i GIFT 'OF Mrs. G. N. LeYfis . E L E M EN T S OF CHEMISTRY; IN WHICH THB RECENT DISCOVERIES IN THE SCIENCE ARE INCLUDED AND ITS DOCTRINES FAMILIARLY EXPLAINED. JUlitstratcti b^ Numerous JEnsratofnfl*, AND DESIGNED FOR THE USE OP SCHOOLS AND ACADEMIES. BY J. Ii. COMSTOCK, M. D. A!cm. Con. M. S. ; Hon. Mem. R. I. M. S. ; Author of Notes to Conv. on Chemistry; Author of Gram, of Chemistry; of Elem. Mineralogy; of Nat History of Quadrapeds and Birds ; of Syst Natural Philosophy, &c. NINETEENTH EDITION. Wtto-lTorfc: PUBLISHED BY ROBINSON, PRATT, & CO. No. 259 PEARL STREET; AND SOLD BY THE PRINCIPAL BOOKSELLERS THROUGHOUT THE UNITED STATES. DISTRICT OF CONNECTICUT, gg. Ii. S. BE IT REMEMBERED, That on the second day of March, in the fifty-fifth year of the Independence of the United States of America, J. L. Comstock, of the said District, hath deposited in this office the title of a Book, the right whereof he claims as Author, in the words following, to wit : " Elements of Chemistry, in which the recent Discoveries in the Science are included, and its Doctrines familiarly explained. Illustrated by numerous Engravings, and design- ed for the use of Schools and Academies. By J. L. Comstock, M. D. Mem. Con. M. S. ; Hon. Mem. R. I. M. S. ; Author of Notes to Conv. on Chem. ; Author of Gram. Chem. ; of Elem. Mineralogy; of Nat. Hist, of Quad, and Birds; of Syst. Nat. Philosophy, strutted thermometers ? What fluid was first employed to indicate the variations of temperature ? 36 THERMOMETER. Fig. 12. A better construction for an air thermometer is represented at Fig 12. It consists of a thin glass bot- tle, containing a small quantity of a colored liquid, and stopped closely by a cork. Through the cork is passed a broken thermometer tube, open at both ends. This tube descends nearly to the bottom of the bottle, and dips into the fluid. There is, therefore, a quantity of air above the fluid which cannot escape, and when this expands by the application of heat, the fluid is forced up the tube. Thus the height of the fluid will indicate the expansion of the air, and consequently, the degree of heat to which the instrument is exposed. There are, however, two objections to the employment of air for this purpose. 'Jts expansions and contractions are so great even by small changes of temperature, that a tube, se- veral feet in length would be required to measure them) and as air suffers condensation by pressure, the variation of the barometer would affect its height, at the same temperature. For these reasons, the air thermometer, for common pur- poses, is both inconvenient and inaccurate, and therefore has long since been laid aside. There is, however, a modifica- tion of this instrument, invented by Mr. Leslie, and called the differential thermometer, which for certain purposes is a very elegant and useful instrument. Fig. 13. A drawing of this instrument is represented by OFig. 13, and it is designed, as its name imports, to _ shew the difference of temperature between two places at short distances from each other. It con- sists of a glass tube terminated at each end by a bulb, and bent as shown in the figure. The tube is partly filled with some colored fluid, as sulphu- ric acid, tinged with carmine, or alcohol, colored by cochineal, the bulbs and other parts of the tube being filled with air. It will be obvious, from the construction of this instrument, that it cannot indicate the temperature of the atmosphere, since an equal expansion of the air in both bulbs would press equally on the fluid in both legs of the tube, and consequently it would rise in neither. But if one bulb is ex- Describe the construction of an air thermometer. What i>re the objections to air ther- mometers? How is the differential thermometer constructed, and for wheat purposes is : useful. THERMOMETER. 37 posed to a higher temperature than the other, then the ex- pansion of the air in this, will be greater than in the other, and consequently the fluid will rise towards the bulb where the air is least expanded. The use of this thermometer, then, consists in showing the difference of temperature to which the two bulbs are exposed, as in experiments on the radiation of heat, already described. The scale affixed to one of the legs, shows the rise in degrees, and is divided into 100 parts. The legs are six inches long, and the bulbs an inch or a little more in diameter. The stand may be of glass or wood. Some of these instruments are so delicate as to be affected by the approach of the hand. Air, being inapplicable to the construction of thermometers for the purpose, of measuring the absolute temperature of places or thingk, for the reasons already noticed, solid bodies are equally so from a contrary defect ;' s their expansion by heat being so small as not to be appreciated without the adaptation of complicated machinery. A perfect substance foi this purpose, would be a fluid, \which would expand uni- formly with equal increments of heat, and which would nei- ther freeze nor boil at any temperature to which it might be exposed Mercury approaches nearer to these conditions than any other substance*, and therefore this is the fluid now almost universally employed. The blowing of the best thermometer tubes requires much experience and skill in the workmen, and is performed only by particular artists. This is the most difficult part of its construction. The mercury is introduced by heating the bulb, and thus rarefying the air within it, and then dipping the open end of the tube into a vessel of the fluid. As the air contracts within by cooling, the pressure of the external at- mosphere forces the mercury to enter the tube to supply its place. When the bulb is nearly filled in this way, the mer- cury is boiled, to expel the air. Having filled about one third of the tube, the open end is sealed hermetically, that is, by melting the glass. This is done while the mercury in the bulb is heated nearly to its boiling point, so as to exclude all the air. Having sealed the end of the tube, the next step in the , Why will not the differential thermometer indicate the temperature of the atmos- phere 1 Why are not solid bodies proper for the construction of thermometers ? What would be a perfect substance for the construction of thermometers? What is the most perfect fluid in our possession for this purpose ? How are thermometer tubes filled! 4 38 THERMOMETER. construction of the thermometer, is its graduation. This is done by ascertaining two fixed and invariable points on the tube, which are the same in every thermometer, and then by making a scale of equal divisions between these two points. These are the freezing and boiling points. The freezing point is found by immersing the bulb of the thermometer in melting snow or ice, for it has been as- certained, that the temperature of water flowing from melting snow or ice, is every where the same, whatever may be the heat of the atmosphere where the experiment is made. The boiling point is slightly affected by the pressure of the atmos- phere ; but the thermometer will be sufficiently accurate for all ordinary purposes, when this point is ascertained by im- mersing the bulb in pure boiling water, open to the air, and on the level of the sea, during pleasant weather. (See Ba- rometer, in Nat. Philosophy.) Fig. 14. The freezing and boiling points are marked with a diamond or file, on the tube ; and on the scale to be afterwards affixed, the freezing point, is marked 32, and the boiling point,' 212. The interval be- tween these two points is then accurately divided in- to 180 equal parts. This is the division of Fahren- heit's scale, the thermometer generally employed in this country, and is the only scale referred to in this work. The commencement of this scale is 32 degrees below the freezing point, and is called zero, being marked with the cipher 0, to signify the total ab- sence of heat. This degree of cold, it is sup posed, Fahrenheit obtained by mixing snow and common salt, and it was probably the greatest de- gree of cold known in his time, though at the pre- sent day certain mixtures produce much greater, and at a future period, the progress of science may show the means of abstracting heat, so as to solidify even the air we breathe. The absolute zero must therefore be considered an imaginary point. Besides the Zero and the freezing and boiling points, marked on Fahrenheit's scale, Fig. 14, there are also noted the temperature of the blood, and the heat of summer, and sometimes other points, as fever heat, &c. How is the freezing point of the thermometer ascertained? How is the boiling point ascertained 1 COLD. 39 Cold. Cold is a negative condition, and depends on the absence, or privation of heat. Intense artificial cold may be produced 'by the rapid absorption of heat during the conversion of solids into liquids. Dr. Black long slace discovered the principle, that when bodies pass from a denser to a rarer state, heat is absorbed and becomes latent in the body so transform- ed, and consequently cold is produced. And also that when bodies pass from a rarer to a denser state, their latent heat is evolved, and becomes sensible. It is known to almost every one, that dissolving common salt in water, particularly if the salt is fine, will render the water so cold, even in summer, as to be painful to the hand. The salt, as it passes from the solid to the liquid state, absorbs caloric from the water, and thus the heat that was before sen- sible, becomes latent, and cold is produced. On the contrary, when a piece of lead or iron, is beaten smartly w^th a hammer, it becomes hot,, because the metal, in consequence of the hammering, has its capacity for calorie reduced, and thus the heat which was before latent, now be- comes sensible. For the same reason, when air is compress- ed forcibly in a tube, or as it is sometimes called, in a fire- pump, as already explained, the heat, which was before latent, becomes sensible, because the condensation lessens its capa- city for caloric. The principle on which all freezing mixtures act, is there- fore the change of state, which one or more of the articles employed undergo, during the process, and this change con- sists in an enlarged capacity for caloric. The degree of cold will then ' depend on the quantity of caloric which passes from a free to a latent state, and this again will depend on the quantity of substance liquefied, and the rapidity of the liquefaction. '' What numbers are marked on the scale at the freezing and boiling points ? What is the number of degrees between these two points 1 What does zero signify 1 How far below the freezing point is the zero of Fahrenheit 1 Is the point of the absolute zero known? What is cold? How may intense artificial cold be produced 1 When bodies pass from a denser to a rarer state, is heat or cold produced ? How is the temperature of water generally known to be affected by dissolving common salt in it ? How is thia change of temperature accounted for ? Why does a piece of iron become hot by ham- mering ^ How do you account for the heat evolved, where air is compressed 1 What is the principle on which freezing mixtures act 7 On what circumstance will the degree of cold produced by freezing mixtures dej)end 1 40 COLD. The substances most commonly employed for this purpose JOLTB those originally used by Fahrenheit, to produce the zero of his thermometric scale ; viz. common salt and snow, or pounded ice. For this purpose the salt should be fine, and the ice, which must always be used in summer, is to be re- duced to small particles in a cold mortar. Fig. 15. The vessel to contain the substance to be :p frozen, may be made of tin, and of the shape represented by Fig. 15. It is