sections, etc. Fig. 1 is an 
 illustration of portions of the above described outfit. 
 
 The outfit used by the U. S. Bureau of Mines is similar to the 
 one described except that smaller sampling cans are used and a 
 spring balance is included as a part of the outfit. An experienced 
 sampler has little use for a spring balance and with the large 
 sample cans the amount of sample cut can be checked up in the 
 laboratory from the weight of the sample and from the data given 
 in the collector's notes as to what aliquot portion of the sample 
 is represented by the final sample. 
 
 For details of the Government sampling outfit, see Tech- 
 nical Paper No. 1, Bureau of Mines, Department of the Interior. 
 
 Car sampling and sampling coal as used. Directions for 
 sampling coal in a car, sampling a coal as unloaded or sampling 
 coal as used are hard to formulate owing to the great difference 
 in moisture, ash and sulphur and in the physical conditions of 
 different lots of coal. The amount of sample to be taken depends 
 upon the variations in these factors and upon the amount of coal 
 sampled and a set of directions which might give satisfactory 
 results on one coal if used on an entirely different coal might be 
 very unsatisfactory; and a set of directions for sampling a bad 
 lot of coal would be unnecessarily expensive if used to sample a 
 comparatively uniform coal. 
 
 The common method of obtaining a sample of coal during a 
 boiler test is as follows: As each lot of coal is weighed, portions 
 taken from various parts are put into a closed barrel, box or a 
 metal container with a closely fitting cover, an effort being made 
 to get an average of fine and lump coal. The amount of sample 
 taken in this way in a day's run where 5 or 6 tons of coal are 
 
64 COAL 
 
 fired should be from 100 to 300 pounds, depending upon the coal. 
 If clean slack or washed nut coal, the smaller amount may be 
 satisfactory. If ash and sulphur are present in considerable 
 amounts and especially if in the form of slate and pyrite, the 
 larger quantity should be taken. In sampling a car as unloaded 
 the same method should be used, small portions being taken at 
 regular intervals during the unloading, the amount taken vary- 
 ing with the coal, 500 or 600 pounds, if the coal is run-of-mine 
 to as low as 200 pounds if fine slack or clean nut. 
 
 Reduction of the large sample. The entire sample taken 
 (200 to 600 pounds) should be spread upon a clean floor, the large 
 pieces of coal, slate and pyrite crushed with a hammer and a 
 heavy iron plate till the largest particles of slate and pyrite do 
 not exceed J inch. This requires that the sample be gone over 
 repeatedly with a shovel so as to bring all portions to the 
 view of the sampler. It should then be thoroughly mixed 
 and divided into quarters. The two opposite quarters should be 
 brushed to one side with a broom. The two remaining quarters 
 should be again mixed, any chunks of slate and pyrite crushed 
 still finer and the sample again divided by quartering. With 
 careful crushing of slate and pyrite this quartering can be repeated 
 a third time if desired. The last portion of sample amounting 
 to 60 to 80 pounds, should be sent to the chemical laboratory 
 for further treatment. If a power crusher or pulverizer is avail- 
 ableand where much sampling is to be done such a machine 
 is almost a necessity the entire 600 pounds should be put through 
 this pulverizer which can be set to reduce it to a fineness of about 
 J inch and finer, in which case the sample can be quartered down 
 repeatedly and the sample sent to the laboratory need not exceed 
 4 or 5 pounds. 
 
 The chute through which the crushed sample passes after 
 being put through the pulverizer may easily be arranged to 
 mechanically divide the sample by an arrangement of partitions 
 to successively divert aliquot parts, so that the final portion 
 diverted is small enough to be sent to the laboratory without 
 further handling. (See Fig. 2.) The space below the end of the 
 chute must of course be sufficient to accommodate a container 
 for holding the portion of the sample which passes through. 
 For example, with samples up to 600 pounds and | passing 
 through the chute the receiving bucket should hold not less than 
 
SAMPLING 
 
 65 
 
 FIG. 2. Sampling Chute. 
 
66 COAL 
 
 80 pounds of coal. In order to further divide this 80-pound 
 sample, an auxiliary hopper may be connected to the top of the 
 chute and the sample again divided by passing through the chute 
 a second time. If desired the divisions in the chute can be ar- 
 ranged so that only YG of the sample passes through and for large 
 samples 1000 pounds or more this is desirable in that it avoids 
 the handling of excessively heavy samples in the second subdi- 
 vision. One laboratory fitted with a sampling chute similar to 
 the one described has a revolving cylindrical mixer between the 
 pulverizer and the sampling chute. The author doubts that this 
 is any decided real improvement as the mixing in the pulverizer 
 is certainly thorough. With the pulverizer fitted with a bar 
 screen, the usual equipment, the pulverized sample escapes from 
 the crusher evenly across the face of the screen and in turn is 
 distributed uniformly in the top of the chute. 
 
 In the arrangement shown in Fig. 2 the discarded portions 
 of the sample are collected in the small bins and must be removed 
 with a shovel by hand. When the elevation of the pulverizer is 
 sufficient the chutes may be arranged to deliver into a common 
 bin of larger capacity which need be emptied only occasionally. 
 A still more efficient arrangement, where the amount of sampling 
 to be done warrants the installation, is to have these discarded 
 portions of the samples removed mechanically by having the chutes 
 deliver them on to a belt conveyor. Mechanical arrangements 
 for conveying the sample to the pulverizer are likewise desirable 
 when large amounts of sample are to be handled. 
 
 In quartering down by hand the work should be done as 
 rapidly as is consistent with good work and should be done pref- 
 erably in a cool room so as to make the moisture losses as small 
 as possible and the portion of the sample sent to the chemical 
 laboratory should be sent in a closed container. Reduction of 
 the sample in a power pulverizer is not only more satisfactory 
 on account of the finer reduction, of the coarse sample but the 
 crushing being done rapidly the chances of moisture loss are like- 
 wise reduced. 
 
 The effects of particles of slate and pyrite upon the sample. 
 These may be perhaps best shown in tabular form and serve to 
 emphasize and make clear the precautions to be observed in 
 sampling. Pyrite has a specific gravity of about 5, contains 
 about 53 per cent of sulphur and on burning forms the equiv- 
 
SAMPLING 
 
 67 
 
 alent of 65 per cent of ash. Slate and shale have a specific gravity 
 of about 2J and the ash may run as high as 80 per cent. A piece 
 of pyrite one inch each way weighs approximately 80 grams (3 oz.) 
 and contains the equivalent of 42 grams (1.6 oz.) of sulphur and 
 the equivalent of 52 grams (1 .9 oz.) of ash, the weight and equivalent 
 amounts of sulphur and ash in pieces of pyrite equivalent "to cubes 
 of varying sizes larger and smaller than one inch are as follows : 
 
 Size in Inches. 
 
 Pyrite 
 Weight in Grams. 
 
 Sulphur 
 Weight in Grams. 
 
 Ash 
 Weight in Grams. 
 
 2 
 
 640 
 
 336 
 
 416 
 
 1 
 
 - 80 
 
 42 
 
 52 
 
 1 
 
 10 
 
 5.25 
 
 6.5 
 
 f 
 
 4.22 
 
 2.21 
 
 2.7 
 
 i 
 
 4 
 
 1.25 
 
 0.656 
 
 0.81 
 
 i 
 
 0.156 
 
 0.082 
 
 0.10 
 
 i 
 
 16 
 
 0.0195 
 
 0.0103 
 
 0.012 
 
 A 
 
 0.00244 
 
 0.0013 
 
 0.0015 
 
 A 
 
 0.00031 
 
 0.00016 
 
 0.00019 
 
 On a one-gram sample reduced to such a size that the largest 
 single particle of pyrite does not exceed ^j inch the weight of sulphur 
 and ash equivalent to a single particle is 0.00019 ash and 0.00016 
 sulphur. Hence the results on a one-gram sample containing par- 
 ticles of this size will be too high or too low by 0.016 per cent on 
 sulphur and 0.019 per cent on ash for each particle more or less 
 than the true average which is contained in the sample as weighed. 
 
 If this proportionate weight of the largest size pieces to the 
 total amount of sample be observed for pieces of pyrite equiv- 
 alent to cubes of different sizes, approximately the following 
 amounts of sample must be taken for each size: 
 
 Size in Inches. 
 
 Sample Weight in Grams. 
 
 Sample Weight. 
 
 ? 
 
 1 
 
 -gV ounces 
 
 
 8 
 
 2 
 
 7 
 
 
 JL 
 
 64 
 
 2| 
 
 
 1 
 
 510 
 
 1 1- poi 
 
 nda 
 
 I 
 
 4090 
 
 9 
 
 
 1 
 
 13700 
 
 30 
 
 
 
 32700 
 
 72 
 
 
 1 
 
 260000 
 
 570 
 
 
 2 
 
 2100000 
 
 4600 ' 
 
 
 3 
 
 16800000 
 
 37000 
 
 
68 COAL 
 
 The preservation of this ratio on the basis of the largest pieces 
 of pyrite being three inches in size means that practically the 
 whole car has to be taken as the sample and in those cases where 
 pyrite occurs as sulphur balls several inches in diameter or the 
 slate occurs in great chunks it is impossible to secure a repre- 
 sentative sample by taking only a small amount of sample from 
 the car. Fortunately, however, the slate and pyrite present in 
 the coal as marketed usually occur in smaller particles and a 
 500- or 600-pound sample with care being observed that no large 
 lumps of slate and pyrite are present ought to be satisfactory 
 for most coal samples as far as slate and ash are concerned. 
 
 It must not be assumed that this possible accuracy in samp- 
 ling of only one piece too many or too few will be actually 
 obtained in practice. Working down the large sample to the 
 small laboratory sample requires that the quartering operation 
 be performed 8 or 10 times and the composition of the reserve 
 portion at each operation is somewhat different from the true 
 average of the whole sample taken. If the quartering is properly 
 done these variations from the true average ought to be both 
 higher and lower and hence tend to partially eliminate each 
 other and the composition of the final portion should approxi- 
 mate that of the original sample. Failure to properly mix and 
 quarter the sample may, however, result in the accumulation of 
 these errors in one direction. For example, a failure to carefully 
 sweep away the heavy particles of the rejected portions w r ould 
 tend to produce a final sample containing more than its share of 
 heavy particles. 
 
 The diameter of the wires composing the sieves cuts down the 
 actual size of the openings from 10 to 15 per cent on the larger 
 sizes to as much as 50 per cent on the fine sieves and the actual 
 volume of particles passing through the different mesh sieves 
 (if the mesh is uniform) compared to the volume calculated is 
 only f to \ for the larger sizes down to as low as f for the finer 
 sieves, hence the sampling conditions are actually more favor- 
 able than is shown by the calculation. However, this is much more 
 than offset by the fact that in practice a variation of only one 
 particle from the true average cannot be obtained and in actual 
 sampling an accuracy varying with the coal and with the skill 
 and care of the sampler of from 0.03 to 0.20 per cent on sulphur 
 and from 0.05 to 0.5 per cent on ash is to be regarded as good 
 
SAMPLING 69 
 
 sampling. The lower values apply to clean coal low in ash and 
 low in sulphur. The higher values apply to coal high in slate and 
 pyrite and with improper mixing and failure to crush the slate 
 and pyrite the actual errors on such coals may be much greater, 
 errors of 1 to 3 per cent for ash and 0.3 to 0.5 per cent for sul- 
 phur being far too common in ordinary sampling practice. 
 
 The passing of the final laboratory sample through a 60-mesh 
 sieve insures a fineness of this final product which in proportion 
 to the sample weighed out is greater than for the larger bulk 
 samples, as with a uniform 60-mesh sieve the largest particles 
 passing through probably do not exceed -fa to TO~O inch in diameter, 
 and the ratio of the largest particle of this size to a one-gram 
 sample is 2 or 3 times the calculated ratio of a ^j-inch particle. 
 Hence as far as duplicate determinations on the actual laboratory 
 samples are concerned, results ought to be and are much closer 
 than can be expected on duplicates of the larger samples. 
 
 Effect of large pieces of clean coal upon the sample. Large 
 lumps of clean coal will not seriously affect the average of the ash 
 and sulphur in the sample and while it certainly is not advisable 
 to include without breaking down lumps of clean coal 8 inches 
 in diameter in a sample, the effect of such a lump of clean coal 
 on a 600-pound sample would not be very serious. For example, 
 a lump of coal 8 inches each way weighs about 20 pounds. 
 Assuming that this lump analyzes 5 per cent ash and 1 per cent 
 sulphur and that the true average of the shipment is 10 per cent 
 ash and 2 per cent sulphur, then this lump will affect the true 
 ash percentage as follows: 10 per cent on 600 pounds = 60 pounds 
 of ash the correct amount; 10 per cej^t of ash on 580 pounds 
 = 58 pounds of ash and 5 per cent of ash on 20 pounds = 1 pound 
 of ash or a total of 59 pounds of ash for the 600 pounds of sample 
 containing the large lump of clean coal, a percentage of 9.83 
 instead of 10 the correct percentage. On the other hand, a piece 
 of shale 8 inches each way containing 75 per cent ash and weigh- 
 ing 40 pounds would affect the true result as follows : 560 pounds 
 of coal with 10 per cent ash = 56 pounds; 40 pounds of shale 
 with 75 per cent of ash = 30 pounds of ash or a total of 86 pounds 
 of ash in the 600-pound sample containing the large lump of 
 shale, a percentage of 14.3 ash instead of 10 the correct per- 
 centage. 
 
 The sampler must, therefore, use common sense and discre- 
 
70 COAL 
 
 tion in sampling rather than to sample by a rigid rule. Common 
 sense and discretion mean to guard against moisture losses and 
 to look out for large pieces of slate and pyrite, to break them 
 down fine and to try to get as near as possible a fair proportion of 
 each in the sample. 
 
 Relation of amount of car sample to the number of cars 
 sampled. Where a number of cars are sampled and the results of 
 the analysis of the mixed samples is the basis of settlement for the 
 entire shipment, the amount of coal taken from each individual car 
 may be considerably less than where only one car is sampled as the 
 errors in the different samples will to a considerable extent tend 
 to balance each other provided a proper method of sampling is 
 used. For example, if 500 pounds is required to secure a repre- 
 sentative sample from a single car, to se"cure an equally repre- 
 sentative sample from 10 cars, it is not necessary to take 500 
 pounds from each car. The average of samples of 200 pounds 
 from each car should be as close to the true composition of 
 the coal in the 10 cars as the analysis of 500 pounds from any 
 single car is to the true composition of the coal in the single car, 
 since the errors in the ten samples will to a large degree counter- 
 balance each other. This is true, however, provided that the 
 sampling is properly done. If the sampling is improperly done 
 the errors in the individual samples are all liable to be in the 
 same direction and hence the average of any number of such 
 samples will not represent a true average of the shipment. The 
 taking of samples from the top of a car only is to be strictly 
 avoided as almost certain to introduce systematic errors. 
 
 TREATMENT OF THE SAMPLE IN THE CHEMICAL 
 LABORATORY 
 
 Air drying. Upon arrival at the laboratory, if necessary, the 
 sample should be reduced by crushing to about J inch and finer 
 and quartered down to 4 to 6 pounds. This portion should then 
 be weighed and allowed to thoroughly air dry by standing exposed 
 to the air of the room for 36 hours or longer or by putting in a 
 drier heated to a temperature of 10 or 15 degrees above the room 
 temperature and having adequate circulation of air, in which case 
 the drying can usually be completed in six to eight hours. (See 
 Fig. 3.) This air drying should be continued until two weigh- 
 
SAMPLING 
 
 71 
 
 ings made at intervals of \ day or so if dried in the labora- 
 tory or two hours or more if dried in the drier show less than 
 \ per cent loss in weight. The more thorough by the air drying is 
 done the less the finely ground laboratory sample is liable to 
 change. The total loss in weight is reported as air drying loss. 
 Reduction of sample. After air drying, the sample should 
 be reduced by passing through crushing rolls or by means of a 
 
 FIG. 3. Drier for Coarse Samples. 
 
 bucking board until it passes an 8-mesh sieve at which point it 
 may belquartered down to about 1 pound. This should be still 
 further reduced, if necessary, until it will pass a 10-mesh sieve. 
 It may then be quartered down to J to f pound and reduced to a 
 powder in a pebble mill or in the absence of a pebble mill bucked 
 down on a bucking board until a 1- or 2-ounce sample is 
 obtained which will pass a 60-mesh sieve. This bucking board 
 sample, or about a 2-ounce portion of the well-mixed sample 
 from the pebble mill, should be placed in a wide-mouth 4-ounce 
 
72 COAL 
 
 bottle and well stoppered. This constitutes the laboratory 
 sample. 
 
 For the fine grinding the author prefers a pebble mill, for 
 coals containing much moisture. The jars used are 7 inches 
 in diameter by 7 inches high inside. The pebbles used are 
 about 1 inch in diameter. For this size jar a speed of from 55 
 to 60 revolutions a minute gives good results, a three-fourth- 
 pound sample being reduced from one-eighth inch to one-sixtieth 
 inch in from 30 to 35 minutes. At the end of the grinding opera- 
 tion the jar is opened and the sample is separated from the peb- 
 bles by pouring the contents of the jar upon a coarse sieve. 
 
 The fine sample of coal is divided down to about 2 ounces 
 by passing through a small riffle sampler or the sample is thor- 
 oughly mixed by hand with a spatula and about 2 ounces taken 
 with a sampling spoon from various parts of the material. This 
 2-ounce portion is then put through the 60-mesh sieve and kept 
 well covered during the sifting to prevent moisture changes. A 
 light flat brass ring (about 2 inches in diameter and weighing 
 about 4 ounces) placed in the sieve, is of very great assist- 
 ance in sifting the sample, preventing caking of the material and 
 clogging of the meshes of the sieve. Usually a few coarse par- 
 ticles, amounting to from one-fourth to one-half per cent of the 
 sample, remain upon the sieve. These are bucked down by hand 
 on a bucking board and thoroughly mixed with the sifted portion 
 of the sample. The whole is then put in a glass bottle and 
 securely stoppered and constitutes the laboratory sample for 
 analysis. 
 
 The jars and pebbles after being cleaned by brushing with a 
 stiff brush (this part of the operation requiring only a minute 
 or so) are ready for the grinding of another sample of coal. When 
 samples of entirely materials are ground, the jars and pebbles 
 may require more thorough cleansing with water and scrub 
 brush, but, as a rule, in their use for coal, dry cleansing is 
 sufficient. 
 
 The riffle sampler used in reducing the sample is shown in 
 figure 4. Two sizes of sampler are used in the laboratory. The 
 larger size has one-inch subdivisions and is used in reducing the 
 sample from 25 pounds down to the amount to be ground in the 
 ball mill (about three-fourths pound). The sample, after grind- 
 ing in the ball mill, is divided down to about 2 ounces by 
 
SAMPLING 
 
 73 
 
 means of the smaller sampler having one-half inch subdivi- 
 sions. 
 
 The sampler is essentially a metal box mounted on legs and 
 fitted with a number of equidistant vertical parallel partitions, 
 the alternate bottoms of the spaces between the partitions slop- 
 ing in opposite directions. The angle of slope should be about 
 60 from the horizontal. If much less than this the coal will not 
 run freely and may clog the sampler. 
 
 The lower portions of the sides of the sampler are open and 
 
 FIG. 4. Riffle Sampler. 
 
 the coal emptied in the top of the sampler runs down the sloping 
 bottoms of the subdivisions and is caught in two buckets below, 
 one-half of the sample being caught in each bucket. To keep 
 down dust the space above the receiving buckets is covered with 
 a metal hood or shield. Three buckets are necessary for con- 
 venience in sampling, two to set under the sampler and the third 
 to contain the portion of the sample to be subdivided. After 
 pouring the material through the sampler one of the buckets 
 containing one-half of that poured through is removed and the 
 empty bucket set in its place. The one-half portion is then 
 
74 COAL 
 
 poured through in turn. The bucket last set under containing 
 one quarter of the original sample is removed and the empty 
 one again set in its place, the subdivision of the sample being 
 continued till the sample is reduced to the amount desired. 
 
 After dividing a sample, the sampler is most conveniently 
 cleaned by directing a blast of air from a handbellows through 
 the subdivisions and any particles of material clinging to the 
 sides or the bottoms of the divisions removed before the appara- 
 tus is used for dividing another sample. 
 
 SPECIAL NOTES ON SAMPLING 
 
 Fineness of final sample. Coals unusually high in pyrite 
 and slate should perhaps preferably be put through an 80-mesh 
 sieve rather than through the 60-mesh but the author is of the 
 opinion that the 60-mesh is amply fine for nearly all samples. 
 Grinding to 100-mesh and finer is to be avoided as the more rapid 
 oxidation of the fine sample may and in some samples certainly 
 does affect the results obtained for calorific value and the ulti- 
 mate composition. Where the sample is ground in a ball-mill 
 the grinding should be continued only long enough to insure the 
 desired fineness of 60-mesh and finer. If left in a longer time the 
 sample will be ground excessively fine and subject to the larger 
 oxidation changes mentioned. 
 
 Grinding of coals containing appreciable amounts of mois- 
 ture. With coals containing appreciable amounts of moisture 
 it is safer in case the sampling is done on the bucking board to 
 reserve a 2-ounce portion of the 10-mesh size for the moisture deter- 
 mination. Plenty of time may then be taken for sampling the 
 bucking board sample and in fact it is a better laboratory sample 
 if spread out and dried for a considerable period of time before 
 being put into the sample bottle. The analytical results obtained 
 upon this sample must be reduced to the moisture content in the 
 coarse sample obtained by determining the moisture on a 5- or 10- 
 gram portion of the 10- or 20-mesh sample. 
 
 It is often assumed with a well air dried coarse sample that there 
 is no danger from moisture changes in bucking down the fine 
 sample on the bucking board. This, however, is a false assump- 
 tion as the results of numerous experiments on different coals have 
 shown that fine samples of coal give up or take up considerable 
 
SAMPLING 75 
 
 moisture with changes in the humidity and temperature of the 
 sampling room. A large number of experiments on this point are 
 given in Bulletin No. 323 of the U. S. Geological Survey which is 
 published as a reprint by the Bureau of Mines as Bulletin No. 28. 
 A large number of comparisons of the bucking board samples and 
 the ball-mill samples, sampled under observed conditions of tem- 
 perature and humidity are recorded. These comparisons show 
 losses in the bucking board samples in some cases as great as 2 per 
 cent. In other cases where the air drying of the coarse samples 
 had been a little too thorough the bucking board samples showed 
 increases in moisture, in some cases amounting to 0.6 per cent. 
 These results are all upon the air dried samples which were pre- 
 sumably close to an air-dry condition. 
 
 The moisture losses upon bucking board samples of undried 
 coal may easily be 4 to 5 per cent with coals at all high in mois- 
 ture. Laboratory experiments on a fine sample of Illinois coal 
 containing 12.4 per cent moisture showed for a one-gram sample 
 spread on a watch glass and exposed to the laboratory air a loss 
 of 2 per cent in 5 minutes. As the time required to buck down a 
 fine sample on a bucking board is often several times 5 minutes 
 the moisture losses on such samples cannot be otherwise than of 
 considerable magnitude. A sample of Illinois coal, the coarse 
 sample of which had previously been well air-dried, showed a 
 loss of 0.93 per cent after 5 minutes' exposure to the laboratory 
 air with a total moisture content of only 4.12 per cent in the 
 sample, from which the conclusion that bucking board samples 
 even on well air-dried samples are not entirely satisfactory seems 
 to be if anything conservative. With low moisture coals such as 
 some of the Arkansas and West Virginia coals the moisture losses 
 on bucking board samples from the well air-dried samples are not 
 likely to be very large, the experiments recorded showing mois- 
 ture losses or changes of only 0.1 or 0.2 per cent; but in higher 
 moisture coals such as Illinois, Indiana, or Ohio the bucking 
 board samples cannot be regarded as entirely satisfactory. 
 
 Omitting the air-drying on the coarse sample. When this 
 is done the reservation of a portion of the 10-mesh sample for the 
 moisture determination is essential if the moisture percentage 
 and the calorific value are desired. If only ash and sulphur 
 results are desired, in many coals, failure to correct to " moisture 
 as received " may not be important. When preliminary air 
 
76 COAL 
 
 drying of the coarse sample is omitted the weighing of the fine 
 sample in the laboratory must be done quickly as serious mois- 
 ture losses may occur and mixing of such a sample on paper pre- 
 vious to weighing should be strictly prohibited as moisture losses 
 are sure to result. 
 
 Bucking board grinding. While slower than power grinding, 
 if used in connection with power crushing and the crushing rolls, 
 the reduction of the sample is not excessively tedious, but if the 
 bucking board is used to grind down a sample from J inch or larger, 
 it is considerably slower on account of the much larger amount of 
 sample to be reduced, and a great danger of bucking board sam- 
 pling is too much quartering down of the rather coarse sample. 
 The crushing rolls and ball-mill avoid this tendency entirely 
 and are to be preferred on this account as well as on account of 
 smaller moisture changes. 
 
 Necessity of making analytical determinations on the fine 
 sample without undue delay. The analytical work upon the 
 laboratory sample should be done promptly as fine samples of coal 
 are known to undergo considerable oxidation changes. Exper- 
 iments recorded in the bulletin just referred to show oxidation 
 changes amounting to as much as 2J per cent of the original 
 weight of the coal during a period of eight months. These oxida- 
 tion changes took place on samples well stoppered with rubber 
 stoppers. Where the sample has more or less free exposure to air 
 the oxidation changes are almost certain to be of considerable 
 magnitude. Certainly reliable results cannot be obtained upon 
 a sample which have stood around the laboratory for any great 
 length of time. 
 
 Equipment for reduction of samples. The equipment used by 
 the author, some of which has already been described and which 
 he has found satisfactory, is as follows: 
 
 (1) A swing hammer pulverizer equipped with a chute for 
 mechanically dividing the samples. Such a pulverizer readily 
 reduces large samples to J inch and the samples can be divided 
 down to 4 or 5 pounds without further treatment. 
 
 (2) A hand or power jaw crusher for reducing coal samples 
 to J inch is very satisfactory, but for rapid reduction of large 
 samples of coal the author prefers the pulverizer. For small 
 samples 25 pounds or less a hand jaw crusher is satisfactory 
 but for large samples power crushers of larger capacity are pref- 
 
SAMPLING 77 
 
 erable. It is hardly necessary to state that an ordinary labora- 
 tory does not need a power equipment of both crusher and 
 pulverizer. 
 
 (3) For crushing the J-inch samples to 10-mesh a pair of 6-inch 
 power rolls are efficient, rapid and satisfactory. 
 
 (4) For reduction of the 10-mesh samples to 60-mesh and finer 
 a pebble mill is very efficient and prevents moisture changes 
 during pulverizing. 
 
 (5) For occasional sampling an ordinary bucking board with 
 a rather heavy muller answers the purpose. 
 
 (6) For air drying of coarse samples previous to pulverizing 
 a drying oven similar to the one shown in figure 3 is very satis- 
 factory. The trays of this drier are of galvanized iron 1 inch 
 deep by 24 by 24 inches. 
 
 (7) In weighing up the air-dried samples on the large trays a 
 Troemner solution scale No. 80 is very satisfactory. 
 
 (8) For mechanical dividing of the samples, riffle samplers 
 similar to that shown in figure 4 are satisfactory. 
 
 (9) Coarse wooden frame sieves from one inch to J-inch and 
 brass sieves from 10-mesh to 80-mesh are a necessary part of the 
 equipment. 
 
 The particular machines used by the author are as follows 
 and have proven satisfactory. Similar machines of other makes 
 are doubtless equally as efficient. 
 
 (1) Jeffrey " baby pulverizer " manufactured by the Jeffrey 
 Manufacturing Company, of Columbus, Ohio. Horse-power 
 required 6 to 8. The " baby pulverizer " easily has a capacity of 
 over 1000 pounds per hour. 
 
 (2) Chipmunk jaw crusher, manufactured by F. W. Braun 
 & Co., Los Angeles, California. Horse-power required 1 to 2. 
 The jaw crushers have a capacity per hour of about 200 pounds 
 for the smaller size to about 1000 pounds for the larger size. 
 
 (3) Six-inch crushing rolls manufactured by the American 
 Concentrator Company, Joplin, Mo. The crushing rolls have 
 ample daily capacity for any ordinary requirement. Allowing 
 time for cleaning between grinding of samples if run to capacity 
 50 to 100 samples of four or five pounds each can easily be 
 reduced by the rolls from J inch to 10-mesh and finer. 
 
 (4) Four-jar ball-mill manufactured by the Abbe Engineer- 
 ing Company, New York. The four-jar ball-mill if provided with 
 
78 COAL 
 
 an extra set of jars and kept running to capacity will grind 40 to 
 50 samples per day. 
 
 (5) The drier, riffle sampler, etc., can readily be constructed 
 by local tinsmiths. The drier described, see figure 3, holds only 
 eight large samples but if supplemented by air drying of samples 
 over night 15 to 20 samples per day can be dried ready for final 
 grinding. If a larger number of samples are to be handled a larger 
 drier should be provided. 
 
