LIBRARY UNIVERSITY OF CALIFORNIA. UNIVERSITY OF CALIF*RNH Engineering DEPARTMENT OF civit ENCINEE library Class k LIT ft N i A GAS AND FUEL ANALYSIS FOR ENGINEERS. A COMPEND FOR THOSE INTERESTED IN THE ECONOMICAL APPLICATION OF FUEL. PREPARED ESPECIALLY FOR THE USE OF STUDENTS at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY. BY AUGUSTUS H. GILL, S.B., PH.D., Professor of Technical Analysis at the Massachusetts Institute of Technology, Boston, Mass. Author of "A Short Handbook of Oil Analysis;" ' Engine R^om Chemistry." Of THE UNIVERSITY OF S-4UFOR FIFTH EDITION, REVISED. FIRST THOUSAND. NEW YORK: JOHN WILEY & SONS. LONDON: CHAPMAN & HALL, LIMITED. 1909. Engineering Library ^vv/ /n -/ Copyright, 1896, 1902, 1907. 1908, BY AUGUSTUS H. GILL. JThr grtrtiltftr Prrsa ffiuiiort Srununn nil uni (Uoutyatty PREFACE. THIS little book is an attempt to present in a con- cise yet clear form the methods of gas and fuel analy- sis involved in testing the efficiency of a boiler plant. Its substance was given originally, in the form of lectures and heliotyped notes, to the students in the courses of Chemical, Mechanical, and Electrical En- gineering, but in response to requests it has been deemed expedient to give it a wider circulation. At the time of its conception, nothing of the kind was known to exist in the English language ; in German we now have the excellent little book of Dr. Ferdinand Fischer, " Taschenbuch fur Feuerungs- Techniker." The present book is the result of six years' experi- ence in the instruction of classes of about one hun- dred students. It is in no sense a copy of any other work, nor is it a mere compilation. The author has in every case endeavored to give credit where any- thing has been taken from outside sources ; it is, how- iii 201692 IV PREFA CE. ever, difficult to credit single ideas, and if he has been remiss in this respect it has been unintentional. The study of flue-gas analysis enables the engineer to investigate the various sources of loss ; and if this compend stimulates and renders easy such investiga- tion, the writer's purpose will have been accomplished. The necessary apparatus can be obtained from the leading dealers in New York City. The author wishes to acknowledge his indebtedness to our former Professor of Analytical Chemistry, Dr. Thomas M. Drown, and to Mrs. Ellen H. Richards, by whose efforts the department of Gas Analysis was established. He will also be grateful for any suggestions or cor- rections from the profession. MASSACHUSETTS INSTITUTE OF TECHNOLOGY, BOSTON, November, 1896. PREFACE TO THE FIFTH EDITION. THE changes made in the present edition include a brief treatment of the subjects of the Storage of Coal and its Spontaneous Combustion, and, in view of the increasing use of liquid fuel, methods of its analysis and testing. As in the past, minor additions and corrections have been made where necessary to bring the book up to present practice. MASSACHUSETTS INSTITUTE or TECHNOLOGY, BOSTON, August, 1908. CONTENTS. CHAPTER I. PAOHS INTRODUCTION. SAMPLING Sampling-tubes. SUCTION APPA- RATUS. GAS-HOLDERS . . i CHAPTER II. APPARATUS FOR THE ANALYSIS OF CHIMNEY-GASES. Apparatus of Orsat, Bunte, and Elliott n CHAPTER III. THE MEASUREMENT OF TEMPERATURE. Thermometers Le Chatelier Pyrometer Metals and Salts 25 CHAPTER IV. CALCULATIONS. "Pounds of Air per Pound of Coal," and Per- centage of Heat Carried off by the Flue gases. Loss due to Foimation of Carbonic Oxide. Loss due to Unconsumed Fuel 28 CHAPTER V. APPARATUS POR THE ANALYSIS OF FUEL AND ILLUMINATING GASES. Apparatus of Hempel 36 CHAPTER VI. PREPARATION OF REAGENTS AND ARRANGEMENT OF THE LABORA- TORY 51 v VI CONTENTS. CHAPTER VII. PAGE FUELS, SOLID, LIQUID, AND GASEOUS: THEIR DERIVATION AND COMPOSITION 58 CHAPTER VIII. FUELS. METHODS OF ANALYSIS AND DETERMINATION OF THE HEATING VALUE. Determination of the Various Constituents. The Mahler Bomb, the Parr Coal-calorimeter, and Junkers Gas-calorimeter .. .* 72 APPENDIX. TABLES.. . 108 LIST OF ILLUSTRATIONS. FTO. PAGE 1. GAS SAMPLING-TUBE 3 2. SAMPLING APPARATUS 4 3. SAMPLING APPARATUS FOR MINE-GASES 5 4. GAS-TUBE 5 5. RICHARDS'S JET-PUMP 8 6. BUNSEN'S PUMP 8 7. STEAM AIR-PUMP 9 8. ORSAT GAS APPARATUS 12 9. BUNTE GAS APPARATUS 17 10. ELLIOTT GAS APPARATUS 21 11. MELTING-POINT BOXES 27 1 2. HEMPEL GAS APPARATUS 37 13. HEMPEL GAS APPARATUS 38 14. MUENCKE'S ASPIRATOR 56 15. COMBUSTION-FURNACE 74 16. MAHLER BOMB 83 17. MAHLER BOMB AND CALORIMETER 84 18. PARR'S CALORIMETER 93 19. JUNKERS' GAS-CALORIMETER, SECTION 99 20. JUNKERS' GAS-CALORIMETER 100 vii GAS AND FUEL ANALYSIS. CHAPTER I. INTRODUCTION AND METHODS OF SAMPLING. UNTIL within recent years, the mechanical engineer in testing a boiler plant has been compelled to con- tent himself with the bare statement of its efficiency, little or no idea being obtained as to the apportion- ment of the losses. Knowing the composition and temperature of the chimney-gases and the analysis of the coal and ash, the loss due to the formation of car- bonic oxide, to the imperfect combustion of the coal, to the high temperature of the escaping gases, can each be determined and thus a basis for their reduc- tion to a minimum established. By the simple analysis of the chimney-gases and determination of their temperature, a very good idea of the efficiency of the plant can be obtained previous to making the engineering test. For example, in a test which the author made in connection with his students, the efficiency was increased from 58 to 70 per cent, upon the results of the gas analysis alone. 2 GAS AND FUEL ANALYSIS. To this end a representative sample must be collected according to the method about to be described. SAMPLING. Before proceeding to take a sample of the gas, the plant for example, a boiler setting from which the gas is to be taken should be thoroughly inspected, and all apertures by which the air can enter, carefully stopped up. A suitable tube is then inserted air-tight in the gas-duct, connected with the sampling or gas apparatus, and suction applied, thus drawing the gas out. Cork, putty, plaster of Paris, wet cotton-waste,- or asbestos may be used to render the joint gas-tight. The place of insertion should be chosen where the gas will be most completely mixed and least contaminated with air. The oil-bath containing the thermometer is similarly inserted near the gas-tube, and the tempera- ture read from time to time. I. Tubes. The tubes usually employed are Bohe- mian-glass combustion tubing or water-cooled metal tubes; those of porcelain or platinum are also some- times used. Glass and porcelain tubes when subjected to high temperatures must be previously warmed or gradually inserted: the former may be used up to temperatures of 600 C. (1200 F.). Uncooled metal tubes, other than those of platinum, should under no circumstances be used.* * Fischer, "Technologic der Brennstoffe," 1880, p. 221, states that the composition of a gaseous mixture was changed from 1.5 to 26.0 per cent carbon dioxide, by the passage through an iron tube heated to a dull red heat, the carbonic oxide originally present reducing the iron oxide with the formation of carbon dioxide. INTRODUCTION AND METHODS OF SAMPLING. 3 The metal tube with the water cooling is made as shown in Fig. I, c being a piece of brass pipe 3 feet long, ij- inches outside diameter, b the same length, J inch in diameter, and a \ inch in diameter. The water enters at d and leaves at e. The walls of FIG. i. GAS-SAMPLING TUBE. the tubes are -fa inch thick. The joint at A should be brazed; the others may be soldered. Platinum tubes from their high cost and small bore are seldom used ; they are attacked by carbon, cyan- ogen, arsenic, and metallic vapors. 