The elements of chemistry and mineralogy
w A o X^. <^ ,F V ^* aV \> ^d< '^rf iP^ # % A A. ^s s \v ^Q, ' « «, s s \V «>%> 9>. */ ^ : ^ * ,^ & %.ax' : <\ c5> <^ \\<&* :TMk\\^:^Mk\\<^ \^.„,% 0° * .% w <^ G ^ , &^W'/^ V^. :V :.\^ >v <■ 0° * tf> ^ ~n ■<?■ HINRICHS' ELEMENTS OF CHEMISTRY AND MINERALOGY. Diese Wissenschaft lasst sich nicht aus Biichern, noch aueh allein durch Besuch von chemischen Vorlesungen, sondern nur durch tleissiges Arbeiten im Laborato- rium erlernen. Hermann Kolbe, (TraadatdoD, gee ct»p. vin.) Dii'- Chem. Lab. Univ. Leipzig. THE ELEMENTS OF PHYSICAL SCIENCE, DEMONSTRATED BY THE STUDENT'S OWN EXPERIMENTS AND OBSERVATIONS. BY GUSTAVUS HINRICHS, A. M IN THREE VOLUMES. VOLUME II. THE ELEMENTS OF CHEMISTRY AND MINERALOGY. WITH TWO PLATES AND JOURNAL OF EXPERIMENTS. DAVENPORT, IOWA, U. S. PUBLISHED BY GRIGGS, WATSON, & DAY. LEIPZIG : F. A. BROCKHAUS. 1871. THE ELEMENTS OF CHEMISTRY AND MINERALOGY, DEMONSTRATED BY THE STUDENT'S OWN EXPERIMENTS. BY GUSTAVUSfHINRICHS, A. M. Professor of Physical Science in the State University of Iowa; Member, or Correspondent, of Scientific Societies at Berlin, Vienna, Koenigsberg, Emden, etc., etc. WITH TWO PLATES AND JOURNAL OF EXPERIMENTS. DAVENPORT, IOWA, U. S. PUBLISHED BY GRIGGS, WATSON, & DAY. LEIPZIG : P. A. BROCKHAUS. 1871. Entered according to act of Congress, in the year 1871, by GUSTAVUS HINRICHS, In the office of the Librarian of Congress, at Washington. riie right of translation and re-publication reserved ^^ n. ^° hv tU« author. Xs / 17 PREFACE TO VOL. I. £/ It is generally understood by those qnaliftad to judge, that the teach ing of elementary science in our schools is not carried on in a scien tific spirit. Recitation from a text book, with occasional exhibition of experiments and specimens, is not calculated to give the beginner conviction in the truth stated, or to initiate him into the method of scientific investigation. In regard to science, our schools are not above the middle ages. Three hundred years ago students repeated the obscure statements of Aristotle, of which a sample is given e454) ; now our students repeat the statements of their text book, without obtaining any valid ground for the conviction they are made to express. The great work done by Galileo for- physical science in general t has not yet reached our schools. The method of scientific research which he first so successfully practiced, and which alone can lead to conviction in the truth of the resuitStObtained, has not yet gained admis- sion to our schools. We venture with the present little work to knock at the doors of our schools in behalf of this method and in the interest of science. AVe do not advocate anything new. For two and a half centuries these very methods have been used, the grand structure of modern sci- ence has resulted, and the course of civilization has been changed thereby. That these same methods art successful in the school room and with beginners, is not a mere conclusion, but a fact established by experi- ence. The few series of experiments printed in the "Journal" of this volume will confirm it. The series here published have been taken from an immense material already accumulated by students in our laboratory. .But this work is so thoroughly different from those which are in general use, that we feel under great obligations to the Publishers for having ventured this publication. Before attempting the use of this book, the student, and especially the tsaclter, should carefully study the Guide at the close of this volume. Iowa City, Iowa, U. S., January, 1871. PREFACE TO VOL. II, These Elements of Chemistry and Mineralogy form simply a con- tinuation of an Elements of Physics. Laboratory practice in chemistry is universally recognized as essen- tial ; but it cannot become universal, if grand laboratories with costly apparatus are required. By excluding special and professional branches, the methods of elementary laboratory practice here given can be fur- nished free of charge by any school to all its pupils. See Chapter VIII. of this volume, for details. No one should judge our chapter on mineralogy except after having tried it in precisely the manner directed. The determination by co- ordinates is novel, and quite satisfactory. While writing these lines, we receive the very cordial welcome which the London " Nature " extends to the first volume of this course in the Elements of Physical Science. We have earnestly endeavored, also, in this second volume, to "point out the right path of discovery " to the student, and to "act on the whole as a faithful and thoroughly painstaking guide." If " Nature," upon examination of this second volume, gives it an equally cordial welcome, we shall feel encouraged, while amidst but too many difficulties we prepare the final revision of the concluding volume of these Elements of Physical Science — The Students' Cosmos. Iowa City, U. S., Oct. 21, 1871. CONTENTS. CHAPTER L— On Heat. I. Modes of Heating II. Radiation and Condensation III. Thermometer and Calorimeter IV. Fusing and Boiling CHAPTER II.— Heat and Mechanical Work CHAPTER III.— Dissociation and Electrolysis CHAPTER IV.— Elements and Compounds. I. The Elements .... II. Chemical Nomenclature CHAPTER V.— Acids and Bases CHAPTER VI.— Chemical Processes. I. Reactions .... II. Synthesis .... III. Substitution .... IV. Double Decomposition V. Complex Processes CHAPTER VII.— Elements op Mineralogy. I. Classification and Determination II. Descriptive Mineralogy CHAPTER VIII.— The Chemical School Laboratory Student's Journal of Experiments. 