CHAPTER IV 
 METHODS OF ANALYSIS 
 
 THE samples from the sampling room or laboratory should 
 be sent to the chemical laboratory in wide-mouth bottles securely 
 closed with rubber stoppers. Ordinary 4-ounce wide-mouth bot- 
 tles are very convenient for coal samples. 
 
 Weighing out a Sample for a Determination. In weighing 
 out portions of the laboratory sample for a determination, the 
 sample should be well mixed. An efficient method of mixing is as 
 follows: The material is thoroughly mixed by giving the bottle 
 15 to 20 rotations with an upending and tilting movement of the 
 bottle to insure mixing of the top and bottom portions of the 
 sample. For satisfactory mixing in this way the sample should 
 not fill the bottle more than half full. After the mixing in the 
 bottle the stopper is removed and the sample still further mixed 
 by means of a sampling spoon and successive small portions taken 
 until the amount required for the determination is secured, espe- 
 cial care being taken to again securely stopper the bottle before 
 setting it aside for other determinations. If the sample more 
 than half fills the bottle it should be emptied out on paper, 
 well mixed and a sufficient amount discarded until the re- 
 mainder is small enough to be properly handled in the sampling 
 bottle. 
 
 Moisture. A one-gram portion of the well-mixed 60-mesh 
 sample is weighed into an empty capsule or crucible and heated 
 for an hour at 105 C. in a constant-temperature oven. The 
 capsule is then removed from the oven, covered and cooled in a 
 desiccator over sulphuric acid. The loss in weight times 100 is 
 considered as the percentage of moisture. The writer prefers, 
 for moisture determinations, porcelain capsules about 1 inch 
 high by 1| inches in diameter at the top. The particular kind 
 used has been obtained from The Henry Heil Chemical Co., of 
 St. Louis, and are designated as porcelain-moisture capsules No. 
 
 79 
 
80 
 
 COAL 
 
 2. They are much more substantial and satisfactory than the 
 ordinary porcelain crucible. 
 
 The lids used in connection with the capsules are stamped 
 from sheet aluminium. They are light and unbreakable and much 
 more convenient to handle than the ordinary covers used with 
 porcelain crucibles. In weighing out the sample at the beginning 
 of the determination the lid is placed upon the balance pan under 
 the empty capsule in which the sample is weighed. 
 
 The oven used for a number of years by the author is a double- 
 
 FIG. 5. Moisture Oven. 
 
 walled copper cylinder, see Fig. 5; the space between the outer 
 and inner walls being filled with a solution of glycerine in water, 
 the proportions being so adjusted that the boiling solution main- 
 tains a temperature of 105 C. in the inner chamber of the oven. 
 The inner cylinder is 4| inches in diameter by 7 inches long. A 
 removable perforated shelf fits into this inner cylinder, the per- 
 forations holding six capsules. The outer cylinder is 6J inches 
 in diameter by 8 inches long. Concentration of the solution is 
 
METHODS OF ANALYSIS 81 
 
 prevented by means of a condenser fitted on to the top of the 
 the outer cylinder. Air is admitted into the inner chamber of 
 the oven through a coil of block tin or copper tubing, which passes 
 around the inner cylinder and is surrounded by the glycerine 
 solution. The inner end of this tubing- is soldered into the rear 
 wall of the inner chamber; the outer end is connected to a flask 
 containing concentrated sulphuric acid. During a determination 
 a current of air dried by passing through . the sulphuric acid is 
 passed through the copper or tin tube into the inner chamber of 
 the oven. Passing over the samples it takes up the moisture and 
 escapes through a small opening in the top of the door of the oven. 
 The air is passed through at such a rate that a volume equal 
 to the capacity of the oven passes through every six or eight 
 minutes. Operating a moisture oven in this way insures a uni- 
 form condition in the oven irrespective of laboratory humidity 
 and temperature conditions and results run at different times 
 are strictly comparable, which is not the case in an ordinary 
 moisture oven. 
 
 The use of sulphuric acid in the desiccator in which the 
 moisture sample is cooled gives more concordant results than 
 where calcium chloride is used. Experiments show that if the dry 
 sample is allowed to remain over calcium chloride for any con- 
 siderable period of time it increases in weight and the results for 
 moisture are accordingly low. To avoid the danger of sulphuric 
 acid, in the desiccator, splashing up on the bottom of the cap- 
 sule when the desiccator is carried around the laboratory, a thin 
 sheet of asbestos paper should be placed below the capsule, care 
 being taken to have it fit loosely enough in the desiccator to 
 allow free circulation of air. 
 
 The cut shows 9 turns of tubing, however, 4 or 5 turns are 
 probably just as efficient and are less expensive. 
 
 Ash. The ash is determined on the residue of coal from the 
 moisture determination. The capsule containing the coal is 
 placed in a muffle furnace and slowly heated until the volatile 
 matter is given off. This slow heating avoids coking the sample 
 and renders it easier to burn to ash. After the volatile matter 
 is expelled the temperature of the muffle is raised to redness and 
 the heating is continued until all black carbon is burned out. 
 The capsule is then removed from the muffle furnace, cooled 
 in a desiccator and weighed. It is then replaced in the muffle 
 
82 COAL 
 
 for thirty minutes, again cooled and re- weighed. If the change 
 in weight is less than 0.0005 gram the ash is considered burned 
 to constant weight. If the variation is greater than this the ash 
 is again ignited for 30 minutes and again cooled and re-weighed 
 the process being continued until the difference in weight between 
 two successive ignitions is less than 0.0005 gram. In the case 
 of coals high in iron, ignition to constant weight is sometimes 
 difficult on account of small variations in weight due to oxidation 
 and reduction of the compounds of iron. The amount of ash as 
 determined represents the ignited mineral matter in the coal. 
 
 In regular routine work the cooling in desiccators may be 
 dispensed with and the capsules cooled on clay triangles in the 
 open air. A set of six triangles mounted on a wood base is very 
 convenient for carrying . the capsules from the furnace to the 
 balance and from the balance back to the furnace. This arrange- 
 ment is lighter and easier to handle than desiccators and the time 
 required for cooling is much less. 
 
 The capsules cooled in air weigh about 0.0005 gram more than 
 if cooled in desiccators, hence the ash results run a trifle high, but 
 for most samples the difference is of very minor importance and 
 the saving in time and labor considerable. If results of highest 
 accuracy are required the cooling should be done in desiccators. 
 
 Volatile matter. A one-gram sample of the fine (60-mesh) 
 coal is weighed into a bright, well-burnished 30-gram platinum 
 crucible with a close fitting cover. The crucible and contents 
 are heated upon a platinum or nichrome triangle for 7 minutes 
 over a Bunsen flame. 
 
 The crucible and residue are cooled and weighed, the loss in 
 weight minus the weight of the moisture in the sample determined 
 at 105 C. times 100 equals the percentage of volatile matter. 
 
 With artificial gas the height of the flame should be 18 to 20 
 cm. With natural gas the height of the flame should be about 
 30 cm. In using artificial gas the bottom of the crucible should 
 be about 7 cm. above the top of the burner. With natural gas 
 the bottom of the crucible should be about 12 cm. above the 
 burner. To protect the crucible from air currents it is desirable 
 to enclose the flame in a chimney. A cylindrical chimney 15 cm. 
 long by 7 cm. in diameter, notched at the top so that the plat- 
 inum triangle is about 3 cm. below the top of the chimney, makes 
 a satisfactory working arrangement. This chimney is preferably 
 
METHODS OF ANALYSIS 83 
 
 of sheet-iron lined with asbestos but a fairly satisfactory chimney 
 can be made by moistening a thick sheet of asbestos and rolling 
 it into a cylinder. This> if well wrapped with wire makes a fairly 
 serviceable chimney. For lignites and coals containing a high 
 percentage of moisture the method should be modified by giving 
 the sample a preliminary heating at a low temperature for several 
 minutes to drive out the moisture in order to avoid mechanical 
 losses which will occur if such a sample is heated over the full 
 flame of the burner from the beginning. This preliminary heating 
 for three to four minutes should be followed by the regular 7- 
 minute application of the full flame, after which the sample is 
 cooled and weighed as in the regular determination. 
 
 The higher the temperature at which the volatile matter is 
 expelled the greater is the percentage of volatile matter obtained. 
 The latest data on this subject (Sept., 1912) is by Fieldner and 
 Hall l . As a result of their experiments they recommend 1000 
 C. as the most desirable temperature at which to make this de- 
 termination. Their results using a No. 4 Meker burner with 
 natural gas compare very favorably with their results obtained 
 by heating the sample in an electric furnace. 
 
 Fixed Carbon. The fixed carbon is the difference between 100 
 and the sum of the moisture, ash and volatile matter. 
 
 Sulphur. Sulphur is determined by either of two methods: 
 
 (a) The Eschka method. 
 
 (b) The determination of the sulphur in the washings from 
 the calorimeter. 
 
 The two methods give closely agreeing results on most sam- 
 ples. As a rule the determination on the washings from the 
 calorimeter run a trifle lower than by the Eschka method and 
 where the exactness of the sulphur determination is of more than 
 ordinary importance the Eschka method should be used. The 
 details of the methods are as follows: 
 
 Eschka Method. One gram of the sample is thoroughly 
 mixed in a 30 c.c. platinum crucible with about one and one-half 
 grams of the Eschka mixture (two parts light calcined magnesium 
 oxide plus one part anhydrous sodium carbonate) ; about one-half 
 gram of the mixture is then spread on top as a cover. 
 
 The burning is done over grain or wood alcohol, gasoline gas 
 or natural gas, experiments having shown that the sulphur con- 
 
 1 Eighth International Congress of Applied Chemistry, Vol. X, p. 139. 
 
84 COAL 
 
 tained in gasoline gas and natural gas is so small that little or 
 none of it is taken up by the Eschka mixture. Ordinary arti- 
 ficial gas is so high in sulphur that its use is not permissible, as 
 blanks are likely to be large and variable and consequently the 
 correction to be applied is uncertain. At the beginning the flame 
 is kept low until the volatile matter is burned out. This requires 
 from 15 to 30 minutes. The heat is then increased and the mix- 
 ture stirred occasionally with a platinum wire, the heating being 
 continued till all traces of unburned carbon have disappeared. 
 
 The mixture in the crucible is then transferred to a 200 c.c. 
 beaker and digested with 75 c.c. of water for at least 30 minutes. 
 The solution is then filtered and the residue washed twice with 
 hot water by decantation and then washed on the filter, small 
 portions of water being used for each of the washings until the 
 filtrate amounts to 200 c.c. Bromine water in excess is then 
 added, and the solution made slightly acid with hydrochloric acid. 
 The amounts of these reagents usually added are 4 c.c. of water 
 saturated with bromine and 3 c.c. of concentrated hydrochloric 
 acid. 
 
 The solution is heated nearly to boiling and the sulphur pre- 
 cipitated with 20 c.c. of a hot 5 per cent solution of barium 
 chloride, slowly added from a pipette during constant stirring. 
 The solution and precipitate are allowed to stand at a temperature 
 a little below boiling for two hours or longer before filtering. 
 The filtrate from the barium sulphate is tested for acidity, with 
 litmus paper, and for excess of barium chloride by adding a few 
 drops of dilute sulphuric acid to a few c.c. of the filtrate in a test 
 tube. The preliminary washing of the precipitate is done with 
 hot water containing 1 c.c. of hydrochloric acid per liter. The 
 final washings are made with hot water alone and the washing is 
 continued until the washings no longer react for chlorine when 
 tested with silver nitrate. 
 
 The precipitate is ignited in a porcelain crucible. The filter 
 and precipitate are placed in the crucible, precipitate uppermost, 
 and the filter folded only enough to prevent loss by spattering. 
 A low heat is used until the paper is entirely " smoked off." The 
 heat is then raised sufficiently to bring the precipitate to dull 
 redness and the heating continued for a few minutes, or until the 
 carbon is burned out. The crucible and precipitate are then cooled 
 and weighed. The weight of barium sulphate less the blank 
 
METHODS OF ANALYSIS 85 
 
 from the reagents, times 0.137, times 100, equals the percentage of 
 sulphur in the sample. 
 
 Sulphur in the calorimeter washings. The determination 
 of the sulphur in the washings from the calorimeter is as follows: 
 The washings are slightly acidulated with hydrochloric acid and 
 filtered from the residue of ash, the filtrate is heated to boiling 
 and the sulphur precipitated as in the Eschka method. 
 
 ULTIMATE ANALYSIS 
 
 The ultimate analysis is best made in a 25-burner combustion 
 furnace. The details of the train and description of the method 
 of work are as follows : 
 
 The purifying train through which the air and oxygen are 
 passed before they enter the combustion tube is arranged in dupli- 
 cate, one part for air, the other for oxygen. The purifying re- 
 agents, arranged in the order named, are sulphuric acid, potas- 
 sium hydroxide, soda-lime and granular calcium chloride. The 
 combustion tube is about 40 inches long and about f inch 
 internal diameter. The tube extends beyond each end of the fur- 
 nace about four inches, the ends of the tube being protected 
 from the heat of the furnace by closely fitting circular shields 
 of asbestos. The rear end of the tube (the end next to the puri- 
 fying train) is closed with a rubber stopper. This end of the tube 
 being kept cool by the protection of the circular shield and by the 
 passage of cool air and oxygen, there is very little danger of vola- 
 tile products being given off by the rubber. The other end of the 
 tube is closed by a well-rolled cork of specially selected quality, 
 the danger from over-heating at this end of the tube being too 
 great to permit of the use of the more convenient rubber stopper. 
 This end of the tube may if desired be drawn out so that the 
 absorption train may be connected to it direct and thereby avoid 
 the danger of leakage from the use of a cork. In selecting a tube 
 for use care should be taken to avoid the heavy walled tubes as 
 the thin tubes are much less liable to breakage. 
 
 The rear end of the tube for 10 inches inside the furnace is 
 left empty; the next 14 inches is filled with a loose layer of wire 
 copper oxide, with a plug of acid-washed and ignited asbestos 
 at either end to hold the oxide in place. The copper oxide is fol- 
 lowed by a layer, about 4 inches long, of coarse fused lead chro- 
 
86 COAL 
 
 mate to stop sulphur products, this being held in place by a final 
 plug of asbestos. 
 
 The absorption train is as follows: The water is absorbed in 
 a six-inch U-tube, filled with granular calcium chloride; the car- 
 bon dioxide is absorbed by potassium hydroxide in an ordinary 
 Liebig bulb, to which is attached a three-inch U-tube containing 
 soda-lime and calcium chloride, the bulb and U-tube being 
 weighed together. This is followed by a final guard tube filled 
 with calcium chloride and soda-lime. The gases formed during 
 combustion are drawn through the train by suction, a Marriott 
 bottle being used to secure a constant suction head. 
 
 The oxygen used is kept over water and is supplied under 
 small pressure. The supply of oxygen and the aspiration during 
 a combustion are so regulated as to keep the difference in pressure 
 between the inside and outside of the tube very small, the pres- 
 sure inward being slightly greater. This reduces the danger of 
 leaks to a minimum, and, if by chance any slight leakage does 
 occur, it is inward rather than outward and the effect upon the 
 determination is small. 
 
 Carbon and hydrogen. Before beginning the determination, 
 the apparatus is tested for leaks by starting the aspirator and 
 shutting off the supply of air. With the aspirator on full, if not 
 more than four or five bubbles of air per minute pass through 
 the potash bulb, the connections are sufficiently tight to proceed 
 with the determination. Air is then admitted to the purifying 
 apparatus, the tube heated to redness throughout and 1000 c.c. 
 or more of air aspirated. The potash bulb and drying tube are 
 then detached and weighed. They are again connected and 500 c.c. 
 of oxygen followed by 1000 c.c. of air aspirated through the train. 
 
 On commencing the second aspiration the burners under the 
 rear portion of the tube are gradually turned down and finally 
 entirely out, so that the empty portion of the tube into which the 
 sample for analysis is to be inserted becomes nearly or quite cool, 
 by the time the aspiration is complete. The burners under the 
 two-thirds of the copper oxide next to the lead chromate are 
 kept lighted and this portion of the oxide kept at a red heat. 
 After aspiration of the 1000 c.c. of air, the potash bulb and drying 
 tube are detached and again re weighed. If the gain or loss in 
 weight is less than five-tenths milligram the apparatus is ready 
 for use. 
 
METHODS OF ANALYSIS 87 
 
 The absorption apparatus is then again connected and 0.2 
 gram of the well-mixed sample weighed into a platinum boat and 
 the boat and sample pushed into place in the combustion tube as 
 quickly as possible and slow aspiration of the train started at the 
 rate of one or two bubbles a second through the potash bulbs and 
 a mixture, in the proportion of about two bubbles of oxygen to one 
 of air, admitted into the train through the purifying apparatus. 
 The burners under the remaining copper oxide and behind the boat 
 are lighted and the moisture and volatile matter gradually driven 
 off. 
 
 This part of the operation requires very careful watching and 
 manipulation to secure correct results. The copper oxide must 
 be at a good red heat or the combustion of the hydrocarbons is 
 liable to be incomplete. If the evolution of the hydrocarbons 
 is too rapid incomplete combustion or absorption also results. 
 Also if the evolution is too rapid back pressure is developed in 
 the train and losses are almost sure to occur, either from mois- 
 ture getting back into the tube of the purifying apparatus or from 
 slight leaks in the train. When the volatile matter is expelled 
 that portion of the tube containing the boat is heated to redness, 
 more oxygen is admitted into the train and the fixed carbon 
 gradually burned off, using care not to allow the combustion to 
 take place too rapidly or fusion of the ash and incomplete com- 
 bustion may result. 
 
 Oxygen is admitted for about 2 minutes after the fixed 
 carbon is burned out, which may be seen by the sudden disap- 
 pearance of the glow. The oxygen is then turned off and air 
 aspirated through the train, the burners under the rear portions 
 of the tube being gradually turned down and out. After 1000 c.c. 
 have been aspirated the absorption apparatus is detached and 
 weighed. One-ninth the increase in the weight of the drying tube 
 equals the weight of the hydrogen and three-elevenths of the 
 increase in the weight of the potash bulb equals the weight of the 
 carbon from the sample. 
 
 The weight of the hydrogen and of the carbon in grams times 
 5 times 100 equal the percentage of each in the sample. After the 
 completion of a determination the platinum boat is removed from 
 the rear of the combustion tube and the ash examined for unburned 
 carbon. If desired the ash may be weighed as a check upon the 
 amount determined by the regular method. With a high per- 
 
88 COAL 
 
 centage of iron in the ash the ultimate ash usually runs a little 
 higher than the results obtained by burning out a gram sample 
 in the muffle furnace owing probably to the more complete oxida- 
 tion of the iron in the sample burned in the combustion train. 
 To make another determination, the absorption apparatus is 
 again connected to the train and another sample weighed into 
 the platinum boat and inserted into the rear of the combustion 
 tube. 
 
 In weighing the sample, the work should be done as rapidly 
 as possible and as soon as weighed the boat and sample should be 
 placed in a glass weighing tube which should be securely stop- 
 pered to prevent moisture losses. The sample is carried from the 
 balance room to the combustion train in the closed weighing 
 tube. The transfer from the weighing tube to the combustion 
 tube should be made quickly and the connections of the com- 
 bustion tube fitted up without undue loss of time. 
 
 Aspiration to constant weight is unnecessary between deter- 
 minations which follow one another immediately, but cannot 
 safely be neglected if the train is allowed to stand for several 
 hours. At the beginning of a series of determinations aspiration 
 to constant weight is always necessary. Also aspiration to con- 
 stant weight is necessary after the re-filling of the potash bulbs 
 or if a new bulb is substituted. The potash bulbs hold sufficient 
 potash for four or five determinations, after which the solution 
 should be replaced by fresh reagent. The potash solution 
 should have a specific gravity of about 1.27, which corresponds 
 to about a 30 per cent solution. The stock solution should be 
 treated with a few drops of permanganate solution to oxidize 
 any ferrous iron or other oxidizable compounds present, which 
 if not oxidized, interfere with the aspiration of the bulb to constant 
 weight. 
 
 NITROGEN 
 
 One gram of the finely pulverized coal is digested with 30 c.c. 
 of concentrated sulphuric acid and 0.6 gram of metallic mercury 
 until the carbon is completely oxidized and the liquid is nearly 
 colorless. The digestion should be continued for at least an hour 
 after the solution has reached the straw color stage. Crystals 
 of potassium permanganate are then added, a few at a time, until 
 a permanent green color remains. After cooling, the solution is 
 
METHODS OF ANALYSIS 89 
 
 diluted to about 300 c.c. with cold water. It is then transferred 
 to a 750 c.c. distillation flask. The excess of mercury is precipi- 
 tated by adding 25 c.c. of potassium sulphide (E^S) solution 
 (40 grams of K2S per liter). About one gram of granular zinc 
 is added to prevent bumping. Enough saturated sodium hydrox- 
 ide (NaOH) solution (usually about 80 c.c.) is added to make the 
 solution distinctly alkaline, the soda being added carefully so 
 as to run down the side of the flask and not mix with the acid 
 solution. The flask is then connected to a condenser, the contents 
 mixed by shaking and then heated over a Bunsen burner until 
 about 200 c.c. of distillate have been obtained. The distillate is 
 collected in a receiving flask containing 10 c.c. of standard sul- 
 phuric acid solution (1 c.c. =0.005 gram of nitrogen) to which 
 cochineal indicator in amount sufficient for titration has been 
 added. The end of the tube carrying the distillate should dip 
 beneath the surface of the acid at all times. The distillate is 
 then titrated with standard ammonia solution (20 c.c. of ammo- 
 nia solution = 10 c.c. of sulphuric acid solution = 0.05 gram of 
 nitrogen) . If trouble is experienced from frothing during distilla- 
 tion it may be prevented by the addition of a small piece of 
 paraffin to the solution before distillation. 
 
 A convenient method of adding the 0.6 gram of mercury is 
 to measure it rather than to weigh it. This can readily be done 
 by partially filling up the opening in a glass stop-cock so that 
 when the cock is turned it carries and delivers a drop of mercury. 
 Such an apparatus correctly calibrated will deliver practically 
 the same amount each time, and the addition of the mercury can 
 be made in one-tenth the time required to weigh out the desired 
 amount. 
 
 For further details of the Kjeldahl process, see Bulletin 107 
 (Revised) U. S, Department of Agriculture, Bureau of Chemistry. 
 
 PHOSPHORUS 
 
 In the determination of phosphorus 5 to 10 grams of sample 
 are burned to ash in the muffle furnace. The ash is mixed in a 
 platinum crucible with four to six times its weight of sodium 
 carbonate and about 0.2 gram of sodium nitrate and is fused 
 over the blast lamp. The fused mass is dissolved in water, acidi- 
 fied and evaporated to dry ness. The residue is taken up in 
 
90 COAL 
 
 hydrochloric acid and the phosphorus determined in the usual 
 way either by weighing the yellow precipitate or titrating it with 
 permanganate or standard alkali. For details of phosphorus 
 determinations see Lord's " Notes on Metallurgy " or other texts 
 on metallurgical analysis. 
 
 OXYGEN 
 
 No reliable method is known for the direct determination of 
 the oxygen in coal and it is, therefore, determined by difference. 
 The sum of the percentages of hydrogen, carbon, nitrogen, sul- 
 phur and ash is subtracted from 100 and the remainder is called 
 oxygen. This result is always inaccurate in that it does not 
 represent the true amount of oxygen in the coal. The amount of 
 the inaccuracy increases with the percentage of the ash and sul- 
 phur. The effects of ash and sulphur upon the value obtained for 
 oxygen have been discussed elsewhere and do not need repetition 
 at this point. 
 
CHAPTER V 
 DETERMINING THE CALORIFIC VALUE 
 
 THE establishment and use of specifications for the purchase 
 and sale of coal based upon the heating value require the actual 
 determination of the heating value of the sample or samples which 
 are used as the basis of settlement, and in analyzing such sam- 
 ples the chemist is expected and required to make this determina- 
 tion along with the determination of moisture, ash and sulphur. 
 At present some form of pressure calorimeter, in which the sam- 
 ple is burned in a steel bomb under 15 to 25 atmospheres pres- 
 sure of oxygen, is generally regarded as the standard type of 
 calorimeter, and specifications for the purchase of coal frequently 
 specify that the heating value shall be determined in a bomb 
 calorimeter. Some of the commoner types of this form of calo- 
 rimeter are : the Mahler, the Atwater, the Emerson, the Williams, 
 and the Kroecker. 
 
 The details of the method of making a determination and the 
 calculation of the results are as follows: This description is based 
 primarily upon the use of a Mahler calorimeter but is applicable 
 with minor modifications to any of the other calorimeters men- 
 tioned. About 2 grams of the 60-mesh sample are pressed into 
 a small briquet by means of a small screw press and mold. The 
 press used by the writer is the iron frame of a 2-quart tincture 
 press manufactured by the Enterprise Manufacturing Company 
 of Philadelphia, Pa. After removal from the mold the briquet 
 is broken into smaller portions and about 1 gram accurately 
 weighed and placed in the platinum combustion tray which is 
 covered with a thin disc of asbestos paper that has been washed 
 with hydrochloric acid and ignited in a muffle furnace. The tray 
 is then attached to one of the platinum terminals fitted to the lid 
 and the terminals are connected by a piece of iron wire (platinum 
 wire should be used when the bomb is platinum lined) about 10 
 centimeters long and formed into a spiral. The ends of the wire 
 
 91 
 
92 COAL 
 
 are attached to the clean platinum terminals, by wrapping the 
 wire tightly around them. The spiral is bent down so that it 
 touches the coal sample in the tray. The lid is placed on the 
 bomb and screwed down tightly against the lead gasket. Oxygen 
 under pressure is admitted gradually into the bomb through 
 the valve stem until the manometer recording the pressure 
 reads 18 to 20 atmospheres. The needle valve is then closed. 
 Very little force should be used in closing it and extra pressure 
 should be avoided. 
 
 The bomb filled with oxygen is placed in the brass bucket 
 Containing from 2400 to 2500 grams of distilled water, the bucket 
 having been previously placed in the insulated jacket. The 
 stirring apparatus is then adjusted so that it touches neither the 
 bucket nor bomb and works freely. The thermometer for record- 
 ing the temperature rise is clamped into position and so adjusted 
 that the lower end of the mercury bulb is about 5 centimeters 
 above the bottom of the bucket. The outside terminals of the 
 bomb are connected with wires leading to the switch. The stirrer 
 is then set in motion and the readings of the thermometer taken 
 by means of a telescope attached to a cathetometer. The ther- 
 mometer is graduated to -^th degree Centigrade and the readings 
 can be interpolated to thousandths of a degree. The stirring 
 should be continued at a uniform rate throughout the determina- 
 tion and should be sufficiently rapid to insure thorough mixing. 
 Preliminary readings are taken at intervals of one minute each 
 for about five minutes or until the rate of change per minute is 
 nearly uniform and a definite rate is established. The switch is 
 then closed and the current turned on for about one-half second. 
 The ignition of the sample is followed by a very rapid increase 
 in temperature and the first two readings after combustion are 
 taken one-half minute apart. Other readings are then taken at 
 minute intervals. The temperature usually reaches a maximum 
 in three or four minutes but the series of readings is continued 
 until a uniform final rate has been established. Not less than 
 five and sometimes as many as seven or eight readings are 
 required to determine the final rate. 
 
 The calculations involved and corrections applied are shown 
 by a typical determination on p. 93. 
 
 The readings from 7-50 to 7-54 are the readings of the pre- 
 liminary period. The increase in temperature during this time 
 
DETERMINING THE CALORIFIC VALUE 
 
 93 
 
 FORM FOR CALORIMETER DETERMINATIONS 
 
 DEPARTMENT OF METALLURGY, 
 
 OHIO STATE UNIVERSITY. 
 SAMPLE No. 5160 
 
 Wet and dry bulbs = 14-22 C. Coal = 
 
 Jacket water =21 C. 
 
 Room temperature = 22 C. 
 
 Time. Readings C. Observed final temperature 
 
 ' ' initial ' ' 
 
 temperature rise 
 Radiation correction 
 Calibration correction 
 Stem correction . . . 
 
 Corrected temperature dif. 
 Water equivalent 1 
 
 Date 5-24-1912. 
 1.0018 gms. 
 