simply a tall ves- sel, holding a few pints, with a close cover, and a rim round the top, for the convenience of handling it. For common purposes, this may be set into any convenient wooden vessel, (hav- ing first introduced the substance to be frozen,) and then surrounded by the freezing mixture. The only care to be taken in this part of the process is, to see that the freezing mixture in the outside vessel reaches as high as the con- tents of the internal one. With two or three pounds of fine common salt, and double this Aveight of pounded ice, three or four pints of iced cream may be made in this way, during the warmest days of summer. The process requires two or three hours, and while it is going on, the vessel should be set in a cellar, or covered with a flannel cloth, as a bad conductor of the external heat. When the thermometer is at 32, the cold generated by the above process, sinks it down to zero, as above stated. By this method, two solids are changed into liquids, and both du- ring the change, absorb caloric from the contents of the inner vessel. The salt melts the ice in consequence of the avidity with which it imbibes moisture, or by reason of its affinity to water, and the water in its turn dissolves the salt. Other substances having a stronger affinity (see affinity) for water than common salt, will produce the same effects still more powerfully. Thus, muriate of lime (see this article) five parts, and ice four parts, will sink the thermometer from 32 to 40 below zero, that is, in the whole, 72 degrees. At this temperature, mercury freezes. A still more effective mixture is four parts of fused potash, and three parts of snow. What are the substances most commonly used as freezing mixtures ? Explain Fig. 15, and show how it is to be used. How far below 32 degrees will a mixture of ice and common salt sink the thermometer 1 Why does the salt melt the ice 1 What substance sinks the thermometer from 32 to 40 degrees below zero? SOURCES OF CALORIC. 41 This is said to sink the mercury from 32 to 50 below zero, that is, 82 degrees. In these experiments the thermometers are rilled with alcohol, instead of mercury. Freezing mixtures are also made of a solid and a fluid. One of the most effectual of this kind is composed of diluted sulphuric acid and snow, or pounded ice. This sinks the mercury from 32 to 23 below zero. Though ice or snow is commonly employed for this pur- pose, still powerful frigioric effects may be produced without either, the absorption of caloric being caused by the rapid solution of a salt in a fluid. One of the most common and cheap among these is a mixture of sulphate of soda or Glau- ber's salt, and diluted sulphuric acid. This sinks the mer- cury from 50 to 3 above the freezing point, that is 47. In describing experiments of this kind, it should always be noted from what point the thermometer begins to descend, otherwise no judgment of the power of the freezing mixture can be formed^ If, for instance, a mixture would cause the depression of the thermometer from, and below any given point, then by repeating the process continually, we should be able to find the absolute zero. Thus, by means of muriate of lime and snow, the thermometer is made to sink 82, that is, from 32 above, to 50 below zero. Now if the same cause would again produce the same effect, by its re-appli- cation, the thermometer would sink to 132 below zero, a degree of cold never yet produced by any means. But an unlimited degree of cold can never be produced by the art of man ; for it is found on experiment, that when the tempera- ture produced by the freezing mixture is greatly below that of the air, the caloric is so rapidly communicated, as, to pre- vent any effect by repeating the process. Mr. Walker, who made a great number of experiments on this subject, was never able to produce a greater degree of cold than that of 100 below the zero of Fahrenheit. Sources of Caloric. The sources of caloric may be reduced to six, viz. The In these experiments, why is alcohol used to fill the thermometer, instead of mercury 7 What is said of sulphuric acid and snow, as a freezing mixture 1 What substances form A freezing mixture without the use of ice or snow? In making experiments with freezing mixtures, why is it necessary to state the degree from which the thermometer begins to fall 1 What is the reason that an unlimited degree of cold ca"mot be produced by art ? What is the greatest degree of cold ever produced ? What are the sources of caloric 7 42 SOURCES OF CALORIC. Sun, Combustion, Electricity, the bodies of living- warm blooded animals, Chemical action, and Mechanical action. The Sun constantly radiates caloric to the earth, and is the great fountain of heat to us and to the whole solai system. Combustion. This supplies the heat employed in the arts, and for culinary purposes. ' In this process the caloric is ex- tricated from the oxygen of the atmosphere, as it unites with the burning body and supports its combustion. The light is supposed to be furnished by the burning body. Electricity. Whenever two bodies in opposite electrical states are made to approach each other, so as to produce a discharge through the air, or along a nonconductor,, there appears a flash of light attended by heat. By the action of Galvanism, which is a modification of electricity, the most intense heat hitherto known has been produced. ' When the electric fluid passes through a piece of metal, or other conductor, of sufficient size, no phenomena are produ- ced ; but in its passage through a nonconductor, or through a conductor which is too small to admit of a free passage, heat is produced. (See Electricity, in Nat. Philosophy.} Vital action. The bodies of air breathing animals are a continual source of heat. The numerc||s theories which have been invented to account for the cause of animal heat cannot here be investigated. That it however depends on the oxygen of the atmosphere which we breathe, seems to be proved by the fact, that animal warmth cannot for any length of time be sustained without it. Chemical action. Chemical action without combustion is capable of producing considerable degrees of heat. If water be thrown on unslacked quicklime, in small quantities at a time, its heat will be gradually augmented to nearly 1000 deg., or so as to ignite wood. The heat in this experiment is accounted for, on the law already explained, that when bodies pass from a rarer to a denser state, caloric is evolved. The slacking lime absorbs the water and retains it as a part of its substance, and thus a fluid is converted into a solid, with the evolution of much caloric. What is the great fountain of heat ? How is heat extricated by combustion 1 When does electricity produce heat 1 What is the cause of electrical heat, according to Sir H Davy 1 What is said of vital action, as a cause of heat 1 What is said of chemical ac- tion as the cause of heat ? How is the heat produced by throwing water on quicklime, accounted for! i SOURCES OF CALORIC. 43 If three parts of strong sulphuric acid and one of water be suddenly mixed together, a degree of heat considerably, above that of boiling water will be produced. In this case the heat is also accounted for on the principle of condensa- tion, for if the two fluids be measured before and after mix- ture, it will be found that their union has occasioned a loss of bulk, and probably also a loss of capacity for caloric. The inflammation of Spirit of Turpentine by nitric acid is a case of intejise chemical action, in which 1000 de- grees of heat are evolved. About an ounce of the turpentine with the same weight of nitric, mixed with a little sulphuric acid, are the proportions. The acid should be poured on the turpentine from a vessel tied to a line several feet long, as the explosion . sometimes throws the burning matter to a considerable distance. Mechanical action. This includes percussion, friction, and condensation. Caloric is evolved by the percussion of hard bodies against each other. This is owing to the condensation of the body struck, in consequence of which its latent heat becomes sen- sible. If a piece of soft iron be struck smartly several times with a hammer, on an anvil, it becomes hot, and even red hot, if the experiment be well conducted. When a piece of steel and a flint are struck together, the condensation produces so much heat as to set fire to the mall particles of steel which at the same time are struck off y'the blow. j Friction. Caloric is evolved, or produced by friction. The friction of machinery when the motion is rapid, frequent- ly causes so much heat as to set the wood on fire. The in- habitants of various nations obtain fire by rubbing pieces of dry wood together. The friction of carriage wheels some- times sets them on fire. The principle on which caloric is produced by friction has not been demonstrated. It cannot be referred to condensa- tion, since the rubbing of two soft bodies together, such as When sulphuric acid and water are mixed, what is the cause of the heat produced 1 How may spirits of turpentine be inflamed by chemical action ? What does mechan- ical action as a source of heat include? How is the evolution of heat by percussion accounted for ? When a piece of steel is struck by a flint, how is the fire produced ? How is the heat produced by friction accounted for? How does condensation pro- duce heat ? 44 LIGHT. the hand against the coat sleeve, or the two hands against each other, causes heat. Count Rumford, who made a laborious and varied course of experiments on this subject, was led to the conclusion that the heat produced by friction could not be connected with the decomposition of oxygen gas, nor with the increase oi density, nor could it be caused by any change in the specific caloric of bodies. Others have also made experiments with a view to determine this question, but as yet no one has pre- tended to give any satisfactory explanation of its cause. The Condensation of an elastic fluid by sudden pressure causes heat, as has already been explained, and illustrated by Fig. 11. The heat evolved in this case arises simply from the diminished capacity of the air for caloric, in conse- quence of its increased density. Light. The next imponderable agent which falls under our notice, is light. ,The investigation of the properties of light, its laws of reflection and refraction, and its effects on the sense of vision, and subjects belonging to the science of Optics. (See Optics in Nat. Philosophy.) Some of the effects of light are however properly considered here, since they pro- duce chemical phenomena. Light may be decomposed by means of a prism, into seven primary colours. The succession of these colors, beginning with the uppermost, is violet, indigo, blue, green, yellow, or- ange, red. The decomposition of light, only requires that a ray shoulcF be admitted through a small aperture into a room, and made to pass through a triangular prism, as represented by Fig. 16. 15 The direction of the ray towards the point c will be changed bv ithe refractive power ol the prism, and at the same time it will be de- composed into the col- To what science does the investigation of the properties of light, with its effects on the sense of vision, belong ? Why do some of the effects of light properly belong to the investigations of chemistry 1 Into how many primary colors may light be divided? What is the succession of these colors, beginning with the uppermost ? How may the lecomposition of be light effected? LIGHT. 