2. Apparatus for the Collection of Samples. A convenient sampling apparatus is shown in Fig. 2. It may be made from a liter separatory funnel in- stead of the bulb there shown fitted with a rubber stopper carrying a tube passing to the bottom and a T tube; both of these, except where sulphur-con- taining gases are present, can advantageously be made of T \-inch lead pipe. The stopper should not be fastened down with wire between the tubes after the manner of wiring effervescent drinks, as this draws the rubber away from the tubes and occasions a leak. The fastening shown consists of a brass plate fitting upon the top of the stopper, provided with screws and nuts which pass through a wire around 4 GAS AND FUEL ANALYSIS. the neck of the separatory. A chain fastened to the plate serves as a convenient method of handling it. In using the apparatus, the bulb is filled with water by connecting the stem with the water-supply and opening one of the pinchcocks upon the T tube; the FIG. 2. SAMPLING APPARATUS. water thus entering from the bottom forces the air out before it. One branch of the T is connected with the sampling-tube and the other with the suction- pump, the stopcocks being open, and a current of gas drawn down into the pump; upon opening the cock upon the stem, the water runs out, drawing a small portion of the gas-current passing through the T after it into the bulb. It is then taken to a convenient INTRODUCTION AND METHODS OF SAMPLING. 5 place for analysis, the tube h connected with a head of water, a branch of the T i, with the gas apparatus, and a sample of gas forced over into the letter for analysis. FIG. 4. GAS-TUBE. FIG. 3. SAMPLING APPARATUS FOR MINE-GASES. Enough water should be left in the bulb to seal the stopcock on the bottom and prevent leakage. This apparatus is better adapted for the needs of the class- O GAS AND FUEL ANALYSIS. room than for actual practice, as it enables the same sample to be given to eight or ten students. As has been shown by several years' experience, the water exercises no appreciable solvent action upon the gaseous mixture in the time about half an hour necessary to collect and distribute the samples. It is often necessary to attach about a yard of J-inch rubber tubing to the stem of the bulb to prevent air being sucked up through it when taking a sample. In the actual boiler-test it is preferable to insert a T instead of this apparatus in the gas-stream, connect the gas apparatus to the free branch of this T, and draw the sample. In making connections with gas apparatus the air in the rubber connectors should be displaced with water by means of a medicine- dropper. In the Saxon coal-mines, zinc cans of ten liters capacity, of the form shown in Fig. 3, are used by Winkler for sampling the mine-gases; they are carried down filled with water and this allowed to run out, and the gas thus obtained brought into the laboratory and analyzed. Small samples of gas may very well be taken in tubes of 100 cc. capacity like Fig. 4, the ends of which are closed with rubber connectors and glass plugs. Rubber bags are not to be recommended for the collection and storage of gas for analysis, as they permit of the diffusion of gases, notably hydro- gen. 3. Apparatus for Producing Suction. I. WATER- PUMPS-^(tf) Jet-pumps, depending for their action upon a considerable head of water, and (&) those depending rather upon a sufficient fall of water. INTRODUCTION AND METHODS OF SAMPLING. 7 (a) Jet-pumps. The Richards' jet pump * is shown in section in Fig. 5 and much resembles a boiler injector; it consists of a water-jet w, a constriction or waist a, a waste-tube 0, and a tube for the inspiration of air. The jet of water forms successive pistons across a, drawing the air in with it and is broken up into foam by the zigzag tube o. This pump is known in Germany as Muencke's, and in England as Wing's; Chapman's pump is also a modified form. It may be easily constructed in glass, the jets pass- ing through rubber stoppers which are wired down, thus admitting of adjustment to the conditions under which it has to work.f (b) Fall-pumps. Bunsen's pump, Fig. 6, consists of a wide glass tube A, drawn out at the bottom for connection with a J-inch lead pipe b, and at the top for connection with c, the tube through which the air is drawn; this tube is usually fused in, although it may be connected with rubber; a is a rubber tube provided with screw cocks connected with the water- supply; d is connected with a mercury column, and the vessel B serves for the retention of any water which might be drawn back into the apparatus evac- uated. The tube b for the best results should be 32 feet in length, equal to the height of a column of water sup- ported by the atmosphere, although for the ordinary purposes of gas-sampling it may be shorter. When water is admitted through a it fills b, acting * Richards, Am. Jour, of Science (3), 8, 412; Trans. Am. Inst. Min. Engrs., 6, 492 (1874). \ The pump 'vill also work well using steam. 8 GAS AND FUEL ANALYSIS. as a continually falling piston drawing the current of air through e and its connections. These various forms of water-pumps should give a vacuum repre- FIG. 5. RICHARDS' JET-PUMP. FIG. 6. BUNSEN'S PUMP. sented by the height of the barometer less the tension of aqueous vapor at the temperature at which they are used, or about 29 inches of mercury. INTRODUCTION AND METHODS OF SAMPLING. 9 II. STEAM-PUMPS. Kochinke describes the appa- ratus in use in the Muldner Hutten in Freiberg, shown at one-fifth size in Fig. 7. It consists of a glass tube drawn down to an opening 6 mm. in diam- FIG. 7- STEAM AIR-PUMP. eter; concentric with this, and held in place by the washer a, is the steam-jet 2 mm. in diameter, passing through the cork b, the cement c, and covering d. It is connected with the steam-pipe at g by webbed rubber tubing/"; the air enters at e. This is said to give very good results and be economical in use of steam. In case neither water nor steam be available, recourse must be had to the ordinary rubber syringe- bulbs, provided with suitable valves, obtainable at any rubber store, or to a bottle aspirator. This consists of two one-gallon bottles, provided with doubly perfor- ated rubber stoppers, carrying tubes of glass or lead bent at right angles. In each bottle one of these tubes passes nearly to the bottom, and these are connected together by a piece of rubber tubing a yard long, carrying a screw pinchcock. The other tube in each case stops immediately under the stopper. Upon filling one of the bottles with water, inserting the stopper and blowing strongly through the short tube, water will fill the long tubes thus forming a siphon, 10 GAS AND FUEL ANALYSIS. and upon lowering the empty bottle, a current of air will be sucked in through the short tube originally blown into; this may be regulated by the screw pinchcock. In inserting the gas-sampling tube care should be taken not to insert it so close to the source of heat as to draw out the gases in a dissociated, i.e. partly decomposed, condition. In case of very smoky fuels it is well to filter the gases through rolls of fine wire gauze or asbestos; in sucking them through a washing-bottle, the water may change the composition of the sample. CHAPTER II. APPARATUS FOR THE ANALYSIS OF CHIMNEY- GASES. IN the writer's opinion the apparatus which is best adapted for this purpose is that of Orsat; it is readily portable, not liable to be broken, easy to manipulate, sufficiently accurate, and in the modification about to be described always ready for use, there being no stopcocks to stick fast. As the Bt-inte and Elliott apparatus are also used for this purpose, they too will be described. Fischer's apparatus, using mercury, is rather too difficult for the average engineer; . Hempel's or More- head's* apparatus