 7-50 
 
 19 
 
 .318) 
 
 
 
 51 
 
 19 
 
 .326 
 
 
 
 
 52 
 
 19 
 
 .334 \ =+0 
 
 0075 
 
 
 53 
 
 19 
 
 .340 
 
 
 
 54 
 
 19. 348 J +0 
 
 0075 
 
 
 +0.0026 
 
 1 
 
 20 
 
 .2 +0 
 
 0030 
 
 
 
 
 
 +0 
 
 0001 
 
 55 
 
 21 
 
 .40 -0 
 
 0028 
 
 
 
 
 
 -0 
 
 0035 
 
 56 
 
 21 
 
 .700 -0 
 
 0043 
 
 
 
 
 
 -0 
 
 0043 
 
 57 
 
 21 
 
 .746 -0 
 
 0043 
 
 
 -0.0043 
 
 
 
 -0 
 
 .0043 
 
 
 58 
 
 21 
 
 .744 
 
 
 
 
 
 
 59 
 
 21 
 
 .740 
 
 
 -0 
 
 0094 
 
 60 
 
 21 
 
 .736 
 
 
 
 
 1 
 
 21 
 
 .734 
 
 =-0 
 
 .0043 
 
 
 2 
 
 21 
 
 .728 
 
 
 
 
 3 
 
 21 
 
 .722 
 
 
 
 
 4 
 
 21 
 
 .718 
 
 
 
 
 21.744 
 19.348 
 
 Calories of heat developed 
 Corrections 
 
 2.396 
 
 = +0.0094 
 = -0.006 
 = +0.0014 
 
 = 2.4008 
 2875 
 
 5750.0 
 1150.0 
 
 00.0 
 
 00.0 
 2.3 
 
 = 6902.3 
 - 101.6 
 
 Heat from sample =6800.7 
 
 Correction for excess sample 
 
 over 1 gram = 12.2 
 
 Calorific value of coal 
 
 = 6788.5 
 
 Wire fuse = 10 cm. 
 
 unburned=2 cm. 
 
 " " burned =8 cm. (1 cm. =2.4 cal.) = 19.2 cal. 
 Titer, 23.8 to 31.6 =7.8 cc. (1 cc.=5 cal.) =39.0" 
 Sulphur in coal 3.34 per cent (.01 gm. = 13 cal.) = 43 . 4 ' 
 
 Total correction 
 
 = 101.6 ' 
 
 Thermometer used, No. 5764 Position 5 c.m. 
 
 Scale reading 18.3. Stem temperature 22 C 
 
 Atmospheres oxygen used = 18 Valve tight. 
 
 At 19 add 4.5 c.c. of water to obtain 2400 gms. 
 
 (Signed) C.H.Y. 
 Checked E.S.D. 
 
 is 19.318 to 19.348 = 0.030 or 0.0075 degree per minute. The 
 switch was closed and the combustion started at 7-54, the maxi- 
 mum observed temperature being at 7-57. From 7-58 to 7-64 
 
94 COAL 
 
 the rate of loss is quite regular. Inspection shows this loss to be 
 about 0.004 degree per minute. The temperature at 7-58 is taken 
 as the end of the combustion period since it is the first reading 
 that falls in line with this rate of loss. The loss during the six 
 minutes following the combustion period is 21.74421.718 = 
 0.026 or 0.0043 degree per minute. The observed temperature 
 increase is the difference between the temperature at the begin- 
 ning and end of the combustion period or 21.744-19.348 = 2.396. 
 The total change in the rate of gain or loss in the system cor- 
 responding to 2.39 increase of temperature is from a rate of 
 +0.0075 to a rate of -0.0043, a total change of 0.0118. A 
 change of rate of 0.0118 with a change of temperature of 2.4 
 (counting to the nearest 0.1) is equivalent to a change of rate of 
 approximately 0.0005 for each 0.1 temperature change, from 
 which the rate of gain or loss at the different readings can be 
 obtained. The rate of gain or loss at the 58th minute is the 
 final rate 0.0043. The temperatures at the 57th and 56th min- 
 utes are within 0.1 of the temperature at the 58th minute and 
 the rate of loss is the same as that at the 58th minute. The 
 temperature at the 55th minute is approximately 0.3 lower and 
 the rate of loss is accordingly less by 0.3X0.0005 = 0.0015 or the 
 rate of change at the 55th minute is -0.0043+0.0015= -0.0028. 
 At 54 J minutes the temperature to the nearest 0.1 is 0.9 higher 
 than at the 54th minute. The rate of change corresponding to 
 0.9 is 9X0.0005 = 0.0045. Subtracting this change from the rate 
 of change at the 54th minute = +0.0030. The actual tem- 
 perature gain or loss for each of the different intervals is found 
 by adding the rates at the beginning and end of the interval and 
 dividing by 2 if a minute interval or by 4 if a half-minute inter- 
 val. The sum of the rates at the beginning and end of the inter- 
 val from 54 to 54J is +0.0075+ (+0.0030) = +0.0105. This 
 divided by 4 and carrying the result to the nearest fourth 
 decimal =+0.0026, the temperature gain during the interval. 
 For the interval 54| to 55, +0.0030+ (-0.0028) =0.0002. This 
 divided by 4 gives 0.00005 or to the nearest fourth decimal 
 = +0.0001. For the minute interval 55 to 56, -0.0028+ 
 (-0.0043) = -0.0071. This divided by 2= -0.0035. The losses 
 in the other intervals are obtained in a like manner. Adding 
 together the different gains and losses the total loss is found to 
 be 0.0094, from which the radiation correction = +0.0094. The 
 
DETERMINING THE CALORIFIC VALUE 95 
 
 calibration correction for the thermometer used= 0.0060. The 
 stem correction = +0.0014. The corrected temperature difference 
 = 2.4008. The water equivalent of the calorimeter system is 
 2875 calories. Multiplying the corrected temperature change by 
 this water equivalent (i.e., by the number of calories necessary 
 to cause a rise of 1 of temperature), the total heat developed 
 during combustion is 2.4008X2875 = 6902.3. 
 
 Corrections. The heat from the burning of the wire fuse is 
 found by multiplying the weight of wire taken by its calorific 
 value (1600 calories per gram = 2.4 calories for 1 cm.). 8.0 cm.X 
 2.4 =19.2 calories. The acidity of the bomb liquor after com- 
 bustion is found by titrating it with a standard ammonia of such 
 strength (0.0059 grams of ammonia per c.c., see acidity correc- 
 tions) that one c.c. corresponds to a heat correction of five calo- 
 ries, assuming the acidity to be entirely due to nitric acid, from 
 which 7.8 times 5 equals 39 calories, the correction due to the 
 formation of nitric acid. 
 
 A large part of the acidity in high sulphur coal is, however 
 due to sulphuric acid, and the heat correction for acid formed, 
 considering it all as nitric acid, is therefore incomplete, a further 
 correction of 13 calories for each 0.01 gram of sulphur present 
 being required. (See acidity corrections.) 3.34 per cent sul- 
 phur in the sample is 0.0334 gram sulphur on a one gram sample 
 taken. Therefore, the correction is 3.34X13 = 43.4 calories. 
 
 The total of these corrections is 101.6 calories. 6902.3, the 
 total heat developed, less this correction of 101.6 gives 6800.7 
 calories of heat from the combustion of the coal. These 6800.7 
 calories are developed by 1.0018 grams of sample. The value 
 per gram is therefore 6800.7 divided by 1.0018. The amount of 
 sample taken is so near one gram that this correction can be 
 approximated as .68 of a calorie for 0.0001 gram of coal. For 
 0.0018 the correction is accordingly 18X0.68 = 12.2. Making 
 this correction gives 6788.5 as the calorific value of the coal. 
 
 The foregoing description of the calculations makes them 
 appear more difficult and troublesome than they really are, as 
 practically all the corrections can be made mentally, and the 
 radiation corrections can be determined very readily if the cal- 
 culator is familiar with the routine of the determination. The 
 use of .printed blank forms saves time and insures regularity 
 and completeness in the records. 
 
96 COAL 
 
 SPECIAL NOTES ON CALORIFIC DETERMINATION 
 
 Complete combustion of the sample. To insure complete 
 combustion from three to five times the theoretical amount of 
 oxygen required should be used which for a one-gram sample 
 of coal is equivalent to approximately from 9 to 15 grams of oxy- 
 gen. In a bomb of the Mahler type with a capactiy of 600 c.c., 
 the author has found it unsafe to use less than 15 atmospheres 
 pressure of oxygen which corresponds to about 11 grams of oxy- 
 gen and in ordinary work 18 to 20 atmospheres corresponding to 
 about 15 grams of oxygen are preferable. The complete ignition 
 of the briquetted sample is more certain if the briquet is not 
 made too hard and is broken up into a number of pieces. The 
 fine sample can be weighed direct and the combustion made upon 
 the coal in this condition if care is used in admitting the oxygen 
 to the calorimeter not to blow any of the fine coal out of the tray. 
 On account of this danger of blowing out fine coal the author 
 prefers briquetting most samples. Anthracite coal and coke will 
 not briquet readily and require to be run in powdered form. 
 The use of a disc of ignited asbestos on the tray to lessen the 
 rate of conduction of heat during combustion is a decided ad- 
 vantage in securing complete combustion of cokes and anthracites 
 which are much more difficult to burn than the ordinary bitu- 
 minous coals. 
 
 Preventing leakage of valve. By use, the valve through 
 which the oxygen is admitted into the calorimeter soon becomes 
 corroded from the action of the acid fumes and rusted through the 
 action of moisture and air. In this condition it is extremely 
 difficult to prevent considerable leakage of oxygen. This leakage 
 may be prevented and the valve made to fit tight by cutting a 
 thin washer of lead about one-thirty-second inch in thickness and 
 fitting into the valve, using care in its insertion not to get it in 
 crosswise and thereby close the opening into the bomb. A very 
 efficient way to insert it is as follows: Hold the valve stem, 
 valve-end up and slip the washer over the tip of the needle. 
 Then with the stem in this vertical position screw the lid on to 
 the stem carefully till the washer is pressed into place. Very 
 slight pressure is required to close the valve when fitted in this 
 way and extra pressure is to be avoided as tending to force lead 
 into the needle opening, which may be entirely closed and will in 
 
DETERMINING THE CALORIFIC VALUE 97 
 
 this event require drilling out before the bomb can be used 
 again. 
 
 Leakage around the lid. As a rule little trouble is experienced 
 from leakage around the lid if the lead gasket is kept smooth. 
 Moistening the gasket with a drop of water before putting on the 
 lid considerably lessens the danger of leakage. The film of water 
 between the gasket and the lid of the bomb appears to be of con- 
 siderable advantage in securing a gas-tight joint. 
 
 Water surrounding the bomb. In the regular routine deter- 
 minations the amount of water used is more conveniently meas- 
 ured than weighed. For this purpose the author uses a Florence 
 flask holding about 2400 c.c. of water when filled to the middle 
 of the neck. The number of grams of water that it delivers is 
 determined by filling it to a fixed mark and weighing at a definite 
 observed temperature. The flask is then emptied and allowed to 
 drain 15 seconds and again re-weighed, an allowance of 2.4 grams 
 being made for the effect of the buoyancy of the air displaced by 
 this amount of water. The difference in weight is the number of 
 grams of water the flask delivers at this temperature. A table 
 is then prepared giving for different temperatures the number 
 of c.c. of water which must be added to the water inside of the 
 flask to obtain 2400 grams. 
 
 The diameter of the necks of the flasks used is from 1 J to If 
 inches. With this size of neck and a uniform time of 15 seconds 
 for drainage, the amount of water can easily be measured to an 
 accuracy of 1 c.c. and the maximum errors of measurement do 
 not affect the calorific value obtained over two or three calories. 
 The time required for measuring is less than that required for 
 weighing and does not involve the continued use of an expen- 
 sive balance and set of weights. 
 
 An example of the method of calibration is as follows: 
 
 Weight of flask filled with water to a definite mark = 2842.5 grams 
 W T eight of empty flask after draining 15 seconds = 450.5 ll 
 
 Difference = 2392.0 " 
 
 Corrections to weights = + .6 " 
 
 Corrections for buoyancy of air = +2.4 " 
 
 Total weight of water delivered = 2395.0 ' l 
 
 Temperature of water = 20 C. For small corrections 1 c.c. 
 
98 COAL 
 
 of water may be taken as equal to one gram and at the tempera- 
 ture of 20 C. the amount of water to be added to the flask in 
 order that it may deliver 2400 grams is 5 c.c. The amounts for 
 other temperatures based on the specific gravity of water at the 
 different temperatures are obtained as follows: 
 
 The volume of the flask in cubic centimeters = 2395, divided 
 
 2395 
 
 by the specific gravity of water at 20 C. is - - =2399.2. 
 
 0.99823 
 
 The density of water for the range covered by ordinary calori- 
 metric work are as follows: 
 
 Degrees C. Density. Degrees C. Density. 
 
 8 
 
 _ 
 
 0.99988 
 
 20 
 
 
 
 0.99823 
 
 10 
 
 = 
 
 0.99973 
 
 . 22 
 
 = 
 
 0.99780 
 
 12 
 
 = 
 
 0.99953 
 
 24 
 
 = 
 
 0.99732 
 
 14 
 
 = 
 
 0.99928 
 
 26 
 
 = 
 
 0.99680 
 
 16 
 
 = 
 
 0.99898 
 
 28 
 
 = 
 
 0.99626 
 
 18 
 
 = 
 
 0.99863 
 
 30 
 
 = 
 
 0.99567 
 
 The weight of the water which the flask will deliver when 
 filled to the mark at any temperature (i) = the volume of the 
 flask, (2399.2) times the density of the water at temperature (t). 
 The amount of water to be added at any given temperature when 
 the flask is filled to the mark is 2400 minus what the flask holds 
 at that temperature. At 10 degrees this particular flask holds 
 2399.2X0.99973 = 2398.6. Hence the correction to be added 
 = 2400 2398.6 = 1.4 grams or 1.4 c.c. Such a table of correc- 
 tions once prepared is pasted on the side of the flask and the 
 proper amount to add for any particular determination readily 
 determined. 
 
 Temperature conditions. More satisfactory rates of gain 
 or loss during a determination are secured if the temperature 
 differences between the air of the laboratory and that of the water 
 inside the inner bucket and in the outer insulating jacket are 
 kept small. The author's practice is to keep the temperature 
 of the water in the outer jacket within a few degrees of room 
 temperature. The water to be used in the inner bucket is cooled 
 till its temperature is about two to three degrees lower than that 
 of the water in the outer jacket, care being taken that this tem- 
 perature is not too near the dew-point. In warm, damp weather 
 to avoid this danger, the water in the outer jacket is kept several 
 degrees above room temperature. 
 
DETERMINING THE CALORIFIC VALUE 99 
 
 With these temperature relations, the greater rate of change 
 during a determination is before the combustion, and the rate 
 of change after the combustion period is small. The larger the 
 rate of change the larger is the possible error. The effects of the 
 larger rate before the combustion period are, after the first min- 
 ute, practically eliminated. By the end of the first minute most 
 of the total temperature rise has occurred and the rate of change 
 during the other minutes of the combustion period approxi- 
 mates in value the final rate. With the final rate small the total 
 corrections are correspondingly small and errors from this source 
 are reduced to a minimum. 
 
 CORRECTIONS TO BE APPLIED 
 
 Correction for nitric acid. The data and calculation of the 
 correction are as follows: In burning the sample in the bomb 
 calorimeter, under pressure, a portion of the nitrogen in the fuel 
 and perhaps is burned of the nitrogen in the small amount of air 
 in the bomb a portion to N20s aqua while in combustion of fuel 
 under a boiler the nitrogen either escapes as free nitrogen or 
 burns to gaseous N2O5 and passes off in the flue gases. The heat 
 of formation of N20s aqua is approximately 1020 calories per 
 gram of nitrogen. The heat of liberation of the nitrogen, as free 
 nitrogen, from the coal is not definitely known but is presumably 
 not far from 0. The heat of the formation of gaseous N2Os from 
 nitrogen and oxygen is approximately 36 calories per gram of 
 nitrogen. In either case the heat change per gram of nitrogen 
 is small and in correcting for the amount of nitric acid in the 
 bomb, the heat of formation of N2Os aqua is usually taken as 
 the nitric acid correction. The reaction for neutralization of 
 nitric acid by an alkali is as follows: 
 
 2HN0 3 +2NH 4 OH = 2NH 4 N03+H 2 O, 
 
 from which it follows that 14 parts by weight of nitrogen as 
 nitric acid equal in neutralizing value 17 parts by weight of 
 ammonia (NHs). A convenient strength for the titrating alkali 
 is one cubic centimeter equivalent to 5 calories of heat. Since 
 1020 calories are produced by the combustion of one gram 
 
100 COAL 
 
 of nitrogen then 5 calories are produced by the combustion of 
 
 5 
 
 gram = 0.0049 gram; 0.0049 gram of nitrogen as nitric acid 
 
 requires HX 0.0049 gram of ammonia for neutralization = 0.00595 
 gram of ammonia per cubic centimeter or 5.95 grams per liter. 
 
 Correction for sulphuric acid. Any sulphuric acid present is 
 titrated with nitric acid and its heat of formation is partially 
 allowed for by considering it as nitric acid. The data for deter- 
 mining the amount of correction necessary and the amount which 
 is allowed for by considering it as nitric acid are as follows: The 
 heat of formation of aqueous sulphuric acid in the calorimeter 
 is approximately 4450 calorics per gram of sulphur. In ordinary 
 combustion in air the sulphur is burned to sulphur dioxide, the 
 heat of formation of which is approximately 2250 calories per 
 gram of sulphur. 
 
 The excess heat due to the formation of sulphuric acid in 
 the bomb is therefore 4450 2250 = 2200 calories per gram of 
 sulphur. In neutralizing with ammonia the reaction for sul- 
 phuric acid is as follows: H 2 SO4+2NH 4 OH = (NH4)2SO4+H 2 O, 
 or in titrating H 2 SO 4 = 2HN0 3 = 2NH 4 OH. Expressed by weight 
 32 parts of sulphur as sulphuric acid 28 parts of nitrogen as 
 nitric acid = 34 parts of ammonia (NHs). Since 32 parts of sulphur 
 as sulphuric acid = 28 parts of nitrogen as nitric acid, one gram of 
 sulphur = | gram of nitrogen in the titration of nitric acid with 
 ammonia. I of 1020 calories = 892 calories as the correction 
 which is applied when sulphuric acid is titrated as nitric acid; 
 2200 892 = 1308 calories per gram of sulphur as an additional 
 correction which should be applied. This amounts to approxi- 
 mately 13 calories for each 0.01 gram of sulphur or when a one- 
 gram sample is burned in the calorimeter, 13 calories for each 
 per cent of sulphur present in the sample. As the amount of 
 sulphur is frequently as high as 4, 5 or 6 per cent this correction 
 is often large and there is no valid reason for omitting it, not- 
 withstanding the statement often seen in print that the cor- 
 rection for the sulphur present is never important. 
 
 Ignition of the iron wire. In igniting the wire fuse a current 
 of 3 or 4 amperes is usually required and an electromotive force 
 of 15 to 20 volts is desirable. Lower voltage such as a current 
 from 4 or 5 dry cells or from a storage battery may be used but a 
 low voltage requires special care in making the connection or fail- 
 
DETERMINING THE CALORIFIC VALUE 101 
 
 lire to ignite often results. If a current of low voltage is used, 
 better contact between the platinum terminals and the wire is 
 secured if the rods and wire are carefully cleaned with emery 
 paper. Moistening the connection between the terminals and 
 the wire with a drop of dilute calcium 'chloride solution is also an 
 advantage in securing certainty of ignition. The usual laboratory 
 practice of using a high voltage current, ,u c h as the current from 
 a 110-volt lighting circuit, is liable to result in errors by leakage 
 of the current after ignition of the wire and it is much bafor to 
 introduce a resistance coil in parallel with the calorimeter and 
 shunt off only a portion of the current through the igniting wire. 
 In this way the voltage through the calorimeter can easily be cut 
 down to 20 volts. 
 
 To lighting circuit 
 
 4-32C.P lamps p Q Q Q 
 
 German silver 
 resistance coil 
 
 witch 
 
 circuit 
 
 FIG. 6. Diagram of Circuit for Igniting Wire Fuse. 
 
 A convenient resistance for furnishing the proper amount 
 of current from a 110-volt lighting circuit is to mount four 32- 
 candle power lamps in parallel. This will give in the neighbor- 
 hood of 3 J to 4 amperes of current which is ample for the size of 
 wire usually used. With this arrangement a 5- or 6-ohm resis- 
 tance coil of German silver or other high resistance wire, as 
 nichrome or climax wire, used in parallel with the calorimeter 
 is a simple way of reducing the voltage. (See Fig. 6.) Whatever 
 be the connection the circuit should be kept closed only long 
 enough to insure burning of the wire. This should not require 
 at most, more than 1 or 2 seconds. If more time is required more 
 current should be used. With leakage of current through the 
 calorimeter and using the current direct from a 110-volt circuit, 
 as much as 20 calories per second may be transmitted to the 
 
102 COAL 
 
 calorimeter, which is an error too large to be neglected. By using 
 the shunt and keeping the voltage below 20 the he?it from 4 
 amperes of current cannot exceed 4 calories per second, and for 
 the time that the circuit is usually closed it is a small error com- 
 pared to the possible large one which may be introduced by using 
 the 110-volt circuit direct. 
 
 Heat developed while the circuit is closed for ignition of the 
 iron wire. The iron ignition wire used (about 0.12 millimeter in 
 diameter and about 3 centimeters between the terminals) if in 
 good contact with the platinum terminals has a resistance of 
 less than one ohm and the amount of heat developed during the 
 fraction of a second that the current passes through the wire 
 before it ignites is small. The resistance of the calorimeter it- 
 self with the insulation in good condition is several millions of 
 ohms. A test on one of the calorimeters indicated a resistance of 
 upwards of twenty million ohms, the test being made on a 120- 
 volt circuit. Pure water is such a poor conductor that after im- 
 mersion of the calorimeter in water the resistance is still high 
 (expressed in thousands of ohms). 
 
 In routine work the distilled water used to surround the calo- 
 rimeter bomb is used over and over again. The resistance of this 
 water, owing to traces of impurities, is not so great as that of the 
 original distilled water, but its resistance is still high. Tests with 
 water which had previously been used in making 40 or 50 calo- 
 rimeter determinations showed with a 120-volt circuit about 1500 
 ohms resistance. Tests with distilled water taken directly from 
 the laboratory supply showed a resistance of about 5000 ohms. 
 With the resistance in excess of 1000 ohms, the heating effect 
 due to leakage of current is quite small and the danger from 
 excessive leakage is either from defective insulation of the bomb 
 itself or from the use of water containing more than traces of 
 impurities. The possible heating effects under these conditions 
 are discussed in the next paragraph. 
 
 The heat developed in a conductor of which the resistance 
 is R ohms by current of I amperes in a time of t seconds is 
 0.2387#/ 2 t calories. 
 
 Using the current from a 110-volt circuit with 4 thirty-two 
 candle power lamps in parallel, the greatest current is approxi- 
 mately four amperes. With the resistance coil (5 ohms re- 
 sistance) in the circuit, the possible heat developed by passage of 
 
DETERMINING THE CALORIFIC VALUE 103 
 
 current through the calorimeter is small. Before the ignition of 
 the iron wire with a low resistance in the calorimeter circuit 
 (a fraction of an ohm) practically all the current passes through 
 the calorimeter, but since I cannot exceed 4, 1 2 cannot exceed 16, 
 and with the resistance less than one ohm, the product of 
 Q.2387RI 2 is less than 4 calories per second. 
 
 After the ignition of the iron wire under normal conditions 
 the resistance of the calorimeter circuit is expressed in thousands 
 of ohms and practically all the current passes through the coil 
 having only 5 ohms resistance. With a resistance of 1500 
 ohms such a small portion of the current flows through the 
 calorimeter that its heating effect is less than one-tenth calorie 
 per second. With defective insulation in the calorimeter, or with 
 very impure water, the resistance may be very much less and the 
 possible effects under these conditions should be considered. 
 
 Take as special cases, resistances of 10 ohms and 100 ohms in 
 the calorimeter. With the circuit closed the total current flowing 
 through the resistance coil and the calorimeter is approximately 
 4 amperes. This varies slightly on account of small changes in 
 the total resistance of the circuit due to the variations in the 
 calorimeter resistance, but this variation in current is so small 
 that it may be neglected in discussing the heat effect in the 
 calorimeter. With the calorimeter and coil connected in parallel, 
 the portion of the total current passing through each is inversely 
 as its resistance is to the sum of the two resistances. With 10 
 ohms resistance in the calorimeter and 5 ohms resistance in the 
 coil the portion of current passing through the calorimeter is 
 
 With 100 ohms resistance in the calorimeter the portion of cur- 
 rent passing through it is: 
 
 5 11 
 
 * V/ A C\ O O TY^ T\^t*f^ 
 
 100+5" 21 '21* 
 
 Applying the formula for heat production with 10 ohms 
 resistance 0.2387X10X(1.3) 2 = 4 calories per second. With 100 
 ohms resistance 0.2387 X 100 X(0.2) 2 = l calorie per second. 
 
104 COAL 
 
 With resistances between 1 and 10 ohms, the heating effects 
 are very close to 4 calories. With resistances of over 10 ohms 
 the heating effects are less than 4 calories per second, from which 
 it appears that using the resistance coil in circuit under no con- 
 dition can the leakage of current per second be large enough to 
 very appreciably affect the results obtained on the calorific value 
 of the materials tested. 
 
 Resistance coil left out of the circuit. Before the burning 
 of the iron wire with little resistance in the calorimeter (less than 
 1 ohm) approximately 4 amperes of current will pass through the 
 calorimeter and the heating effect is small (less than 4 calories 
 per second). After the burning of the iron wire, under normal 
 conditions, with the resistance expressed in thousands of ohms, 
 the heating effect due to current passing through the calorimeter 
 is also small. In the special test upon the calorimeter showing 
 1500 ohms resistance, the heating effect of the current flowing 
 through the circuit is between two and three calories per 
 second. 
 
 ^ With the lower resistances, which may occur, due to defects 
 in the insulation or the use of very impure water, the effect may be 
 of considerable magnitude and the possible effects with resistances 
 between 1 and 1500 ohms should be considered. Small increases 
 in the resistance in the calorimeter diminish the amount of cur- 
 rent flowing only slightly and the amount of heat produced in- 
 creases very nearly in proportion to the increase in resistance. 
 
 With 1/2 and 3 ohms resistance in the calorimeter, the heat 
 produced is approximately 4, 8 and 12 calories per second. With 
 larger increases in resistance the change in current due to the 
 change in the total resistance of the circuit should be considered. 
 The total resistance of the circuit is the resistance of the lamps 
 1(HO ohms), plus the resistance in the calorimeter, plus the 
 resistance in the remainder of the circuit. The resistance of the 
 rest of the circuit is small and the total resistance outside the 
 calorimeter is therefore approximately that of the lamps. 
 (1(110 ohms)l. The total resistance of the circuit is approxi- 
 mately 27 ohms plus the resistance of the calorimeter. 
 
 E 
 
 Ohm's law for current flowing through a conductor is /= . 
 
 Considering as special cases the effect of 10, 100 and 1000 ohms 
 resistance in the calorimeter: 
 
DETERMINING THE CALORIFIC VALUE 105 
 
 (a) With 10 ohms resistance the current is - = 3 amperes. 
 
 .27-j-lO 
 
 (6) With 100 ohms resistance the current is -=0.9 
 
 27 -f- 100 
 
 ampere. 
 
 (c) With 1000 ohms resistance the current is - = 0.1 
 
 27+1000 
 
 ampere. 
 
 Applying the formula for heat developed in the calorimeter: 
 
 (a) 0.2387 X 10 X(3) 2 = 21 calories per second. 
 (6) 0.2387XlOOX(0.9) 2 = 19'calories per second. 
 (c) 0.2387X1000X(0.1) 2 = 3 calories per second. 
 
 With normal conditions, good insulation in the calorimeter 
 and water practically free from impurities, the effects of leakage 
 of current are unimportant, but with defective insulation or water 
 high in impurities, the values obtained under conditions (a) and 
 (6) show that the possible effects during the time that the switch 
 is closed for ignition of the iron wire (about 2 or 3 seconds) may 
 be of such magnitude (40 to 60 calories) as to change appreciably 
 the calorific value obtained for the materials tested. The use of 
 the resistance coil in the circuit is a safeguard against such pos- 
 sible errors. 
 
 Water equivalent of the calorimeter. The accuracy of the 
 calorimetric values obtained is to an important degree depen- 
 dent upon the accuracy with which the water equivalent of the 
 apparatus has been determined. This may be determined by 
 several methods: 
 
 (1) From the weights of the different parts by multiplying 
 each by its respective specific heat. The water equivalent is 
 equal to the sum of the specific heats of the different parts. 
 
 (2) By adding definite weights of warmer or colder water to 
 the system and noting the corresponding increase or decrease 
 in temperature. 
 
 (3) By combustion of the same weight of material but vary- 
 ing the amount of water used. 
 
106 COAL 
 
 (4) By electric methods. 
 
 (5) By combustion of a substance of known calorific value, 
 as naphthalene, benzoic acid or cane sugar. 
 
 The author's experience with the first three of these methods 
 has not been very satisfactory. The fourth method requires 
 instruments and equipment beyond the reach of most commercial 
 and technical laboratories and practically the only available 
 method which is satisfactory is that of the determination by 
 combustion of a substance of known calorific value. At present 
 the materials available are naphthalene, benzoic acid and cane 
 sugar, samples of which together with certificates of their heat- 
 ing values can be obtained from the U. S. Bureau of Standards. 
 