45 ors already named, the violet corresponding with 1. and the red with 7. It may be observed by the figure, that the red is refracted least, and the violet most, from the direction of the original ray, these two colours terminating the under and the upper parts of the spectrum. These seven, are called the primary colours, since they cannot by any known means be again decomposed, or sepa- rated into other colours. The whole seven are called the solar spectrum. The heating powers of these several colours are different. Take a sensible air thermometer (fig. 13) and move the bulb in succession through all the coloured rays, waiting at each for the fluid to rise, or fall. ..The thermometer will be found to indicate the greatest heat in the red ray, next in the green, and so on in a diminishing ratio to the violet. When the thermometer is moved a little beyond the red ray, but in a line with the spectrum, the heat is still greater than in the ray itself. These heating rays are invisible to the eye, and hence it is concluded that there exists in the so- lar beam, a distinct ray which causes heat, but no light. The illuminating power of each primary ray in the solar spectrum, is different from the other. This is proved by permitting the spectrum to fall on a large printed sheet, of the same sized type, when it will be found, that at the same distance, the parts illuminated by some of the rays can be read, while those illuminated by others are indistinct. Light is capable of being absorbed by certain substances ; of remaining in them for a time, and then of being extricated unaltered. Such bodies are called solar phosphori. Phosphorescence. Phosphorescence may be defined, the emission of light without sensible heat, or without combustion. A considerable number of substances have the power of absorbing a quantity of light when exposed to the rays of the sun, and of emitting it again, so as to become luminous in Which ray is most, and which is least refracted, from the direction of the original ray 1 What are these seven colours called ? What are the whole called ? What is said of the heating powers of the different rays 1 Is the greatest heating power in the red ray, or beyond it 1 Are "the heating rays visible, or invisible! How is it proved that the illuminating powers of the different rays differ 1 . What is phosphorescence ? What are solar phosphori ? What is said of the power of bodies to absorb and emit light! 16 PHOSPHORESCENCE. the dark. Most substances lose this property in a short time, but acquire it again by another exposure to the sun, and this may be repeated any number of times. Several substances by this treatment become so luminous as to render minute* objects visible in the dark. Canton's phosphorus is of this kind, and may be prepared as follows : (Calcine common oys- ter shells in the fire for an hour ; then select the purest and whitest parts, and reduce them to fine powder. Mix three parts of this powder with one of sulphur, and having pressed the mixture into a crucible, keep it red hot for one hour. Then let the crucible cool, and select the brightest and purest parts, which cork up in a dry vial for use/ When this composition has been exposed for a 'few minutes to the light of the sun, and then carried into the dark, it will be sufficiently luminous to show the hour by a watch dial. The same property is possessed by compositions called Homberg's and Baldwin's phosphorus. The diamond, also, possesses this property, as shown by the celebrated experi- ment of Dufay, who,! having exposed a diamond to the light, immediately covered it with wax, and on removing the wax several months afterwards, found that it shone in the dark. Some substances phosphoresce by friction ; some by scratching, and others by heat. N ; That variety of carbonate of lime called dolomite, gives light on being rubbed. Loaf sugar mixed with whites of eggs and dried, as is done for the frosting of cake, emits a streak of light on being scratched with a sharp point. Several va- rieties of fluate of lime, and of marble, emit light when coarsely powdered and thrown on a hot plate of iron, so as to be seen in the dark. A piece of tobacco pipe, or a piece of quicklime, when heated by the compound blowpipe, or by other means to a degree which would only make other bodies red, give out a brilliant phosphorescent light, which is so intense as to be come intolerable to the eyes. Another kind of phosphorescence may be observed during the decomposition of certain animal substances. Thus, if a small piece of fresh herring, or mackerel, be put into- a two What is Canton's phosphorus 1 How is Canton's phosphorus prepared 7 What i3 necessary in order to make this substance shine in the dark ? How did Dufay confine the light in a diamond? What is said of the phosphorescence of other substances'? What is said of the phosphorescence of a piece of tobacco pipe, or quicklime ? How may piece of fish be made to exhibit phosphorescence 7 PHOSPHORESCENCE. 47 ounce vial of sea water, or into pure water, with a little com- mon salt, and the vial be kept in a warm place for two or three days, there will then appear a luminous ring on the surface of the water, and if the vial be shaken, the whole will give a phosphorescent light. Light produces very material effects on the growth of all vegetables, t from the most humble plant, to the tallest tree of the forest. Plants, vegetating in the dark, are white, feeble, almost tasteless, and contain but little combustible or carbo- naceous matter. On exposing such plants to the light of the sun, their colours become green, their tastes become much more intense,' and the quantity of their combustible matter becomes greatly increased. These changes are strikingly obvious, and beyond all doubt depend on the agency of light. Light not only affects the naMral, but in many instances, the artificial colours of things^Rn this respect, however, its effects appear not to be red^Rle to any general taw, for in some instances it destroys, jK. in Others it augjpients, or even creates, the colours of bodkC * J 7 On exposing bees wax to the fun and moj/ture, its coloui is discharged, and it becomes white ; it is^also 'well known that the colours of printed goods, and of casrats, are changed or faded, by the same influence; and that Be former mode of bleaching, consisted in exposing the cl$fi to the united influence of light, air, and moisture. On the contrary, the colours of plants appear to be exclu- sively owing to their exposure to light, and various chemical preparations, such as phosphorus, and the nitrate and chloride of silver, become dark coloured, and even black, by the influ- ence of light. Light has also an important and curious influence on the crystallization of salts. Make a strong solution of the sul- phate of iron, in water, and place it in a shallow dish. Cover one half of the dish with a black cloth, and set it in a darkened room, permitting only a single ray of light to enter, so as to strike upon the solution in the uncovered part of the cHlL. Thus one half of the solution will be exposed to the light, while the other half will be in darkness. After, the dish has stood in this situation for a day or two, it will be fourfS. that no How are plants affected by growing in the dark ? What changes ate effected by the light of the sun on plants which have grown in the dark ? How are the artificial colours of things affected by light! To what do the colours of plants appear to be entirely owing'/ What substances become dark coloured by the influence of light? 48 ELECTRICITY. signs of crystallization are to be seen in that part of the solu tion which has been kept in the dark, while that part which has been exposed to the light will be completely crystallized. Another curious fact connected with this subject, is, that plants emit oxygen gas, through the influence of the sun's light. To make this obvious, fill a tall glass vessel, such as a bell glass, with water, and invert it into another vessel of water. Then introduce into the bell glass some sprigs of mint or any other plant of vigorous growth, and expose the whole to the action of the sun. Small bubbles of air will soon ap- pear, as though issuing from the leaves of the plant. These will, one after another, detach themselves and arise to the upper part of the vessel, and on examination, the air thus extricated will be found to consist of very pure oxygen gas, (See Oxygen.) In this experiment, the water serves only as the means of collecting the oxygen ; the water itself not being decomposed by the plant, but only the air which it contains. The air which we breathe contains^ quantity of carbonic acid, which is decomposed l$y the organs of the plant, the carbon being retained, while the oxygen is emitted. (See Vegetation.) Electricity. The third imponderable agent is Electricity, including Galvanism. The ancients knew nothing of electricity as a science. They knew indeed that amber and glass, when rubbed, would attract light substances ; and about the beginning of the eigh- teenth century, it was discovered that a certain stone called tourmaline, would attract feathers and hair when heated, and that some precious stones would do the same when rubbed. As an important science, electricity can claim no higher date than the age of Franklin. Galvanism is of much more recent date than electricity, science owes its name and origin to an accidental dis- ery made by Galvani, an Italian, in 1791. Galvani was professor of anatomy at Bologna, and his great discovery seems to have been owing indirectly to the sickly condition of his ^fe. This lady being consumptive, was advised to How is it shown that light has an influence on the crystallization of salts ? How is it BF demonstrated thai plants emit oxygen gas through the influence of the sun's light ? De- scribe the chemical changes by which plants extricate oxygen gas. Was electricity known to the ancients as a science 1 What is the date of electricity as a science? To what, circumstance does galvanism owe its origin ? ELECTRICITY. 49 lake soup made of the flesh of frogs, as the most delicate nu- triment. One of these animals, ready skinned, happened to lie on a table in the professor's laboratory, near which stood an electrical machine, with which a pupil was making expe- riments. While the machine was in action, the pupil chan- ced to touch one of the legs of the frog with a knife which he held in his hand, when suddenly the dead animal was thrown into violent convulsions. This singular circumstance excited the attention of the sick lady, who was present, and it was communicated to her husband, who was out of the room at the time. Galvani immediately repeated the experiment, and soon found that the convulsions took place only when a spark was drawn from the electrical machine, the knife at the same time touching the nerve of the frog. He also ascertained from further investigations, that the same contractions were excited without the agency of an electrical machine, provi- ded he employed two metals, such as zinc and silver, one of which was made to touch the nerve, while the other touched the muscle of the frog. [See Galvanism,] It is from such a beginning that the now important science of Galvanism had its origin. Electricity, as an agent, is considered as an exceedingly subtle fluid, so light as not to affect the most delicate ba- lances,-^ moving with unmeasurable velocity, and pervading all substances. It is therefore its effects on other bodies, only, or its phenomena, which it is in our power to examine. The simple facts on which the whole science of electricity is ^founded, may be stated in a few words. If a piece of glass, amber, or sealing wax, be rubbed with the dry hand, or w r ith flannel, silk, or fur, and then held near small light bodies, such as straws, hairs, or threads, these bodies will fly towards the glass, amber, or wax, thus rubbed, and