2 10 13 21 33 46 57 66 72 91 94 102 112 117 129 156 163 CHAPTER I. ON HEAT. 1. The S u n is our principal source of heat. The heat obtained by combustion of wood and of other vegetable materials is also due to the sun ; for plants require sunshine in order to grow. 2. Heat effects very remarkable changes in the sub stances upon which it acts.* These effects of heat may be classified as changes involume, changes in aggre- gation, and changes in compositi on. 3. That heat effects changes in volume is a matter of common experience, and may also be shown by the fol- lowing apparatus, called a thermometer. A glass or tin flask, of about 25 cc. capacity is com- pletely filled with water, and closed by a stopper through which passes a narrow, long tube ; as the stopper is pressed down, the water rises in the tube. A centimeter scale, divided to halves, is attached to the tube. If now the flask is placed in a vessel containing hot water, the level of the water in the tube will rise. If thereafter, the flask is put into cold water, or surrounded by ieet the level will sink. The rise and fall of the level evidently constitutes a change in the volume of the water, brought about by the heat added to, or taken away from the flask. *The effects on our own orgaodsin, especially the production of the sensation of warmth, cannot be considered in, the elements of physical science. Chapter I. 4. That heat produces changes in aggregation has already been demonstrated in the Elements of Physics. Articles 113 and 151. The solid i c e is by heat fused to liquid w a t e r, and the latter by additional heat changed into gaseous steam. By removing heat, steam is again condensed to water, and water frozen to ice. Iodine also is readily exhibited in these three states of aggregation by applying or removing heat. (Elements of Physics. 113.) 5- A crystal of blue vitriol gently heated in a glass tube changes to a white powder, while the colder parts of the glass tube become covered with numerous drops of water. In this case heat has changed the state of combination, the blue vitriol being resolved inlo a white powder and water. 6. Such changes in the composition of substances are often termed chemical processes. Changes in volume and aggregation, not affecting the composition of bodies, are distinguished as p h y s i c a 1 processes. These latter processes shall be studied in the first two chapters, while the chemical processes will be treated of in the balance of this volume. 7. To study these different effects of heat experiment- ally, we must first become familiar with the various modes of applying heat for experimental purposes. I. MODES OP HEATING. 8. For the student's experiments, the flame of a g 1 a s s alcohol lamp is a sufficient source of heat. For the blow-pipe, a common candle may replace this lamp. Illuminating gas, burnt in a Bunsen burner, is better than the above, but not everywhere accessible. If used, its flame should be turned down until suitable for the small quantities to be heated. 9. The substances to be heated are supported over the flame in vessels of glass, porcelain, or plati- Modes of Heating. n u m. The vessels are either exposed to the heat direct or by means of sand b a t h, air bath or water bath. Charcoal is extensively used as support when the blow-pipe flame is to be applied. 10. No experiment can give a satisfactory result, unless it is performed exactly as directed. But to understand the directions, the student must be perfectly familiar with the terms used to designate the various forms of appara- tus employed. Hence the student should carefully study the following pages. * 11. The glass alcohol lamp should contain good alcohol, and be provided with a sufficiently long, well- trimmed wick. At the close of the experiment, the flame is extinguished by blowing, and the closely-fitting glass- cap is put on to prevent the evaporation of the alcohol. Carefully avoid the soiling of the wick or its support, so that the lamp burns with a pure, pale flame. 12. The Bunsen burner consists of a narrow, vertical gas-jet, surrounded by a vertical brass tube one centimeter in diameter, and partly open below. The flame formed at the top of the wide tube results from the combustion of the intimate mixture of gas and air formed in the wider tube. This flame of the Bunsen burner is but faintly lumin ous, but intensely heating, and free from s o o t, so as to leave apparatus exposed to it clean. The common gas burners give a highly luminous flame, which deposits much soot, and hence cannot be used for experiments on heat. 13. The glass vessels used as support for substances to *Ifc is expected that the teacher exhibit these apparatus to the class while this subject is under consideration. Since the student of course has to pay the cost of all apparatus he breaks, as well as the cost of the material he wastes by improper work, he will save himself much money by a very careful study of this section prior to his beginning the experi- ments of the next section. Besides, by avoiding breakage and waste, the student will not delay the experimental work of his fellow-students, nor cause his teacher additional trouble and'vexation. Chapter I. be heated, are, retorts, flasks, beakers, dishes, watch glasses, test tubes, and common glass tubes. These will readily be distinguished and described by the student, while the teacher exhibits thern to the class. All these glass vessels must be thoroughly annealed, and of uniform thickness, in order to withstand moder- ately sudden changes of heat. They should be scrupulously washed ( with common water*) and rinsed (with distilled water) immediately after and again before use. Those outer parts which are to be exposed to the direct influence of heat, should furthermore be wiped dry, in order to avoid breakage from the flame ( or heated sand. See 18). 