 The calorific values of these materials as given by different 
 authorities are as follows; 
 
 Naphthalene: 
 
 Berthelot , 9692 
 
 Atwater 9628 
 
 Fischer and Wrede 9640 
 
 U. S. Bureau of Standards (standard sample) . 9610 
 
 Benzoic acid: 
 
 Berthelot 6322 
 
 Stohmann 6322 
 
 Fischer and Wrede 6333 
 
 U. S. Bureau of Standards (standard sample) . 6320 
 
 Cane Sugar: (sucrose) 
 
 Stohmann 3955 
 
 Berthelot 3961 
 
 Fischer and Wrede 3957 
 
 The equation for determination of the water equivalent (X) 
 of the bomb, bucket, stirrer, etc., is as follows: 
 
 (Grams of water+X) X temperature rise = the amount of 
 sample X the calorific value + the heat due to the ignition of the 
 fuse+the heat due to the formation of nitric acid. 
 
 Carefully determined water equivalents based upon a num- 
 ber of determinations upon two or more of the standard materials 
 ought to have not only relatively high accuracy but enable differ- 
 
DETERMINING THE CALORIFIC VALUE 107 
 
 ent laboratories to work upon a common basis and make their 
 results comparable. 
 
 Errors in the graduation of the thermometer used. These 
 errors if not corrected for may be of considerable magnitude and 
 every calorimeter operator should take some means of insuring 
 the elimination of a greater part of the errors or at least assuring 
 himself that the errors are not large enough to materially affect 
 the accuracy of results. Three methods of checking up gradua- 
 tion errors are available : 
 
 (a) Calibration of the thermometer by divided threads. To cali- 
 brate accurately by this method requires skill and attention to 
 details, and to cover the working range several threads of dif- 
 ferent lengths should be used and many readings taken. With 
 thermometers in which the mercury threads break easily and 
 regularly, the method, while it requires considerable time, pre- 
 sents no serious difficulties aside from care and attention to 
 details but with some thermometers the author has found it 
 exceedingly difficult to secure threads of the desired length. 
 
 As an example of the method, a thermometer graduated from 15 
 to 25 and graduated to hundredths of a degree was checked at 
 each whole degree by the use of threads approximately 2 and 5 
 in length. By the measurement with the 5 thread a direct deter- 
 mination was obtained for 20. By the 2 thread direct deter- 
 minations were made for 17 and 23 and as secondary determina- 
 tions 19 and 21; 16 was obtained by the 5 thread from 21, 
 24 by the 5 thread from 19; 18 and 22 by the 2 thread 
 from 20. A number of readings should be taken for each of the 
 thread lengths at a slightly different position and the mean of 
 these readings taken as the length for that position. By gently 
 tapping the thermometer the thread of mercury may be easily 
 slipped a few thousandths of a degree or sufficiently to give a 
 new set of readings. For example, the readings on the 5 thread 
 measurements from 15 to 20 = 5.028, 5.027, 5.028, 5.027, 
 5.026, 5.027, 5.026, 5.027 -average 5.027. 
 
 20 to 25 = 5.017, 5.019, 5.019, 5.018, 5.018, 5.017, 5.017, 
 5.019, 5.018 = average 5.018. The sum of the two threads 
 = 5.027+5.018 = 10.0450. According to the Reichsanstalt 
 certificate for this thermometer the true temperature interval of 
 15 to 25 is 10.02, hence the true length of the measured dis- 
 tance, 10.045, is 10.065 and the true length of the 5 thread is 
 
108 COAL 
 
 one-half of this value = 5.0325, from which the correction at 20 
 is 5.0325 - 5.0270 = +0.0055. The measurement of the 2 thread 
 and the establishment of other points by the measurements with 
 this thread is done in the same manner. 
 
 By the use of a 2| thread in connection with the 2 and 5 
 threads as many values for J readings were determined as 
 desired. The determination of the correction for intermediate 
 points was determined graphically by plotting the curve for the 
 determined points. 
 
 In measuring the mercury thread the operator should work 
 in a room at a uniform temperature or make corrections for 
 variations in the observed lengths of thread at different tem- 
 peratures. For example, a thread of mercury 5 long for a two 
 degrees difference in temperature varies 0.0016 degree in length 
 so that temperature differences of more than a fraction of a degree 
 cannot be neglected if high accuracy is desired. The readings 
 should be made by means of a telescope mounted on a fixed sup- 
 port movable in a horizontal direction. A cathetometer laid on 
 its side is very satisfactory. In reading the thread the thermometer 
 should be turned so that the ends of the short divisions touch 
 the lower edge of the mercury column but do not cross it. This 
 position of the ends of the divisions with reference to the ends of 
 the mercury thread permits sharper readings. 
 
 The method of divided threads gives only the relative lengths 
 of the degrees and in itself shows nothing as to their absolute 
 values and unless the highest and lowest readings have been 
 checked the numerical, difference is assumed as the true value. 
 This, of course, may make all the degrees too large or too small 
 but does not affect their relative values to each other, and in 
 calorimeter work usually what is desired is the relative value and 
 hence a failure to know the absolute value is not necessarily of 
 any serious consequence. In the calibration described it is 
 assumed that the errors in the graduation of the few hundredths 
 of a degree, that the threads are longer or shorter than 5, 2J and 
 2, cannot materially affect the results. If threads are used of 
 lengths considerably different from these values, this assumption 
 of no material error does not necessarily hold true. For fuller 
 details of calibration see Physical Measurements by Kohlraush 
 or text-books on Physics, 
 
DETERMINING THE CALORIFIC VALUE 109 
 
 (6) Comparison with another standard thermometer. Another 
 method of determining the graduation errors is to compare the 
 thermometer with another thermometer which has already been 
 standardized. Making comparison readings to thousandths of a 
 degree requires special equipment and special precautions to 
 insure thorough mixing of the liquid- surrounding the bulbs and 
 to prevent rapid temperature changes in this liquid. 
 
 A simple and inexpensive equipment which the author has 
 recently made use of in this work is a 500 c.c. Dewar vacuum 
 flask. The two thermometers to be compared are inserted 
 through a two-hole cork and the two bulbs brought close together 
 but not quite touching one another. A thin strip of cork inserted 
 between the stems just above the bulbs and a rubber band 
 wrapped moderately tight around both stems is very efficient 
 for holding them in their proper positions. The upper ends of 
 the stems should be secured in a similar manner. In making 
 temperature comparisons the flask is filled about three-fourths 
 full of water at any desired temperature, the cork and thermom- 
 eters inserted into position and the water around the bulbs well 
 mixed by inverting the flask. The readings are taken through 
 a telescope, the stems being tapped previous to taking a reading. 
 A number of pairs of readings should be taken, the flask being 
 inverted between each pair of readings. The average of the read- 
 ings of each thermometer are taken as the reading at that tem- 
 perature. The true reading for each thermometer is obtained 
 by adding to the observed reading the stem correction for the 
 thread of mercury exposed (see page 110). This method of 
 comparison has the advantage that owing to the slow radiation 
 changes- in a vacuum flask as many readings as desired may be 
 taken at practically the same temperature. To make a com- 
 parison at another temperature it is only necessary to warm or 
 cool the contents of the flask to approximately the temperature 
 desired and take a series of readings at the new temperature. 
 One slight objection to the method is the possibility of the vacuum 
 flask going to pieces and destroying the thermometers. This 
 danger is, however, very slight if care be used in handling the 
 flask. The author recommends, however, that flasks covered 
 with metal or canvas be used so that in case of possible breakage 
 there will be no danger to the eyes from particles of flying glass. 
 
110 COAL 
 
 If the precautions regarding care in handling the flask are observed 
 the danger of breakage is very small and the author's experience 
 with the method has been entirely satisfactory. 
 
 The Bureau of Standards at Washington is equipped to do 
 comparison work at a nominal charge and in many cases it may 
 be preferable for the calorimeter operator to send thermometers 
 there to be checked, as they will probably do it better than he 
 can do it himself and the Government comparison will certainly 
 carry more weight in a court of law than a comparison by a 
 private individual. One objection to having the Government 
 calibrate thermometers is that several weeks necessarily elapse 
 before they are returned to the laboratory and in a busy labo- 
 ratory this may be a very serious objection. 
 
 (c) Comparison of the readings obtained at different tempera- 
 tures on the same standard material. The errors in graduation 
 may be checked by running a number of check determinations 
 on a material of constant composition at temperatures covering 
 the working range of the thermometer. For example, if sets of 
 duplicate determinations on naphthalene made at a number of 
 different temperatures covering the range of the thermometer 
 agree closely, evidently the graduation errors of the thermom- 
 eter are not liable to be serious. Checking a thermometer by 
 this method may not be regarded as an actual calibration but it 
 does serve to guard against any serious graduation errors. 
 
 Stem temperature corrections. (Corrections should be made 
 to the observed temperature readings on account of differences 
 between the temperature of the emergent stem and the tempera- 
 ture of the liquid surrounding the bulb.) Most thermometers are 
 graduated and calibrated for total immersion of the stem and 
 bulb. As ordinarily used in calorimetric work a portion of the 
 stem containing the mercury column always projects above the 
 water and is usually either colder or warmer than the temperature 
 of the water surrounding the bulb. Hence to secure readings for 
 total immersion a correction must be applied. As ordinarily ex- 
 pressed this correction is N(T 0X0.00016, where N = degrees of 
 thread above the liquid, t = the temperature of the stem as observed 
 by an auxiliary thermometer, T = the temperature of the bulb 
 and the factor 0.00016 = the difference between the expansion of 
 glass and mercury for one degree Centigrade. With N = 5,t= 15, 
 
DETERMINING THE CALORIFIC VALUE 111 
 
 T = 20, N(7X)X0.00016 = 0.004, the amount that the mercury 
 reads too low. Hence this correction must be added. With T = \5, 
 t = 20, the value is this amount too high and hence has to be sub- 
 tracted from the observed readings. To secure the true tempera- 
 ture difference in a calorimetric determination corrections of both 
 the initial and final readings must be made. This correction may 
 be done at one operation by combining the two corrections into 
 the form of Kd(T ' + T" '-S-t) in which # = 0.00016, !F' = the 
 initial temperature at the beginning of a determination, T" = the 
 final temperature at the end of the combustion period, d = ih& 
 observed temperature rise during a determination or T" T", 
 /S = the scale reading to which the thermometer is immersed, 
 Z = the temperature of the emergent stem measured by an aux- 
 iliary thermometer. Corrections with a plus sign are to be added 
 to the observed temperature difference. Corrections with a 
 minus sign are to be subtracted from the observed temperature 
 difference. 1 
 
 Tabulation of stem corrections. A convenient method for 
 applying the corrections is to solve the correction equations for 
 the differences usually found in calorimetric work and arrange 
 the results in tabular form for use as needed. The temperature 
 rise for a given calorimeter on coal work ranges from 2.4 to 2.8 
 with an average for most coals of between 2.5 and 2.7. The 
 initial temperature should be 2 to 3 below the room tem- 
 perature. For example, a table of corrections to observed tem- 
 perature differences computed from the values for N(T t) 
 X 0.00016 for the temperature at the beginning and end of the 
 combustion period to cover the above mentioned conditions is 
 as follows: The values given are for observed temperature rises 
 of 2.5 and 2.7 Centigrade, where N = length of the emergent 
 thread at the beginning of the combustion, T r = the observed 
 temperature in the calorimeter at the beginning of the combus- 
 tion, = the observed, temperature of the emergent stem meas- 
 ured by an auxiliary thermometer. The corrections for observed 
 rises of temperature of 2.5 and 2.7 degrees and for different values 
 for N and (T t) are as follows: 
 
 Testing of Thermometer, Bureau of Standard Circular No. 8. 
 
112 
 
 COAL 
 
 STEM TEMPERATURE CORRECTION TABLE. 1 
 
 Initial 
 
 Observed Rise in Temperature =2.5. 
 
 Length of 
 
 T-t = 
 
 Emergent 
 
 
 Thread. 
 
 
 
 
 
 
 
 
 
 
 N. 
 
 -4 
 
 -3.5 
 
 -3 
 
 -2.5 
 
 -2 
 
 -1.5 
 
 1 
 
 -0.5 
 
 -0 
 
 1 
 
 - . 0002 
 
 .0000 
 
 + . 0002 
 
 + . 0004 
 
 + .0006 
 
 + . 0008 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 1.5 
 
 .0000 
 
 + . 0002 
 
 + . 0004 
 
 + . 0006 
 
 + .0008 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 2 
 
 + .0002 
 
 + . 0004 
 
 + . 0006 
 
 + .0008 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 2.5 
 
 + .0004 
 
 + . 0006 
 
 + .0008 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 3 
 
 + . 0006 
 
 + . 0008 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 + . 0022 
 
 3.5 
 
 + . 0008 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 + . 0022 
 
 + .0024 
 
 4 
 
 + .0010 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + .0020 
 
 + . 0022 
 
 + . 0024 
 
 + .0026 
 
 4.5 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + .0020 
 
 + .0022 
 
 + .0024 
 
 + . 0026 
 
 + . 0028 
 
 5 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + .0020 
 
 + .0022 
 
 + . 0024 
 
 + . 0026 
 
 + .0028 
 
 + . 0030 
 
 5.5 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 + .0022 
 
 + . 0024 
 
 + .0026 
 
 + . 0028 
 
 + . 0030 
 
 + . 0032 
 
 6 
 
 + .0018 
 
 + . 0020 
 
 + . 0022 
 
 + . 0024 
 
 + . 0026 
 
 + .0028 
 
 + . 0030 
 
 + . 0032 
 
 + . 0034 
 
 6.5 
 
 + . 0020 
 
 + .0022 
 
 + . 0024 
 
 + .0026 
 
 + .0028 
 
 + . 0030 
 
 + . 0032 
 
 + . 0034 
 
 + . 0036 
 
 7 
 
 + . 0022 
 
 + . 0024 
 
 + . 0026 
 
 + . 0028 
 
 + .0030 
 
 + . 0032 
 
 + .0034 
 
 + .0036 
 
 + .0038 
 
 7.5 
 
 + . 0024 
 
 + .0026 
 
 + . 0028 
 
 + . 0030 
 
 + . 0032 
 
 + . 0034 
 
 + .0036 
 
 + .0038 
 
 + . 0040 
 
 8 
 
 + .0026 
 
 + . 0028 
 
 + . 0030 
 
 + . 0032 
 
 + .0034 
 
 + .0036 
 
 + .0038 
 
 + . 0040 
 
 + .0042 
 
 Observed Rise in Temperature =2.7. 
 T-t = 
 
 N. 
 
 -4 
 
 -3.5 
 
 -3 
 
 -2.5 
 
 -2 
 
 -1.5 
 
 -1 
 
 -0.5 
 
 -0 
 
 1 
 
 -.0001 
 
 + .0001 
 
 + . 0003 
 
 + . 000f> 
 
 + . 0007 
 
 + . 0009 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 1.5 
 
 + .0001 
 
 + . 0003 
 
 + . 0005 
 
 + . 0007 
 
 + . 0009 
 
 + .0011 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 2 
 
 + . 0003 
 
 + . 0005 
 
 + . 0007 
 
 + . 0009 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 +.0020 
 
 2.5 
 
 + . 0005 
 
 + . 0007 
 
 + . 0009 
 
 + .0011 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 + .0022 
 
 3 
 
 + . 0007 
 
 + . 0009 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 + . 0022 
 
 + . 0025 
 
 3.5 
 
 + . 0009 
 
 + .0011 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + .0020 +.0022 
 
 + . 0024 
 
 + . 0027 
 
 4 
 
 + .0012 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + . 0020 
 
 + . 0022 
 
 + . 0025 
 
 + .0027 
 
 + . 0029 
 
 4.5 
 
 + .0014 
 
 + .0016 
 
 + .0018 
 
 + .0020 
 
 + .0022 
 
 + .0025 
 
 + .0027 
 
 + . 0029 
 
 + .0031 
 
 5 
 
 + .0016 +.0018 
 
 + . 0020 
 
 + .0022 
 
 + . 0025 
 
 + . 0027 
 
 + . 0029 
 
 + .0031 
 
 + . 0033 
 
 5.5 
 
 + .0018 
 
 + . 0020 
 
 + . 0022 
 
 + . 0024 
 
 + .0027 
 
 + . 0029 
 
 + .0031 
 
 + . 0033 
 
 + . 0035 
 
 6 
 
 + . 0020 
 
 + . 0022 
 
 + . 0025 
 
 + .0027 
 
 + . 0029 
 
 + .0031 +.0033 
 
 + . 0035 
 
 + . 0038 
 
 6.5 
 
 + . 0022 
 
 + . 0024 
 
 + . 0027 
 
 + . 0029 
 
 + .0031 
 
 + .0033 +.0035 
 
 + .0037 
 
 + .0040 
 
 7 
 
 + . 0025 
 
 + . 0027 
 
 + .0029 
 
 + .0031 
 
 + .0033 
 
 + .0035 +.0038 
 
 + . 0040 
 
 + . 0042 
 
 7.5 
 
 + .0027 
 
 + .0029 
 
 + .0031 
 
 + . 0033 
 
 + . 0035 
 
 + .0037 
 
 + . 0040 
 
 + .0042 
 
 + .0044 
 
 8 
 
 + . 0029 
 
 + .0031 
 
 + . 0033 
 
 + . 0035 
 
 + . 0038 
 
 + .0040 
 
 + . 0042 
 
 + . 0044 
 
 + . 0046 
 
 1 T =the initial observed temperature in calorimeter. 
 
 t =the observed temperature of emergent stem measured by auxiliary thermometer. 
 
 From these values the corrections for &uy conditions usually 
 found can be approximated readily to about 0.001. To secure 
 this degree of accuracy N and T t need be read to only the 
 nearest 0.5 and the observed temperature rise need not be 
 closer than 0.1 to the amount of rise on which the values are 
 calculated. For example, corrections for rises between 2.4 and 
 2.6 can be taken from the correction based on 2.5 and correc- 
 tions for rises between 2.6 and 2.8 taken from the values based on 
 
DETERMINING THE CALORIFIC VALUE 113 
 
 a rise of 2.7 without any appreciable error. As an illustration, 
 suppose the initial temperature of the calorimeter 7 = 16. 5, the 
 temperature of the emergent stem = 19, the scale reading of 
 the emergent stem = 12 and the observed temperature differ- 
 ence during the determination = 2. 8. Then A^ = 16. 5 12 = 4.5. 
 T = 16. 5 19= 2.5. From the table the correction corre- 
 sponding to initial thread length N of 4.5 and Tt= 2.5 and an 
 observed rise of 2.7 degrees is found to be +0.002. Inspection 
 of the table furthermore shows that in a difference in rise of 
 2.5 to 2.7 the correction change is only about 0.0002, hence the 
 additional correction corresponding to the rise of 2.8 instead 
 of 2.7 is approximately 0.0001 and can be entirely neglected, 
 which makes the observed correction approximately +0.002. 
 
 As may be observed from the table, the amount of the cor- 
 rection varies from practically nothing up to 0.005. With a 
 water equivalent for the calorimeter of 3000 calories this latter 
 amount is equivalent to a correction of 15 calories, a possible 
 correction too large to be omitted if a high standard of accuracy 
 is desired. 
 
 For similar working conditions where the correction was 
 omitted in standardizing the calorimeter with naphthalene, ben- 
 zoic acid or cane sugar, its omission on determinations made on 
 coal introduces little or no error as one correction practically 
 balances the other. Unfortunately similar working conditions 
 day after day cannot be maintained and the stem corrections 
 at different times may vary from less than 0.001 to over 0.004. 
 The carrying out of the values of other corrections, such as titre 
 and burning of wire fuse, to fractions of a calorie and then omit- 
 ting this correction entirely is to say the least not very consistent 
 practice, and the author believes that the use of a table similar 
 to the one given, whereby the errors can be eliminated regularly 
 instead of hit or miss is well worth the little extra trouble which 
 its use involves. 
 
 Correction for variations in the specific heat of water. Since 
 the specific heat of water is different for different temperatures 
 exact calorimeter determinations require corrections for deter- 
 minations made at temperatures other than that at which the 
 water equivalent of the calorimeter was determined. In making 
 this correction the use of a thermal capacity table for water is a 
 
114 
 
 COAL 
 
 great convenience. Such a table based on Barnes' values for 
 specific heats of water is given by Loeb 1 as follows : 
 
 SPECIFIC HEAT AND THERMAL CAPACITY OF WATER FROM TO 50 C. 
 
 Temp. 
 C. 
 
 Specific 
 Heat. 
 
 Thermal 
 Capacity. 
 
 Difference. 
 
 Temp. 
 
 c. 
 
 Specific 
 Heat. 
 
 Thermal 
 Capacity. 
 
 Difference. 
 
 
 
 1.00940 
 
 0.00000 
 
 
 25 
 
 .99806 
 
 25.05131 
 
 
 i 
 
 1.00855 
 
 1.00898 
 
 1.00898 
 
 26 
 
 .99795 
 
 26.04932 
 
 .99801 
 
 2 
 
 1.00770 
 
 2.01710 
 
 1.00812 
 
 27 
 
 .99784 
 
 27.04720 
 
 . 99788 
 
 3 
 
 1.00690 
 
 3.02440 
 
 1.00730 
 
 28 
 
 .99774 
 
 28 . 04499 
 
 . 99779 
 
 4 
 
 1.00610 
 
 4.03090 
 
 1.00650 
 
 29 
 
 .99766 
 
 29.04269 
 
 .99770 
 
 5 
 
 1.00530 
 
 5.03660 
 
 1.00570 
 
 30 
 
 .99759 
 
 30.04031 
 
 . 99762 
 
 6 
 
 1.00450 
 
 6.04150 
 
 1.00490 
 
 31 
 
 .99752 
 
 31 . 03786 
 
 .99755 
 
 7 
 
 1.00390 
 
 7.04570 
 
 1.00420 
 
 32 
 
 .99747 
 
 32.03536 
 
 .99750 
 
 8 
 
 1.00330 
 
 8.04930 
 
 1.00360 
 
 33 
 
 .99742 
 
 33.03280 
 
 .99744 
 
 9 
 
 1.00276 
 
 9.05233 
 
 1.00303 
 
 34 
 
 .997,38 
 
 34.03020 
 
 .99740 
 
 10 
 
 1.00230 
 
 10.05486 
 
 1.00253 
 
 35 
 
 . 99735 
 
 35 . 02757 
 
 .99737 
 
 11 
 
 1.00185 
 
 11.05694 
 
 1.00208 
 
 36 
 
 .99733 
 
 36 . 02491 
 
 . 99734 
 
 12 
 
 1.00143 
 
 12.05858 
 
 1 . 00164 
 
 37 
 
 .99732 
 
 37.02224 
 
 .99733 
 
 13 
 
 1.00100 
 
 13.05980 
 
 1.00122 
 
 38 
 
 . 99732 
 
 38.01956 
 
 .99732 
 
 14 
 
 1.00064 
 
 14.06062 
 
 1.00082 
 
 39 
 
 .99733 
 
 39.01689 
 
 .99733 
 
 15 
 
 1.00030 
 
 15.06109 
 
 1.00047 
 
 40 
 
 .99735 
 
 40.01422 
 
 .99733 
 
 16 
 
 1.00000 
 
 16.06124 
 
 1.00015 
 
 41 
 
 .99738 
 
 41.01159 
 
 .99737 
 
 17 
 
 .99970 
 
 17.06109 
 
 .99985 
 
 42 
 
 .99743 
 
 42.00899 
 
 .99740 
 
 18 
 
 . 99941 
 
 18.06064 
 
 .99955 
 
 43 
 
 .99748 
 
 43 . 00644 
 
 .99745 
 
 19 
 
 .99918 
 
 19.05994 
 
 .99930 
 
 44 
 
 .99753 
 
 44 . 00395 
 
 .99751 
 
 20 
 
 .99895 
 
 20.05900 
 
 .99906 
 
 45 
 
 .99760 
 
 45.00152 
 
 .99757 
 
 21 
 
 . 99872 
 
 21.05783 
 
 .99883 
 
 46 
 
 . 99767 
 
 45.99916 
 
 .99764 
 
 22 
 
 .99853 
 
 22.05645 
 
 .99862 
 
 47 
 
 .99774 
 
 46.99686 
 
 .99770 
 
 23 
 
 .99836 
 
 23.05490 
 
 .99845 
 
 48 
 
 .99781 
 
 47.99464 
 
 .99778 
 
 24 
 
 . 99820 
 
 24.05318 
 
 . 99828 
 
 49 
 
 .99790 
 
 48.99250 
 
 .99786 
 
 25 
 
 . 99806 
 
 25.05131 
 
 .99813 
 
 50 
 
 .99800 
 
 49.99045 
 
 .99795 
 
 From this table the differences in the thermal capacity of water 
 throughout the temperature range at which calorimeter 'work is 
 usually done may easily be calculated. For example, with a 
 Mahler calorimeter having a water equivalent of approximately 
 500 calories and using 2400 grams of water in the calorimeter, 
 the water equivalent of the system equals approximately 2900 
 calories and a rise of 3 corresponds approximately to 8700 calories 
 of heat. As this is several hundred calories higher than the 
 heating value of the best coal, 3 may be taken as representing 
 the maximum rise of the thermometer during a determination 
 where one gram of coal is used. The thermal capacity of 2400 
 
 1 Jr. Ind. and Eng. Chcm., 1911, p. 175. 
 
DETERMINING THE CALORIFIC VALUE 115 
 
 grams of water for the different 3 intervals from 14 to 30 C. 
 is as follows: 
 
 Temperature. 
 
 Thermal 
 Capacity. 
 
 Difference. 
 
 Temperature. 
 
 Thermal 
 Capacity. 
 
 Difference. 
 
 14 to 17 
 
 7201.13 
 
 2 21 
 
 21 to 24 
 
 7188.84 
 
 1.32 
 
 15 to 18 
 
 7198.92 
 
 2 04 
 
 22 to 25 
 
 7187.66 
 
 1.18 
 
 16 to 19 
 
 7196.88 
 
 1 90 
 
 23 to 26 
 
 7186 . 61 
 
 1.05 
 
 17 to 20 
 
 7194.98 
 
 1 72 
 
 24 to 27 
 
 7185. 65 
 
 0.96 
 
 18 to 21 
 
 7193 . 26 
 
 1 64 
 
 25 to 28 
 
 7184.83 
 
 0.82 
 
 19 to 22 
 
 7191.62 
 
 1 46 
 
 26 to 29 
 
 7184.09 
 
 0.74 
 
 20 to 23 
 
 7190.16 
 
 
 27 to 30 
 
 7183.46 
 
 0.63 
 
 From which the corrections corresponding to a water equiva- 
 lent determination made at any particular temperature may 
 readily be tabulated. For example, assume that the water equiv- 
 alent of the calorimeter is determined at the temperature range 
 18 to 21. Then for determinations made upon coal for this 
 range no correction is necessary but for determinations made at 
 temperatures above or below corrections should be used. Calcu- 
 lating from the differences in the thermal capacity at different 
 temperatures, the correction for each thousand calories of heat 
 developed by the coal is as follows: 
 
 Temperature. 
 
 Correction Calories. 
 
 Temperature. 
 
 Correction Calories. 
 
 14 to 17 
 
 +0.90 
 
 21 to 24 
 
 -0.51 
 
 15 to 18 
 
 +0.65 
 
 22 to 25 
 
 -0.64 
 
 16 to 19 
 
 +0.42 
 
 23 to 26 
 
 -0.76 
 
 17 to 20 
 
 +0.20 
 
 24 to 27 
 
 -0.87 
 
 18 to 21 
 
 no correction 
 
 25 to 28 
 
 -0.97 
 
 19 to 22 
 
 -0.19 
 
 26 to 29 
 
 -1.05 
 
 20 to 23 
 
 -0.35 
 
 27 to 30 
 
 -1.13 
 
 From which it may be seen that in a coal having a calorific 
 value of 7000 calories the corrections to be applied range from 
 the extremes of +6 calories to 8 calories. If the water equiva- 
 lent determination of the calorimeter instead of being made at an 
 intermediate temperature as 18 to 21 is made at a higher or 
 lower range, as 25 to 28 or 15 to 18, the maximum correction 
 for a determination would be greater than the 8 calories in the 
 case assumed. 
 
116 COAL 
 
 With a water equivalent made at intermediate temperatures 
 the correction to be applied is usually not large and can be 
 neglected in routine work, but for work of the highest accuracy, 
 this correction must be used along with other corrections of 
 similar magnitude, which have been already discussed. 
 
 Effect of hydrogen in the sample upon observed calorific 
 value. Any hydrogen in the sample not already combined with 
 oxygen during combustion unites with oxygen to form water 
 which condenses and the remaining gas expands as a result of the 
 disappearance of this oxygen. This expansion absorbs heat, the 
 amount absorbed being proportional to the amount of oxygen 
 which disappears. Approximately 1.36 calories are absorbed for 
 each 0.01 gram of hydrogen which unites with oxygen. For coals 
 containing 4 per cent of available hydrogen the correction amounts 
 to about 5| calories. 
 