for a moment will adhere to them.' The substances hav- ing this power of attraction, are called electrics, and the agen- cy by which this power is exerted is called electricity: Some bodies, such as certain crystals, exert the same power when heated, and others become electric by pressure. Although these are simple facts on which the science is based, yet electricity exhibits a vast number of curious and What is said of electricity as an agent 7 Is it in our power to examine electricity as a eubstance 1 How are we enabled to examine the properties of this agent ? Describe the simple phenomena of electricity. What are electrics? What is electricity ? By what process besides friction, do some bodies become electric ? g 50 ELECTRICITY. Fig. 17. interesting phenomena, depending on the variety and kind of machinery, and the quantity of the electrical influence employed. When a piece of glass, or other electric, has been rubbed, so as to attract other bodies, it is said to be excited, and it it is found that most substances /are capable of this excitement when managed in a peculiar manner. The most common are, amber, glass, rosin, sul- phur, wax, and the fur of animals,' When an excited electric is presented towards a small ball, made of pith, or cork, and sus- pended by a string, Fig. 17, the ball is attracted t.o the elec- tric, and adheres to it for a moment. And if two such balls be suspended so as to touch each other, and the excited Fig. 18. electric be made to touch one of them, the other will instantly recede from the one so touched, that is, they will mutually repel each other, and remain for a short time in the posi- tion shown by Fig. 18. If while they are in this position, one of them be touched with the finger, or a piece of metal, they will again in- stantly attract each other, and come together, and if suspended apart, will forcibly approach each other, as represented by Fig. 19. Fig. 19. In the explanation of these phenomena, we sup- I pose that all bodies are pervaded with the electric fluid, but that when in equilibrium, like air and water, it produces no obvious effects, and that it is only when this equilibrium is disturbed, or when some bodies contain more of the fluid than others, that electrical effects can be produced. When an electric is rubbed with the hand, or other exciting substance, it receives a portion of the electric fluid from that substance, consequently the electric, then, has a greater portion of electricity than is natural, while the hand, or other substance, has less. When two bodies are in different When is an electric said to be excited? What are the most common electrics! What effect does an excited electric produce on a suspended pith ball 7 What is the effect on two pith balls in contact? When the balls are thrown apart by repulsion, what effect is produced by touching one of them with the finger 1 Explain these phenomena. Are all bodies supposed to be pervaded by the electrical fluid ? Sup- pose an electric is rubbed by the hand, does it in consequence contain more or less electricity than before? Whence does the electric obtain this additional quantity ol electricity ? ELECTRICITY. 51 electrical states, that is, when one has more, or less than the natural quantity, they attract each other. This is illustrated by Fig. 1 7, where the ball is represented as moving towards the excited electric. But when two bodies have each more or less than the natu- ral quantity, they repel each other. This is illustrated by Fig. 18, where the repulsion is caused by the communication of an uncommon share of the fluid from the excited electric to one ball, and from this ball to the other, and thus the two balls have more than their ordinary quantity of electricity, and are in the same electrical state. On touching one of the balls with the finger, they again attract each other, |because the finger deprives this ball of a part of its electricity,.- while the other ball is not affected, and thus the two balls are thrown into different electrical states. This is illustrated by Fig. 19. To account for electrical phenomena, Dr. Franklin sup- posed, as above stated, that all terrestrial things had a natural quantity of that subtle fluid, but that its effects became appa- rent, only when a substance contained more or less than the natural quantity, which condition is effected by the friction of an electric. Thus, when a piece of glass is rubbed by the hand, the equilibrium is lost, the electrical fluid passing from the hand to the glass, so that now the hand contains less, and the glass more, than their ordinary quantities. These two states he called positive and negative, implying the presence and absence of the electrical fluid. If now a conductor of electricity, such as a piece of metal, be made to touch the positive body, or is brought near it, the accumulated fluid Avill leave this, body and pass to the conductor, which wiL then contain more than its natural quantity of the fluid. But if the conductor be made to touch a negative body, then the conductor will impart a share of its own natural quantity of the fluid to that body, and consequently will contain less than ordinary. Also, when one body, positively, and the other negatively electrified, are connected by a conducting sub- stance, then the fluid rushes from the negative to the positive side, and the equilibrium is restored. When do bodies attract each other through the influence of electricity? When do bodies repel each other through this influence 1 When the balls are thrown apart by repulsion, why do they attract each other on touching one of them with the finger 1 How are these phenomena accounted for on Dr. Franklin's Hneory 1 What are the posi rive and negative electrical states ? ELECTRICITY. This theory, originally invented by Dr. Franklin, will ac- count satisfactorily for nearly every electrical phenomenon. There is, however, another theory, that of Dufay, which is still embraced by some writers. This theory supposes that there are two kinds of electrici- ty, which are termed the vitreous and resinous, corresponding with the positive and negative of Franklin. This theory is founded on the fact, that when two pith balls, cr other light bodies, near together, are touched by an excited piece of glass, or sealing wax, they repel each other. But if one oi the balls be touched by the glass, and the other by the wax, they will attract each other. Hence Dufay concluded that electricity consists of two distinct fluids, which exist together in all bodies: that these two fluids attract each other, but that they are separated by the excitation of an electric, and that when thus separated, and transferred to non-electrics, as to the pith balls, the mutual attraction of the twp electricities, causes the balls to rush towards each other. The electricity corresponding with the positive of Franklin, is called vitreous, 'because it is obtained from glass; while the other is called resinous, because it is obtained from wax and resin. In respect to the merit of those two theories, we can only say here, that Franklin's is by far the most simple, and ac- counts equally well for nearly every electrical phenomenon. Somebodies permit the electrical fluid to pass through them without difficulty. These are called conductors. They are the metals, water, and other fluids, except the oils, steam, ice, and snow. The best conductors are gold, silver, platina, brass, and iron. The conductors are non-electrics, that is, they show no signs of excitement when rubbed, under com- mon circumstances. The electrics are non-conductors, that is, they will not conduct the electric fluid from a negative to a positive substance, and when excited, this fluid accumulates on their surfaces, because they have not the power of con- Does Dr. Franklin's theory account for most of the phenomena observed ? What do the positive and negative states imply 1 How does Dufay's theory differ from Franklin's? How do the vitreous and resinous electricities of Dufay correspond with the positive and negative of Franklin? Why is one kind of electricity called vitreous and the other resinous ? Which theory is said -to be the most simple, and therefore to be preferred 1 What bodies permit electricity to pass through them without difficulty, and what are they called ? What are the best conductors ? What is the difference between conductors and non-conductors 7 ELECTRICITY. 53 ducting it away. A body is said to be insulated, when it is supported by a non-conductor. A man standing on a stool supported by glass legs, or standing on a cake of wax, is in- sulated. When one body, or system of bodies, is in the posi- tive state, the other part, or system, being contiguous, is in- variably in the negative state. If one end of a stick of seal- ing-wax, or glass rod, be positive, the other end will be nega- tive, and if one side of a plate of glass be positive, the other side will be negative. (See Electricity in Nat. Philosophy.} Chemical Effects of Electricity. The chemical effects of electricity are most conspicuous in that form of this agency known under the name of Gal- vanism, but there are many instances in which common elec- tricity produces important chemical changes. When powerful electrical discharges are passed through a glass tube containing pure water, by means of a gold or pla- tina conductor, the water is decomposed, and resolved into its two elements, hydrogen and oxygen (see these articles,) which Fiff. 20. immediately assume the gaseous form.) If af- terwards the gaseous mixture thus obtained be submitted to electrical shocks, the re-union -of these elements will again be effected, the hydrogen will be inflamed, while its combus- tion will be supported by the oxygen; the gaseous mixture will entirely disappear, and water will be formed. The method of performing this experiment is shown by Fig. 20, where a represents a glass tube containing the two gases, and b, c, the two elec- trical conductors, the points of which approach so near, as to permit the fluid to pass through the gases, from one point to the other. To explain the phenomena of the decomposition of the water by electrical: agency, we have to suppose that the two gases are naturally in opposite states of electricity, but that Why does electricity accumulate, when a non-conductor is excited? When is a body said to be insulated? When one side of a body is positive, in what electrical state will the other side be ? What are the effects of powerful electrical shocks on water ? What are the effects of the same on a mixture of hydrogen and oxygen ? Explain Fig. 20, and show how the latter experiment is performed. What is it necessary to suppose, in order to explain the decomposition of water by electrical agency ? 