14. For our purposes a glass flask of 25 to 50 cc. capacity, a few watch glasses (5 cm. diam.), and three or four test tubes ( 1 cm. diam., 7 or 8 cm. long) are quite sufficient. A few lengths of glass tubing will also be required — some 3 mm. internal diameter, for blow-pipe work, and some 5 mm. internal diameter, for other work, such as distillation, etc. 15. Crucibles and dishes of porcelain are very useful, but not necessary for beginners, since tire blow-pipe and glass tube may be substituted for the cru- cible, and the watch glass for the dish. Still, the teacher may exhibit some of the forms of porcelain ware in use in laboratories. 16. Platinum is used, as support for substances to be heated, in the shape of c r u cib 1 es, d i s h es, foil, strips, and wire. Only the last three forms are re- quired by the beginner in blow-pipe work. We shall therefore defer the description of these forms of platinum until we take up the description of the blow- pipe, when the charcoal support also will be noticed. ♦Aided by washers, consisting of a piece of sponge tied to a small stick, or pieces of paper shaken in the flask until the paper is reduced to a pulp. Modes of Heating. 17. A glass vessel to be heated is but rarely exposed to the direct flame by supporting the vessel on a triangle of iron wire^above the flame. It is best to place the glass vessel on a square piece of ( brass ) w i r e-g auze, which really prevents the flame from striking the glass vessel. This property of a wire-gauze may be exhibited by pres- sing such a gauze down upon a flame ; the flame will then appear as if cut off by the gauze. 18. Beginners will always do well to support the glass vessel on a sand bath, rather than over the direct flame, or even the gauze. A sand bath consists simply in a thin, shallow, sheet- iron dish, partly filled with coarse sand, which has been freed from dust by washing and drying. 19. If but a moderate heat is required, or if it be essential to prevent the heat from rising above that of boilingwater, the water bath is used. In its simplest form the water bath consists of a tin cup, about 10 cm. in diameter and 6 cm. high, closed by a cover provided with a circular opening of about 5 cm. in diameter. Before use, the bath is filled about two- thirds full with water, placed over the flame, and the vessel to be heated put over the opening in the cover. The student should be very careful to see that the water in the water bath does not get too low. 20. The airbath is a vessel of iron or copper,, wherein the apparatus to be heated may be placed while the air bath is exposed to a flame. The beginner does not require this bath. 21. The preceding modes of heating correspond to the application of heat by boilers, stills, and retorts, in the arts. In none of the above cases is an excessive de- gree of heat produced. But in the various furnaces so extensively used in the arts, very high degrees of heat result. To imitate these furnaces on a small scale for Chapter I. experimental purposes, the blow-pipe is used in the labora- tory. 22. The blow pipe is a small, bent tube, used to produce a line jet of air, by means of which a flame is blown aside so as to concentrate its hear in a small space. The best form of blowpipe, as represented in figure 1, cunsists of five parts. The m out h-p i e c e, a, is of horn ; the main tube, b, a i r-c liaiuber, c, and main j e t, d, are of brass or German silver, while the jet proper, e, is of platinum. This latter is represented in full size in a section below d, in the figure. The metallic pieces fit into one another with gentle friction, and may betaken apart ; only the mouth-piece, a, is firmly attached with sealing wax to the tube, b. The hole in the platinum jet is very fine. By proper care it never gets clogged ; but, if it should get stopped in the hands of the beginner, the jet should be given to the teacher to be burnt out.* Never touch anything with the platinum jet, except the flame. 23. It "is not very difficult to learn to blow if the fol- lowing directions are carefully obeyed : Firmly close your lips, distend the cheeks as widely as possible, and breathe slowly, regularly, and deeply through the nostrils alone — always keeping the cheeks fully dis- tended during inhalation as well as during exhalation. When you can do this for several minutes at a time, grasp the blow-pipe tube firmly with the right hand and press the mouth piece against your lips. Support the tube on the thumb, third and fourth fingers, while the first and second fingers press the tube against the former just be- low the ring, f, on the tube. Thus the tube will be held firm as by a vise, and without special effort. See figure 2. Bring the jet almost into the flame of a candle, f or *It must never be drilled out. +The wick of which has been bent asid6 in the direction of the jet. Mode* of Heating. alcohol lamp ; you will then see it blown aside, as shown in figure 3. Continue to keep this blow-pipe flame steady, firm, and of the shape of a sharp cone. The flame must be kept as steady as if it were a solid body. Hold, by means of your left hand, a piece of iron wire ( about one fourth of a millimeter thick) in the luminous point, b, of the blow-pipe flame. You will thus be able to see whether your blow-pipe flame is steady or flickering. Practice this experiment until you can keep the flame steady, at least during one minute. The iron wire then- will fuse, and burn often with scin- tillations; thus proving that the heat in the point of the bio w-p ipe flame is very intense. 