 The calculation of this effect in brief is as follows: The 
 mechanical equivalent of heat has been determined as 42,350 
 gram-centimeters = 1 calorie. In consideration of gas volumes 
 
 pV 
 
 is known to be a constant where V is the volume in gram- 
 molecules. Let p = 1 atmosphere pressure = 1033 grams per square 
 centimeter. Let V = l gram molecular volume of gas =22.4 
 liters = 22400 cubic centimeters. Let 7 7 = 273 absolute = C. 
 
 pV 1033X22,400 
 Substituting these values for = =84,750 gram- 
 
 J. 2i t o 
 
 centimeters, which expressed in calories = 84, 750 -^ 42,350 = 2 
 
 pV 
 calories. = 2 calories or pV = 2T which = 546 calories. Two 
 
 grams of hydrogen at C. and 760 mm. pressure = 22.4 liters. 
 0.01 gram of hydrogen = 0.1 12 liter. The equivalent volume of 
 oxygen uniting with 0.01 gram of hydrogen = 0.056 liter. With 
 pF = 546 calories, 22.4 liters = 546 calories, from which 0.056 
 liter = 1.36 calories as the amount of heat absorbed as a result of 
 the contraction of the oxygen equivalent to 0.01 gram of hydro- 
 gen. Naphthalene (CioHg) contains about 6J per cent hydrogen, 
 hence if the heat as burned under conditions of constant pres- 
 sure is desired, the observed calorific value obtained in the 
 bomb calorimeter should be increased by 6jX 1.36 = about 8.5 
 calories. 
 
 The value given for naphthalene by the Bureau of Standards 
 
DETERMINING THE CALORIFIC VALVE 117 
 
 is the observed value obtained in a bomb calorimeter and in 
 using naphthalene as a standard for determining the water equiv- 
 alent of another calorimeter the observed value is the one that 
 should be used. If, however, the heating value of naphthalene 
 is compared with the heating value of carbon or coal as burned 
 under ordinary conditions the observed value should be increased 
 by 8.5 calories. 
 
 The available hydrogen in coal runs from 2J to 4J per cent 
 which corresponds to corrections of from 4J to 7 calories. Petro- 
 leum contains about 14 per cent hydrogen which corresponds to 
 a correction of about 20 calories. 
 
 The formation of nitric and sulphuric acids during combustion 
 likewise causes a small absorption of heat on account of the oxy- 
 gen used up. The amount absorbed = 0.58 calorie for 0.01 gram 
 of nitrogen and 0.25 calorie for 0.01 gram of sulphur, and for the 
 amounts of nitrogen and sulphur in coal this can be neglected 
 without any appreciable error. 
 
 For the highest grade of work the correction due to hydro- 
 gen should be taken into consideration and applied. However, 
 its omission in commercial work cannot cause any very large error. 
 
 Use of a cover on the water jacket of the calorimeter. A 
 cover on the water jacket is presumably an improvement over 
 the common open top calorimeter owing to the smaller radiation 
 changes but unless used properly a cover may introduce errors 
 larger than the errors that are supposed to be eliminated, and in 
 using a covered calorimeter the author strongly advises begin- 
 ning the determination at a temperature several degrees below 
 the jacket water temperature 'so that the temperature of the calo- 
 rimeter at the end of the combustion period will still be below the 
 temperature of the surrounding jacket water. If this precaution 
 is not observed a high final rate is very apt to be obtained due to 
 the surrounding jacket being below the dew point, as compared 
 to the surface of the water in the calorimeter bucket, and a much 
 more rapid evaporation from the surface of the calorimeter 
 water occurs during the final period than at the beginning period 
 when the jacket walls are warmer than the water in the calo- 
 rimeter. 
 
 Impurities in oxygen. Compressed oxygen of a high degree 
 of purity for calorimetric work is readily obtained on the market 
 at a comparatively low cost. The author has never found hydro- 
 
118 COAL 
 
 carbons present in the oxygen in sufficient amounts to seriously 
 affect the calorimeter determination. Their presence, however, 
 is always a possibility and a safe rule which should be strictly 
 followed is to run blanks on naphthalene, benzoic acid, or cane 
 sugar on every new tank of oxygen and if impurities of any con- 
 sequence are found they should be corrected for or better still 
 the tank should be rejected and a fresh supply of oxygen obtained. 
 
CHAPTER VI 
 SUMMARY OF CHEMICAL DETERMINATIONS AND RECORDS 
 
 A SUMMARY of these may help to make clear just what relation 
 the various determinations have to one another, and to the sam- 
 ple of coal and serve to prevent uncertainty and confusion in the 
 meaning and use of the terms. 
 
 Chemical records. The air drying of the coarse sample and 
 the analytical determinations on the air-dried sample neces- 
 sitate the recalculating of results to obtain the analyses of the 
 " sample as received." Some of the analytical records of a well 
 conducted laboratory are shown by the following record of a 
 regular laboratory sample: 
 
 Laboratory sample number 1561 
 
 Per Cent. 
 
 Loss of moisture in air-drying of coarse sample 3. 10 
 Analysis of air-dried sample: 
 
 Proximate: 
 
 Moisture 1.01 
 
 Volatile matter 29 . 53 
 
 Fixed carbon 62 . 67 
 
 Ash.. 6.79 
 
 100.00 
 Ultimate: 
 
 Hydrogen 5 . 04 
 
 Carbon 79.35 . 
 
 Nitrogen 1 . 63 
 
 Oxygen 6 . 39 
 
 Sulphur 0.80 
 
 Ash.. 6.79 
 
 100.00 
 
 Calorific value determined, 7984 calories = 14,371 B.t.u. 
 
 Calorific value calculated from ultimate analysis, 7890 calories = 14,202 B.t.u. 
 
 119 
 
120 COAL 
 
 The analysis of the " sample as received " is obtained from 
 the results on the air-dried sample by multiplying each result by 
 
 _ 
 
 - and adding to the moisture result so obtained the 3.10 
 J-UU 
 
 per cent loss on the coarse sample and to the hydrogen and oxy- 
 gen results so obtained this 3.10 per cent moisture loss in the 
 proportion in which the two elements unite to form water or -J- 
 of the moisture loss to the hydrogen and | of the loss to the 
 oxygen. 
 
 Performing these operations, the analysis on the " sample as 
 received " is as follows: 
 
 " Sample as received: 
 
 Per Cent. 
 
 Proximate: 
 
 Moisture 4 . 08 
 
 Volatile matter. . 28.61 
 
 Fixed carbon 60 . 73 
 
 Ash.. 6.58 
 
 100.00 
 
 Ultimate: 
 
 Hydrogen 5 . 23 
 
 Carbon 76 . 89 
 
 Nitrogen 1 . 58 
 
 Oxygen 8.95 
 
 Sulphur 0.77 
 
 Ash.. 6.58 
 
 100.00 
 
 Calorific value determined, 7736 calories = 13, 925 B.t.u. 
 
 Calorific value calculated from ultimate analysis, 7645 calories = 13, 761 B.t.u. 
 
 Dry coal. The result on the air-dried sample must not be 
 confounded with the " dry coal " of the mechanical engineer, 
 which may be obtained from either of the above ultimate anal- 
 yses by subtracting from the hydrogen and oxygen shown in the 
 analysis the amount of hydrogen and oxygen present in the mois- 
 ture of the proximate analysis corresponding to the ultimate, then 
 dividing each of these remainders and each of the other per- 
 centages of the ultimate analysis by 100 minus the moisture 
 present in the proximate analysis. 
 
SUMMARY OF CHEMICAL DETERMINATIONS 121 
 
 Performing these operations, the ultimate analysis for the 
 dry coal " on this sample is as follows: 
 
 Hydrogen 4 . 98 
 
 Carbon 80.15 
 
 Nitrogen 1 . 65 
 
 Oxygen 5 . 55 
 
 Sulphur 0.81 
 
 Ash.. 6.86 
 
 100.00 
 
 The volatile matter, fixed carbon and ash of the proximate 
 analysis reduced to the " dry coal " are: 
 
 Volatile matter 29 . 83 
 
 Fixed carbon 63 . 31 
 
 Ash . . 6 . 86 
 
 100.00 
 
 Calorific value determined = 8065 calories, 14,517 B.t.u. 
 
 Calorific value calculated from ultimate analysis, 7970 calories = 14,346 B.t.u. 
 
 This seems to be a multiplication of results but all appear 
 to be necessary. The " as received " results certainly cannot be 
 dispensed with, as they represent the actual sample. The results 
 on the air-dried sample are the actual results obtained in the 
 laboratory and are of interest as showing the analysis of the coal 
 when in an approximately air-dried condition. The chemist has no 
 use for the " dry coal " results but it is necessary for the mechan- 
 ical engineer in calculating the heat balance by the code pre- 
 scribed by the American Society of Mechanical Engineers, who 
 report results calculated to a " dry coal " basis. The " dry coal " 
 basis is also convenient in comparing boilers burning the same or 
 similar coals. 
 
CHAPTER VII 
 IMPROVEMENT OF COAL BY WASHING 
 
 THE proximate analysis of coal may show the need of im- 
 provement by washing, but as these results show only the 
 amounts of sulphur and ash present they furnish no information 
 of whether or not the impurities or sulphur may be removed by 
 treatment. Whether or not coal can be improved by washing 
 depends upon the mode and nature of the occurrence of the ash 
 and sulphur present. 
 
 Sulphur. If present as organic sulphur it cannot be removed 
 by washing. If present as pyrite, finely disseminated through the 
 coal, it cannot be removed by washing to any considerable extent. 
 If present as pyrite in flakes or lumps of appreciable size it may 
 be removed by washing, especially if the coal is crushed suffi- 
 ciently to separate a large part of the pyrite from the surround- 
 ing coal. 
 
 Ash. The same remarks as to distribution of sulphur are 
 applicable to ash. If the ash is disseminated uniformly 
 through the coal, washing will effect little improvement. If on 
 the other hand a large part of the total ash is present as slate 
 or as bone coal, washing will result in a decided lowering of the 
 ash content in the washed coal. Clean coal has a specific gravity 
 of about 1.27 to 1.32. The specific gravity of bone coal, slate and 
 pyrite ranges from about 1.4 to 5. Laboratory tests on small 
 portions of the coal are often sufficient to show the possible 
 improvement of the coal by washing. For illustration, if on float- 
 ing the coal on a calcium chloride solution of 1.35 specific gravity 
 a large portion sinks, evidently the amount of clean coal is low 
 and the amount of bone coal is high. If on the other hand only 
 a small amount of comparatively very heavy material sinks, 
 the indications are that a considerable part of the ash and sul- 
 phur is present in a comparatively small amount of heavy res- 
 idue. By taking weighed amounts of coal at different sizes and 
 subjecting these weighed amounts to treatment on solutions of 
 
 122 
 
IMPROVEMENT OF COAL BY WASHING 123 
 
 different specific gravities ranging from 1.35 to 1.55 or 1.65, a 
 separation into low, medium and high ash material may be 
 effected. From the amounts and analyses of these different 
 materials the distribution of the ash and sulphur can be deter- 
 mined and the possible improvement of the coal by washing 
 estimated. 
 
 The apparatus used for making washing tests may be very 
 simple but if much testing is to be done, equipment adapted to 
 the work should be obtained. Some of the necessary equip- 
 ment is as follows: 
 
 (1) A set of sieves, J-, f- and J-inch, 20-mesh and 60-mesh. 
 
 (2) For the washing work ordinary laboratory beakers, fun- 
 nels, etc., may be used but a better equipment is as follows: 
 
 For holding the washing solution, two or more copper cyl- 
 inders about 5 inches in diameter by 8 inches deep fitted with a 
 handle for lifting and with a lip for pouring. For filtering, two 
 or more 7-inch copper funnels having a stem about 3 inches long 
 by 1^ inch in diameter and fitted with a 60-mesh brass filter 
 gauze 2 to 3 inches in diameter. For skimming off the light coal 
 a semi-circular gauze skimmer fitted with a handle and having 
 the circumference of the skimmer just a trifle smaller than the 
 circumference of the copper cylinder. 
 
 The process is as follows : The sample for testing is put 
 through a jaw crusher and reduced till it all passes a J-inch sieve. 
 In crushing care is taken not to force the feeding of the sample 
 through the crusher as choking of the crusher tends to make an 
 undue amount of fine sample. After the sample is so reduced 
 that it all passes the coarse sieve the very fine portion 60-mesh 
 and finer is sifted out as this fine portion slimes badly and cannot 
 be successfully washed. The amount of this fine portion is 
 usually between f and 4 per cent of the total sample. It is weighed 
 and analyzed for ash and sulphur if desired. In sifting out this 
 fine portion a preliminary sifting on a 20-mesh sieve is desirable, 
 sifting that portion which passes through the 20-mesh on to the 
 60-mesh and adding the over-size of the 60-mesh to the over-size 
 of the 20-mesh. This is much more rapid and satisfactory than 
 the attempt to sift the entire sample direct on the 60-mesh. 
 
 The copper cylinder is filled about two-thirds full of washing 
 solution, and about one-half of the coal to be washed (assuming 
 3 to 4 pounds as the amount to be tested) is poured into the cyl- 
 
124 
 
 COAL 
 
 inder and stirred up well to insure thorough wetting and freeing 
 from air bubbles. The lighter portion is then skimmed off and 
 transferred to the 7-inch funnel. The remainder of the sample is 
 then poured into the cylinder and stirred up as before and the 
 lighter portion skimmed off and added to the first portion in the 
 funnel. The heavy portion is then filtered through another fun- 
 nel. As soon as the light and heavy portions have drained, the 
 washing solution filtrate is removed (to be used for other tests) 
 and the samples washed with water. They are then air-dried, 
 weighed, crushed and analyzed for moisture, ash and sulphur. 
 
 If J-inch size samples are to be tested somewhat larger sam- 
 ples 6 to 8 pounds should be used for the tests, in which case 
 the copper cylinders and funnels should be proportionately 
 larger. The washing solutions used are calcium chloride and 
 zinc chloride. In separation of very clean coal a solution as low 
 as 1.33 in specific gravity may be used. The usual solution used 
 has a specific gravity of 1.35. In separation of coal with moder- 
 ate amounts of ash, solutions of specific gravity from 1.4 to 1.45 
 are used and in separating bone coal, etc., solutions with a specific 
 gravity as high as 1.6 to 1.7 may be used. 
 
 The method of calculating and the results obtained may be 
 shown by the following tests taken from Bulletin No. 9 of the 
 Ohio Geological Survey, pages 306-307. 
 
 PUBLICATION No. 11 
 Unwashed coal, ash 10.81, sulphur 5.04 
 
 
 Portion. 
 
 Ash. 
 
 Sulphur. 
 
 Compared with 
 Original Sample. 
 
 Ash. 
 
 Sulphur. 
 
 \ inch to iro inch = 
 
 94.52 
 
 66.7 
 
 27.82 
 
 6.48 
 21.05 
 
 3.68 
 8 : 83 
 
 4.32 
 
 5.86 
 
 0.50 
 
 2.45 
 
 2.46 
 0.23 
 
 Lighter than 1.35 . = 
 
 Heavier than 1.35. ...*.= 
 ^5 inch and finer ... = 
 
 
 4 62 
 
 5 inch to iTo inch = 
 
 96.9 
 
 87.3 
 9.6 
 
 7.83 
 33.88 
 
 4.20 
 14.24 
 
 10.68 
 
 6.84 
 3.25 
 
 0.24 
 
 5.14 
 
 3.67 
 1.37 
 
 0.11 
 5.15 
 
 Lighter than 1.45 = 
 Heavier than 1.45 = 
 
 ^V inch and finer . . . . = 
 
 
 2.2 
 
 10.33 
 
IMPROVEMENT OF COAL BY WASHING 125 
 
 PUBLICATION No. 29 
 Unwashed coal, ash 8.94, sulphur 2.11 
 
 
 Portion. 
 
 Ash. 
 
 Sulphur. 
 
 Compared with 
 Original Sample. 
 
 Ash. 
 
 Sulphur. 
 
 \ inch to Y> inch = 
 Lighter than 1.35 = 
 Heavier than 1.35 = 
 
 -g-o inch and finer . = 
 
 99.3 
 0.5 
 
 85.5 
 13.8 
 
 6.16 
 27.64 
 
 1.14 
 
 8.83 
 
 5.27 
 3.81 
 
 0.04 
 9.12 
 
 0.97 
 1.22 
 
 0.01 
 2.20 
 
 
 COKE 
 
 
 Percentage 
 Yield. 
 
 Ash. 
 
 Sulphur. 
 
 Phos. 
 
 Coke from unwashed coal = 
 Percentage of the sulphur in the coal 
 left in the coke = 
 Coke from washed coal lighter than 
 1.35 . = 
 
 59.86 
 59.80 
 
 15.54 
 10.35 
 
 1.80 
 51.1 
 93 
 
 016 
 
 Percentage of the sulphur in the coal 
 left in the coke. = 
 
 
 
 48 8 
 
 
 
 
 
 
 
 Coal No. 11 shows 66.7 per cent of washed coal containing 
 6.48 per cent ash and 87.3 per cent of washed coal with 7.83 per 
 cent ash as against 10.81 per cent in the original coal. The 
 washed coal in both tests shows a material reduction in the 
 amount of sulphur present. Coal No. 29 shows 85.5 per cent of 
 washed coal with 6.16 per cent ash and 1.14 per cent sulphur. 
 The coke from this washed coal runs 10.35 per cent ash and 0.93 per 
 cent sulphur, which indicates the possibility of production of 
 high grade coke from some Ohio coals. For further details of 
 washing tests on coal see Bulletin No. 9 of the Ohio Geological 
 Survey, also Bulletin No. 5 of the U. S. Bureau of Mines, Depart- 
 ment of the Interior. 
 
CHAPTER VIII 
 PURCHASE OF COAL UNDER SPECIFICATIONS 
 
 Total heating value as an index of the commercial value. 
 
 As has previously been stated under the heading of "The com- 
 mercial value of coal,' r other things being equal, the value of coals 
 of similar composition is proportional to the total calories or 
 British thermal units which a unit of the coal contains. The 
 value of different coals may conveniently be compared by deter- 
 mining how many large calories or British thermal units are 
 obtained for one cent or how much one million heat units cost for 
 each of the several coals. 
 
 For example, suppose the price asked for coal (A) is $2.50 
 per ton of 2000 pounds with a heating value of 12,200 B.t.u. 
 and the price asked for coal (B) is $2.25 per ton with 11,500 
 B.t.u. The cost of 1,000,000 B.t.u. for each of the coals is as 
 follows : 
 
 Other factors affecting the value of coal. The style of fur- 
 nace, draft, smoke producing qualities of the coal and comparative 
 amounts of ash and sulphur are additional factors which may 
 have to be considered in determining what is the best and cheap- 
 est coal. No definite rule can be laid down to govern some of 
 these points. The experience of the engineer in charge of the 
 plant or the experience of a consulting engineer who is an expert 
 along these lines is perhaps the best guide as to what is likely 
 to be the best fuel for the particular plant. In general, the higher 
 the moisture, ash and sulphur the more objectionable the coal, 
 
 126 
 
PURCHASE OF COAL UNDER SPECIFICATIONS 127 
 
 Actual boiler tests upon the fuel are sometimes necessary to 
 determine what fuel is the best for a particular plant. 
 
 Advantages and disadvantages in purchasing coal under 
 specifications. In the consideration of the purchase of coal 
 under specifications some of the points to be noted are as follows: 
 
 (1) Where the consumer buys direct from the operator who 
 handles coal from a certain definite locality and of a quality 
 known by experience to be satisfactory, the advantage in pur- 
 chasing under specifications based on analysis and heating value 
 may not be worth the extra expense involved in sampling and 
 analyzing the coal. 
 
 (2) In markets where the coal supply is varied and where it 
 is sold under trade names which may be uncertain or misleading, 
 large buyers should be able to buy coal to better advantage 
 under specifications based on analysis and heating value. 
 
 (3) Some advantages in the purchase of coal under specifica- 
 tions are: 
 
 (a) Guards against delivery of poor and dirty coal. 
 (6) Prevents disputes arising from the condemnation of the 
 coal based on its physical appearance. 
 
 (c) Places bidders on a strictly competitive basis as to the 
 
 price and the quality. 
 
 (d) Broadens the field for obtaining coal by ignoring trade 
 
 names and making moisture, ash, sulphur and heating 
 value the basis of bids. 
 
 (e) The analytical results and heating values of the samples 
 
 which serve as a basis of settlement also afford a ready 
 check upon the manner in which the coal is being 
 burned. 
 
 (4) The purchase of coal under specifications involves con- 
 siderable expense in the sampling of the coal and in the analysis 
 of the samples. This expense adds to the price of the coal and 
 for small consumers may increase the cost to such an extent as 
 to make the purchase under specifications unprofitable. When 
 large quantities of fuel are used, the expense of sampling and 
 analysis figured per ton of coal should be so small that any decided 
 improvement in the quality of the coal should more than offset 
 this expense. This reduction in expense per ton is accomplished 
 by combining the samples from a number of cars so that each 
 laboratory sample analyzed may represent from 5 to 15 cars of 
 
128 COAL 
 
 coal. The sampler and chemist must necessarily use precautions 
 in combining the different samples into one sample for analysis. 
 Especial care must be taken to avoid moisture losses and to see 
 that the portion of each sample taken is proportional to the 
 tons of coal it represents. 
 
 Specifications. In drawing up specifications for the purchase 
 of coal some of the points to be considered are as follows: 
 
 (1) The specifications for ash, sulphur and heating value 
 should be adapted to the grades of coal which are available and 
 should be sufficiently wide in their range as to enable all dealers 
 in suitable grades of coal to submit bids. 
 
 (2) The negative value of ash in coal, due to extra expense 
 in handling the ash and greater trouble to operate the fire together 
 with the possible lower efficiency should be taken into consider- 
 ation. The United States Government counts this negative 
 value at two cents per ton for each per cent of ash above the 
 standard ash established for a particular specification. 
 
 For example, in comparing the bids on the following coals: 
 Aj bid $2.20 a ton, heating value 12,000 B.t.u. and ash 8 per cent; 
 B, bid $2.25 a ton, heating value 12,100, ash 7 per cent. Taking 
 the lower ash 7 per cent as the standard, the 1 per cent excess 
 of ash in A is regarded as equivalent to 2 cents more per ton 
 on the bid price, hence the bid price for A is raised to $2.22 per 
 ton before the estimation of the cost per million B.t.u. is made. 
 On these two coals with this change for ash the cost per million 
 B.t.u., 
 
 For A _*2.22X 1,000,000 _ 
 
 12,000X2000 
 
 "V 
 
 $2.25X1,000,000 
 "12^60X2000 
 
 (3) Payment for the coal is based upon the amount of coal 
 weighed and the sample should be taken at the time of weighing. 
 The precautions to prevent moisture loss in the sample have 
 been given in detail under " Sampling." 
 
 (4) Payment for the coal is based on the coal " as received " 
 and specifications for bids should require that B.t.u. be on the 
 coal " as received " rather than on the " dry coal." 
 
 (5) For comparative purposes it is more convenient to have 
 
PURCHASE OF COAL UNDER SPECIFICATIONS 129 
 
 the ash expressed on the " dry coal " basis. This involves the 
 use of a double standard of B.t.u. on the " coal as received " 
 and of ash on the " dry coal." The Government specifications 
 for bituminous coals are on this double standard. 
 
 (6) Ash in the " dry coal " can be determined at any time 
 from analysis of a given sample of the coal, but the B.t.u. of the 
 coal as delivered or the actual amount of dry coal in a shipment 
 can only be determined b. the taking of a sample at the time 
 of delivery, as the amount of any moisture variation in the coal 
 after weighing cannot be determined unless comparison is made 
 with the analysis of the sample taken at the time of weighing. 
 
 (7) Premiums or bonuses should be allowed if the coal is better 
 than specifications and a penalty should be exacted if the coal 
 is lower in heating value or higher in ash than specifications. 
 Some objections to a premium or bonus are: 
 
 (a) Municipalities may in some cases be prohibited by law 
 
 or charter from paying a bonus. This is hardly an 
 objection to the principle, though it may prevent its 
 operation in special cases. 
 
 (b) The cost of the coal may be increased by having to pay 
 
 a bonus. This seems hardly a valid objection as if 
 the purchaser gets a better grade of coal he certainly 
 should be expected to pay for it; and on the other hand 
 if he fails to get a good grade of coal he is entitled to 
 pay for just what he gets and should demand a penalty 
 of the seller. Bonuses and penalties are vital items 
 in the purchase based on analytical results and heating 
 value and the author believes that the test of time 
 will prove the soundness of the principle involved and 
 the practicability of its operation. 
 
 (8) The contract should contain provisions for insuring regular 
 delivery of the coal and for insuring its quality to within certain 
 prescribed allowable variations. 
 
 Reports from twenty cities purchasing coal under specifications 
 given in the Municipal Journal, Vol. 32, p. 350-351, are very 
 favorable to the system. One report indicates a saving of 25 
 per cent, others 10 per cent. Some call special attention to 
 a much more satisfactory supply of coal. 
 
 Abstracts of the specifications of some of the cities are as 
 follows : 
 
130 COAL 
 
 New York City. The B.-t.u. standard per pound dry coal 
 for broken coal is 13,200 to 12,000 for buckwheat No. 3. The 
 ash, 11 per cent in broken coal to 19 per cent in buckwheat No. 
 3. The volatile combustible matter is 8 per cent maximum and 
 volatile sulphur 1.5 per cent. Moisture is 4 per cent for broken 
 coal to 6 per cent for buckwheat No. 3. If the moisture is in 
 excess of the limit, the gross weight of the coal is corrected by an 
 amount directly in proportion to such excess of moisture, that 
 is, with 2 per cent excess moisture the gross weight of the coal is 
 reduced by 2 per cent. After this reduction the weight is reduced 
 by 1 per cent for each per cent of ash in excess of the standard. 
 The gross weight after correction for excess moisture is reduced 
 by 1 per cent for each 100 B.t.u. below the standard, 5 per cent 
 for each 1 per cent of volatile sulphur in excess of the standard, 
 2 per cent for each 1 per cent' volatile combustible matter in 
 excess of the standard. Payment is made on the gross weight 
 less the deductions as described. 
 
 Cleveland. The standard calorific value for all coal is 13,005 
 B.t.u., and moisture is not to exceed 3 per cent, ash 13 per cent 
 or sulphur 3.5 per cent. The price per ton of coal is increased 
 above or reduced below the contract price according as the 
 heating value is more or less than the standard, the increase being 
 1J cents per ton for each 100 B.t.u. up to 13,900 and 2 cents per 
 ton between 13,900 and 15,000, remaining constant at 2.6 cents 
 for all over 15,000. Reduction at the rate of 1J cents per ton 
 down to 12,600, 2 cents per ton from 12,600 to 12,000, 3 cents 
 per ton from 12,000 to 11,000, 4 cents per ton from 11,000 to 
 10,000 and the constant amount of $1.00 where the heat units 
 fall below 10,000. 
 
 Toronto. 13,000 B.t.u. is taken as the standard, 10 per cent 
 ash, 2 per cent moisture and 1 J per cent sulphur. If coal delivered 
 shows a lower heating value than the standard, the city may reject 
 or accept it, the amount paid in the latter case being " such a re- 
 duced price as shall make the uniform coal equal in heating value 
 to the city to the contract grade," and there shall be deducted 
 from the contractor's price for such coal a proportionate amount; 
 and if the coal shall show a higher heating value than specified 
 the contractor shall receive a proportionate allowance. 
 
 Norfolk. The standard is 14,500 B.t.u., 2J per cent moisture, 
 7 J per cent ash, 1 per cent volatile sulphur and 22 per cent volatile 
 
PURCHASE OF COAL UNDER SPECIFICATIONS 131 
 
 combustible matter, but a bidder may submit a proposition for 
 coal of a different standard. If a coal delivered shows moisture, 
 ash, sulphur and volatile combustible matter in excess of require- 
 ments the price is to be fixed by arbitration, the contractor and 
 the city each appointing one arbitrator and these two selecting 
 a third. The gross tonnage of the coal is reduced at the rate of 1 
 per cent for each 100 B.t.u. below or increased 1 per cent for 
 each 100 B.t.u. above the standard analysis. 
 
 Grand Rapids. The city requires that the heating value per 
 pound of dry coal be stated by the bidder and if calorimeter 
 tests show the coal to fall below this standard a rebate is made 
 from the contract price and an increase if the coal comes above 
 the standard, the rebate or increase being made in exact propor- 
 tion to the B.t.u. For instance, if the bidder guarantees 15,000 
 B.t.u. per pound and the coal contains only 14,000 the contractor 
 would receive yf of the contract price. Any coal which shows 
 more than 5 per cent less heat units than the fixed standard may 
 be rejected. Standards are established for different kinds of coal 
 varying between the limits of 15,000 to 11,000 B.t.u., a minimum 
 of 44 to 71 per cent fixed carbon, a maximum of 15 to 6 per cent 
 ash and a maximum of 3 to f per cent sulphur. 
 
 Details of the purchase of coal by the United States Govern- 
 ment under specifications together with the form of specifica- 
 tions, proposals, guarantees, contracts, bonds, etc., are given 
 in Bulletin 41 of the United States Bureau of Mines. 
 
CHAPTER IX 
 
 ANALYSIS OF FLUE GASES 
 
 Composition of flue gas. Flue gas consists of carbon dioxide 
 (CO2), oxygen (62), nitrogen (%), small amounts of carbon 
 monoxide (CO), and small amounts of sulphur dioxide (862), 
 and sometimes probably traces of hydrogen (H2) and hydro- 
 carbons The gas also contains water vapor but in ordinary flue 
 gas analysis the water vapor is not considered, as the analysis is 
 made on the basis of dry gas. In technical analysis, usually 
 only the carbon dioxide, oxygen, and carbon monoxide are deter- 
 mined, the remaining gas being considered as nitrogen. 
 