5* 54 GALVANISM. when united to form water, the electricity is in a state of equi librium. When therefore water is submitted to the power of ihis agent, this equilibrium is destroyed, the negative gas or oxygen passing to the positive conductor, while the hydrogen being in a positive state, passes to the negative conductor. Thus the fluid is decomposed, and assumes the gaseous form of its constituents. The union of the two gases, and the consequent recompo- sition of water/ is simply in consequence of the heat evolved by the electrical shock, as it passes through themT) A degree of heat by any other means, sufficient to inflame the hydro gen, would produce the same effect. Precisely the same phenomena are produced by galvanism, both in respect to the decomposition of water, and the re union of its elements. When sulphate of copper is submit ted to the action of a powerful electrical machine, 'the salt is decomposed, and the metal is revived around the negative wire. Other metallic salts undergo the same decomposition. These effects arise from the different electrical states of the elements of which the salts are composed, the positive ele- ment being attracted to the negative conductor, and the con- trary. It will be seen directly, that the indentity of galvanism and electricity is proved by many similar results. Galvanism. It has already been stated, that the science of galvanism had its origin from an accidental discovery made by a pupil of Galvani, an Italian professor. This subject was afterwards prosecuted by Galvani, with the most untiring ardor and with great success ; and as his disco veriesrvvere made known, from time to time, to the scien- tific world, philosophers in all parts of Europe vied with each other in repeating his experiments, in varying them in all possible ways, and in making new experiments to account for the cause of the novel and surprising' phenomena they observed. An account of these researches belong to the history of Galvanism, and cannot be included in this concise epitome of the science. How dose electricity act to recompose water from its two elements 1 What >s said in respect to galvanism, as producing the same results as electricity? When sulphate of copper is submitted to the action of electricity, what phenomena ensue 1 How is this effect on the salts accounted for ? What is said of the interest excited among philoso phers by the discovery of galvanism ? GALVANISM. 55 it must suffice here, to state that the discoveries of Profes- sor Volta of Pavia) have contributed more towards the pro- gress and development of the true principles of this science, than the united researches of all his co-labourers. The dis- covery and invention of the Galvanic,, or Voltaic pile, the en- tire merit of which belongs to the 'Professor of Pavia, re- moved all doubt respecting the identity of electricity and gal- vanism, and is said to have been the result of deep medita- tion and reasoning. Volta's discovery was published in 1800, and since that time several modifications, and many improve- ments in the mode of extricating the galvanic influence, have been made ; they all, however, appear to be founded on his original invention. To make this subject plain, it is necessary to state, that Galvani found that when the different parts of a recent ani- mal, as the nerves and muscles, were made to touch each other, and then the opposite ends of this series made to com- municate by means of two different metals, signs of electri- city were always apparent;, Hence Galvani concluded that the different parts of animals were in opposite states of elec- tricity, and that the metals only served to restore the equili- brium. On the contrary, Volta maintained that the electrical excitement was owing to the contact of the two metals, and that the animal substances only served to conduct the fluid from the positive to the negative metal. 'And to show that this was the true theory of the phenomena; he proved by di- rect experiment, that when a piece of zinc, and a piece of silver, are placed in contact, and moistened, they are both excited, the zinc positively and the silver negatively. Thus, when a piece of silver, as a dollar, is placed on the tongue, and a piece of zinc under the "tongue, and then their two edpes made to touch each other, electricity will pass from the sine to the silver, of which the person will be sensible, not only by a peculiar metallic taste, but by the perception cf a slight flash of light, particularly if the eyes be closed. The quantity of electricity evolved by two pieces of metal, exceedingly small, Volta tried the experiment of adding What philosopher next to Galvani, has made the most successful researches on the A? tu re of galvanism 7 Who discovered the galvanic pile 1 What is said concerning the fntity of electricity and galvanism? From what experiment did Galvani conclude that the different parts of animals are in different electrical states! By what simple ex- periment is it shown that when moistened zinc and silver touch each other, electricity paarfe.^ from one to the other ? 56 GALVANISM. many pieces, arranging them in pairs, with a conductor be- tween them, and found that the galvanic influence was in- creased in proportion to the number of plates thus combined. Such attempts led him finally to construct the Voltaic pile already mentioned. \This pile consists of a multiplied num- ber of galvanic . series, terminating at one extremity by a positive, and at the. other by a negative conductor. The conditions necessary for galvanic excitation are en- tirely different from those under which common electricity is obtained. (We have seen that electricity is accumulated when an electric or non-conductor is rubbed with the dry hand, or with another non-conductor, as a piece of silk or fur. In or- dinary galvanic excitation, such substances as are called elec- trics are not concernecL These substances afe all conductors of the electric fluid ; one of them a simple conductor, the other two having each the additional power of different degrees of electrical, or gal vanic excitement. These three substances are usually zinc, water, and cop- per, and these, arranged in the order named, compose a sim- ple galvanic circle. The water, which is mixed with a small quantity of acid, not only serves as a conductor of the galvanic fluid, from the positive to the negative metal, but also by acting slightly on the metals, is the efficient cause of the galvanic excitation. Fig. 21. This arrangement, together with the course of the electrical agent from one metal to the other, and through the water to the first metal again, will be understood by Fig. 21. Suppose c to be a plate of copper, and z a plate of zinc, touching each other at the top, and placed I in a vessel of acidulated water. Then the action -* of the acid will produce an evolution of electri- city from both metals, that from the zinc being positive, and that from the copper negative. The electrical fluid will therefore pass from the zinc through the water to the copper, and from the copper by contact to the zinc, and so in a per- petual circuit in the direction of the arrows. What is the principle on which the Voltaic pile is constructed 1 What is the differ- ence between the substances used to collect electricity, and galvanism ' Wliat three substances usually compose a simple galvanic circle ? What is the use of the water and acid employed in the extrication of galvanism ? Explain Fig. 21, and show the course of the galvanic fluid. GALVANISM. 57 It is a multiplication of this principle, that is, by forming a series of simple galvanic circles, which composes the gal- vanic pile, or pile of Volta, already mentioned. This compound galvanic circle is constituted by a series of simple circles, so united, as to concentrate the influence of the whole at a given points It may be constructed as follows: Provide three glass rods, say of two feet in length each, and fix these in an angular direction from each other in a base of wood. Provide also circular plates of copper and zinc, two or three inches in diameter, about the eighth or tenth of an inch thick, and in number proportionate to the power of the intended pile. Next cut out the same number of. circu- lar pieces of card paper, or of woollen cloth, that there are pieces of either metal, but less in size. ^Having thus obtained the elements of the pile, its construction consists in placing first on the base, or board within the rods, a plate of copper, then on this a plate of zinc, and next, on the zinc, a piece of the paper, or cloth, dipped in salt water, or acidulated water, Fiff 22 t ^ lls f rmm ' a single galvanic circle. The same arrangement is observed throughout the whole series, that is, copper, zinc, paper; copper, zinc, paper ; except in the last circle, or top of the pile, which ends with the zinc. Fig. 22, repre- sents such a pile, a, b, being the glass rods and z, x, the pieces of wood, the upper piece having holes to admit the rods in order to make them secure. Such a series, affords a constant stream of the galvanic influence, hut is always most powerful when first constructed, or before the plates become oxidated. On this account, after having been some time in use, it re- quires to be taken in pieces, the plates cleaned from rust, and then again reconstructed, when it regains its original energy. A pile composed of two dozen plates of each metal, will give a small shock, which, when taken by the hands, may be felt to the elbows. The mode of receiving the shock, is by wetting the hands, and then having placed one of them in How is the pile of Volta constructed 1 After the frame is made, and the plates of metal and paper prepared, how is the pile then constructed? When does the pile ope- rate most powerfully 1 How may the pile, after the plates have become oxidated, be made as powerful as at first ? What is the mode of receiving the shock from the galvanic pile? 58 GALVANISM. contact with the zinc plate, which terminates one end of the pile, touch with the other hand, the copper plate which ter- minates the other end of the pile. Or these two plates may be touched with a wire, wound with a wet rag and held in the palm of each hand. ("When experiments are to be made by passing the galvanic influence through any substance, this is done by connecting a wire with each terminating plate : the two moveable ends of the wire being then brought near each other, and the substance placed between them, the fluid passes from the positive to the negative side, and so through the sub- stance. These wires are called the poles of the Voltaic pile. , Any number of these piles may be connected together by making a metallic communication from the last plajte of the one, to the first plate of the other, always observing to pre- serve the order of succession from the zinc to the copper, and from the copper to the zinc. In this manner a galvanic battery is constructed, the power of which will be propor- tionate to the number of plates employed. The galvanic fluid, it ought to have been observed, is ex- tricated only on condition that one of the metals employed be more easily oxidated, or more readily dissolved in an acid, than the other. Any two metals will form an effective gal- vanic apparatus on this condition, and it is always found that the metal having the strongest affinity for oxygon is positive, while the other is negative. .Thus, any metal, except that which has the least affinity for oxygen, of all, may form the positive or negative side, by having another metal more or less oxidable than, itself, placed in contact with it. Copper, in contact with zinc, is negative, because zinc is most easily dissolved, or has the strongest affinity for oxygen, of the two. But when copper is in contact with silver, it becomes positive, while the silver is negative ; and for the same reason silver becomes positive when in contact with gold, or platina. The greatest effect is produced, other cir- cumstances being equal, when two metals are placed together, one having the greatest, and the other the least affinity for oxygen, as zinc and platina. When it is required to pass the electricity through a substance, how is this done? What are the wires or conductors called ? How is a galvanic battery constructed 1 How must the metals differ, in respect to their affinity for oxygen, in order to evolve galvanism"? In what electrical state is the metal which has the strongest affinity for oxygen 1 What will be the state of copper when in contact with zinc 7 What will be the state of copper when in contact with silver or gold? What metals will produce the greatest effect on tjiis account ? GALVANISM. 