24. By close inspection you will notice that the most luminous point, b, of the blow-pipe flame is really but the vertex of a hollow luminous cone, indicated by the shaded portion in figure 3. This point of greatest heat is also termed the fusing point or f using regio n of the blow-pipe flame. This bright, luminous cone is surrounded by a faint hol- low cone of light, c, termed the outer flame of the blow-pipe. Inside of the bright hollow cone is the inner flame, d, of the blow-pipe. These three regions of the blow-pipe flame have very different properties ; hence the great importance of learn- ing to keep the flame perfectly steady, so that only one of these regions acts upon the object. The abbreviations, o-fl. and i-fl. are often used to denote respectively the outer, c, and inner, d, blow-pipe flame. 25. On the smooth surface of a piece of c h a r c o a If a small piece of lead — about one or two centigrams — is placed, as indicated in figure 4. Heated in the out- er flame the lead fuses, partly volatilizes and burns, fBy means of a saw the charcoal is cut into blocks about 5 cm, wide, 10 cm. long and 2 cm. thick. The surface to be used is sm.oth.ed with a knife — over a tin box, to receive the dust. Be careful to keep your ringers clean. Chapter I. covering the charcoal with a well defined, elliptical i ti- er natation of a yellowish color. Perfect definition of this incrustation is a good test for perfect steadiness^of the flame. If you, thereafter, direct the inner flame upon any part of the incrustation, jtou will in a few instants convertkthat part of the incrustation into minute globules of metallic lead. From this it appears that the i-fl. and o-fl. have oppo- site properties. Since the inner flame reduces the incrustations again to metallic lead, this part of the flame is oiten called the reducing flame. -^The outer flame, then, is termed the oxidizing flame. 26. Besides the charcoal-support here spoken of, we use platinum and glass-tube supports for substances to be heated in the blowpipe flame. The platinum supports are the foil, the strip, and the wire. The platinum foil is a triangular piece of thin sheet platinum, about 1.5 cm. wide at the base, and 3 cm. long. For use, its vertex is held by a pair of steel tweezers,* or by inserting the vertex in a partly split-up match. The platinum strip is cut from the same sheet platinum, and is about one mm. wide, three or five cm. long. It is held in the same manner as the foil. The platinum w i r e is about half a millimeter thick and as long as the strip. One end of this wire is bent into a circular 1 o o p of about two mm. diameter, by twisting the wire around the platinum jet of the blow- pipe. 27- The platinum foil is used for f u s i o n a n d fl u x_ i n g, being heated from below. The platinum strip is used for fl a m e-c o 1 o r a t i o n s ; the wire-loop for borax *A small ring sliding along the tweezers keeps these shut so as to hold the foil firmly without special effort on the part of the student. Modes of Heating. b e a d 8. These different applications may be exhibited by the teacher before the class. We shall, in the following, return more fully to this subject. For practice the student may simply heat the platinum as indicated : the foil from below, the strip at the fusing point, and the loop at the same point, but in such a manner that the flame passes through the loop at right angles to the plane of the same. When these platinum pieces are first inserted into the fusing point of the flame they usually tinge the outer flame yellow. After some heating this color disappears, the outer flame becoming colorless. If you now touch the cooled strip with the so-called carefully cleaned fin- ger, you will see the yellow color reappear upon re-heat- ing the strip — thus proving that the carefully cleaned fingers contain something ( salt ) which tinges the flames. This fact also shows the necessity of most careful clean- ing* of the platinum wire. Certain substances fusing readily together with platinum, it is important that the student should use the platinum only when expressly directed, in order to prevent the loss of this expensive metal. 28- The glass s u pp or t for blow-pipe use consists in a narrow ( 3 mm. wide ) glass tube, 5 cm. long, either closed at one end or open at both ends. In the former case (closed tube) heat alone can act upon the substance in the tube, the air being practically excluded as well as in a covered crucible. In the open tube a current of air necessarily passes along the tube, especially if the latter is held obliquely. ♦This is accomplished by first fusing some sodium bisulphate on the platinum, then dissolving the fused mass with water, assisted by gentle friction, if need be,— followed by thorough washing and rinsing with water. Potassium bisulphate an swers equally well. The platinum strip and foil should also be kept smooth. To smoothen the foil or strip, hold them on a clean piece of glass, and repeatedly push the nail of a finger along the platinum in one direction only. 2 10 Chapter I. For the purpose of practice, a minute fragment (one or two cgr.) of pyrite may be heated in each of these tubes, and the results noted. 