 Analysis of the gas. In making the analysis a measured 
 volume of the gas is treated successively with a series of reagents 
 that absorb the several constituents, the volume remaining being 
 read after each absorption. The measurement of the gas is made 
 in a graduated tube or burette which should be surrounded by 
 a water jacket to insure constant temperature during the time 
 of the analysis. The measurements of the gas are all done at 
 atmospheric pressure and as the time of making analyses is short, 
 it is assumed that the barometer remains constant during that 
 period, while the use of the water jacket should prevent any 
 appreciable temperature changes. However, a thermometer 
 hung in the water jacket is a decided advantage if the apparatus 
 isexposed to draughts of air or in a room where the temperature 
 varies. 
 
 Sampling the gas. The tubes best adapted for sampling 
 depend upon the particular conditions under which the sample 
 has to be taken. In collecting samples at very high temperatures, 
 1500 to 1600 C. (2700 to 2900 F.) a quartz tube is perhaps the 
 best means of obtaining a sample. Such a tube stands high 
 temperatures and has no action on the gas. It is somewhat expen- 
 sive and must be handled with care to prevent breakage bills 
 becoming excessive. In sampling at these high temperatures 
 
 132 
 
ANALYSIS OF FLUE GASES 
 
 133 
 
 the tube is inserted and removed at the taking of each sample. 
 If the tube is allowed to remain in the furnace, slag, etc., soon 
 destroy it. In sampling at temperatures from 400 to 800 C. 
 (750 to 1500 F.) water jacketed iron tubes permanently installed 
 during the period of the test are satisfactory. Sufficient water 
 must be used to insure proper cooling if entirely satisfactory 
 results are desired. (See Fig. 7.) 
 
 A disadvantage of the quartz and water jacketed tubes just 
 described is that the sample drawn is from only one portion of 
 the furnace and does not necessarily represent the average of 
 the gas coming off at that time. Shifting the end of the tube to 
 
 SAMPLING TUBE: 
 
 WATER -JACKETED SAMPLING TUBE 
 
 FIG. 7. Sampling Tubes. 
 
 different portions of the furnace during a series of tests partially 
 eliminates error, but cannot be regarded as entirely satisfactory. 
 Sampling gas from boiler flues. As a rule, the temperature 
 of the gas from a boiler flue is considerably below 330 C. (625 F.) 
 and at temperatures less than this, an ordinary iron sampling 
 tube may be used. (See Fig. 7.) The tube should cross the flue 
 at a right angle and extend to within 6 inches of the further wall. 
 The end of the tube is closed with a cap and 'along the lower 
 side of the tube are a number of small holes ^ inch in diameter 
 distributed at regular intervals of 6 inches apart. The last hole 
 should be not less than 6 inches from the near wall of the flue. 
 The diameter of the holes given as -^ inch is based on the use of 
 a pipe not less than 1 inch in diameter. If the holes are too large 
 
134 COAL 
 
 in proportion to the diameter of the pipe, too much of the gas 
 will enter through the holes which are nearest to the aspirator. 
 
 Aspiration of the gas. During a test, gas should be drawn 
 continuously from the flue by means of a steam or water aspira- 
 tor. The gas should be passed through a bottle (about 16-oz.) 
 filled with absorbent cotton to filter out the dirt and should bubble 
 through water in a second bottle. (See Fig. 8.) The use of the 
 water bottle is to enable the operator to ascertain the rate and 
 regularity of the aspiration. In connecting the sampling tube 
 to the bottles and Orsat apparatus, rubber tubes should be avoided 
 as much as possible. Any long length of pipe or tube should be 
 of iron or lead with only short rubber connections at the joints. 
 All rubber connections should be well wired and the apparatus 
 tested for leaks by closing the stop cock on the sampling tube 
 and noting whether the aspiration of gas continues for any length 
 of time or whether it ceases to bubble through the water as soon 
 as a partial vacuum is produced. If any leaks are discovered 
 they must be stopped, otherwise air will be introduced into the 
 gas analyzed and give incorrect results. 
 
 Apparatus for making the analysis. Some form of Orsat 
 apparatus is very generally used in making the flue-gas deter- 
 minations. A typical one is shown in Fig. 8. This differs from 
 most of those sold by dealers in that the absorption pipettes are 
 connected at the rear to a tube connecting to the two bottles 
 below, which form a water seal protecting the reagents from the 
 action of the air. The ordinary Orsat apparatus as furnished 
 by the supply houses has small thin rubber bags for attaching 
 to the rear of the absorption pipettes but these soon rot and leak 
 and are generally not so satisfactory as the water bottles which 
 are permanent and need only to have the rubber tube connections 
 renewed occasionally. 
 
 Operation of the Orsat Apparatus. Sufficient water is poured 
 into the levelling bottle so that when the three-way cock is opened 
 and the bottle raised, the gas will escape and the water fill the 
 burette to a point in the capillary tube. A few drops of sulphuric 
 acid and a piece of litmus paper should be added to the water 
 in the levelling bottle in order to insure against an alkaline reac- 
 tion. The adjustment of the level of the reagents in the absorp- 
 tion pipettes to a fixed point in the capillary tube is best made 
 as follows: The stop-cock to each of the absorption pipettes 
 
ANALYSIS OF FLUE GASES 
 
 135 
 
 being closed, the 3-way cock is opened to the air and the levelling 
 bottle lowered sufficiently to draw in 25 to 30 c.c. of air. The 
 
 FIG. 8. Orsat's Apparatus. 
 
 3-way cock is then closed. Now, holding the levelling bottle 
 high enough so that the air is under some pressure, the stop- 
 
136 COAL 
 
 cock to the first pipette is opened. Some air will rush over and 
 the level of the liquid will be lowered. The levelling bottle 
 is then gradually lowered until the liquid in the absorption pipette 
 begins to rise. The lowering of the levelling bottle is continued 
 gradually until the liquid in the absorption pipette reaches the 
 mark on the capillary. The stop-cock is then closed. The level- 
 ling of the reagents in the other pipettes is done in the same 
 manner. 
 
 This method of levelling prevents the suction of any of the 
 reagents up into the capillary tubes. The author prefers, in using 
 the apparatus, that the marked point on the capillary of the 
 absorption pipette be placed considerably below the stop-cock 
 (in the apparatus shown in Fig. 8, the marks are below the 
 rubber connections rather than above them). This position 
 of the mark on the capillary greatly diminishes the danger of 
 allowing the reagent to pass up into the stop-cock and above and 
 while a little more residual gas is left in the capillaries, in a series 
 of analyses any individual errors so introduced are eliminated 
 in the average of the series. 
 
 Drawing a sample into the Orsat apparatus. If the burette 
 is not completely filled with water, it is filled by raising the level- 
 ling bottle and opening the 3-way cock to the air until the water 
 enters the capillary. The cock is then closed and the levelling 
 bottle lowered. If the apparatus is tight the level of the water 
 in the capillary and the level of the reagents in the absorption 
 pipettes should remain constant. If any leaks are present they 
 must be stopped before trying to make an analysis. If the appara- 
 tus is tight, the 3-way stop-cock is turned so as to connect the gas 
 burette with the gas bottles through which the gas is passing 
 to the aspirator and the pinch cock on the rubber tube (see Fig. 
 8), is opened and 50 or 60 c.c. of gas drawn into the apparatus. 
 The pinch cock is then closed, the levelling bottle raised, the 3- 
 way cock opened to the air, and the gas is forced out of the appara- 
 tus till the water again enters the capillary. This preliminary 
 drawing of gas is essential in order to fill the capillaries and 
 rubber tube with gas having approximately the same composi- 
 tion as the sample to be analyzed. 
 
 With the levelling bottle lowered, the 3-way cock is again 
 opened to the gas supply, the pinch cock again opened and gas 
 drawn in until over 100 c.c. are obtained. The pinch cock and 
 
ANALYSIS OF FLUE GASES 137 
 
 3-way cock are then closed. The levelling bottle is raised until 
 the gas in the burette reads zero. The rubber tube connecting 
 the levelling bottle to the burette is then pinched with the thumb 
 and finger and the 3-way cock opened to the air to allow the excess 
 of gas to escape. The cock is then closed, the levelling bottle 
 adjusted and the reading of the gas noted. It should read zero 
 or at most 0.1 or 0.2 c.c. above zero. The actual reading is 
 recorded, the levelling bottle raised and the gas run over into 
 the first absorption pipette containing the potassium hydroxide 
 solution. The cock is closed and the gas allowed to remain in the 
 pipette for about a minute. It is then run back into the burette, 
 the levelling bottle adjusted and a reading taken. A second 
 absorption in the potassium hydroxide pipette is then made and 
 a second burette reading taken. This reading should check the 
 first one. If not, a third absorption is necessary. The difference 
 between the initial readings and the reading after absorption in 
 the potassium hydroxide pipette equals the percentage of carbon 
 dioxide. The gas is next run into the pyrogallic acid pipette and 
 run back and forward several times before a reading is made. 
 After a reading it is again run back and forward several times 
 and a second reading taken. The absorption and readings are 
 continued until the last two readings agree exactly. The difference 
 between the final reading from pyrogallic acid absorption and the 
 absorption in the potassium hydroxide pipette equals the per- 
 centage of oxygen present. The determination of carbon mon- 
 oxide is made in a similar manner by running the residual gas 
 into the cuprous chloride pipette and allowing it to stand for some 
 little time. The absorption is continued until two readings 
 check. The difference between the reading from the pyrogallic 
 acid pipette and the reading after the absorption by cuprous 
 chloride equals the percentage of carbon monoxide present, 
 provided that all of the oxygen had been completely absorbed, 
 as any oxygen not taken out by the pyrogallic acid pipette is 
 taken up by the cuprous chloride and hence counts as carbon 
 monoxide. 
 
 In beginning a series of analyses it is necessary to draw several 
 preliminary samples oi the flue gas in order to saturate the water 
 in the burette with the gases being analyzed. Otherwise, the first 
 few results will be too low due to the absorption of the gas in 
 the water. 
 
138 COAL 
 
 REAGENTS USED AND THEIR PREPARATION 
 
 For absorbing carbon dioxide (CC>2) a 25 per cent solution of 
 potassium hydroxide is used. For absorbing oxygen (62) an 
 alkaline solution of pyrogallic acid is generally used. For absorbing 
 carbon monoxide (CO) an acid or ammoniacal solution of cuprous 
 chloride is used. The preparation of these reagents is as follows: 
 
 Potassium hydroxide (KOH) solution. Dissolve 100 grams of 
 the best quality potassium hydroxide in 300 grams of water. 
 Let the solution stand in a closed bottle till any oxide of iron 
 settles and use only the clear solution. If many analyses are to 
 be made it is best to prepare a large quantity of this solution and 
 keep it ready for use. 
 
 Pyrogallic acid solution. The white re-sublimed acid should 
 be used. In ordinary flue gas analysis 15 grams of pyrogallic 
 acid are dissolved in 150 c.c. of the 25 per cent potassium hydroxide 
 solution, the solution of the pyrogallic acid being made at the 
 time the Orsat apparatus is filled. 
 
 Cuprous-ammonium chloride solution. This is prepared 
 as follows : 250 grams of ammonium chloride ' are dissolved in 
 750 c.c. of water in a bottle provided with a good rubber stopper 
 and 200 grams of cuprous chloride are added. The latter on 
 frequent agitation dissolves, leaving a little cupric oxychloride 
 behind, forming a brown liquid which keeps for an indefinite 
 time, especially if a copper spiral long enough to reach from the 
 top to the bottom of the solution is inserted into the bottle. In 
 contact with air the solution forms a precipitate of green cupric 
 oxychloride. In order to make it ready for use, it is mixed with 
 one-third its volume of ammonia, specific gravity 0.910. 
 
 Acid cuprous chloride solution. To prepare 125 c.c. of solution 
 the process is as follows : 12 grams of pulverized and recently ignited 
 cupric oxide (CuO), are dissolved in 125 c.c. of concentrated hydro- 
 chloric acid. Next 40 grams of crystallized copper sulphate 
 (CuSO45H2O) are dissolved in about 200 c.c. of water, adding 
 a few drops of sulphuric acid. To this solution are added 12 grams 
 of granular or mossy zinc which is added carefully to avoid violent 
 effervescence. This zinc may be added to the copper sulphate 
 solution before the copper sulphate has entirely dissolved. The 
 zinc precipitates the copper as a brown powder and the excess of 
 zinc is dissolved in the sulphuric acid more of which is added 
 
ANALYSIS OF FLUE GASES 139 
 
 if necessary to complete the solution. The liquid is then decanted 
 closely and washed by decant ation till free from zinc sulphate. 
 The precipitated copper is then transferred to a small flask (about 
 150 c.c. capacity) and the water used in transferring poured off 
 as completely as possible. The solution of the cupric oxide in 
 hydrochloric acid is then added to the flask which is stoppered 
 loosely and shaken occasionally until the solution becomes almost 
 or entirely clear. The rapidity of reduction may be increased 
 by dropping into the flask several long pieces of sheet copper 
 or copper wire which accelerate the reduction of the upper por- 
 tion of the liquid. After the solution has become practically 
 clear it is either transferred at once to the absorption pipette 
 of the Orsat apparatus or poured into a stock bottle containing 
 strips of metallic copper. The solution should almost fill this 
 stock bottle w r hich must be well stoppered. 
 
 Filling the Orsat apparatus. The old solutions in the absorp- 
 tion pipettes are removed by forcing air from the gas burette 
 into the absorption bulbs and forcing the liquid into the rear 
 bulbs. Each is then emptied by a small syphon first filled with 
 water and inserted to the bottom of the bulb. The first rear bulb 
 the one nearest to the measuring burette is then filled with a 
 proper amount of potassium hydroxide solution. To fill the second 
 bulb with pyro solution place a large funnel into the bulb and put 
 into it 12 grams of pyrogallic acid. This is then washed down in 
 to the bulb with 120 c.c. of the 25 per cent potash solution. If 
 this amount of reagent does not properly fill the pipette more or 
 less potash solution should be taken and the amount of pyrogallic 
 acid increased or reduced proportionately. The filling of this 
 pipette should be done as quickly as possible and as soon as filled 
 it should be stoppered to protect from the action of the air. The 
 third bulb is filled with cuprous chloride solution, the proper 
 amount being poured into the pipette as quickly as possible 
 and the pipette stoppered to protect the reagent from the air. 
 The stoppers are next removed from the absorption bulbs and the 
 stoppers on the connections to the water sealed bottles securely 
 pushed into place, as it is essential that there be no leakage if 
 the reagents are to be properly protected from the air. 
 
 Absorbing power of reagents. 100 c.c. of a 25 per cent 
 potassium hydroxide solution will quickly and completely absorb 
 500 or 600 c.c. of carbon dioxide. Theoretically it is capable of 
 
140 COAL 
 
 absorbing several thousand c.c. but practically it should never be 
 used to any where near its theoretical limit and it is advisable to 
 use fresh reagent in the Orsat apparatus after 50 or 60 flue gas 
 determinations have been made as the loss of time due to the slow- 
 ness of the absorption of carbon dioxide more than counter- 
 balances the slight cost for new reagent. 100 c.c. of the alkaline 
 pyrogallic acid solution is capable of absorbing several hundred 
 c.c. of oxygen and if the reagent is kept properly protected from 
 the air the Orsat solution should easily be good for 30 or 40 deter- 
 minations of oxygen. However, the author prefers to begin each 
 day's work with an Orsat apparatus with a new solution of pyro- 
 gallic acid, as any slowing up in the absorption by an old solution, 
 which frequently occurs if a solution is used a second day, more 
 than makes up for the trouble or expense of renewing the solution 
 each day. 
 
 100 c.c. of cuprous chloride solution should readily absorb 
 50 c.c. of carbon monoxide. However, the last traces are 
 absorbed very slowly or not at all by a solution which has 
 previously absorbed very much carbon monoxide, and the author 
 prefers to renew the cuprous chloride solution in the Orsat 
 apparatus quite frequently even though the actual absorption 
 during the tests upon which it has been used do not total up 
 very many c.c. 
 
 Care of apparatus. In setting up the Orsat apparatus, the 
 capillary tubes and absorption pipettes should be washed with 
 dilute hydrochloric acid and then rinsed with pure water. The 
 ends of the tubes fitting into the rubber tube connections should 
 be coated with vaseline and the connections should be securely 
 wired to prevent leaks; the stop-cocks should be well lubri- 
 cated with vaseline or some similar lubricant. In cleaning 
 out an old solution of cuprous chloride it is sometimes advis- 
 able to wash out the cuprous chloride pipette with rather strong 
 hydrochloric acid to dissolve any precipitated cuprous chloride 
 which cannot be removed by the use of pure water. If at any 
 time any reagent gets into a stop-cock or capillary it should be 
 at once flushed out with water and if necessary the apparatus 
 disconnected and cleaned. Before putting the apparatus away 
 all stop-cocks should be loosened slightly and given an applica- 
 tion of vaseline if needed. If the apparatus is to be set away for 
 any great length of time, it is advisable to remove the stop-cocks 
 
ANALYSIS OF FLUE GASES 141 
 
 entirely and to insert a narrow strip of paper into eaeh socket 
 before replacing the stop-cock. These strips of paper are perma- 
 nent safe-guards against the cocks sticking, as is frequently the 
 case if the apparatus is set away without any care being given to 
 them. The gas burette should be left filled with gas or air 
 rather than with water so that if any leak develops there can be 
 no possibility of drawing reagents up in the capillaries. 
 
 DISCUSSION AND INTERPRETATION OF ORSAT RESULTS 
 
 These may perhaps best be understood by discussing the 
 reactions which take place during combustion of a coal. The 
 average analysis of a number of samples of Ohio No. 6 coal 
 (Hocking or Middle Kittanning coal) is as follows : 
 
 Carbon 69.03 
 
 Total hydrogen 5 . 43 
 
 Nitrogen 1 . 26 
 
 Oxygen 13 . 62 
 
 Sulphur 3 . 30 
 
 Ash 7.36 
 
 Available hydrogen 3 . 73 
 
 The available hydrogen is obtained from the total hydrogen 
 by subtracting from the total hydrogen J of the oxygen in the 
 coal = 5.43 -(-J- of 13.62) -3.73. The reactions for complete 
 combustion of this coal in air (air = by volume one part of oxygen 
 and 3.8 parts of nitrogen) are as follows. 
 
 C+O 2 +3.8 N 2 = C0 2 +3.8 N 2 ; 
 2H 2 +0 2 +3.8N 2 = 2H 2 0+3.8N 2 ; 
 
 S+0 2 +3.8 N 2 =SO 2 +3.8 N 2 ; 
 
 N 2 = N 2 . 
 
 Gas reactions are most easily handled if the gases produced 
 are figured with a molecular volume as the unit for calculation. 
 A molecular volume of gas is the volume which the molecular 
 weight of the gas in grams occupies. Under standard conditions, 
 C. and 760 mm. of mercury pressure, this = 22.4 liters (0.79 
 cu.ft.). As an illustration, the molecular weight of carbon dioxide 
 (CO 2 ) =44. The molecular weight of carbon monoxide (CO) =28. 
 44 grams of carbon dioxide (CO 2 ) or 28 grams of carbon monoxide 
 
142 COAL. 
 
 (CO) =22.4 liters by volume, at C. and at a pressure of 760 mm. 
 of mercury. 
 
 1 molecular volume of CO2 = 12 grams of carbon or 0.01 gram 
 carbon = 0.000833 molecular volume of CC^. 
 
 1 molecular volume of H20 = 2 grams of hydrogen (H^) or 
 0.01 gram of hydrogen = 0.005 molecular volume H 2 O. 
 
 1 molecular volume of SO 2 = 32 grams of sulphur or 0.01 gram 
 of sulphur = 0.00031 molecular volume of SO2. 
 
 1 molecular volume of N2 = 28 grams of N2 or 0.01 gram of 
 nitrogen = 0.000357 molecular volume of N2. 
 
 From these relations the molecular volumes of the products 
 of complete combustion of 1 gram of coal with no excess air are 
 as follows : 
 
 For the carbon to C+O 2 +3.8N 2 = CO 2 +3.8N 2 = 69.03 X 
 0.000833 = 0.0575 molecular volume of CO 2 + (0.0575X3.8 = 
 0.2185) molecular volume N2. 
 
 For the available hydrogen to 2H 2 +O 2 +3.8N 2 = 2H 2 O+3.8N 2 
 = 3.73X0.005 = 0.01865 molecular volume H 2 + 
 
 3 8 
 (0.01865 X = 0.0354) molecular volume N 2 . 
 
 The hydrogen present in the coal in the form of water = J the 
 oxygen in the coal = of 0.1362 = 0.0170 gram of hydrogen. 
 This hydrogen to 2H 2 O = 1.70X0.005 = 0.0085 molecular volume 
 H 2 0. 
 
 For the sulphur to S+0 2 +3.8N 2 = SO 2 +3.8N 2 = 3.30X0.00031 
 = 0.001 molecular volume SO 2 + (0.001X3.8 = 0.0038) molecular 
 volume N 2 . 
 
 For the nitrogen in the coal to N 2 = 1.26X0.000357 = 0.00045 
 molecular volume of N 2 . 
 
 Collecting together the nitrogen from the air required for 
 complete* combustion, 0.2185+0.0354+0.0038 = 0.2577 molecular 
 volume of nitrogen. 
 
 If 100 per cent excess air be assumed the nitrogen in this 100 per 
 cent excess air = therefore 0.2577 molecular volume and the oxygen 
 
 in this 100 per cent excess air = - - =0.0678 molecular volume. 
 
 0.0 
 
 Collecting these values for the products of combustion, 
 allowing the 100 per cent excess of air, the molecular volumes of 
 
ANALYSIS OF FLUE GASES 143 
 
 gas from the complete combustion of one gram of coal are as 
 follows : 
 
 CO2 = 0.0575 molecular volume 
 
 O 2 = 0.0678 
 
 H 2 O (vapor) = = 0.0271 
 
 S0 2 = 0.0010 
 
 N 2 = 0.5158 
 
 Total molecular volumes = 0.6692 = 15.0 liters at C. and 760 
 mm. pressure. 
 
 The Orsat analysis of the gas determines only the carbon 
 dioxide, the carbon monoxide, and the oxygen present. With 
 complete combustion it is assumed that no carbon monoxide is 
 produced and the analysis has only to do with carbon dioxide and 
 oxygen, the difference being nitrogen. The sulphur dioxide 
 formed during combustion amounts by volume to about -gV of the 
 volume of carbon dioxide and a small portion of this sulphur 
 dioxide may be absorbed by the potassium hydroxide solution 
 and hence count, as carbon dioxide. However, it is altogether 
 probable that the greater part is absorbed in the water in the 
 Orsat apparatus or elsewhere before the actual carbon dioxide 
 determination is made and for all practical purposes the volume 
 of the sulphur dioxide in the Orsat determination may be neg- 
 lected. The excess of water vapor in the gas condenses and the 
 Orsat gases are saturated with water vapor at the temperature at 
 which they are analyzed. With no change in temperature, the 
 proportion of water vapor present during an analysis remains 
 unchanged and the absorption of the gas by the potash or pyro- 
 gallic acid or cuprous chloride pipette represents the percentage 
 of carbon dioxide, oxygen, and carbon monoxide present in the 
 gas, as the effect of the presence of water vapor merely diminishes 
 the pressure of the residual gas analyzed, but it has no effect 
 on its relative percentage composition. 
 
 Referring to the reactions given (p. 141) for the combus- 
 tion of the Ohio No. 6 coal, for one gram of coal burned 
 there are present in the flue gas, assuming theoretical combustion, 
 50 per cent excess air and 100 per cent excess air, gases as fol- 
 lows : (H 2 O vapor and SO 2 are omitted from the tabulation since 
 they do not enter into the Orsat analysis). 
 
144 
 
 COAL 
 
 Gas Compo- 
 sition. 
 
 Theoretical Combustion. 50 Per Cent Excess Air. 
 
 100 Per Cent Excess Air. 
 
 Mol. Vol. 
 
 Per Cent. 
 
 Mol. Vol. 
 
 Per Cent. 
 
 Mol. Vol. 
 
 Per Cent. 
 
 CO, 
 
 o. 
 
 N 2 
 
 0.0575 
 0*2581 
 
 18.22 
 
 '81.78 
 
 0.0575 
 0.0339 
 0.3870 
 
 12.02 
 7.09 
 80.89 
 
 0.0575 
 0.0678 
 0.5158 
 
 8.98 
 10.58 
 80.44 
 
 0.3156 
 
 100.00 
 
 0.4784 
 
 100.00 
 
 0.6411 
 
 100.00 
 
 The effect of the formation of carbon monoxide instead of 
 carbon dioxide is to lower the nitrogen percentage since only one- 
 half as much air is required to burn carbon to carbon monoxide 
 as is required to burn it to carbon dioxide and less residual nitrogen 
 remains after the absorption of carbon dioxide, oxygen and 
 carbon monoxide. 0.01 gram of carbon to CO = 0.000833 molec- 
 ular volume of CO = .00158 molecular volume of N2 as against 
 0.00316 molecular volume of N2 required for an equivalent 
 amount of carbon to CO2. With 50 per cent excess air and 
 0.01 gram of carbon burned to CO instead of CO2, the products 
 of combustion of 1 gram of coal, omitting the tabulation of 
 and S02 are as follows; 
 
 Mol. Vol. 
 
 CO 2 0.0567 
 
 O 2 - 0.0337 
 
 CO 0.00083 
 
 N 2 0.3841 
 
 0.4753 
 
 Per Cent. 
 
 11.93 
 
 7.09 
 
 0.17 
 
 80.81 
 
 100.00 
 
 The higher the sulphur and the available hydrogen the more 
 oxygen is required for combustion and the greater the volume 
 of nitrogen in the residual gas. 0.01 gram of available hydrogen 
 requires air for combustion equivalent to 0.0095 molecular volume 
 of N. With 50 per cent excess air this equals 0.0143 molecular 
 volume of N2+0.0013 molecular volume of 02 = 0.0156 molecular 
 volume increase in the residual gas. In this case, assuming the 
 other constituents of the coal to remain the same, the products of 
 combustion of 1 gram of this coal containing 4.73 per cent available 
 hydrogen (omitting H^O and SO2 from the tabulation) are as 
 follows: 
 
ANALYSIS OF FLUE GASES 145 
 
 Mol. Vol. Per Cent. 
 
 CO 2 0.0575 11.64 
 
 O 2 0.0352 7.12 
 
 N 2 .. 0.4013 81.24 
 
 0.4940 100.00 
 
 With 50 per cent excess air, 1 per cent more of available hydro- 
 gen raises the nitrogen about 0.35 per cent. The effect of sulphur 
 is about I as great as the effect of an equal weight of hydrogen 
 or an increase of 1 per cent in sulphur increases the nitrogen by 
 about 0.05 per cent. 
 
 With 100 per cent excess air present the effects of hydrogen 
 and sulphur are about f as great as with 50 per cent excess or 
 approximately 0.24 for the hydrogen and 0.03 for the sulphur. 
 The available hydrogen in the sample calculated is 3.73 per cent 
 and an increase in available hydrogen of 1 per cent higher than 
 this amount is more than is ever actually found. Most coals 
 contain less than 4 per cent. On the basis of not over 4 per cent 
 available hydrogen and with the amount of carbon corresponding 
 to that usually found in coals high in available hydrogen and with 
 50 per cent excess air corresponding to approximately 12 per cent 
 of carbon dioxide in the flue gas, the nitrogen 'should not run 
 above 81 per cent. With larger excess air, as 100 per cent, 
 corresponding to approximately 9 per cent of the carbon dioxide 
 in the flue gas, the nitrogen should be appreciably less than 81 per 
 cent. With smaller excess air and higher carbon dioxide and 
 the absence of carbon monoxide, the nitrogen may possibly 
 exceed 81 per cent. 
 
 The effects of the presence of unburned hydrogen should be 
 considered as to its relation upon the Orsat analysis and the heat 
 balance. If it be assumed for illustration that of the 3.73 per 
 cent available hydrogen, one part escapes as free hydrogen and 
 the remaining 2.73 burn to water, allowing 50 per cent excess air, 
 the products of combustion from 1 gram of coal (omitting 
 vapor and SOo from the tabulation), are as follows: 
 
 CO 2 
 
 Mol. Vol. 
 
 0575 
 
 Per Cent. 
 
 12 29 
 
 2 
 
 0.0326 
 0.3727 
 
 6.97 
 79.67 
 
 H 2 .. . 
 
 . 0050 
 
 1.07 
 
 
 
 
 Total.. . 0.4678 100.00 
 
146 COAL 
 
 Deducting the sum of the carbon dioxide and oxygen (19.26) 
 from 100 = 80.74 as the percentage of nitrogen obtained. This is 
 only 0.15 per cent lower than the figure obtained for complete 
 combustion, hence as far as any visible effects in the Orsat deter- 
 mination are concerned, unburned hydrogen has little effect upon 
 the totals of the carbon dioxide, oxygen, and carbon monoxide. 
 A failure of this amount of hydrogen to burn would mean, how- 
 ever, a loss of 334 calories or 5 per cent of the total heat in the 
 fuel. 
 