for the analysis of illuminating-gas might also be used; it is, however, not customary. ORSAT APPARATUS. Description. The apparatus Fig. 8, is enclosed in a case to permit of transportation from place to place; furthermore, the measuring-tube is jacketed with water to prevent changes of temperature affecting the gas-volume. The apparatus consists essentially of the levelling-bottle A, the burette B, the pipettes P f , P", P'", and the connecting tube T. * No. 143 Lake Street, Chicago. XI 12 GAS AND FUEL ANALYSIS. Manipulation. The reagents in the pipettes should be adjusted in the capillary tubes to a point on the stem about midway between the top of the pipette and the rubber connector. This is effected by open- ing wide the pinchcock upon the connector, the FIG. 8. ORSAT'S GAS APPARATUS. bottle being on the table, and very gradually lower- ing the bottle until the reagent is brought to the point above indicated. Six inches of the tubing used corre- spond to but o.i cc., so that an error of half an inch in adjustment of the reagent is without influence upon the accuracy of the result. The reagents having been thus adjusted, the burette and connecting tube are completely filled with water by opening d and raising the levelling-bottle. The apparatus is now ANALYSIS OF CHIMNEY-GASES. I J ready to receive a sample of gas (or air for prac- tice). In case a flue-gas is to be analyzed d is con- nected with z, Fig. 2, A lowered and about 102 cc. of the gas forced over by opening //; or d may be connected with aT joint in the gas-stream; the burette after filling is allowed to drain one minute by the sand-glass, c snapped upon its rubber tube, and the bottle A raised to the top of the apparatus. By gradually opening c the water is allowed to run into the burette until the lower meniscus stands upon the 100 or o mark (according to the graduation of the apparatus). The gas taken is thus compressed into the space occupied by 100 cc., and by opening d the excess escapes. Open c and bring the level of the water in the bottle to the same level as the water in the burette and take the reading, which should be 100 cc. Special attention is called to this method of reading: if the bottle be raised, the gas is compressed; if lowered, it is expanded. Determination of Carbon Dioxide. The gas to be analyzed is invariably passed first into pipette /*', con- taining potassium hydrate for the absorption of carbon dioxide, by opening e and raising A. The gas dis- places the reagent in the front part of the pipette, laying bare the tubes contained in it, which being covered with the reagent present a large absorptive surface to the gas; the reagent moves into the rear arm of the pipette, displacing the air over it into the flexible rubber bag which prevents its diffusion into the air. The gas is forced in and out of the pipette by raising and lowering^, the reagent finally brought approximately to its initial point on the stem of the 14 GAS AND FUEL ANALYSIS. pipette, the burette allowed to drain one minute, and the reading taken. The difference between this and the initial reading represents the cubic centimeters of carbon dioxide present in the gas. To be certain that all the carbon dioxide is removed, the gas should be passed a second time into P' and the reading taken as before; these readings should agree within .o. I per cent. Determination of Oxygen. The residue from the absorption of carbon dioxide is passed into the second pipette, P" , containing an alkaline solution of potas- sium pyrogallate, until no further absorption will teke place. The difference between the reading obtained and that after the absorption of carbon dioxide, repre- sents the number of cubic centimeters of oxygen present. Determination of Carbonic Oxide. The residue from the absorption of oxygen is passed into the third pipette, P'" 9 containing cuprous chloride, until no further absorption takes place; that is, in this case until readings agreeing exactly (not merely to o. i) are obtained. The difference between the reading thus obtained and that after the absorption of oxygen, represents the number of cubic centimeters of carbonic oxide present. Determination of Hydrocarbons. The residue left after all absorptions have been made may consist, in addition to nitrogen, the principal constituent, of hydrocarbons and hydrogen. Their determination is difficult for the inexperienced, and, if desired, a sample of the flue-gas should be taker!, leaving as little water ANALYSIS OF CHIMNEY-GASES. 1 5 in the apparatus as possible, and sent to a competent chemist for analysis. Accuracy. The apparatus gives results accurate to 0.2 of one per cent. Time Required. About twenty minutes are re- quired for an analysis; two may be made in twenty-five minutes, using two apparatus. Notes. The method of adjusting the reagents is the only one which has been found satisfactory: if the bottle be placed at a lower level and an attempt made to shut the pinchcock c upon the connector at the proper time, it will almost invariably result in failure. The process of obtaining roo cc. of gas is exactly analagous to filling a measure heaping full of grain and striking off the excess with a straight-edge ; it saves arithmetical work, as cubic centimeters read off repre- sent percent directly. It often happens when e is opened, c being closed, that the reagent in P' drops, 'due not to a leak as is usually supposed, but to the weight of the column of the reagent expanding the gas. The object of the rubber bags is to prevent the access of air to the reagents, those in P" and P tn absorbing oxygen with great avidity, and hence if freely exposed to the air would soon become useless. Carbon dioxide is always the first gas to be removed from a gaseous mixture. In the case of air the per- centage present is so small, 0.08 to o. I, as scarcely to be seen with this apparatus. It is important to use the reagents in the order given ; if by mistake the gas be passed into the second pipette, it will absorb not only oxygen, for which it is intended, but also carbon 1 6 GAS AND FUEL ANALYSIS. dioxide; similarly if the gas be passed into the third pipette, it will absorb not only carbonic oxide, but also oxygen as well. The use of pinchcocks and rubber tubes, original with the author, although recommended by Naef,* is considered by Fischer, f to be inaccurate. The ex- perience of the author, however, does rot support this assertion, as they have been found to be fully as accurate as glass stopcocks, and very much less troublesome and expensive. In case any potassium hydrate or pyrogallate be sucked over into the tube T or water in A, the analysis is not spoiled, but may be proceeded with by connect- ing on water at d, opening this cock, and allowing the water to wash the tubes out thoroughly. The addi- tion of a little hydrochloric acid to the water in the bottle A will neutralize the hydrate or pyrogallate, and the washing may be postponed until convenient. After each analysis the number of cubic centimeters of oxygen and carbonic oxide should be set down upon the ground-glass slip provided for the purpose. By adding these numbers and subtracting their sum from the absorption capacity (see Reagents) of each reagent, the condition of the apparatus is known at any time, and the reagent can be renewed in season to prevent incorrect analyses. BUNTE APPARATUS. Description. The apparatus Fig. 9 consists of a burette bulbed to avoid extreme length provided * Wagner's Jahresb. 