59 Since the invention of Volta, a great variety of different uiethods have been devised, in order to extricate the galvanic fluid with greater convenience, or with greater power ; and also to modify its action for different purposes. Among these inventions, the galvanic trough is one of the most convenient and common in this country, though by far less powerful in proportion to the surface of the metal em- ployed, than several others. In this arrangement, the plates of copper and zinc are pla- ced with their flat surfaces in contact, and are soldered toge- ther on the edges. These plates are then fixed in grooves, cut in the opposite sides of a long narrow mahogany box, leaving between them narrow intervals. The box of course is open on one side, the ends and bottom being made water tight, and also the cells between the plates, by cement. In fixing the plates, it is obvious that all the zinc surfaces must be on one side, or face in the same direction, and all the cop- per surfaces on the other side. Fig. 23. Fig. 2%cepresents such a trough, furnished with con- ductors of brass wire, w, w, which are fastened to the two end njates, or merely '* dipped into the cells, The latter is the most convenient method, on account of its allow- ing the operator to graduate the shock at pleasure, by inclu- ding between the poles a greater or less number of the plates. \The conductors pass through the glass tubes, a, a, so as to . aiiow the operator to handle them without receiving the shock himself, and then pass to a glass plate on which the subject of experiment is laid. Wlien this trough is to be used, the cells between the plates are filled with water containing in solution a quantity of common salt, or made slightly sour by muriatic, sulphuric, or nitric acid. If the water is made warm, the action will be much increased. Care must be taken that too much acid be not used, for if the action on the zinc plates is such as to What method of extricating the galvanic power is said to be among the most con- venient 1 Describe the construction of the galvanic trough. In what order must the plates of zinc and copper be placed? Which is eaid to be most convenient, to .connect the poles to the plates, or merely to dip them into the cells'? What are tiie uses of the glass tubes a o 7 When the trough is to be used, with what are tne cells Illed ? 60 GALVANISM. occasion the emission of bubbles of hydrogen, the galvanic action ceases almost entirely. After the trough is filled with the water, its edges, and also those of the plates, must be wiped dry, and care must be taken that it does not leak, otherwise the electric fluid will be conducted away by the water. Want of attention to these circumstances, will sometimes occasion an entire failure of a galvanic experiment. Another mode of arranging the galvanic apparatus, is by means of a row of glasses, each containing solution of com- mon salt, or a dilute acid. In each glass is placed a plate of copper and another of zinc, not in contact, but so con- nected by slips of metal, or by wires, that the zinc in one cup shall be connected with the copper of the next cup ; the zinc in the second cup with the copper of the third, and the copper of the third with the zinc of the fourth, and so on through the series ; except the terminating cups, which con- tain only a single plate each, one of copper and the other of zinc. This arrangement will be understood by Fig. 24, where Fig. 24. ^ a, a, a, are the glasses, z the zinc, x the copper, and w the wires by which they are connected. The advantage of this method consists in the exposure of the two sides of the plates to the m ^_ action of the acid ; while by soldering the plates, as in the construction of the trough just described, one of the surfaces of each metal is protected from the acid, and contributes nothing to the effect. But the bulk of this apparatus, and the danger of breaking the glasses in case of transportation, prevents its general adoption. A convenient and more compendious modification of this principle has therefore been contrived, and is called the trough battery. \ In this arrangement, the zinc and copper plates are united in pairs, as just described, by means of slips of metal, which are soldered to each other. Twelve pairs of these plates are then fastened to a piece of baked wood, being placed at such a distance apart as to fit the cells of a trough which contains the water and acid. The trough may be made of baked mahogany, with partitions of glass, or What caution is necessary in respect to the quantity of acid, and also in respect to dry- jig the edges of the trough 7 Describe the mode of extricating galvanism by means erf glass cups. Why is the apparatus made with cups objectionable 7 In wliat is called Ilie trough battery, how are the plates united 7 GALVANISM. 61 what is better, the whole may be made of earthen, or Wedge- wood's ware. When this battery is to be used, the cells in the trough are partly filled with water, containing an acid or salt in solu- tion, and then the plates being connected with the slip of wood, are all let down into the cells at the same instant, by means of a pulley, each cell containing one plate of zinc and another of copper. Where great power is wanted, any number of these troughs may be connected together, by passing a slip of cop- per from the positive end of one, to the negative end of the other trough. [For the use of a laboratory, this is by far- the most convenient, as well as the most powerful means of ob- taining large quantities of the galvanic fluid, yet devised. When an experiment is finished, the operator, in a few min- utes, can raise all the plates from their troughs by means of pullies, and thus they are suspended, ready to be let down again when wanted. The power also, with the same extent of surface, is double that of the galvanic trough, where the 5 plates are soldered together, since with the present method, 'the entire surface of each metal is exposed to the action of the acid, The plates can likewise be more readily cleaned, and the whole apparatus more easily kept in repair. The Galvanic Battery of the Royal Institution of Great Britain, is constructed on the above plan. It is of immense power, consisting of 200 troughs of Wedgewood's ware, each containing ten cells, and receiving ten double plates of cop- per and zinc, each plate containing a surface of 32 square inches. The whole number of double plates is therefore 2000, and the whole metallic surface exposed to electricaj excitation at the same instant, is equal to 128,000 square inches. It was by means of this apparatus that Sir Humphrey Davy performed his brilliant experiments, and succeeded in decomposing the alkalies, and showing their metallic basesi (See potash and soda.) Chemical effects of Galvanism. It is a singular, and, per- In the trough battery, how are the plates of metal brought into contact with the acid ? What are said to be the advantages of this method 1 Why is this battery more power- ful than the galvanic trough in which the plates are soldered together ? What peculiar conveniences has this arrangement 1 What number of double plates does the battery of the Royal Institution consist of? What important discoveries did Sir H. Davy make by means of this battery ? 6 62 GALVANISM. haps, unaccountable fact, that the extent of the continuous surface of the metals, from which the galvanic fluid is ob- tained, has an influence over its effects, when employed for various purposes. We should suppose, both from reasoning and analogy, that the amount of galvanic action would, in every case, be proportioned to the number of square inches of metallic surface, and that it could make no difference in the result, whether the individual pieces of metal were large or small. But experience shows that this is not the case. The effect of a battery composed of large plates, and one of .small plates of the same extent of surface, fis quite different. ( That composed of the large plates having the most intense chemical, or heating power, while that consisting of small ones has the greatest effect on the animal system.') Thus, a man can bear with little inconvenience the shock from Mr Children's battery, composed of plates six feet long and two feet and a half wide ; while he would be stunned, or per- haps killed, by the shock from the same amount of surface, were it divided so as to proceed from plates of only two 01 three inches in diameter. And yet Mr. Children's' battery gives the most intensely brilliant caloric effects, while the caloric agency of the small plates is comparatively slight and insignificant. The decomposing chemical effects of galvanism have been much more extensively employed than those of common elec- tricity. Indeed, the decomposing power of electricity was little known before the brilliant discoveries of Sir H. Davy, by means of galvanism : but since that time, Dr. Wollaston has shown that most, if not all of the chemical effects of the galvanic battery, may be produced by electricity. The decomposition of water by means of electricity, was effected by the Dutch chemists long before the discovery of galvanism. A description of the method of doing this lias already been given, while treating of electricity. This seems to have been the most important chemical decomposition effected by electricity, before the discoveries of Galva.nl and Volta. Since that period, the science of chemistry bas owed to Is there any difference in the effect of a battery composed of large or small plates, when the extent of their surfaces is the same 1 What, is the difference between the effects of large and small plates? Will electricity produce the same chemical effects a . galvanism ? Was the decomposition of water effected by <> same 01 n opposite states of electricity 1 GALVANISM. 67 bustion, oxygen, chlorine, and iodine, are all negatively elec- trified. From such considerations, Sir H. Davy not only accounts for the chemical agency of the galvanic fluid, but also for that force called affinity, or chemical attraction, which impels bodies of different kinds to unite, and form compounds. Thus, oxygen being naturally negative, and hydrogen naturally positive, they unite with a force or energy proportional to the difference of their electrical states. The decomposing force of the galvanic battery may readily be accounted for on the same principle ; for if water be pre- sented to any substance of a higher state of positive electri- city than its hydrogen, then a decomposition would ensue, because the oxygen would leave the hydrogen, and attach it- self to that substance for which it had the strongest attrac- tion. The voltaic battery produces this effect, by offering to the two constituents of water stronger opposite electrical energies than these two substances have for each other. Thus, supposing the electrical force of hydrogen for oxygen to be equal to 3, and that of oxygen to hydrogen to be equal to 3, then they would combine with a force equal to 6. But if we suppose the galvanic battery to offer to the oxygen a posi- tive electrical energy equal to 4, and at the same time to the hydrogen a negative energy equal to 4, then it is obvious that their combining force would be overcome, and that the oxygen would fly to the positive, and the hydrogen to the negative poles of the battery, and thus that compound would be reduced to its original elements ; and we find that this is exactly what happens as a fact, when the water is exposed to the galvanic circle. This, it must be acknowledged, is one of the most beauti- ful theories ever invented, and at the same time agrees with the phenomena observed in most energetic chemical changes. But there are still