29. To succeed well with the blow-pipe, it is not suf- ficient to be able to produce a steady blow-pipe flame, and to apply constantly that region which is to be used ; it is equally essential to take but a minute quantity of the substance to be acted upon. One centigram will in most eases prove quite sufficient. The test object should hardly ever measure more than a millimeter in any direc- tion. 30- It will have been observed that precisely the same modes of heating here described are in constant use on a large scale in the arts. In these experiments only minute quantities being used — but in the arts the same operations often are performed on tons at a time. Now it is true that the properties of a substance do not depend upon the absolute amount of the substance. See Elements of Physics, article 111. But at the same time the use of minute quantities in experi- mentation makes extreme care and clean- liness absolutely imperative, if the properties are to be distinctly and unmistakably recognized by the student. II. RADIATION AND CONDUCTION. 31. The simple apparatus described in article 3, constitutes a thermometer, if it is provided with a centimeter scale ;* for the higher the column of water in the tube, the greater the degree of heat. We shall make use of this exceedingly simple thermometer to demon- strate the law of cooling, and the principal facts in regard to radiation and conduction. *A strip of card paper one centimeter wide, divided into centimeters and halves, attached to the tube by a few loops of thread and some sealing wax to keep it in place, will answer well enough Radiation and Conduction. II The height of the column of water expressed by the number on the scale is called the temperature, or degree of heat of the water in the thermometer. 32. If the thermometer is heated on the water bath and thereafter exposed to the air in the room, the tem- perature of the thermometer will be observed to sink — first rapidly, then more slowly. The thermometer cools, losing part of its heat to the surroundings. The air in immediate contact with the thermometer becomes warmed and, expanding thereby ( see 3 ), ascends, yielding its place to other portions of air, which in the same manner become warmed and are thereby removed ; this diffusion of the heat of the thermometer is called convection. But the greater part of the heat of the thermometer is r a d i a t e d in all directions. 33. The velocity, v, of cooling isdirectly proportional to the excess, e, of tempera- ture of the cooling body over the sur- rounding; or, if o is a constant quantity, this law of cooling may be expressed by v=c.e. To demonstrate this law, first determine the tempera- ture, t, of the surrounding by placing the thermometer in the position where it afterward is to cool, and keeping the thermometer in this place until it is stationary (neither sinks nor rises) ; read the temperature, t, now indicated. Then heat the thermometer on the water bath, by placing it on the watch glass so as to prevent its getting moist. Now remove it to the place occupied before, and accurate- ly observe the time at which the sinking column passes the successive ( half and full) divisions on the scale. This can be best done by t w o students working together, stu- dent A counting aloud the beats of a second pendulum (Elements of Physics, 39 ),the other student, B, observing the sinking column. Student Bhas on a slip of paper, entered one below the other, the divisions of the 12 Chapter L 6cale above t ; while A counts aloud, B enters the Dum- ber, n, called by A when the column exactly passes a given division, h, on his paper at the corresponding place. Then the observations are entered in the journal of ex- periments in the following form : — No. h D i v e The first column gives the number of the observ- ation made, the second the division or height, h, of the column at the number, n, seconds entered in the third column. In the fourth column the interval, i, seconds is recorded, expressing the time (in seconds) required to sink one (or one-half) division (cm). Hence the ve- 1 o c i t y, v, of cooling is v=L that is, the number of divisions which the column sinks in o n e second. By subtracting the temperature, t, of the surroundings from each, h, we obtain the e x c e s s, e, in temperature of the thermometer over the surrounding, e = h — t. By finally dividing each, v by e, you obtain values in the last column not differing niuch* from one another. The mean of all these values you call c. The law of cooling was first demonstrated by New- ton. 34. If the cooling thermometer is placed upon a piece of iron or other metal, the velocity of cooling will in- crease very much ; if it is packed in cotton contained in a paper box, the velocity of cooling will be diminished. By such experiments it can readily be proved, that metals are good conductors of heat, while woolen cloth, hair, and cotton are very poor conductors. Wood is also a rather poor conductor ; stone a better con- •It is best only to uefe the values e, which are at lea§t from 5 to 10 cm. Thermometer and Calorimeter. 13 ductor than wood, but very much less a conductor than the metals. Among the metals, silver and copper are found to be the best conductors for heat. Iron, lead, and especially platinum, are much less perfect conductors. The low con- ductibility of platinum contributes very much to make it a good support in blow-pipe experiments. 35. If such a thermometer has one portion of its side wall of bright glass, another portion painted with dull lampblack, a third coated with gold-leaf; if it furthermore during the cooling is packed with cotton in a paper box, one side of which has a circular opening somewhat less than the above coverings; then it will be found that the velocity of cooling is least when the gilt side radiates, greatest when the lampblack radiates, and intermediate for the glass. These observations prove, that lampblack is the best radiator, metallic gold the poorest radiator, while glass is intermediate. In a like manner the radiating power of other substan- ces might be determined. 