1885, p. 423. f Technologic d. Brennstoffe, foot note p. 295. ANALYSIS OF CHIMNEY-GASES. at the top with a funnel F and three-way cocky, and a cock / at the bottom. These stopcocks are best of the Greiner and Friedrichs obliquely bored form. The burette is supported upon a retort- stand with a spring clamp. A "suction-bottle " S, an 8-oz. wide- mouthed bottle, fitted similarly to a wash-bottle, except that the delivery- tube is straight and is fitted with a four-inch piece of -inch black rubber tubing, serves to withdraw the re- agents and water when necessary. A reservoir to contain water at the tem- perature of the room, fitted with a long rubber tube, should be provided for washing out the reagents and filling the burette. Manipulation. Before using the apparatus, the keys of the stopcocks should be taken out, wiped dry, to- gether with their seats, and sparingly smeared with vaseline or a mixture of vaseline and tallow and replaced. The FIG. 9. BUNTE'S completeness of the lubrication can be GAS AppARATUS - judged by the transparency of the joint, a thoroughly lubricated joint showing no ground glass. The burette is filled with water by attaching the rubber tube to the tip at / and opening the stopcocks at the top and bottom ; j is connected with the source whence the gas is to be taken, turned to communicate with the burette and opened, about 102 cc. of gas allowed to run in, and/ and / closed. 1 8 GAS AND FUEL^ ANALYSIS. The cup ^is filled with water to the 25-00. mark, j turned to establish communication between it and the burette, the burette allowed to drain one minute by the sand-glass, and the reading taken, the cup being refilled to the mark if necessary. The readings are thus taken under the same pressure each time, i.e., this column of water plus the height of the barometer; and as the latter is practically constant during the analysis, no correction need be applied, it being within the limits of error. Determination of Carbon Dioxide. The " suc- tion-bottle " is connected with the tip of the burette, / opened, and the water carefully sucked out nearly to /. The bottle is now disconnected, the burette dis- mounted from its clamp, using the cup as a handle, and the 25 cc. of water turned out. The tip is immersed under potassium hydrate contained in the No. 3 porcelain dish, and the cock / opened, then closed, and the tip wiped clean with a piece of cloth. The burette is now shaken, holding it by the tip and the cup, the thumbs resting upon / and /; more reagent is introduced, the absorption of the gas caus- ing a diminished pressure, and the operation repeated until no change takes place. The cup is now filled with water, j opened, and the reagent completely washed out into an ordinary tumbler placed beneath the burette. Four times filling of F should be suffi- cient for this purpose. The cup is now filled to the 25-cc. mark, j opened, and the reading taken as before. The difference between this reading and the initial represents the number of cubic centimeters of carbon ANALYSIS OF CHIMNEY-GASES. 1 9 dioxide; this divided by the volume of the gas taken gives the per cent of this constituent. Determination of Oxygen. The water is again sucked out, and potassium pyrogallate solution intro- duced, similarly to potassium hydrate; this is dis- placed by water, and the reading taken as before. The difference between this and the last reading is the volume of oxygen present. Determination of Carbonic Oxide. The water is removed for a third time, and acid cuprous chloride solution introduced and the absorption made as before; this is washed out, first with water containing a little hydrochloric acid to dissolve the white cuprous chlo- ride which is precipitated by the addition of water, and finally with pure water, and the reading taken as before. The difference between this and the preced- ing gives the volume of carbonic oxide present. Notes. Especial care should be taken not to grasp the burette by the bulb, as this warms the gas and renders the readings inaccurate. The stopcocks can conveniently be kept in the burette by elastic bands of suitable size. When the apparatus is put away for any considerable time, a piece of paper should be inserted between the key and socket of each stopcock to prevent the former from sticking fast. To ascer- tain when the absorption is complete, the burette is mounted in its clamp and allowed to drain until the meniscus is stationary, the dish containing the reagent raised until the tip is covered, /opened, and any change in level noted. If the meniscus rises, the absorption is incomplete and must be continued; if it remains stationary or falls, the absorption may be regarded as 2O GAS AND FUEL ANALYSIS. finished. In case the grease from the stopcocks becomes troublesome inside the burette, it may be removed by dissolving it in chloroform and washing out with alcohol and then with water. The object in sucking the water not quite down to /, thus leaving a little water in the burette, is to discover if / leaks, the air rushing in causes bubbles. The object in washing out each reagent and taking all readings over water is to obviate corrections for the tension of aqueous vapor over potassium hydrate, hydrochloric acid, or any of the reagents which might be employed. The tension of aqueous vapor over seven per cent caustic soda is less than over water. Accuracy and Time Required. The apparatus is rather difficult to manipulate, but fairly rapid about twenty-five minutes being required for an analysis and accurate to one tenth of one per cent. ELLIOTT APPARATUS. Description. The apparatus Fig. 10 consists of a burette holding 100 cc. graduated in tenths of a cubic centimeter and bulbed like the Bunte apparatus the bulb holding about 30 cc. ; it is connected with a levelling-bottle similar to the Orsat apparatus. The top of the burette ends in a capillary stopcock, the stem of which is ground square to admit of close con- nection with the "laboratory vessel," an ungraduated tube similar to the burette, except of 125 cc. capacity. The top of this "vessel " is also closed with a capil- lary stopcock, carrying by a ground-glass joint a thistle-tube F, for the introduction of the reagents. The lower end of this " vessel " is closed by a rubber ANALYSIS OF CHIMNEY-GASES. 21 stopper carrying a three-way cock o, and connected with a levelling-bottle D. The burette and vessel are held upon a block of wood supported by a ring stand by fine copper wire tight- ened by violin keys. Manipulation. The ground-glass joints are lubricated as in the Bunte apparatus. The levelling- bottles are filled with water, the stopcocks opened, and the bottles raised until the water flows through the stop- cocks m and n. m is connected with the source whence the gas to be analyzed is to be taken, n closed, D lowered and rather more than 100 cc. drawn in, and m closed, n is opened, D raised and E lowered, nearly 100 cc. of gas introduced, and n closed; by opening m and raising D the remainder of the gas is allowed to escape, the tubes being filled with water and m closed, n is opened and the water brought to the reference-mark; the burette is allowed to drain one minute, the level of the water in E is brought to the same level as in the burette, and the reading taken. Determination of Carbon Dioxide By raising E, opening n, and lowering D, the gas is passed over into the laboratory vessel; F is filled within half an inch Fio. 10. ELLIOTT GAS APPARATUS. 22 GAS AND FUEL ANALYSIS. of the top with potassium hydrate, o closed, m opened, and the reagent allowed to slowly trickle in. A No. 3 evaporating-dish is placed under , and this inside a jacket A. At the right is shown a portion of the oxygen-cylinder and the gauge. For the following directions for its use the author is indebted to the kindness of Professor Silas W. Holman of the Institute of Technology. * Scheurer-Kestner Jour. Soc. Chemical Industry, 7, 869. f Hempel, " Gasanalytische Methoden," p. 347. \ Mahler, Jour. Soc. Chemical Industry, n, 840. Mayer, Stevens indicator, (1895) 134. FUEL ANALYSIS HEATING VALVE. 