some facts for which it does not satisfacto- rily account ; nor is it absolutely certain, that in any case, chemical attraction is owing to the different electrical states of the combining bodies, so that in the present state of know- ledge, this theory must be taken only as a probable and high- ly ingenious hypothesis. How is the decomposing force of galvanism accounted for? What is said in re- ation to the truth, or probability, of the electrical theory advanced by Sir H. Davy 1 Is it certain that in any case chemical attraction is caused by opposite electrical otateel 68 GALVANISM. Heating effects of Galvanism. One of the effects of galv* nic action is the evolution of heat ; and where the action is strong, it is accompanied with light, but not otherwise. There is a remarkable difference between the conditions necessary to the evolution of heat by galvanic action, and by common electricity. In common electricity, there is no pro- duction of heat, where the fluid moves through a perfect con- ductor, and without obstruction. When it moves along a rod of metal, no sensible heat, or light, is evolved, unless the conductor is too small for the quantity. But in its passage through non-conducting substances, as air, or dry wood, both heat and light are a consequence. But when galvanism passes through a perfect conductor, and the circuit remains entire, and when no light is evolved, there is still an elevation of temperature caused by its passage. This is readily proved, by making the two poles of the bat- tery meet in a vessel of water containing a thermometer, when it will be found that the temperature of the water will soon be raised, and if the experiment be continued, the fluid will boil by the heat evolved. If the battery consists of an extensive series of electrical circuits, very powerful calorific effects are produced by the passage of the fluid through metallic wires. Iron wire is melted and falls down in globules, and steel wire burns, with corruscations too brilliant for the unprotected eye. The heating effects of galvanism seem to depend on the conducting power of the metal employed, the heat being in an inverse ratio to the power of the conductor. This is cu- riously illustrated by passing the fluid through a wire, or chain, composed of alternate portions, or links, of platina and silver, soldered together, when it will be found that the silver will scarcely be warmed, while the platina will be intensely ignited. It appears from some experiments made with Mr. Chil- dren's great battery, that the heat excited by Voltaic action is more intense than that produced by any other means. What is said of the heating effects of galvanism ? What are the different conditions under which heat and light is evolved by electricity and galvanism ? When galvanism is passed through a perfect conductor, what effect is produced 1 What is the effect when it is passed through water ? How are metallic wires affected by powerful galvanic action ? When galvanism is passed through a chain, the links of which are alternately silver arid nlatina, what is the effect on each metal 1 What is said of the power of Mr. Children' mattery ] ATTRACTION. 69 Many substances were fused by it, which were exposed to the best wind furnaces without any impression. A piece of platina wire, one thirtieth of an inch in diameter, and eighteen inches long, became instantly red, then white hot, with a brilliancy insupportable to the eyes, and in a few se- conds was fused into globules. Still this battery had little effect on water, or on the human frame, the shock being felt no higher than the elbows. But still more brilliant effects were produced by the battery of the Royal Institution, when pieces of charcoal were attach- ed to its poles and then brought near each other. This battery, when the cells were filled with a mixture of 60 parts of water, and one part of nitric, and one of sulphu- ric acid, afforded the most splendid and impressive results. When pieces of charcoal about one inch long and the sixth of an inch in diameter, were placed in the circuit, and made to approach each other, a bright spark was seen to issue from one to the other, and in a moment the charcoal became igni- ted to whiteness. Then by widening the space between the charcoal points, a constant discharge continued when they were four inches apart, affording a most brilliant ascending arch of light, broad in the middle, and terminating in points it the charcoal, resembling in shape, two cones, applied base Fig. 28. to base. The shape of this ^^ 7 brilliant phenomenon is re- presented at Fig. 28, where a and b are the poles of the battery with pieces of char- coal attached to them, arid between these the ascending arch of light. When any substance was held in this arch, it be- came' instantly ignited; platina, one of the most infusible of all the metals, melted in it as readily as wax in a candle; quartz, sapphire, magnesia, and lime, all entered into fusion ; and points of diamond and plumbago, rapidly disappeared, seeming to evaporate with the heat. Attraction. By attraction is meant that property in bodies which gives What effect does this battery have on the human frame 7 What are the effects when pieces of charcoal are placed near each other, in a powerful galvanic circuit '{ Describe Fig. 28. What substances were fused by the battery of the Royal Institution 1 What is tho fourth imponderable agent belonging to our list? 70 ATTRACTION. them a tendency to approach each other, whether they exist in atoms, or masses. Attraction has received various names, according to the circumstances under which it is observed to act. Thus/that kind of attraction which extends to all kinds and quantities of matter, and to all distances, is called attrac- tion of gravitation. This attraction extends reciprocally from one planet to another, and from all the planets to the fixed stars, and is the cause of the orbicular motion of the heavenly orbs, f It also extends to all terrestrial masses of matter, and is the cause of their weight, or tendency to ap- proach the centre of the earth. The force of gravitation is directly as the quantity of mat- ter, and inversely as the square of the distance. The quan- tity of matter being given, and the attracting force at a cer- tain distance, say four feet, being known, then this force will increase, or diminish, as the square of the distance. Thus, if one body attracts another, at the distance of two feet, with a force of 36 pounds, then at the distance of four feet, its force of attraction will be only \ as much, or 9 Ibs., and so in this ratio whatever the distance may be. (See Natural Philo- sophy.) By attraction of cohesion, or aggregation, is meant that force which tends to preserve bodies in masses by acting on the particles of which they are composed. This attraction is supposed to act only at insensible distances, as when the atoms of bodies touch each other, and only when the par- ticles of matter are of the same kind. Chemical Attraction is that power which forces the particles of bodies of different kinds to combine and form a compound. This force is also called affinity, because this kind of union takes place only between particular substances. Like the attraction of cohesion, it acts only at insensible distances, that is, the particles of bodies must be brought into the immediate vicinity of each other before they will combine. But it dif- fers from cohesive attraction in taking place only between heterogeneous atoms, or among particles of different kinds of matter. Several other kinds of attraction are described, (See What is meant by attraction ? What is attraction of gravitation 1 What are the laws of attractive force ? Suppose a body is attracted with a force of 36 pounds, at the dis- tance of two feet, what wi J the force be at the distance of four feet ? What is meant by attraction of cohesion 1 What is chemical attraction ? How do cohesive and chemical attractions differ 1 In what respect is a knowledge of chemical attraction important ? ATTRACTION. 71 Natural Philosophy,) but it is chemical attraction, or affinity, which must more immediately occupy our attention here. Affinity. Chemical attraction is a subject of the highest importance in the study of chemistry, since a knowledge of the whole science includes little more than an acquaintance with the laws and effects of affinity, that is, of chemical at- traction and repulsion. We have already noticed that this science is founded on experiment, and from deductions arising from facts thus dis- covered. Now chemical experiments are only the means of discovering chemical affinities, and a knowledge of these affi- nities are the facts on which the whole science is founded. By experiment we know that some bodies have an affinity to each other ; that is, we know that on presenting them to each other under certain circumstances, they will combine, and form a third substance, which differs from either of the first. We know also by the same means, that other substan- ces, when presented together in the same manner, will repel each other ; that is, they will not combine, nor can they be made to unite so as to form a third substance. . This kind of knowledge it is impossible for man to acquire without actual experiment; for by no process of reasoning could he ever determine before hand, whether two bodies would attract or repel each other, any more than he could tell what they were composed of by mere inspection. We know, for instance, that when we mix acid and water, the two liquids unite, or blend together ; now, by reasoning (rom analogy, we should have the same grounds for believing ihat any other fluid would unite with water, that we had for believing that an acid would, and therefore that oil and water would combine, as well as acid and water'. But experiment shows, that on this subject, neither reason nor analogy lends us the least aid, for, on mixing the oil and water, we find that they mutually repel each other, and though blended to- gether by force, they again separate as soon as the force is removed. It is then only by actual experiment that we can decide In what does a knowledge of the science of chemistry chiefly consist? What are vhe facts on which the science of chemistry is founded ? How is it known that some niKlies attract, while others repel each other 1 Is it possible to gain any knowledge o v-hemistry, except by experiment 1 What reason would there be to suppose, without experiment, that oil arid water would not combine 7 What is the first condition neces- sary to effect chemical union ? 72 AFFINITY. whether two bodies have an affinity for each other, and con- sequently whether they are capable of forming a chemical compound, or not. There are several circumstances which affect the results of chemical affinity, or conditions on which its action depends, which will be mentioned in their turn.'