36. The facts and laws here demonstrated are of very general application in common life and in the arts. The student should point out a number of such applications. III. THERMOMETER AND CALORIMETER. 37. No two thermometers, such as described in article 31, will indicate the same number on their scale, although put in the same place. They are, therefore, unfit for gen- eral use. Besides they are not very susceptible to small changes in temperature. 38. The thermometer now in general use consists of a stout glass tube, 5 mm. external diameter, with a very narrow flat* hole, figure 5. A cylindrical bulb of com- *The hole is flat in order that the mercury filling it may be visible although but of a minute volume- The thread or rather ribbon of mercury filling a good ther- mometer tube can hardly be seen edgewise, although from the front, it is easilv observed. 14 Chapter I. paratively thin walls, but of an external diameter not greater than that of the tube, has been blown on one end of the tube. The tube and bulb are now completely filled with mercury at a high temperature, when the free end of the tube is closed by fusion. Upon cooling, the mercury column recedes toward the bulb, leaving a vacuum above it. (Elements of Physics, 129.) If the bulb is inserted in a vessel containing small pieces of ice, the mercury column will first sink and then remain station ary. The point on the tube at which the mercury then remains in melting ice, is marked zero, and termed the freezing point of water. Thereafter the thermometer is placed in water, and this by means of heat brought to boiling. The mercury rises with the heating of the water, but remains stationary again while the water boils. The point at which the mer- cury stands fixed in boiling water is marked 100, and called the boiling point.* The distance between 0 and 100 is divided into 1U0 equal parts called degrees Centigrade or Celsi- us; the division is carried on above and below, thus giving a scale reaching from 30 degrees below zero to 200 or 300 degrees above zero. Degrees below the freezing p unt are usually called negative, and preceded by the sign — minus. 39. Mercury solidifies at about — 40°, so that the mer- cury thermometer cannot be used for the determination of low degrees of heat'. For this purpose other thermome- ters, containing alcohol (usually tinged red to distin- guish it from the glass ) are used. Mercury boils at about 325°. Hence for the determi- nation of high temperatures air thermometers are required, i. e., thermometers containing air instead ofmer- *In a water bath, the temperature, therefore, never can exceed 100°. See arti- cle 19 Thermometer and Calorimeter \h cury. But since air is very much affected by pressure, the air thermometer requires intricate calculations on the in- fluence of the varying pressure of the atmosphere. Two other thermometer scales are much used in the arts. Reaumur's scale marks the freezing point 0°, the boiling point 80°. On Fahrenheit's scale the freezing point is marked 32°, the boiling point 212°. These scales are, if necessary, distinguished by adding the in i t i al of the name of the inventor to the number of degrees. Thus, 50QC=40oR = 122°F. In the United States and in Great Britain the Fahren- heit scale is in general use in the arts ; on the continent of Europe, Reaumur's scale prevails. In science, the Cen- tigrade or Celsius scale is very generally used. It will be used exclusively in this work. 40. By performing a c curate determinations of volume at different accurately determined temperatures, the amount of expansion ( see 3 ) has been deter- mined. It has been found that one cubic centimeter of the following substances taken at 0° expands by heating to 100° to the values given below : Air, 1.366. Lead, 1.0084. Water, 1.043. Silver, 1.0057. Mercury, 1.018. Copper, 1.0051. Glass, 1.003. Gold, 1.0045. Steel, 1.0036. Iron, 1.0036. Platinum, 1.0025. If we except the expansion of air, these values of the expansion from 0° to 100° are so small, that the methods by which these quantities are determined cannot be stud- ied in the elements, but must be deferred to the course in principles of physical science. Here we shall add the curious fact that certain bodies con tract, while being heated, at certain temperatures. Thus water contracts from 1.0000 to 0.9999 while heated from 0° to 4°. It is, therefore, one ten-thousandth more 10 Chapter I. densest 4° than at 0°. Above 4° water expands contin- ually while heated. 41. With a good mercury thermometer the experiment on cooling ( 33 ) may be repeated.* The thermometer may be inserted in a flask containing a known amount of water, or of mercury ; the amount of liquid may be changed, and the experiment may be otherwise modified. Another even more important experiment for students, is the verification of the fixed points ( 0 and 100 ) on the thermometer scale. The student should also be required to observe the tem- perature of the air at given hours of the day during a week. Great care should always be taken to read the tempera- ture correctly and without disturbing the thermometer by the heat of the body of the observer. In more refined experiments the thermometer is therefore read from a dis- tance by means of a telescope. 