8.3 Preparation of Bomb. Remove the ring upon which it sits in the calorimeter. Wash out the bomb. It need not be dry. Leave cover off. See that the lead-ring washer P, Fig. 16, is in good condition. Unless its upper surface is fairly smooth the cover cannot be tightly closed. Repeated screwing on of the cover raises a burr of lead. When this becomes noticeable it must be removed by cutting with a knife- blade. If there is difficulty in mak- ing the cover tight, it is most likely to be due to this cause. Grease the screw 5 upon the out- side of the bomb slightly with tallow or a heavy oil, but be sure that none of the grease gets beyond the lead ^$^^^s$s/ washer. FIG. 16. MAHLER'S Secure the bomb very firmly in the BOMB. heavy clamp on the table. Place the top on a ring or in a clamp of a lamp-stand and in an upright position. Put in position the platinum tray C and the rod E, Fig. 17. Twist on the loop of ignition-wire (fine platinum or iron). This must make good electrical contact with both E and the pan or its supporting rod. Failing this the current will not flow to fuse the wire. Failure to ignite is almost always traceable to this cause. Pour into the tray a known weight of the substance 84 GAS AND FUEL ANALYSIS. to be burned. If this be coal, slightly over one gram should be used. It is usually best inserted from a small test-tube weighed before and after, with due precautions against loss. The ignition-wire should dip well into the coal. The fineness required in the combustible depends FIG. 17. MAHLER'S APPARATUS COMPLETE. upon its nature. Anthracite coal should be in a very fine powder, at least 100 mesh. Trial wiU show whether any unburned grains remain, indicating that the com- bustible is too coarse. The standard which carries the pressure-gauge should be screwed to the table near the bomb-clamp, and the oxygen cylinder must be placed near by so that the three may be easily connected by the flexible copper tube. FUEL ANALYSIS HEATING VALVE. 85 The top carrying the charge is then cautiously (to avoid loss of charge by jarring or draft) transferred to the bomb and screwed carefully home. The lifting is best done by hooking the fingers beneath the milled head at the top of the valve-screw R. The top must be set up hard by the wrench which takes the large nut cut on the cover. In setting this up it is desirable to use no more force than is necessary to secure a gas- tight bearing of the tongue of the cover against the lead washer P. Just the force required can only be learned by experience, but it is always considerable. A slight leak is unimportant, but it is not difficult to secure a tight seal if the lead washer be kept in good condition. To fill with oxygen proceed as follows: Screw down the valve-screw R gently to close the valve. Connect the copper tube to the oxygen-tank gauge, and to the bomb at N. See that there are leather washers at the joints. Turn the connecting nuts firmly but not violently home. The connections to the oxygen-tank and gauge are usually left undis- turbed, and only that at N has to be made each time. It is now necessary to test for leakage in the con- nections. To do this, as R is closed, it is only neces- sary to open the oxygen-tank cautiously by means of its wrench until the gauge indicates 5 or 10 atmos- pheres and then close it. As the tank when freshly charged has a pressure of 120 atmospheres, and the gauge reads only to 35 atmospheres, care must be used in all manipulations not to overstrain the gauge, also avoid suddenly releasing the pressure on the gauge. When this pressure is on, any leak in the connections 86 GAS AND FUEL ANALYSIS. will be indicated by a drop in the gauge reading. If a leak exists, it must be removed or rendered extremely slow before proceeding further. It is most likely to be found in the joints, which must be tightened one by one until the leak stops. Now to fill the bomb it is next necessary to open R. This could be done by merely turning back the milled head, or the nut just above it. But as this would put a twist into the copper connecting-tube (which many times repeated would break it), the better way is, holding one wrench in each hand, to loosen the connecting nut above N by a half-turn, holding R by the wrench and nut, then to turn the nut open a half-turn or until it is again tight in. This leaves the connections tight and R open into the bomb. The oxygen is then turned slowly on, and the bomb gradually fills. If a gram of coal is to be burned, a pressure of 25 atmospheres gives the proper amount of gas in the bomb. Note that the valve R and the inlet- tube have small borings. Thus the inflow of gas will be slow and the pressure in the connecting-tube will be higher than in the bomb. If, therefore, the tank be closed quickly, the gauge-reading will fall somewhat until these pressures equalize, and will then remain stationary unless there is a leak. The tank-cock must always be kept well under control to avoid overcharg- ing either gauge or bomb. When the bomb is full, close first the tank-cock. Then, to close R, put the wrenches on the nuts and, holding one from turning, set the other down until R is tight, but not too tight. Avoid straining R, which closes tight very easily. By this method the copper FUEL ANALYSIS HEATING VALVE. 87 tube is not twisted. There is of course a slight leak of gas from the bomb after N leaves the nut and before R is closed, but the time required for the half- turn is so short and the outflow so slow that the loss is insignificant. There is no need to hurry in this operation. Be deliberate and careful of the apparatus. A valve like R is a nice piece cf workmanship, and to endure much usage it must be treated with care. The bomb is now ready to be undamped and set into the ring preparatory to transfer to the calorimeter. It can be left standing indefinitely, but must be handled with caution (best by lifting with fingers beneath R, to avoid spilling the charge). Preparation of Calorimeter. The outer jacket of the calorimeter should be filled with water at about the room temperature or a few degrees higher. If left standing from day to day it will usually be nearly enough right. It is well to stir it (blow air through it) somewhat before beginning work, if it has stood for some time. Be sure that the inner surface of this "jacket, i.e., the one which is next the calorimeter, is thoroughly dry, and do not let any water spill into it or remove it if it does so. Thoroughly dry the outer surface of the calorimeter and keep it so. Moisture depositing on or evaporating from the surface of the calorimeter is sure to cause an irregular error which may spoil otherwise good work. Put the calorimeter in place. Transfer the bomb to it, and adjust the stirrer so that it works properly. Pour in the proper amount of water, about 2.25 88 CAS AND FUEL ANALYSIS. liters, at a suitable temperature, best by using marked flasks carefully calibrated beforehand. Insert the thermometer. See that the electrical attachments are ready for instantaneous use. The whole is then ready for the combustion. Combustion Observations. With apparatus all in place run the stirrer briskly and continuously until the completion of the work. Allow about five minutes for everything to come to a normal condition. Then take temperature readings to at least 0.01 at each quarter minute for at least five minutes. Record the times (h. m. s.) and corresponding thermometer-read- ings, thus: Remarks. After 5 m stirring Time. Temp. 2 h I5 m 0" 15. 24 15 .24 30 25 45 .25 16 o 25 15 .26 30 .36 25 o 15 15.6 30 9 45 16.2 26 5 etc. etc. Coal ignited Exactly at the beginning of a noted minute close the electric circuit through the fuse-wire. If the arrangements are right, this will cause the coal to ignite at once and the combustion is almost instan- taneous. Owing to the time required to transmit the FUEL ANALYSIS HEATING VALUE. 