 In a similar way it may be shown that the presence of large 
 amounts of methane in the gas would have little effect upon the 
 percentage result obtained for nitrogen. With 50 per cent excess 
 air and assuming 0.01 gram of carbon and a corresponding amount 
 (0.0033 gram) of hydrogen remaining as methane (CHU), the 
 products of combustion of 1 gram of the coal (omitting H^O and 
 SC>2 from the tabulation), are as follows: 
 
 Mol Vol. Per Cent. 
 
 CO 2 0.0567 12.12 
 
 O 2 .. , 0.0327 6.99 
 
 N 2 0.3776 80.71 
 
 CH 4 .. . 0.00083 0.18 
 
 Total 0.46783 100.00 
 
 The sum of the nitrogen and methane equals 80.89 which is 
 the same as the value for nitrogen assuming complete combustion 
 and 50 per cent excess air. 
 
 The above calculations may serve to make clear why the 
 nitrogen from- different determinations is not a fixed quantity, 
 and also that the value obtained for nitrogen is not necessarily 
 all nitrogen. By applying similar calculations to any coal for any 
 observed or assumed set of conditions, possible and probable per- 
 centages may be readily calculated and may serve to prove or dis- 
 prove speculations as to the possible or probable effects of unburned 
 hydrogen, carbon, etc. Such calculations usually make plain 
 or certain the fact that as a rule irregular determinations cannot 
 be satisfactorily explained in such a way and that irregular 
 results are more probably due to errors of manipulation, leaks 
 in the apparatus, etc. 
 
 Errors in the Orsat determination. (1) Leaks in the appara- 
 tus or connections leading to the sampling tube. 
 
ANALYSIS OF FLUE GASES 147 
 
 (2) Errors due to reagents getting into the apparatus, espe- 
 cially into the capillary connecting tube. 
 
 (3) Errors in levelling. 
 
 (4) Errors due to insufficient time of drainage of the burette 
 before taking a reading. 
 
 (5) Use of old reagents and failure to absorb completely tend 
 to give low results for carbon dioxide, low results for oxygen, high 
 or low results for carbon monoxide, but a low total for the three. 
 
 (6) Errors due to temperature changes during a determination. 
 Nos. 1, 3, 4 and 5 need no special comment, except to call 
 
 attention to possible errors from these causes. 
 
 No. 2. Any absorption of oxygen or carbon dioxide by traces 
 of potassium hydroxide or pyrogallic acid solution in the connect- 
 ing tube gives of course too low a result for oxygen or carbon 
 dioxide and consequently too high a result for nitrogen. Many 
 high nitrogens are probably due to carelessness in this particular. 
 
 No. 6. Errors due to temperature changes during a determina- 
 tion may be of considerable magnitude, which may perhaps best 
 be shown by a particular example. Suppose the temperature 
 of the gas at the beginning of a determination = 20 C. At the 
 end of the carbon dioxide absorption = 20 C. At the end of the 
 oxygen absorption = 21 C. and at the end of the carbon monoxide 
 absorption = 22 C., what is the effect upon an analysis, the 
 observed readings of which are as follows: 
 
 Observed Readings. Observed Per Cent. 
 Initial readings = 0.0 
 
 CO 2 10.00 10.00 
 
 O 2 19.00 9.00 
 
 CO 19.00 0.00 
 
 N 2 81.00 
 
 Since there is no temperature change during the carbon dioxide 
 determination the determined percentage of carbon dioxide (10 per 
 cent) equals the true percentage present. During the determina- 
 tion of oxygen the temperature increases one degree or from 293 
 degrees absolute to 294 degrees absolute. Hence the observed 
 volume of residual gas (81 c.c.) is -g-gT larger than the volume of 
 the gas at 20 C. -gi^ of 81 =0.27 c.c. or the corrected volume 
 of the residual gas is 80.73, from which the corrected percentage 
 of oxygen = 9.27 as against 9.00 observed. Likewise, for carbon 
 
148 
 
 COAL 
 
 monoxide, the observed volume 81.00 at 22 is -jf-g- larger than the 
 volume of the gas at 20 or the volume of the residual gas cor- 
 rected to 20 C. is approximately 80.46 c.c. and the corrected 
 percentage of carbon monoxide is 0.27 instead of zero, the deter- 
 mined percentage. This error appears large enough but there 
 is still another effect to be considered. The aqueous tension 
 of the water vapor of the gas at 20 C. = 17.4 mm. of mercury, 
 at 21 C. = 18.5 mm. of mercury, at 22 = 19. 7 mm. of mercury. 
 Assuming a total observed barometric pressure of 740 mm. of 
 mercury, the actual pressure of the gas in the burette at the 
 different temperatures is therefore, 
 
 for 20 C., 740-17.4 = 722.6; 
 for 21 C., 740-18.5-721.5; 
 for 22 C., 740-19.7 = 720.3; 
 
 and the corrected volume of the 81 c.c. at 21 C. allowing for this 
 change is less by of81=0.12c.c. and the corrected volume of 
 
 2.3 
 
 the 81 c.c. observed at 22 C. is less by of 81 = approximately 
 
 /20.3 
 
 0.26 c.c. This error adds to the error introduced by the tempera- 
 ture changes. 
 
 Combining the two corrections, the true reading and percentages 
 are as follows: 
 
 
 Observed 
 
 Observed 
 
 Corrected 
 
 to 20 C. 
 
 
 Reading. 
 
 Per Cent. 
 
 True Reading. 
 
 True Per Cent. 
 
 Initial reading 
 CO 2 
 O 2 
 
 0.00 
 10.00 
 19.00 
 
 10.00 
 
 9.00 
 
 10.00 
 19.40 
 
 10.00 
 
 9 40 
 
 CO. 
 
 19 00 
 
 00 
 
 19 81 
 
 41 
 
 N 2 
 
 
 81 00 
 
 
 80 19 
 
 
 
 
 
 
 
 
 100.00 
 
 
 100.00 
 
 The above corrections are obtained as follows: 
 
 For oxygen, correcting from 21 to 20 C. = 100-19 = 81 c.c. 
 
ANALYSIS OF FLUE OASES 149 
 
 293 721 5 
 
 <MU^799"fi = ^'^' The correct oxygen reading is there- 
 
 fore 100 - 80.60 = 19.40. 
 
 For carbon monoxide, correcting from 22 to 20 C., 100-19 
 
 293 720 3 
 = 81 c.c. 81XX = 80.19. The correct carbon monoxide 
 
 reading is therefore 100-80.19 = 19.81. 
 
 With an initial temperature of 20 C., a change of 1 during 
 the determination of any constituent introduces an error of about 
 0.4 per cent. If the temperature has increased the observed result 
 is too low. If the temperature has decreased the observed result 
 is too high. For higher temperatures the effect of aqueous tension 
 is appreciably larger. For 30 C. (89 F.) the error for 1 change 
 of temperature being approximately 0.06 per cent more than at 
 20 C. 
 
 The magnitude of these errors certainly shows the impossibility 
 of securing accurate results with unjacketed burettes and shows 
 the possibility of serious errors even where jacketed burettes are 
 used, if the apparatus is exposed to draughts or rapid temperature 
 changes. The use of a thermometer in the water jacket and the 
 taking of temperature observations before and after the absorp- 
 tion serve as a check on this error and allow for corrections if 
 temperature changes are noted. 
 
 ALTERATION OF SAMPLES ON STANDING AND EFFECTS 
 UPON THE ORSAT RESULTS 
 
 The foregoing discussion of the Orsat analysis and results is 
 based on the supposition that the samples are drawn directly into 
 the Orsat apparatus and analyzed at once. When samples are 
 collected in sample tubes or bottles, or in metal tanks, the possible 
 and probable alteration of the samples and the effect upon the 
 Orsat determination should be considered. 
 
 The changes to which a stored sample are liable are, (1) 
 leakage, (2) chemical changes, (3) absorption of the gas in the water 
 over which it is collected or over which it is allowed to stand. 
 
 (1) Leakage. The danger from alteration of a stored sample 
 from leakage should not be overlooked. Samples stored in rubber 
 containers or in containers with rubber connections of any length 
 
150 COAL' 
 
 are practically sure to alter if kept for any considerable time, 
 and sample tubes closed by stop-cocks even if well lubricated and 
 well tied are liable to possible leakage. A slight leak in a rubber 
 connection or around a stop-cock, if the sample is analyzed 
 promptly, may not have any measurable effect upon the sample 
 but if the sample is stored and the leakage allowed to continue 
 during twenty-four or forty-eight hours the sample may be so 
 changed in composition as to render any results obtained upon 
 it entirely worthless. Every rise or fall in the temperature of 
 the gas from that at which it was collected subjects it to an in- 
 creased or diminished pressure and hence any slight leaks are 
 likely to be continually acting. 
 
 If samples must be collected and kept before being analyzed 
 the author prefers to so take them that they will be under con- 
 siderable pressure when sealed and any leakage be continually 
 outward rather than alternately inward and outward. Also if 
 collected and kept over water the exposure to water while collect- 
 ing should be reduced to a minimum and the amount of water 
 allowed to remain in contact with the sample should be relatively 
 small in comparison to the volume of the sample. (For example 
 preferably not over one volume of water to 10 volumes of gas.) 
 
 Leakage of sample outward may merely change the volume of 
 the sample without altering its composition. However, as carbon 
 dioxide diffuses through small orifices less readily than the lighter 
 gases (oxygen, nitrogen and carbon monoxide), a considerable 
 leakage of gas especially if through rubber may result in the 
 residual gas being higher in carbon dioxide than the original sample. 
 Leakage inward is certain to raise the oxygen content since 
 the oxygen percentage of the air surrounding a sample is certain 
 to be much higher than the oxygen content of the flue-gas sample. 
 The effects of leakage and consequent alteration of the composi- 
 tion of the sample upon the value of the Orsat determination are 
 discussed in detail later. 
 
 (2) The chemical alteration of the sample. The chief sources 
 of error from chemical changes are the absorption of oxygen by 
 reducing reagents in the water over which the sample is collected 
 or stored, and the absorption of carbon dioxide as carbonate by 
 salts of calcium which may be in the water, or in some cases the 
 enrichment of the gas in carbon dioxide by its liberation from 
 bi-carbonate salts in the water. The usual reducing agents are the 
 
ANALYSIS OF FLUE GASES 
 
 151 
 
 ferrous salts of iron which readily use up oxygen, and water which 
 carries iron in solution should not be used in filling the tanks or 
 tubes in which gas samples are to be collected. Rain-water, well 
 water or hydrant water which has been exposed to the air for some 
 time before using is to be preferred to water taken directly from 
 the pump or water main. The water should, however, not be 
 too thoroughly aerated, as if saturated with air it will give up 
 oxygen to flue-gas samples kept over it. To avoid as much as 
 possible errors from chemical changes, the exposure of the sample 
 to water should be reduced to a minimum and only a small amount 
 of water be allowed to remain in contact with the sample. 
 
 ALTERATION OF SAMPLES BY ABSORPTION IN THE WATER 
 OVER WHICH THEY ARE COLLECTED OR STORED 
 
 Samples collected over water are certain to suffer alteration 
 from this cause and the extent of such alteration and the effect 
 upon the Orsat determination should be well understood by every- 
 one who has to do with gas sampling. 
 
 The following values for solubilities are taken from Landolt 
 and Bernstein's tables, the solubilities being given in volumes of 
 gas absorbed by one volume of water at the temperatures given 
 and with the gas at a pressure of 760 mm. of mercury. 
 
 
 C. (32 F.). 
 
 15 C. (59 F.). 
 
 30 C. (86 F.). 
 
 O 2 
 
 0489 
 
 03415 
 
 0.02608 
 
 N 2 
 
 . 02388 
 
 0.01786 
 
 0.01380 
 
 CO 
 
 03537 
 
 02543 
 
 0.01998 
 
 CO 2 
 
 1.713 
 
 1.019 
 
 0.665 
 
 
 
 
 
 The solubilities of these gases for the same temperature 
 varies directly as the pressure of the gas and for a mixture of gases 
 the solubility of each gas is proportional to the partial pressure of 
 each gas independent of the other gases present. The partial 
 pressure exerted by each gas in a gas mixture is proportional to 
 the percentage of each gas. For example in a mixture of 20 per 
 cent oxygen and 80 per cent nitrogen under atmospheric pressure 
 
152 COAL 
 
 the partial pressure of the oxygen is 0.20 of an atmosphere and 
 the partial pressure of the nitrogen is 0.80 of an atmosphere. 
 
 The solubility of a mixture of gases (flue gas) in water should be 
 considered under several particular conditions : 
 
 (1) An unlimited supply of gas and a limited supply of water. 
 With an unlimited supply of gas and a limited supply of water 
 the volumes of gas which can be absorbed by the water at any 
 given temperature and pressure may be calculated directly from 
 the solubility values previously given. 
 
 (2) A limited supply of gas and an unlimited supply of water. 
 With a limited supply of gas and an unlimited supply of water 
 the gas will be entirely dissolved in the water. 
 
 (3) A limited supply of gas and a limited supply of water. With 
 a limited supply of gas and a limited supply of water the gas will 
 dissolve in water until a condition of equilibrium is attained. 
 This condition of a limited supply of gas and a limited supply 
 of water is the one that exists where gases are stored in sampling 
 tubes or containers over water and the possible alteration of such 
 samples should be well understood. This may perhaps best be 
 shown by an example. For illustration, what is the solubility 
 and the resultant volume and composition of one liter of gas 
 stored over one liter of pure distilled water at a temperature of 
 15 C. (59 F.), at an atmospheric pressure of 742.7 mm. of mer- 
 cury, the composition of the original gas being, 
 
 CO 2 10.0 per cent 
 O 2 9.0 
 
 CO 0.5 
 
 N 2 ?80.5 
 
 100.0 
 
 The pressure of aqueous vapor at 15 C. = 12.7 mm. of mercury 
 or the total pressure of the gas present = 742. 7 12.7 = 730 mm. 
 of mercury. From the values for solubilities given for 760 mm. 
 pressure of gas and 15 C. the solubilities of CO2, 62, CO, and 
 N2 in 1000 c.c. of water for 730 mm. are found to be, 
 
 C0 2 = 978.8 c.c. 
 
 O 2 = 32.79 ll 
 
 C0= 24.42 " 
 
 N 2 = 17.17 " 
 
ANALYSIS OF FLUE GASES 153 
 
 Since the partial pressure of each constituent of a mixture is 
 proportional to the percentage of each constituent present, the 
 solubilities of the different gases in 1000 c.c. of water at 15 C. 
 (assuming an unlimited supply of gas) are as follows: 
 
 CO 2 = 978.8 X^ =97. 88 c.c. 
 
 1UO 
 
 2 = 32.79X^ ; = 2.94 " 
 
 1UU 
 
 00=24.42x14=0.12." 
 
 N2= 1 
 
 For 1000 c.c. of the original gas the volumes of the constituents 
 arc as follows: 
 
 10 per cent C0 2 = 100 c.c. 
 
 9 " O 2 - 90 " 
 
 0.5 " CO = 5 " 
 
 80.5 " N 2 - 805 " 
 
 100.0 1000 ( 
 
 Comparison of the amount of each gas in 1000 c.c. of the 
 mixture with the solubility in 1000 c.c. of water based on the 
 supposition of an unlimited supply of gas shows at a glance that 
 the solubility of oxygen, carbon monoxide and nitrogen from the 
 limited supply of gas (1000 c.c.) is not very far from the amount 
 taken up from an unlimited supply, since the amount of each 
 dissolved is small compared to the amount of each present in 
 1000 c.c. of the gas. 
 
 With an unlimited supply of gas the solubility of carbon 
 dioxide is 97.88 c.c. Since the total c.c. of carbon dioxide in one 
 liter of the gas is only 100 c.c. if this amount were absorbed, only 
 2.14 c.c. of carbon dioxide would be present in the residual gas. 
 The volume of the residual gas, allowing for this absorption and 
 allowing for the absorption of oxygen, carbon monoxide and 
 nitrogen is 885 c.c. or the 2.14 c.c. of carbon dioxide = 2.4 per cent 
 
154 COAL 
 
 of the residual gas. The solubility of carbon dioxide in 1000 c.c. 
 of water with this per cent present in the gas over the water is 
 978.8X0.024 = approximately 2.3 c.c. and the actual condition of 
 equilibrium for solubility of the carbon dioxide in the 1000 c.c. of 
 water is evidently somewhere between these two extremes of 
 solubility, 2.3 c.c. and 97.88 c.c. or something over 50 c.c. 
 
 As a preliminary approximation, assume the solubility of 
 carbon dioxide from the limited volume of gas (1000 c.c.) to be 
 51 c.c.; oxygen 3 c.c.; and carbon monoxide 0.12 cc.. and for 
 nitrogen 14 c.c., then the amounts and percentages of gas remain- 
 ing are as follows: 
 
 CO 2 = 100 - 51 = 49 c.c. = 5 . 26 per cent 
 O 2 = 90- 3 = 87 " = 9.33 " 
 CO = 5-0.12= 4.88 " = 0.52 
 N 2 =805- 14 = 791. " =84.89 " 
 
 Total 931.88 ' 100.00 ll 
 
 Multiplying the solubility of each gas at 730 mm. pressure 
 and at 15 C. by the percentage of gas remaining, the amounts 
 of gas dissolved in 1000 c.c. for these percentages are as follows: 
 
 CO 2 = 978.8 XO. 0526 = 51. 48 c.c. 
 O 2 = 32.79X0.093 == 3.04 " 
 CO == 24.42X0.0052= 0.127 " 
 N 2 = 17.17X0.849 =14.58 " 
 
 From which it is seen that the first approximation for solubility 
 does not give actual equilibrium, but a second approximation 
 using values based on the ones already obtained will give practical 
 equilibrium. 
 
 These values are about as follows : 
 
 CO 2 absorbed = 51. 25 c.c. 
 2 " = 3.05 " 
 
 CO = 0.13 " 
 
 N 2 " =14.6 " 
 
ANALYSIS OF FLUE GASES 155 
 
 Using these values the volumes, percentages and equilibrium 
 conditions are as follows: 
 
 - P Cent. 
 
 CO 2 = 100 -51.25= 48.75= 5.24=51 .28 c.c. 
 
 2 = 90- 3.05= 86.95= 9.34= 3.06 " 
 
 CO= 5-0.13= 4.87= 0.52=0.13 " 
 
 N 2 = 805-14.6 =790.4 = 84.90 = 14.6 " 
 
 Total 930.97 100.00 
 
 The values obtained serve to show the possible changes that 
 gas stored over water may undergo. The actual solubilities 
 under working conditions will differ from these values on account 
 of the fact that ordinary water contains dissolved in it some 
 carbon dioxide, oxygen and nitrogen, hence the solubilities under 
 ordinary conditions will not be as high as the calculated. 
 
 Chemical changes may also enter in to alter the composition 
 of the final sample so that any calculated solubility change can- 
 not be depended upon for great accuracy. 
 
 The values obtained in the foregoing illustration serve, how- 
 ever, to emphasize and make clear the following facts : 
 
 That the alteration of the sample in carbon dioxide may be 
 very great and that the composition of the remaining sample is 
 as a result higher in both oxygen and nitrogen. 
 
 Effect of the solution of CO2 upon other determinations. 
 The excess-air ratio as determined by the ratio between oxygen and 
 nitrogen is not however affected by the solubility of carbon dioxide 
 and in so far as carbon dioxide is concerned the excess air may be 
 determined almost as accurately on a stored sample as on one 
 freshly taken, provided of course that chemical changes have not 
 used up oxygen. 
 
 In the illustration given above, the excess air in the original 
 sample containing 10 per cent of carbon dioxide calculated from 
 the oxygen-nitrogen ratio, is 73.9 per cent. The excess air in the 
 sample after it has reached equilibrium over the 1000 c.c. of water 
 is 71.8 per cent or a change of only 2 per cent in the figured excess 
 air with a change of nearly 5 per cent in carbon dioxide (nearly 
 one-half of the amount originally present) and a change of over 4 
 per cent in nitrogen. 
 
 The calculation of heat loss due to formation of carbon mon- 
 oxide rather than carbon dioxide is made inaccurate by any 
 
156 COAL 
 
 absorption of carbon dioxide. In the original sample the amount 
 of carbon burned to carbon monoxide is yj-g- of the total carbon 
 in the coal, while in the sample which has reached equilibrium 
 over the 1000 c.c. of water, the carbon burned to carbon monoxide 
 is -j 5 7 2 6 of the total carbon present, or a ratio almost twice as large 
 as the true ratio r~(hr> so that with large amounts of carbon mon- 
 oxide present in the gas the absorption of carbon dioxide in the 
 water, before the determination of the Orsat analysis, makes the 
 heat balance inaccurate in so far as the heat loss due to carbon 
 monoxide is concerned, but for the more important item of excess 
 air the absorption of carbon dioxide is without effect. 
 
 EFFECT OF A WATER SEAL UPON COMPOSITION OF 
 SAMPLES 
 
 Where samples are stored in bell jars or inverted cylinders 
 and protected from the atmosphere by a water seal the action of 
 this water seal should be noted. The surface of the water in con- 
 tact with the gas continually tends to reach a condition of equilib- 
 rium with respect to the gas above it. Likewise the surface of 
 the water seal which is exposed to the air is continually tending 
 to reach a condition of equilibrium with respect to the air above 
 it. Since the composition of the stored gas and the composition 
 of the air on the outside are radically different, equilibrium con- 
 ditions on the two sides are different and the result is a continual 
 absorption of carbon dioxide from the sample into the water which 
 gradually diffuses through the water seal and escapes into the open 
 air on the other side. Likewise there is in the opposite direction a 
 continual absorption of oxygen from the air into the water and dif- 
 fusion of this oxygen through the water seal into the stored gas. 
 The final effect, if the sample is stored long enough, will be that 
 the composition of the sample will approximate that of the outside 
 air, the excess carbon dioxide and carbon monoxide gradually 
 diffusing and escaping and the oxygen content of the sample con- 
 tinually increasing from diffusion inward. On account of this 
 diffusive action the author prefers in storing samples over water 
 that there be no actual contact of the water seal with the outside 
 air. 
 
 Details of the determination of hydrogen and hydro-carbons 
 
ANALYSIS OF FLUE GASES 157 
 
 in the flue gases and are given in special texts upon gas analysis- 
 The determination of carbon monoxide as made in the Orsat 
 apparatus is satisfactory only when small amounts of carbon 
 monoxide are present in the gas, as is the case in a boiler flue 
 gas. In the analysis of a gas high in carbon monoxide, as gas 
 from an iron blast furnace or gas from a gas producer, the 
 method and apparatus used should be such as to secure rapid 
 and complete absorption of the large amount of carbon monoxide 
 present. For the description of suitable methods and apparatus 
 special texts on gas analysis should be consulted. 
 
CHAPTER X 
 
 ANALYTICAL TABLES 
 
 COMPARATIVE COMPOSITION OF DIFFERENT FUELS 
 
 Fuel. 
 
 Moisture, Per Cent. 
 
 Remarks. 
 
 Wood 
 
 30 to 60 
 
 Green wood 
 
 Peat 
 
 50 to 90 
 
 As dug. 
 
 Lignite 
 
 30 to 45 
 
 As minod 
 
 Bituminous coal 
 Semi-bituminous coal. . . . .* 
 
 2 to 25 
 1 to 5 
 
 As mined. 
 As mined 
 
 Anthracite coal. 
 
 1 to 3 
 
 As mined 
 
 
 
 
 COMPOSITION AND HEATING VALUE OF AIR-DRIED MATERIALS 
 
 
 Wood. 
 
 Peat.s 
 Florida 
 No. 1. 
 
 Lig- 
 rute, 1 
 North 
 Dakota 
 No. 2. 
 
 Bituminous Coal. 
 
 Semi- 
 bitu- 
 minous 
 Coal.i 
 
 Anthra- 
 cite 
 Coal.i 
 
 Illinois, 1 
 No. 6. 
 
 Ohio, 
 Hock- 
 ing, 4 
 
 Penn. 
 No. 5. 
 
 Pitts- 
 burgh.2 
 
 W. Va. 
 
 No. 7, 
 New 
 River. 
 
 Penn. 
 No. 3. 
 
 Proximate: 
 Moisture 
 Vol. matter 
 
 20.0 
 
 21.00 
 51.72 
 22.11 
 5.17 
 
 16.70 
 
 37.10 
 39.49 
 6.71 
 
 5.13 
 32.68 
 47.46 
 14.73 
 
 3.00 
 39.00 
 50.50 
 7.50 
 
 1.00 
 35.00 
 
 57.85 
 6.15 
 
 0.76 
 20.54 
 73.61 
 5.09 
 
 2.08 
 
 7.27 
 74.32 
 16.33 
 
 Fixed carbon 
 
 
 Ash 
 
 
 Ultimate: 
 Carbon 
 
 
 40.0 
 
 7.2 
 .8 
 50.7 
 
 100.00 
 
 46.57 
 6.51 
 2.33 
 38.97 
 5.17 
 .45 
 
 100.00 
 
 55.16 
 5.61 
 .91 
 30.98 
 .63 
 6.71 
 
 100.00 
 
 60.51 
 4.88 
 1.23 
 14.20 
 4.45 
 14.73 
 
 100.00 
 
 70.70 
 5.20 
 1.30 
 11.95 
 3.35 
 7.50 
 
 100.00 
 
 78.75 
 5.14 
 1.55 
 7.56 
 .90 
 6.10 
 
 100.00 
 
 82.41 
 4.38 
 1.05 
 
 5.87 
 1.20 
 5.09 
 
 100.00 
 
 75.21 
 
 2.81 
 .80 
 4.08 
 .77 
 16.33 
 
 Hydrogen 
 Nitrogen 
 
 Oxygen 
 
 Sulphur 
 
 Ash 
 
 1.3 
 
 Determined calo- 
 rific value = 
 Calculated calo- 
 rific value -T- 
 
 100.0 
 4200 
 
 100.00 
 
 4515 
 4338 
 
 100.00 
 
 5273 
 5071 
 
 100.00 
 
 6199 
 6059 
 
 100.00 
 
 7155 
 7100 
 
 100.00 
 
 7865 
 .7845 
 
 100.00 
 
 8254 
 7942 
 
 100.00 
 
 6929 
 
 6886 
 
 1 U.S.G.S. Professional Paper No. 48. 
 
 2 U.S.G.S. Bulletin No. 290. 
 
 s U.S.G.S. Bulletin No. 332. 
 
 * Ohio Geol. Survey, Bulletin No. 
 
 158 
 
ANALYTICAL TABLES 
 
 159 
 
 0510 
 
 6' 6 
 
 O) ' ^-( 
 
 - 
 
 -H 
 
 < m 
 
 w 2 ?:.- 
 W .> ^ '? 
 
 ' 
 
 CC "o > 
 
 ^ 
 
 A^uoqinv 
 
 I-HT-ICOCOCOCOCO I-H 
 
 CO CO 
 
 ---" 
 
 !-H >O IO 
 
 pdUlUUO^Q 
 
 o o >o 
 ic 10 oo 
 
 ss^ 
 
 CO OS ^ 
 
 CI 
 
 re 
 
 |3 
 
 10 co 10 os 
 
 CO CO CO CN 
 
 (N CN CO CM 
 
 
 s 
 
 
 ssl 
 
 po'SS 
 
 iii 
 
 t- co co 
 
 CD CO CO t'- 
 
 CD S rH 
 
 S8 
 
 CD <M CO O 
 
 b- GO CO 00 
 CO CO CO CO 
 
 
 T 1 
 
 
 56355507 
 7104 6995 
 6703 j 6753 
 
 SOUOI^Q 
 
 N I-H "IN 
 
 I-H GO 'C 
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 161 
 
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ANALYTICAL TABLES 
 
 163 
 
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 lO 10 t^ 
 
 CO rH rH 
 
 
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 CO rH O O t^ 
 
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 <N 
 
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 ci 05 oo 05 i-i 
 
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 co co co co co 
 
 ^ 
 
 10 X 10 05 rH CO O5 t-' 
 
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 M 
 
 3 G 
 
 11 
 
 J5 3 
 
 
 Screened coal 
 Brown lignite 
 Screened 
 Run-of-mine 
 Lump 
 
 c 
 
 3 
 tf 
 
 v : ' .. ; 
 
 
 v* ^' ' 5 ' ' 
 
 iMUil 
 
 
 Iliiiit 
 
 t, o 
 
 j: 
 
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 COM 
 
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 17 samples 
 9 samples 
 65 samples 
 s. 
 