42 The thermometer merely measures the degree of heat, not the amount of heat. To understand this important point, suppose you pour 10 cc. water into a small flask and 100 cc. of the same water into a beaker ; suppose the water to have the temperature of the room, 16°. A thermometer inserted into either vessel will there- fore indicate the same d e g r„e e of temperature. If, now, both vessels are heated on the water bath, then after some time the water in both will have reached the temperature of say 30. Again the thermometer indicates then the same temperature in the beaker and in the flask ; the temperature of the water in each was raised 14 de- grees, namely from 16 to 30 degrees. But it is evident, that it requires more of heat to raise 100 grams of water 14 degrees, than to raise 10 grams *A good thermometer cannot be had except at a cost of several dollars. Hence be very careful while handling thermometers. Thermometer and Calorimeter 17 of water this same number of degrees. The a mount of heat imparted to the 100 cc, water in the beaker is ev- idently 10 times as great as the amount of heat imparted to the 10 cc. water in the flask. Hence it is evident that the amount of heat imparted to a body or taken from a body does not merely depend upon the change in temperature of the body, but also the weight of the body and even the specific nature of the body. Heat, then, must be measured in its own unit, the calory. 43. A calory is the amount of heat re- quired to raise the temperature of one gram of water, one degree centigrade — from 0° to 1°. A kilocalory is 1000 calories, or the heat required to raise the temperature of one kilogram one degree. The term calory is used for the sake of brevity in- stead of the phrase unit of amount of heat. In practice the word calory is often abreviated thus : c al. 44. A calorimeter is an apparatus for measur- ing the amount of heat in calories. In its simplest form the calorimeter consists of a light flask ( about 200 cc. capacity ) with a light, sensitive ther- mometer, and a known weight, w, grams of water. If the temperature of this water rises t° — indicated by the thermometer — w times t calories = w. t cal. have been imparted to the water. For example, to 100 grams of water of 16° in the calorimeter add by a 10 cc. pipette 10 grams of water of 38° ; shake, and read the temperature of the mixture. Tou will find it 18°. Hence the 100 gr. in the calorimeter rose 2°, re- quiring 200 calories. The 10 gr. added lost 20° in tempe- rature, or gave off 10X20 =200 calories, equal to the heat imparted to the water in the calorimeter. 3 18 Chapter L In all cases the amount of heat (in calor- ies) imparted to the calorimeter, is equal to the amount of heat lost by the heat- ing body. For this experiment ( and also for 45), it is best to have a large amount of water of both temperatures at hand in large vessels, so that the temperature does not readily change. Then one thermometer io the calorimeter is sufficient.* 45. -But it requires also a certain amount, c, of heat to change the temperature of the calorimeter { flask and thermometer ) one degree. This value, c, is termed the water-value of the calorimeter. To determine the same, add a known weight, W, grams of water to the w grams of water in the calor- imeter. Yery carefully observe the temperature of the calorimeter-water, w, the added water, VV, and the tempera- ture of the mixture. You will thus find how many de- grees, T, the added water was cooled, and how many degrees, t, the calorimeter was heated. To heat w grams t degrees requires w. t calories. To heat the calorimeter of water-valve c grams the same num- ber of degrees requires c t cal. additional. Hence the calorimeter received wt + ct calories. The W grams of water added, lest T degrees, or W T cal. Hence we have wt + ct=WT Frorn^this follows c _ 3L W— w a8 tthe number of grams of water equivalent to the calorimeter ( flask and thermometer). For actual practice it is well to make W and w ♦Either transfer by pipette of known volume, or weigh after the reading of the Thermometer has been taken. Thermometer and Calorimeter . 19 nearly equal, and to have the hot water only 10 or at most 15 degrees warmer than the cold water. See re- marks at close of 44. 46. Calorimeter with chamber. If the mat- ter experimented upon cannot be mixed with the water in the calorimeter, this apparatus is provided with a chanr ber wherein the body is placed while giving off its heat. Thus to determine the amount of heat produced by the combustion of charcoal the combustible is burnt in a metallic chamber surrounded by the^water of a sufficient- ly large calorimeter. The amount of water, w, in the calorimeter, and the water value, c, of the calorimeter are known as well as the change, t, in temperature produced by the combustion of a known weight ( n grammes ) of charcoal. Then if n grams produce wt + ct cal.>. one gram of charcoal produces by its combustion w t + c t , cal. n 47. In this manner Favre and S i 1 b e r m a n found that one gramme of the following substances produces by complete combustion the number of calories stated oppo- site its name : GASES AND, LIQUIDS. Hydrogen .... 34,460 cal. Marsh gas 13,060 " Oleiiant gas 11,860." Oil of turpentine.. 10,850 " Olive oil 9,860 " Ether . . 9,030 " Alcohol 8,960 " Wood spirits 5,300 " SOLIDS. Anthracite 8,460 cal. Charcoal 8,080 " Coal, good 8,000 " Tallow 8,000 " Coke ...8,000 " Wood, dry 4,025 * " moist ...3,100 Phosphorus . . . .5^750 Sulphur 2,260 Iron .1,580 " Common illuminating gas consists essentially of olefiant and marth gas, and produces about 12,000 cah per gram by combustion. a 20 Chapter I. 48. The specific heat, s, of any substance is the number of calories required to heat one gram of the substance one degree centigrade. According to 43 the specific heat of water is therefore o n e. For most other substances the specific heat is much less than one, especially for the heavy metals, like gold, mercury and lead. 49. To produce a change of t degrees in the tempera- ture of a substance of specific heat, s and weight, w, re- quires, therefore, s. w. t. calories. 