89 heat through the bomb to the water, the temperature, however, will continue to rise for two or three minutes. Keep up the steady stirring and the quarter-minute temperature-readings for at least ten minutes after ignition, recording as above. One or two observations may be unavoidably lost before and after ignition, but this does not materially affect the results. The read- ings during the rapid rise are also less close. As soon as the rise begins to slow down, however, the hundredths of a degree must again be secured. This makes a series of observations of 15 to 20 minutes' duration. The use of the readings to obtain the cooling correction and the corrected rise of tem- perature of the calorimeter is given under the heading " Cooling Correction " farther on. This completes the observations unless it is desired to test the character of the products of combustion. The bomb should now be opened and rinsed, as the nitric acid formed by the oxidation of the nitrogen in the coal and air attacks the metallic lining unless it be of gold. Also the top is more easily unscrewed at first than later. Leave the top off. Before unscrewing the top of the bomb be sure to open the valve R to relieve the presure. Heat Capacity of Bomb and Calorimeter. The heat capacity of the bomb may be found : 1. From the weights and assumed specific heats of the parts. 2. By raising the bomb to an observed high tem- perature and immersing in water, i.e., by the usual *' method of mixtures." 3. By burning in it a substance of known heat of QO GAS AND FUEL ANALYSIS. combustion, such as pure naphthaline, and calculating back to find the heat capacity of the bomb. The first method is not reliable. Errors of several per cent may enter in the assumed specific heats. The second method is very difficult of exact per* formance, owing to the size and form of the bomb. The third method is by far the most reliable, but of course depends on the correctness of the assumed heat of combustion of the substance used. That of naphtha- line has been so well determined by Berthelot and others,* and the substance is so easily and cheaply obtained in a pure state, that dependence can be placed on the results. This method has the great advantage that it involves the use of the apparatus in precisely the same way as in subsequent determina- tion, so that any systematic errors of method tend to cancel one another. It also determines at the same time the heat capacity of the calorimeter and stirrer just as used. The capacity of the calorimeter and stirrer may best be determined in connection with that of the bomb by the third method just described. Otherwise it may be found by the first method, or by a method similar to the second, viz., by pouring into the calorim- eter when partly full water of a known temperature different from that of the water in the calorimeter, noting all temperatures and weights. This last method, however, is very unsatisfactory in practice owing to the small heat capacity of the calorimeter and to the losses of heat in pouring the water, etc. * i gram of naphthaline evolves 9692 C. This is the average of 150 determinations by four different obervers. FUEL ANALYSIS HEATING VALUE. 91 A general expression for computing the heat of combustion from the bomb observations is as follows: Let n represent the number of grams of combustible, H the heat of combustion sought, W the weight of water in the calorimeter, and k the heat capacity, or water equivalent, of bomb, calorimeter, stirrer, thermometer, etc. ; /, and , represent the initial and final temperatures of the water. Then nH= W(t,-t t ) + ((,-(,), whence H= l -(W+k}(t,-t l ). This expression is exact if t t is corrected for loss by cooling as described in the methods for " Cooling Correction," p. 85. The value of k may be determined by either of the following methods; a simplification may, however, be introduced which will save much labor if an accuracy of not more than about one per cent is sought, pro- vided that k is found by burning naphthaline or other known substance. Use enough of this substance to cause about the same rise, , ^, , (within i) as will be caused by one gram of coal. Omit the cooling correc- tion entirely, using for , the maximum temperature attained. Then compute k\ this value will be erro- neous by a small amount owing to the neglect of the correction. Now in subsequent measurements on coal also neglect the cooling correction, using for / the maximum observed temperature as before, thus leav- ing an error in / a . Since the rise / /, in both cases will be nearly the same, the error in k will almost 92 GAS AND FUEL ANALYSIS. exactly affect that in / in the coal-test, and the result- ing value of H will be nearly free from this error. This method of course implies that W is nearly con- stant and that t v is systematically arranged to be either about at the air-temperature or a definite amount below it, as described under " Cooling Correction," so that the cooling loss is about the same. The time- interval from t l to , must for the same reason be- nearly constant in all cases. Cooling Correction. In all careful calorimetric work, one of the most troublesome sources of error is the loss or gain of heat by the calorimeter from its surroundings. This loss or gain is due to radiation, to air-convection currents, and to evaporation or con- densation. Unavoidable irregularities in the condi- tions and the smallness of the quantities to be measured render the amount of the correction variable and its determination uncertain. Many methods of making the correction have been proposed. One of the best of these is the first of the two given below, but the second, although a little more troublesome in the execution of the work, appears to be more trustworthy in its results. The second method is to be used. First Method. This is described in the Physical Laboratory Notes, I,* under " Specific Heat of Solids." In this method the water at the outset should be at such a temperature that it is gaining very slowly. For an open calorimeter this is about i or 2 below the air-temperature, but varies with circumstances. Water which has been long standing in the room is generally about right. Second Method. For the discussion and detail* * Obtainable from A. D. Machlachlan, Bookseller, Boston. FUEL ANALYSIS HEATING VALUE. 93 reference may be had to an article by Professor Holman in Proc. American Academy of Arts and Sciences, 1 895 , p. 245 ; also in The Technology Quarterly, 8, 344. Parr's Calorimeter.* This " has the advantage of operating without an oxygen gas supply ; its manipu- lation is simple and the extraction of the heat rapid, owing to the compact mass in which the heat is gen- erated. It is especially adapted to soft coal, and while designed for technical purposes, its factor of error is well within 0.5 per cent." " It depends for its action upon the liberation of oxygen from a compound which shall in turn absorb the products of combustion, conditions admirably met in sodium peroxide; this ob- viates the necessity of pro- viding for an outlet for those gases and also any loss aris- ing from the heat they might carry off." "A, Fig. 18, is the calor- imeter of about two liters capacity, insulated by two outer vessels of indurated fiber, B and C, so placed as to provide further insulation by the air-spaces b and c. FIG. 18. PARR'S CALORIMETER. The cover is double, to cor- respond, with an air-space between, the two parts being connected for convenience in handling. The cartridge D has a capacity of about 25 cc. ; it rests on a pivot below, extends through the covers, and has a small removable pulley at the end. Turbine wings * Parr, J. Am. Chem. Soc.. 22, 646 (1900). 