 73 tn tn 
 
 'S.'a'E 
 B S 
 g g S 
 
 CM CO rj< 
 
 
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 10 CO 
 
 GO 
 
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 Colfax Co 
 Socarro Co 
 
 NOKTH DAKOTA 
 
 Stark Co 
 
 Williston, N. D. . . . 
 Williams Co 
 McLean Co 
 
 
 ::::::: 
 
 
 
 Note 1 = Average o 
 Note 2 = Average o 
 Note 3 = Average o 
 
 - 
 a 
 
 I 
 
 gg 
 
 2 
 3 
 
 3 
 ~ 
 O 
 
 I 
 
 Note 4 = Average o 
 
 Note 5 = Average o: 
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 OHIO 
 Jackson Co. . . . 
 
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ANALYTICAL TABLES 
 
 165 
 
 frj/a 
 
 S S :S 
 
 b- 05-00 
 
 (NOOOO5W'-H 
 
 . .10 ti co w S co 
 
 ic 36 
 
 o co 
 
 I ss 
 sd 
 
 8 
 
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 >0 01 O >0 
 
 01 CO 00 CN 
 
 t^ >O 00 CO 
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 05 CO 04 O 
 
 CO CN 
 
 O 01 CO CO CO 
 
 t> CO iO CO CO 
 
 -^ _,' rH 01 IN 
 
 
 CM X 
 Tjt 04 
 
 (N ^1 
 
 d 10 10 10 10 
 
 I s - GO GO O5 GO 
 
 O iO 05 05 05 
 
 O i O O O 
 
 qsy 
 
 g 
 
 O -! 
 
 b- 04 
 
 b- 00 
 
 a.in^siop\[ 
 
 fi 
 
 i. rltlrlr : 1 
 
 3-3 av^ 3 - 3 3 
 
 CO 05 
 
 o 6 
 
 (x, t p pq . Q 
 
 OHIO Cont 
 See Note 7). 
 See Note 8). 
 
 LAND 
 Co. . 
 
 ODE 
 ide 
 
 EE 
 Co. 
 Co. 
 
 3 * 
 
 TENNESS 
 laibne 
 amell 
 
 Claibor 
 Campb 
 
 Roane Co 
 
 oc o> 
 00 
 
166 
 
 COAL 
 
 COOOCOCOCOCOCOCOCO 
 
 TH co eo 
 
 CO 
 
 CM CM <N (N CO W W 
 
 
 
 ^ 
 
 CMCMCMCMCMCM^COb 
 
 CO ^ 
 
 
 
 CO 
 
 CO CM O OS I-H CO * 
 CM CO t^ CO CO OS CO 
 00 05 ^ OS 03 00 CM 
 CO CO Tf< CO ^^ ^H CO 
 
 CO O 00 CO O 
 OS IN "C I-H OS 
 OS O CM CM i-H 
 
 2| 
 
 OIO'^OSCMIOCOCOCO 
 
 111 
 
 
 
 r*- r^. - - co b- 
 
 00 1C OS O CS 
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 rH OS 
 
 g||i||||| 
 
 OS CO I-H 
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 ^H ,-H CM C CO 
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 1C CO OS N- CD 
 
 si 
 
 OCse0006C5C3CSG6 
 
 T-l O OO 
 
 CM 
 
 CM r^ -^ CM O I-H rH 
 
 CS 00 t- CO 1C O CO 
 
 CM * CM 1C I-H 
 CO I> CO CO 00 
 
 S2 
 
 OOOOOCOt^OOCSCSCO 
 
 383 
 
 2 
 
 O OS t^ ^H t^ CS OS 
 
 ci;^^ 05 ^ 
 
 b- 00 
 
 CMOOt^iOCOCSO^O 
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 sc 
 
 o o o 
 
 00 
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 tf CM OS CM CO OS CD 
 CM T(< 1C CO CO CD CM 
 
 S^CM^3 
 
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 OOC^MCMOiCOOO 
 
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 CO 
 
 OS CM 1C CS t>- 1C 1C 
 
 1C O CO CS CM O CO 
 
 i-l t^. 1C GO t^ 
 1C CM CO --H CO 
 
 So 
 
 OOCsosooos-^coos 
 
 t>t>-COCDCDCOCDt > -iO 
 
 os Tt< co 
 
 K 
 
 CD t O CO CS CS CO 
 
 CO t^ CS t^ * 
 
 ic ic co co co 
 
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 co co oo 
 
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 CM OS t^ 1C I-H ^- 00 
 
 CO I-H -H CM CS CO t^ 
 
 b- CO 1C 1C 00 
 
 1C t^ i-H CS Tt< 
 
 1C 1C 1C * 1C 
 
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 1C 1C 
 
 COOOCOOO-'t-'fTfiCO 
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 eo d eo Tt< Tji d d d o 
 
 f- OS 1C 
 
 d d d 
 
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 O CM t^ OS CO 1C i-i 
 
 CM OS CD r- CO CD CM 
 
 i-I d d o' d d -i 
 
 I-H CM 00 1C 1C 
 
 CO t^ CO Tf Tf 
 
 C 00 
 
 OS TJ4 
 
 d co 
 
 tOCOiCCMCMCSiOCOt- 
 
 05 **' CM CO <** <* 00 OS b- 
 
 O 00 O 
 CM 00 CO 
 
 oo 
 
 co oo oo co co co cs 
 
 l> 1C T* CO O CM l> 
 
 TJH" 1C -t * 00 CO CS 
 
 CO t>- CO CO OO 
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 T-i ,-H CM 1C *" 
 
 CO 00 
 
 co t^ 
 
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 00 CO 'CO - 
 
 
 
 00 ^ CM CO iO CD IN 
 CM OS 00 * O 10 
 
 ^ O OS I-H <* 
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 ^CN 
 
 1C iO -<f iO -* >O iO 'O ** 
 
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 CM CO CO 
 
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 CO iC O * t^ 1C I-H 
 
 1C 1C CO 1C CO CD CO 
 
 333S3 
 
 s 
 
 SoOJiCOCMCOt^t^ 
 
 co r^ o 
 
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 CO CO <0 OS CM OS l> 
 
 OS I-H CD X I-H CM O 
 
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 CO CO CO CO -H r-l CM 
 
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 CO OS 
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 ICOOOCO.-HC5COCC10 
 
 ICeOCOCMCOCOiOTflCO 
 
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 G 
 1 
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 oj ' eo I-H '. '. <u 
 a u M fl 
 
 .-< . .-H 
 
 8 >> '. S 
 9 - o, a ^; 9 
 
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 8 :e 
 
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 Kittitas Co 
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 Kittitas Co 
 
 WEST VIRGINIA 
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 Clarksburg, W. Vr 
 
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ANALYTICAL TABLES 
 
 167 
 
INDEX 
 
 Accuracy of chemical work, 51, 52. 
 
 Acid, 
 
 cuprous chloride solution, 138; 
 nitric, correction for formation of, 
 95, 99; pyrogallic, 138; standard, 
 89; sulphuric, correction for forma- 
 tion of, 100; sulphuric, use of, in 
 desiccators, 81. 
 
 Air, 
 
 composition of, 16; drier for coarse 
 samples, 71; drying of samples, 
 70; excess, 16, 142; excess, calcu- 
 lation of, 16; specific heat of, 24. 
 
 Alteration of samples, 76, 149, 151. 
 
 Alumina, effect on fusibility of ash, 5. 
 
 Amperes, required to ignite wire fuse, 
 100. 
 
 Analysis of coal, 79-90. 
 
 determination of ash, 81; of car- 
 bon, 86; of fixed carbon, 83; of 
 hydrogen, 86; of moisture, 79; of 
 nitrogen, 88; of oxygen, 90; of 
 phosphorus, 89; of proximate com- 
 position, 43-45; of sulphur, 83; 
 of ultimate composition, 85; of 
 volatile matter, 82. 
 
 Analysis of gas, 132. 
 
 for carbon dioxide, 137; tor carbon 
 monoxide, 137; for nitrogen, 132; 
 for oxygen, 137. 
 
 Analytical records, 
 forms of, 119; meaning of, 119. 
 
 Analytical tables, 158-168. 
 
 Anthracite coal, analysis of, 158. 
 
 Apparatus, 
 
 for analyzing gas, 134; for sampling 
 gas, 133; for sampling laboratory, 
 76; for washing coal, 123; Orsat, 
 134. 
 
 Aqueous tension, effect of on re- 
 sults of gas analysis, 148. 
 
 Asbestos disc, use of in calorimetric 
 work, 96. 
 
 As"h in coal, 
 
 amount of, 6; clinkering of, 8; 
 composition of, 4; corrected, 3; 
 determination of, 81; distribution 
 of, 6; effect of on commercial value, 
 128; fusibility of, 4; meaning of 
 term, 3; removal of, by washing, 
 122; specific heat of, 24. 
 
 Available heating power of coal, 13. 
 calculation of, 25; effect of mois- 
 ture on, 37; variation of, 36. 
 
 B 
 
 Ball mill grinding, 72; advantage of, 
 
 75, 76. 
 
 Benzoic acid, calorific value of, 106. 
 Bituminous coal, composition of, 158. 
 Boiler flues, sampling gas from, 133. 
 Boiler Tests, 
 
 heat balance of, 28, 32, 33, 34; 
 
 need of, 14. 
 British thermal unit, 
 
 definition of, 9; relation of, to 
 
 calorie, 10. 
 British thermal value, relation of, to 
 
 calorific value, 9. 
 
 169 
 
170 
 
 INDEX 
 
 Bucking board grinding, 76. 
 losses of moisture during, 75. 
 
 Bureau of Mines, 
 
 bulletins, No. 5, 125, 159; No. 41, 
 Purchase of Coal, 131; Technical 
 Paper, No. 1, sampling, 63; sam- 
 pling outfit used by, 63. 
 
 Bureau of Standards, 
 
 calibration of thermometer by, 
 110; circular No. 8 of, on thermo- 
 meters, 111; standards furnished 
 
 [ by, 106. 
 
 Calcium chloride, 
 
 use in desiccators, 81; solution of, 
 for washing coal, 124. 
 
 Calculation of, 
 
 calorific determination, 94; calori- 
 fic value, 10; heat balance, 13-23; 
 heating power of Ohio No. 6 coal, 
 25-32; heating value of coal from 
 proximate analysis, 39; ultimate 
 analysis, 54. 
 
 Calibration of thermometers, 107. 
 
 Calorie, 
 
 definition of, 9; relation to British 
 thermal unit, 10. 
 
 Calorific value, 
 
 calculating the, 10, 39, 41; deter- 
 mining the, 91-118; of benzoic 
 acid, 106; of cane sugar, 106; of 
 carbon, 10, 11; of coal, 9; of coals, 
 53, 158-168; of naphthalene, 106; 
 relation of, to British thermal 
 value, 9; special notes on the 
 determining of, 96. 
 
 Calorimeter, 
 
 kinds of, 91 ; leakage around lid of, 
 97; method of operating a, 91-92; 
 use of cover for, 117; valve, 
 preventing leakage of, 96; wash- 
 ings, sulphur in, 85; water equiv- 
 alent of, 105. 
 
 Calorimeter determination, 
 
 corrections to, 95; method of cal- 
 culation, 93-94. 
 
 Cane sugar, 
 
 calculation of calorific value of, 12; 
 calorific value of, 106. 
 
 Cans, for coal samples, 61, 63. 
 
 Carbon, 
 
 calorific value of, 10, 11; deter- 
 mination of, 86; fixed, 83. 
 
 Carbon dioxide, 
 
 absorption by potassium hydroxide 
 solution, 139; absorption in water, 
 151; determination of, in flue gas, 
 137; effect of solution of, upon 
 excess air calculation, 155; specific 
 heat of, 24. 
 
 Carbon monoxide, 
 
 absorption by cuprous^ 1 chloride 
 solution, 140; calculation of car- 
 bon burned to, 19; determination 
 of, in flue gas, 137, 157; heat loss 
 due to, 19; solubility in water, 
 151; specific heat of, 24. 
 
 Car sampling, 63, 70. 
 
 Cathetometer, use of, 92, 108. 
 
 Centigrade degree, relation to 
 Fahrenheit degree, 9. 
 
 Chemical determinations, summary of, 
 119. 
 
 Chute, sampling, 64-65. 
 
 Clinker in coal, 
 
 formation of, 5, 6; influence of 
 sulphur on, 8. 
 
 Coal, 
 
 analysis of, 79-90; anthracite, 
 composition of, 158; ash of, 3-6, 8, 
 45; bituminous, composition of, 
 158; calorific value of, 9, 10, 46; 
 clay in, 4; combined water in, 48; 
 combustible matter in, 44, 49; 
 commercial value of, 37, 126; 
 composition of, 45-53, 158-168; 
 dry, 120; drying of, 70; fixed car- 
 bon in 45; heating value of, 9, 
 10, 39, 53, 158-168; hydrogen in, 
 available, 48, total, 48; improve- 
 ment by washing, 122-125; mois- 
 ture in, 2, 43, 48, 80, 81; nature of, 
 VII; nitrogen in, 47, 88; origin of, 
 VII; oxygen in, 11, 48, 51, 52, 90; 
 
INDEX 
 
 171 
 
 phosphorus in, 89; purchase of, 
 126-131; pyrite in, 6, 66, 122; 
 residual, 38, 51; slate in, 4, 66, 
 122; sulphur in, 6, 7, 46, 49, 66, 
 83, 122; unburned, 20; heat loss 
 due to, 20; calculation of loss due 
 to, 20; variation in, VII; volatile 
 matter in, 44, 49, 82; weathering 
 of, VIII. 
 
 Coals of United States, composition 
 of, 159-168. 
 
 Code, heat balance, 34. 
 
 Combustion, 
 
 incomplete, 19; products of, 15; 
 reactions of complete, 141 ; specific 
 heats of products of, 23. 
 
 Commercial value of coal, 37. 
 
 estimation of, 126; factors affect- 
 ing, 126. 
 
 Cover, use of, on calorimeter, 117. 
 
 Crusher for reduction of samples, 76. 
 
 Crushing rolls, 77. 
 
 Cuprous chloride solution, 
 
 absorbing power of, 140; prepara- 
 tion of, 138. 
 
 Current, electric, 
 
 for igniting iron wire, 100; leakage 
 of, in calorimeter determination, 
 104. 
 
 D 
 
 Damour, specific heats according to, 
 
 23-24. 
 
 Density of water, 98. 
 Desiccators, use of sulphuric acid in, 
 
 81. 
 
 Dewar flask, 109. 
 Dew point, effect on calorimetric 
 
 work, 98. 
 
 Drier for coarse samples, 71. 
 Dry coal, 120. 
 X)ulong's formula, 10. 
 
 modification of, 12. 
 
 E 
 
 Electric current, 
 
 heat developed by, 102 ; use of 
 for igniting wire fuse, 100. 
 
 Equipment, 
 
 for laboratory washing of coal, 123; 
 for reduction of samples of coal, 
 76; for sampling coal in the mine, 
 61. 
 
 Errors, 
 
 in calorific determination, 96-117; 
 in chemical determinations, 52, 57; 
 in gas analysis, 137-149; in sam- 
 pling coal, 57, 60, 66; in sampling 
 gas, 133; in specific heats of gases, 
 24; in thermometers, 107; in 
 water equivalent of calorimeter, 
 105. 
 
 Eschka method for sulphur, 83. 
 
 Excess air, 16. 
 
 calculation of, 16-18; effect of 
 solution of carbon dioxide upon 
 calculation of, 155. 
 
 Fahrenheit degree, relation to Centi- 
 grade degree, 9. 
 
 Fixed carbon, 
 
 determination of, 83; heating 
 value of, 45; in coal, 45. 
 
 Flasks, use of, in calorimetric work, 
 97. 
 
 Flue gases, 
 
 analysis of, 132-157; composi- 
 tion of, 132; sampling of, 132. 
 
 Formula, 
 
 for calculating excess air, 16; for 
 calculating heating value, 10, 12; 
 for calculating unburned coal, 20. 
 
 Fuels, comparative composition of, 
 158. 
 
 G 
 
 Gas, 
 
 flue gas, analysis of, 132-157; ap- 
 paratus for analyzing, 134; com- 
 position of, 132; sampling of, 132. 
 reactions, calculation of, in molec- 
 ular volumes, 141; samples, ab- 
 sorption in water, 151, 152; alter- 
 ation of, 149-150; changes in, 
 
172 
 
 INDEX 
 
 152; keeping of, over water, 151; 
 
 leakage of, 149; taking of, 132; 
 
 tubes for, 133. 
 Gases, 
 
 solubility of, in water, 151; specific 
 
 heats of, 24. 
 Grinding of samples, 
 
 in ball mill, 72; on bucking board, 
 
 76. 
 
 " H," 
 
 calculation of, 39; definition of, 
 39; variation of, for different coals, 
 47. 
 
 Heat, 
 
 developed by electric current, 102; 
 developed in calorimeter by leak- 
 age of current, 103, 104; latent, 
 of water vapor, 15; mechanical 
 equivalent of, 116. 
 
 Heat balance, 
 
 calculation of boiler heat balance, 
 13-32; calculation of, using printed 
 forms, 28-29; calculation of, using 
 thermal capacity tables, 31; of 
 American Society of Mechanical 
 Engineers, 34; on coal as fired, 33, 
 as burned, 33; on combustible 
 fired, 33, burned 33; on dry coal 
 fired, 33, burned, 33; separation 
 of losses in, 34-35. 
 
 Heating value of coal, 
 
 available, 13, variation of, 36; 
 British thermal value of, 9; cal- 
 culation of, from ultimate analysis, 
 10; from proximate analysis and 
 from " H," 39; calorific value of, 
 9; determination of, 91; total, 9. 
 
 Heat losses during combustion, 14-23; 
 from formation of carbon mon- 
 oxide, 19; from incomplete com- 
 bustion, 19, 21; from radiation, 
 21; in excess air, 14, 26; in latent 
 heat of products of combustion, 
 14-15; in sensible heat of products 
 of combustion, 13-21; unaccounted 
 for, 21. 
 
 Heat producing constituents in coal, 
 10. 
 
 Hydrocarbons, 21. 
 
 effect of, on determination of 
 nitrogen in flue gas, 146. 
 
 Hydrogen, 
 
 available, 48; determination of, 
 86; effect of, on observed calorific 
 value, 116; effect of unburned on 
 determination of nitrogen in flue 
 gas, 146; heating value of, 10, 21; 
 in coal, 117; in naphthalene, 116; 
 in petroleum, 117; total, 48; un- 
 burned in flue gas, 21. 
 
 Incomplete combustion, 19. 
 
 Iron in coal ash, 3, 8. 
 
 Iron wire, 
 
 correction for, 95; current and 
 voltage for igniting, 100; ignition 
 of, 100. 
 
 K 
 
 Kjeldahl method for nitrogen, 89. 
 
 Latent heat of evaporation of water, 
 15. 
 
 Leakage, 
 
 around lid of calorimeter, 97; of 
 electric current during a calor- 
 imeter determination, 102, 104; 
 of valve of calorimeter, 96. 
 
 Lewis and Randall, specific heats 
 according to, 24. 
 
 Lignite, 
 
 moisture in, 2; North Dakota, 46, 
 53, 158. 
 
 Logarithms, calculation of heat bal- 
 ance using, 28-29. 
 
 M 
 
 Mahler calorimeter, description of, 
 
 use of, 91. 
 Marks and Davis, latent heat of 
 
 evaporation according to, 15. 
 
INDEX 
 
 173 
 
 Mercury, use of in nitrogen deter- 
 mination, 89. 
 
 Methane, in flue gas, 21. 
 
 calorific value of , 21 ; effect upon the 
 value obtained for nitrogen, 146. 
 
 Method, 
 
 Eschka, for sulphur, 83; Kjeldahl, 
 for nitrogen, 89. 
 
 Methods of analysis, 79-90. 
 
 Mines, Bureau of, 63, 125, 159. 
 
 Moisture in air, effect on heat bal- 
 ance, 22. 
 
 Moisture in coal, 1, 43. 
 
 amount of, 2, 48; losses in sam- 
 pling, 75; method of determining, 
 79; oven for determining, 80. 
 
 Molecular volume, 
 
 definition of, 141; use of, in gas 
 reactions, 141-146. 
 
 N 
 
 Naphthalene, calorific value of, 106. 
 Nitrogen, 
 
 amount in certain coals, 47; deter- 
 mination of, 88; effect on calcula- 
 tion of excess air, 18; in flue gases, 
 132. 
 
 in the Orsat determination, effect 
 of carbon monoxide upon, 144; 
 of high available hydrogen upon, 
 144; of methane upon, 146; of 
 sulphur upon, 144; of unburned 
 hydrogen upon, 145. 
 specific heat of, 24. 
 
 Ohio Geological Survey, 
 
 Bulletin No. 9 of, 10, 39, 41, 124, 
 
 159; sample cans used by, 61. 
 Ohio No. 6 coal, 
 
 calculation of available heating 
 
 power of, 25; composition of, 25; 
 
 products of complete combustion 
 
 of, 141-143. 
 Ohio State University, 
 
 heat balance calculations at, 33; 
 
 sampling outfit used at, 63. 
 
 Ohm's law, 104. 
 
 Orsat determination, 
 
 description of, 134-137; errors in, 
 147. 
 
 Orsat results, 
 
 discussion of, 141-149; 
 effect of carbon monoxide on, 144; 
 of excess air on, 144; of hydrogen 
 on, 146; of methane on, 146; of 
 water vapor on, 143. 
 
 Orsat's apparatus, 134, 
 
 care of, 140; drawing sample into, 
 136; figure of, 135; filling of, 139; 
 operation of, 134; reagents for, 138. 
 
 Oven, 
 
 for drying coarse samples, 71; for 
 moisture determinations, 80. 
 
 Oxygen, 
 
 absorption of, by pyrogallic acid, 
 140; amount of, in certain coals, 
 48; determination of, in coal, 90; 
 determination of, in flue gas, 137; 
 distribution of, in coal, 11; for 
 calorimeter work, impurities in, 
 117; in excess air, 16; specific 
 heat of, 24. 
 
 Peat, composition of, 158. 
 
 Phosphorus, determination of, in coal, 
 89. 
 
 Potassium hydroxide solution, 
 
 absorbing power of, 139; for Orsat 
 apparatus, 138; for ultimate anal- 
 ysis, 88. 
 
 Products of combustion, 15. 
 
 sensible heats of, 31, 32; specific 
 heats of, 23. 
 
 Proximate analysis of coal, 43-45. 
 
 Purchase of coal under specifications, 
 126-131. 
 
 advantages and disadvantages of, 
 127. 
 
 Pyrite, 
 
 amounts in coal, 6; composition 
 of, 7, 8; distribution of, in coal, 
 8; effects of, on accuracy of sam- 
 
174 
 
 INDEX 
 
 pling coal, 66; effects of, on ash of 
 coal, 8; heating value of, 7; in 
 unwashed coal, 122; in washed 
 coal, 124-125. 
 
 Pyrogallic acid, solution of, 138. 
 absorbing power of, 140. 
 
 R 
 
 Radiation correction, in calorimeter 
 
 determination, 94. 
 Reagents, 
 
 absorbing power of, 139; for gas 
 
 analysis, 138; preparation of, 138. 
 Records, summary of chemical, 119. 
 Residual coal, 38, 51. 
 
 heating value of, 39. 
 Resistance, 
 
 for reducing voltage, 101; of 
 
 water, 102. 
 Richards, values for specific heats 
 
 according to, 24. 
 
 Sample of coal, 
 
 air dried, 119; air drying of, 70; 
 amount of, to be taken, 60, 64, 70; 
 apparatus for reducing amount of, 
 66, 72, 73; as received, 120; cans 
 for, 61, 63; effect of clean coal 
 upon, 69; effect of slate and pyrites 
 upon, 66; fineness of, 74; grinding 
 of, 71, 74, 76; method of taking, 
 car, 63, 70; method of taking, 
 mine, 59; reduction of, 64, 71, 72, 
 73. 
 
 Sample of gas, 
 
 alteration of, by absorption in 
 water, 151-153; by chemical 
 changes, 150; by leakage, 149. 
 analysis of, 132-137; collection of, 
 132. 
 
 Samplers, mechanical, 66, 73. 
 
 Samples of coal, 
 
 alteration of fine, 76; equipment 
 for reduction of, 76; mixing of, 
 79; oxidation of fine, 76; weighing 
 out of, 79. 
 
 Sampling, 57-78. 
 
 cars of coal, 63; coal as used, 63; 
 coal containing much moisture, 74; 
 coal in the mine, 59-60; errors in, 
 57-58, 66, 69; outfit, portable, 
 61-62; tubes for gases, 133. 
 
 Silica, in coal ash, 4. 
 
 Silicates, fusibility of, 5. 
 
 Slack coal, 
 moisture in, 2. 
 
 Smoke, heat loss due to, 22. 
 
 Solution, 
 
 acid, cuprous chloride, 138; am- 
 monia, 89, 95; calcium chloride, 
 124; cuprous ammonium chloride, 
 138; for washing coal, 124; potas- 
 sium hydroxide, 88, 138; sodium 
 hydroxide, 89; sulphuric acid, 89; 
 zinc chloride, 124. 
 
 Soot, heat loss due to, 22. 
 
 Specifications for purchase of coal, 128. 
 abstracts of, for certain cities, 129- 
 131; of U. S. Government, 131. 
 
 Specific gravity of coal, 122. 
 
 of solutions for washing coal, 122. 
 
 Specific heat, 
 
 of gases, 23-24; of water, 114. 
 
 Standard, 
 
 materials, 106; solution of am- 
 monia, 89, 95; solution of sul- 
 phuric acid, 89; thermometers, 109. 
 
 Standards, Bureau of, 106, 110, 111. 
 
 Sulphate, ferrous in coal, 7. 
 heating value of, 7. 
 
 Sulphur dioxide, 8. 
 in flue gas, 143. 
 
 Sulphuric acid, 
 
 in desiccators, 81; correction for in 
 calorimeter work, 100; standard, 
 89. 
 
 Sulphur in coal, 
 
 amount of, 6, 100; determination 
 of, 83; effect of, on clinkering of 
 ash, 8; forms of, 6; heating value 
 of, 7; in weathered coal, 7; organic, 
 6; removal by washing, 122. 
 
 Sulphur in coke, 49. 
 
 Sulphur in volatile matter, 49. 
 
INDEX 
 
 175 
 
 Survey, 
 
 Ohio Geological, Bulletin No. 9 of, 
 10, 39, 41, 124, 159; sample cans 
 used by, 61; washing tests from, 
 124. 
 
 U. S. Geological, Bulletin No. 290 
 of, 45, 159; Bulletin No. 332 
 of, 159; Professional Paper No. 
 48 of, 45, 159. 
 
 Table, 
 
 of corrections for stem temperature, 
 112; of density of water, 98; of 
 solubilities of gases, 151; of specific 
 heats of gases, 24; of specific heat 
 of water, 114; of thermal capacity 
 of gases, 30; of thermal capacity 
 of water, 114. 
 
 Temperature, 
 
 changes, effects on Orsat results, 
 147-148; conditions in calorimeter 
 work, 98; correction for stem of 
 thermometer, 110; final in calor- 
 imeter work, 93; initial in calor- 
 imeter work, 93. 
 
 Thermal capacity, 
 
 definition of, 27; of gases, 30; of 
 water, 114. 
 
 Thermometers, 
 
 calibration of, 107; comparison of, 
 110; correction to reading, 107-1 12; 
 errors in graduation of, 107; 
 standard, 109; stem temperature 
 correction for, 110; stem tempera- 
 ture correction, tabulation of, 112. 
 
 Total heating value of coal, 9. 
 
 Tubes, for sampling gas, 133. 
 
 U 
 
 Ultimate analysis, 51. 
 accuracy of, 52; calculation of, 54; 
 calculation of calorific value from, 
 10; determination of, 85; effect of 
 errors in, on heat balance, 56; of 
 certain coals, 53. 
 
 United States, 
 
 Bureau of Mines, 63, 125, 159; 
 Bureau of Standards, 106, 110, 111; 
 composition of coals of, 159-168; 
 Geological Survey, 45, 159; Gov- 
 ernment purchase of coal by, 131. 
 
 Vacuum flask, 109. 
 
 Value of coal, 
 
 basis for determining comparative, 
 126, 128; British thermal value, 
 9; calorific value, 9; factors affect- 
 ing, 126. 
 
 Volatile matter, 
 
 amount in certain coals, 49; com- 
 position of, 49; determination of, 
 82; heating value of, 50. 
 
 Voltage, 
 
 desirable in calorimeter work, 100; 
 reduction of, by shunt, 101. 
 
 W 
 
 Washing coal, 
 
 improvement of by, 122-125; labor- 
 atory equipment for, 123; results 
 of, 124. 
 
 Water, 
 
 combined in clay, 4; combined in 
 coals, 48; density of, 98; effect of, 
 on available heating power, 22; 
 equivalent of calorimeter, 105; 
 measuring of, in calorimeter work, 
 97; resistance of, 102; seal, effects 
 of, on gas samples, 156; surround- 
 ing calorimeter bomb, 97; total in 
 coals, 48; vapor, effect of, on gas 
 analysis, 143; vapor, latent heat of, 
 14; vapor, specific heat of, 24. 
 
 Weathered coal, VII. 
 sulphur in, 7. 
 
 Weighing out samples, 79. 
 
 Wire, 
 
 fuse used in calorimeter deter- 
 mination, 95; high resistance, 101. 
 
 Wood, composition of, 158. 
 
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