50- Accordingly the specific heat of a substance not affected by water may be determined by immersing a known weight of the substance, heated to a known tem- perature, into the water of a calorimeter, and carefully observing the resulting temperature. If, then, the water in the calorimeter, together with the water value of the calorimeter, be W grams, the change in temperature in the calorimeter be T, the calorimeter will have received W. T calories. If at the same time the w grams of the substance lost t degrees in temperature, the substance gave of s. w. t calories to the calorimeter ; see 49. Hence W T = s w. t from which the specific heat s of the substance W. T s= - w. t 51. By means of a lead weight or ball of w = 500 grams, heated i n the water of the water bath to about 90°, then immersed into a beaker-calorimeter containing about 300 grams of water of common temperature, the specific heat of lead may be determined by the student. About one hundred grams of glass fragments, heated in a beaker on the water bath, will also give a good re- sult. 52. Careful experiments of this kind have given for Fusing and Boili?uj. 21 the following bodies the specific heat given opposite the names : MINERALS. Marble 0.216 cal. Calcite 0.205 " Siderite 0.182 Hematite 0.164 Pyrite 0.130 Blende 0.115 JBarite ..0.109 Galenite 0.053 Glass 0.198 Water 1.000 Air 0.237 METALS. Lead 0.031 cal Platinum 0.032 " Gold 0.032 " Mercury 0.033 " Tin 0.056 " Silver 0.057 " Copper .... ....0.096 " Brass 0.094 " Zinc 0.096 " Iron 0.114 " Phosphorus 0.189 Sulphur 0.203 Charcoal 0.241 Accordingly it requires only 33 calories to heat 100 grams of mercury 10 degrees, while it requires 1000 calories to heat an equal weight of water the same num- ber of degrees. IV. FUSING AND BOILING. 53. The conversion of a solid into a liquid by means of heat is termed f u s i o n (see 4, and also Elements of Physics, 113 and 151). But not all substances are fusi- ble; some are volatized or even decomposed ( see 6 ) by heat, without fusing. The change from liquid to solid by cooling is termed solidification. 54- Volatilization is the conversion of a liquid into vapor or gas by means of heat. But not all liquids are volatile, some decomposing (see 5) by heat without volatilization. Water, kerosene, and alcohol are volatile liquids; sweet oil is a non-volatile liquid. Liquids, which are non-volatile are, also, at times, called fixed liquids. By cooling, the vapor formed is condensed again to a liquid. This change of aggregation is also often called 1 i q u e f a c t i o n.* *The water on the surface of the earth shows all these changes in aggregation on a grand scale ( see Cosmos). It evaporates, and as steam forms part of the ai- Chapter I. 55. Yolatization takes place mainly at the surface of the liquid ; hence it is accelerated in wide and shallow vessels. If a liquid is volatilized intentionally the process is also called evaporation. This operation is usually performed on the water bath. If the liquids yield combustible or obnoxious vapors, evaporation lias to be performed with great care in appa- ratus specially prepared for this purpose. 56. K a volatile liquid such as w a t e r is heated in a flask on a sand bath, volatilization at the surface will soon be accompanied by the formation of small bubbles of vapor at the bottom and walls of the flask. These bub- bles will ascend, and diminish in size, producing the well- known simmering sound. After some further heat- ing, the bubbles formed will no longer condense, but rise through the liquid, increasing in size as they rise to the surface, where they burst. The liquid will at the same time be put into a violent commotion by these bub- bles. In this state the liquid is said to b o i 1. Hence : A liquid boils when vapor is formed throughout its entire mass in bubbles, which increase in size as they rise through the liquid, thereby commoting the liquid. 57. If the vessel be completely closed, the liquid will not boil ; vapor will continue to form until the pres- sure thereof opens the vessel by explosion. It is not even necessary that the vessel should be com- pletely closed ; if the opening be insufficient to permit the vapor to escape as fast as formed, explosions may also inosphere at all times. Upon cooling, a portion of this steam condenses, and becomes visible as cl ouds, f og s or dews. Kain is condensed vapor de- scending from higher parts of the air. Hail, snow, frost, and ice result when the temperature sinks below the freezing point. Fusing and Boiling. 23 occur upon continued heating. Examples : accidental explosions of steam boilers. 58. In the process of distillation, boiling and liquefaction take place at the same time in different por- tions of the apparatus. A distilling apparatus, therefore, always consists of two parts, the fl a s k or retort, where- in the liquid to be distilled is boiled, aud the co n d e n- s er, wherein the vapor formed is liquefied again. The heat imparted to the liquid in the flask, to convert the liquid into vapor, has to be removed from the vapor in the condenser in order to re- convert the vapor into liquid. This is usually accomplished by passing a slow current of cold water along the tube wherein the vapor escapes from the flask. If the volatilized substance condenses to the solid form, this process is no longer called distillation, but sublimation. 