94 GAS AND FUEL ANALYSIS. fastened to spring clips are placed on the cartridge, and a short cylinder E, open at both ends, is provided for directing the current set up by rotation of the vanes attached to the cartridge. The stem G of the cartridge is so arranged as to permit the passage of a short piece of No. 12 copper wire to ignite the charge ; it is provided with a valve D at the lower end to pre- vent the escape of the enclosed air." Manipulation. One gram of coal ground to pass a loo-mesh sieve, dried at 105, is put into the cartridge, 16-18 grams of sodium peroxide added, the top screwed on, and the whole shaken to thoroughly mix the contents. The peroxide should be fine enough to pass a 2 5- mesh sieve. The cartridge is tapped to settle the charge to the bottom, placed in the calor- imeter, two liters of water poured in, and rotated 50 to 100 revolutions per minute. The water should be 3 to 4 degrees lower than the room temperature. When the temperature has become constant, the thermometer is read, a hot wire dropped down G, igniting the charge, which burns completely. The extraction of the heat is effected in about five minutes; the reading of the maximum temperature is taken and the calculations made as follows : The rise of temperature is corrected, first, for that produced by the hot wire; this amounts to 0.006 C. per i inch of No. 12 copper wire: second, for the heat produced by the combination of the sodium peroxide with the carbon dioxide and water formed by the combus- tion ; this amounts to 27 per cent of the total indi- cated heat. If C= the heat of combustion of the coal, C' the calories indicated, t the rise of tempera- ture, and w the water employed, then FUEL ANALYSIS HEATING VALUE. c > = (/ _ 0.006) xw, C = C f - ' / C = 0.006) X w X 0.73. . Instead of using a gram of coal some prefer to use half this quantity, mixing it thoroughly and rapidly with the peroxide in a watch-glass with a spatula and transferring it to the combustion-chamber. Ignition by an electrically heated platinum wire is to be preferred to that by dropping a hot copper wire into the mixture. Accidents have been caused from the failure of the valve to work. The combustion-chamber should be perfectly dry within and without. Ashes and coke are difficult of ignition : this can be effected by adding a second charge of peroxide with half a gram of good coal, the combustion factor of which has been determined, and thoroughly mixing the charges and repeating the ignition. For stirring, the smallest size electric or water motor furnishes sufficient power. In the formulae w the water employed -f- the water equivalent of the calorimeter. BertJiier" s Method. Another method of direct determination was proposed by Berthier in 1835.* It uses as a measure of the heating value the amount of lead which a fuel would reduce from the oxide ; in other words, it is proportional to the amount of oxygen absorbed. The method is as follows f : Mix one gram of the * Dingler's Polytechnisches Journal, 58, 391. f Noyes, McTaggart & Graver, J. Am. Chem. Soc., 17, 847 (1798). 96 GAS AND FUEL ANALYSIS. finely powdered dry coal with 60 grams of oxide of lead (litharge) and 10 grams of ground glass. This mixing can be done with a palette-knife on a sheet of glazed paper; the mixture is transferred to a fire-clay crucible (Battersea C size), covered with salt, the crucible covered and heated to redness in a hot gas- furnace or the hottest part of the boiler-furnace for 1 5-20 minutes. After cooling, the crucible is broken and the lead button carefully cleaned and weighed. Multiply the weight of the lead button obtained by 268.3 calories (or 483 B. T. U.) and divide the prod- uct by the weight of coal taken. The result is the number of calories per gram or B. T. U. per pound. One gram of lead is theoretically equivalent to 234 calories (C) ; owing to the hydrogen present this factor gives results about two per cent too low. The results obtained by the author using " horn-pan " scales in one case by this method were within 2.8 per cent of those yielded by the bomb calorimeter, which are as close as those obtained by any calorimeter save Parrs. The method would seem worthy of more attention than it has received. b. Determination of Heating Value by Calculation. The method of determination of the heating value first described, though exact, has the disadvantages that the apparatus is costly and the compressed oxygen is not easily obtained. To obviate these, it has been sought to obtain the heating value by calculation from the chemical analysis, the heating value of the constituents being known. This has the disadvantage that we have no absolute knowl- FUEL ANALYSIS HEATING VALUE. 97 edge nay, not even an approximate idea as to how the carbon, hydrogen, water, and sulphur exist in the coal, so that any formula must of necessity be quite removed from the truth. Dulong was the first to propose the method by calculation, and his formula* is Soooc + 3450o(// J0) TT IOO r, h, and o representing the percentages of carbon, hydrogen, and oxygen in the coal. Many modifications of this, considering the water formed, the heat of vaporization of carbon, or the volatile hydrocarbons, have been proposed. Bunte \ finds that the following formula \ gives results varying from -f- 2.8 to 3.7 per cent: 8080^+ 288oo// o + 25005 6oow IOO s and w represent the percentages of sulphur and water respectively. It is, however, inapplicable to anthracite coal. It would scarcely seem that the sulphur would be worth considering unless high, one per cent affecting the result but 0.3 per cent. Mahler employs the formula* 8140^ + 34500/2 3000(0 + ri) IOO o and n representing oxygen and nitrogen, and states that it gives results within 3 per cent. The results obtained by these formulae for anthracite coal are as a rule considerably too low. * H burned to liquid water. JH burned to aqueous vapor. f Jour, fiir Gasbelouehtung, 34, 21-2$ wid 41-47. 98 GAS AND FUEL ANALYSIS. Goutal * has proposed the formula p - 8l5 f + 100 as being more readily applicable than the preceding. This gives the results in calories. P represents the calorific power; c, the percentage of fixed carbon (coke ash) ; M, the percentage of volatile matter (100 [coke -f- ash -f- water]) ; A is a coefficient which varies with the amount of volatile matter M, viz. : M = 2 to 15 A = 13000 15 to 30 i oooo 30 to 35 9500 35 to 40 9000 The results upon a series of American coals varied less than 2 per cent from those obtained by the calorimeter. REFERENCES. An admirable discussion of the errors incident to the use of the Mahler calorimeter and others of that type will be found in a paper by G. A. Fries, Bulletin No. 94 (1907), U. S. Dept. of Agriculture, Bureau of Animal Industry, "Investigations in the Use of the Bomb Calorimeter." * Revue de chimie ind., 7 (1896), 65; abs. in The Analyst, 24, 107. FUEL ANALYSIS HEATING VALUE. 99 CALORIFIC POWER OF GASEOUS FUEL. a. Direct Determination. Perhaps the best apparatus for the determination of the heating value of gases is the Junkers calorimeter, Figs. 19 and 20. The following description is taken FIG. 19. JUNKERS GAS-CALORIMETER (SECTION). from an article by Kuhne in the Journal of the Society of Chemical Industry, vol. 14, p. 631. As will be 100 GAS AND FUEL ANALYSIS. seen from Fig. 19, this consists of a combustion-cham- ber, 28, surrounded by a water-jacket, 15 and 16, this being traversed by a great many tubes. To prevent loss by radiation this water-jacket is sur- FIG. 20. JUNKERS GAS-CALORIMETER. rounded by a closed annular air-space, 13, in which the air cannot circulate. The whole apparatus is constructed of copper as thin as is compatible with strength. The water enters the jacket at I, passes down through 3, 6, and 7, and leaves it at 21, while FUEL ANALYSISHEATING VALUE. ioi the hot combustion-gases enter at 30 and pass down, leaving at 31. There is therefore not only a very large surface of thin copper between the gases and the water, but the two move in opposite directions, during which process all the heat generated by the flame is transferred to the water, and the waste gases leave the apparatus approximately at atmospheric temperature. The gas to be burned is first passed through a meter, Fig. 20, and then, to insure constant pressure, through a pressure-regulator. The source of heat in relation to the unit of heat is thus rendered stationary; and in order to make the absorbing quantity of heat also stationary, two overflows are provided at the calo- rimeter, making the head of water and overflow con- stant. The temperatures of the water entering and leaving the apparatus can be read by 12 and 43; as shown before, the quantities of heat and water passed through the apparatus are constant. As soon as the flame is lighted, 43 will rise to a certain point and will remain nearly constant. Manipulation. The calorimeter is placed as shown in Fig. 20, so that one operator can simultaneously observe the two thermometers of the entering and escaping water, the index of the gas-meter, and the measuring-glasses. No draft of air must be permitted to strike the ex- haust of the spent gas. The water-supply tube w is connected with the nipple a in the centre of the upper container; the other nipple, b, is provided with a waste-tube to carry away the overflow, which latter must be kept running while the headings are taken. 102 GAS AND FUEL ANALYSIS. The nipple c through which the heated water leaves the calorimeter is connected by a rubber tube with the large graduate, d empties the condensed water into the small graduate. The thermometers being held in position by rubber stoppers and the water turned on by e until it dis- charges at c, no water must issue from d or from 39, Fig. 19, as this would indicate a leak in the calorim- eter. The cock e is now set to allow about two liters of water to pass in a minute and a half, and the gas issuing from the burner ignited. Sufficient time is allowed until the temperature of the inlet-water becomes constant and the outlet approximately so; the temperature of the inlet-water is noted, the read- ing of the gas-meter taken, and at this same time the outlet-tube changed from the funnel to the graduate. Ten successive readings of the outflowing water are taken while the graduate (2-liter) is being filled and the gas shut off. A better procedure is to allow the water to run into tared 8-liter bottles, three being used for a test, and weighing the water. The thermometer in the outlet can then be read every half-minute. EXAMPLE. Temp, of incoming water, 17.2 " " outgoing " 43.8 Increase, 26.6 Gas burned, 0.35 cu. ft. _ liters water X increase of temp. _ 2 X 26.6 cu. ft. gas 0.35 = I52.3C. From burning one cubic foot of gas 27.25 cc. of water were condensed. This gives off on an average 0.6 C. per cc. FUEL ANALYSIS HEATING VALUE. 103 27.25 X 0.6= 16.3 C; 152.3 16 i == 136 C. per cubic foot; 136 X 3-96823= 540 B. T. U. The calorific pouer obtained without subtracting the heat given off by the condensation of the water represents the total heating value of the gas. This is the heat given off when the gas is used for heating water or in any operation where the products of combustion pass off below 100 C. The net heating value represents the conditions in which by far the greater quantity of gas is consumed, for cooking, heating and gas engines, and is the one which should be reported. It should, however, be corrected, as shown on page 106, to the legal cubic foot, that is, measured at 30 inches barometric pressure, and 60 F. saturated with moisture. The apparatus has been tested for three months in the German Physical Technical Institute with hy- drogen, with but a deviation of 0.3 per cent from Thomson's value. This value may vary nearly that amount from the real value owing to the method which he employed. b. By Calculation. Oftentimes it may be impracticable to determine the heating value of gases directly; in such cases recourse must be had to the calculation of its calorific power from volumetric analysis of the gas. To this end multiply the percentage of each con- stituent by its number as given in Table IV, and the sum of the products will represent the British Thermal Units evolved by the combustion of one cubic foot of 104 GAS AND FUEL ANALYSIS. the gas.* It is assumed that the temperature of the gas burned and the air for combustion is 60 F., and that of the escaping gases is 328 F., that correspond- ing to the temperature of steam at 100 pounds abso- lute pressure. As has been already stated, column 3 in Table IV is based upon the assumption that the gas, and air for its combustion, enter at 60 F., and the products of combustion leave at 328 F. ; in column 4 it is assumed that the entering temperature of both gas and air is 32 F., and the combustion-gases are cooled to 32 F. In case these conditions are varied, the amount of heat which the gas and air bring in must be determined; this is found in the usual way by multi- plying the proportionate parts of I cubic foot, as shown by the analysis, by the specific heat of the gas, and this by the rise in temperature (difference between observed temperature and 32 F.). The quantity of air necessary for combustion is found by multiplying the percentage composition of the gas by the number of cubic feet necessary for the combustion of each constituent. An example will serve to make this clear. The analysis of Boston gas is as follows:* CO 2 "Illuminants. 1 " O CO CH 4 H N 2.9 15.0 o.o 25.3 25.9 27.9 3.0 Or in one cubic foot there are * H. L. Payne, Jour. Analytical and Applied Chem., 7, 230. t Jenkins, Annual Report Inspector oi Gas Meters and Illuminating Gas, 1896, p. ii. FUEL ANALYSIS HEATING VALUE. 105 .029 CO 2 259 CH 4 .150 " illuminants " 279 H .253 CO.. 030 N Let us assume that the gases, instead of passing out at a temperature of 328 F., leave at the same temperature as that of the chimney-gases, p. 29, 250 C. or 482 F. The calculation of the heat carried away is similar to that there given. 0.15 cu. ft. of "illuminants*' produces, Table III, 0.3 cu. ft. CO 2 and 0.3 cu. ft. steam; 0.253 cu. ft. of carbonic oxide produces .253 cu. ft. CO,; 0.259 cu. ft. methane produces 0.259 cu - ft- CO a and .518 cu ft. steam; 0.279 cu - ft- hydrogen produces .279 cu. ft. steam. From the combustion of the gas there results .812 cu. ft. CO a , 1.097 cu. ft. steam, and 5.90 X 79.08 or 4.665 cu. ft. N. The quantity of heat they carry off is as follows: Vol. Vol. Sp. Ht. Rise. B.T.U. CO 2 812 X .027 X 450 9-9 N 4.66 X .019 X 45= 39-9 Excess of air.. 1.2 X .019 X 450 = 10.2 Steam 1.097 X .0502 X 1229 = 67.7 Total heat lost = I2 7-7 106 CAS AND FUEL ANALYSIS. The loss due to the steam is found by multiplying the weight of steam found by the " Total Heat of Steam," as found from Steam Tables.* The tables, however, do not extend beyond 428 F. ; it can be calculated by the formula Total heat = A = 1091.7 -|- o.3.'.-... . . . . . 8vo, 3 00 1 Briggs's Modern American School Buildings 8vo, $4 00 Byrne's Inspection of Materials and Wormanship Employed in Construction. 16mo, 3 00 Carpenter's Heating and Ventilating of Buildings 8vo, 4 00 * Corthell's Allowable Pressure on Deep Foundations 12mo, 1 25 Freitag's Architectural Engineering 8vo, 3 50 Fireproofing of Steel Buildings 8vo, 2 50 Gerhard'r Guide to Sanitary Inspections. 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