} There are also se- 'veral kinds of affinity, which have received different names, depending on the conditions under which its action takes place. TKese appellations and conditions will also claim at tention as they occur. With a few exceptions, the first condition necessary to effect chemical combination is, that one or both the bodies should be in a fluid state, since however strong the affinity of two bodies may be to each other, their particles cannot unite unless they are free to move. Hence, to effect the combination of solids, their cohesion must first be destroyed .either by solution in a fluid, or by means of heat. The acids and alkalies have a strong affinity for each other, but on mixing them, even when in the finest powder, no chemical combination ensues, because in all chemical compounds the union takes place between the- atoms of the combining substances. But on pouring a quantity of water upon such a mixture, chemical action instantly ensues, and\a third substance, dif- fering entirely from the alkali or the acid, is the result of the combination. This compound is called a salt. In like manner, if zinc and copper be reduced to the finest powder, and mixed ever so intimately by mechanical force, there will still be no intimate union between their particles. But if heat be applied so as to reduce them to a fluid state, they combine with considerable energy, and form a yellow alloy, called brass, which differs greatly from the zinc or copper of which it is formed. Simple Affinity. The most simple cases of affinity are afforded by the mixture of two substances which have the power of combining with each other, in 'any proportion. Water and sulphuric acid, or water and alcohol, form such combinations. What are termed neutral salts, which are formed by the union of a pure acid, and a pure alkali, are instances of the same kind, only that they do not combine in all proportions. In a great variety of instances, after two What is necessary, in order to effect the chemical combination of solids'? Why will not solids combine as well as fluids ? In what manner may copper and zinc be made o combine 1 What are the most simple cases of affinity 7 Give an illustration of this affinity. AFFINITY. 73 substances have combined, when mixed alone, or without the admixture of any other substance, this first union may be destroyed by the intervention of another, or a third sub- stance, having a stronger attraction for one of these sub- stances than they have for each other. This forms an in- stance of what has been termed by Bergman, Elective Af- Single Elective Affinity, is exercised when one composi- tion is destroyed, and at the same time another is formed. There are many familiar examples of this kind of decompo- sition, some of which we witness almost every day. Cam- phor dissolved in alcohol or in strong spirits, makes a trans- parent solution ; but if water be poured into this solution, it instantly becomes turbid, and the camphor separates from its connection with the alcohol, and rises to the surface of the fluid. This separation takes place because the alcohol has a -stronger affinity for the water than for the camphor^ and the turbidness is caused by the insolubility of the camphor in water, in consequence of which it takes the solid form. Soap is composed of oil, an alkali, and water. The oil and water have no affinity for each other, but the alkali has a strong affinity both for the oil and water, and consequently the three substances unite and form a compound. But if an acid be mixed with a solution of soap, the compound is de- composed, for the alkali has a stronger attraction for the acid than for the oil and water, and consequently the oil is rejected and rises to the surface, while the acid and the alkali form a new compound. This affinity is called elective, because when one substance is mixed with several others it seems to manifest a choice be- tween them, and elects one with which it unites, to the rejec- tion of the others. It is most probable that every substance has an affinity for many other substances. We know indeed that this is true in a great variety of instances, since experiment shows that one substance will form several compounds with other substances, in succession, and that these compounds may in succession What is single elective affinity ? Give an example of the exercise of this kind of ifFnity. When water is poured into a solution of camphor in spirit, why is the camphor separated 1 What is the composition of soap ? When an acid is mixed with a solution of soap, why does the oil rise to the surface ? Why is this kind of affinity called elective 1 What is said relative to the attraction of one substance for many others ? 7 74 AFFINITY. be destroyed by the application of other substances which have a stronger affinity to the first. As an example, suppose sulphuric acid, or the oil of vitriol, to be the first substance, or the one towards which several other substances have a chemical attraction, but in different degrees of force, then a compound formed between the acid and the substance having the least affinity, will be destroyed by the substance having the next stronger degree of affinity, and this second compound would be decomposed by the sub- stance having the next degree of affinity, and so of every substance having a stronger attraction for the acid. Thus, sulphuric acid has an affinity |br barytes, stronlian, potash, soda, lime, ammonia, and magnesia, and the force of this affinity is in the order in which they are named; that is, barytes has the strongest and magnesia the weakest. A com pound therefore of magnesia and sulphuric acid would be de- composed by the addition of^ammoniaj and one of ammonia and the acid, by the addition of lime, and so on /but none of these substances would decompose that formed between the acid and barytes, because these substances have the strongest affinity for each other. No chemical facts appear on first view more simple or in- ^elligible than those which are explained by the operation of elective affinity. But we shall find on a more minute exami- nation, that this force abstractedly considered, is only one of several causes, which are concerned in chemical decomposi- tions, and that its action is modified, and sometimes subverted by counteracting causes, to be mentioned hereafter. Double Elective Affinity, takes place whenever two compounds, each consisting of two ingredients, mutually decompose each other, and by a double interchange of these principles form two neio compounds. We have seen that, in single elective affinity, one new compound is formed by the addition of a single substance, while the ingredient thus rejected remained un combined, or alone, in the, solution. Thus, when lime is added to a compound of magnesia and sulphuric acid, the lime and acid unite, while the magnesia What are the substanaes named, as having an affinity for sulphuric acid, and in what order is the force of this affinity with respect to the substances 1 Suppose soda and sul phuric acid to be combined, which of the substances named would decompose the com pound 1 Which of the substances named would decompose sulphate of barytes ? When does double elective affinity take place? AFFINITY. 75 is rejected, and remains solitary in the solution, having no- thing on which to bestow its affinity. In double elective affinity, an interchange of the principles belonging to each compound is effected, and thus the old compounds are destroyed, and new ones formed 5 and it is curious and interesting to observe the consequences, of what we should call the likes and dislikes of the particles of mat- ter for each other, were they animated. It often happens, that a compound of two ingredients can- not be destroyed by the application of a third, or fourth in- gredient, separately ; but if the third and fourth be combined, and then the two compounds be brought into contact with each other, decomposition and interchange of principles will ensue. Thus, sulphate of soda is composed of soda and sulphuric acid, and is the substance called glauber\s salt. Now when lime is added to a solution of this salt, there en- sues no decomposition, because the soda attracts the acid, more strongly than the acid attracts the lime. If muria- tic acid be adcled to the same solution, there still follows no decomposition, ( because the sulphuric acid has a greater affinity for the soda, than the soda has for the muriatic acid. But if the lime and muriatic acid be previously combined, forming a muriate of lime, and this compound be added to the solution of the sulphate of soda, then a double decompo- sition follows, and two new compounds are formed out of the old ingredients. The lime of the muriate of lime, and the sulphuric acid of the sulphate of soda, having stronger af- finities for each other, than the first has for muriatic acid, or the second for soda, mutually abandon their old connec- tions, and having combined with each other, form a new com- pound under the name of sulphate of lime. The soda and muriatic acid being thus rejected, and their former unions dissolved, they combine themselves anew, and form another compound, known under the name of muriate of soda, or common salt. These changes will perhaps be better under- stood by the diagram, which follows. In this kind of affinity, how many old compounds are destroyed, and how many new ones formed at the same time 1 Why does not lime decompose sulphate of soda ? Why does not muriatic acid decompose sulphate of soda? What are the chemical changes effected when muriate of lime is added to a solution of sulphate of soda 7 What are the names of the new compounds formed by the decomposition of sulphate of soda, nod mu- riate of lime ? 76 COHESION. Muriate of Soda. Sulphate f Soda. Soda. Muriatic acid. Sulphuric acid. Lime. Muriate Lime. Sulphate, of Lime. On the outside of the vertical brackets are placed the names of the original compounds, sulphate of soda and muriate oi lime, and above and below the diagram those of the new com- ppunds. The upper line is strait, to indicate that the muri- ate of soda remains in solution, while the middle of the lowei one is directed downward, to show that the sulphate of lime is precipitated, or falls to the bottom of the vessel. Causes which counteract or modify the effects of chemical affinity. It has been stated that the effects of chemical action are often modified, or even subverted, by counteracting causes. The principal causes which have a tendency to counteract chemical combinations sue cohesion, quantity of matter, elas- ticity, and gravity. Cohesion. By cohesion, we mean that attractive force by which the particles of bodies are kept together, and in conse- quence of which, masses are formed. This force may modi- fy, or entirely counteract that of chemical attraction ; for the more strongly the particles of any substance are united, the greater the obstacle to a chemical union with those of other bodies, because the successful effects of affinity depend on a mutual penetration of particles. Hence the formation of che- mical compounds, with some exceptions, requires that at least one of the ingredients should be in the state of a liquid, so that the particles of each should have free mutual access. Where the affinities are strong, and the cohesion slight, the union is effected with considerable energy, under such cir- cumstances. Thus, masses of carbonate of ammonia, of con- siderable size, will be dissolved by nitric acid ; but when the Explain the diagram illustrating these changes. What are the principal causes which promote or counteract chemical changes ** What is meant by cohesion 1 How does cohesion prevent solution ? COHESION. 77 force of cohesion is great, it is a strong barrier to the opera- tion of affinity. Thus, a mass of carbonate of lime, or mar- ble, will remain for days in an acid, when, were it reduced to powder, it would be dissolved in a few minutes. In all such cases, therefore, mechanical division is required before rapid solution, or intense chemical action, can be ef- fected. Cohesion being thus overcome, solution is readily accomplished, "because the solid now presents a greater extent of surface to the action of the fluid. Heat is another means of counteracting the cohesion of bodies, the repulsive power of caloric being indeed the great opposing force of that of cohesion, and provided its quantity be proportionate to the force of attraction, will so overcome it as to render all solid bodies liquid. Different substances, 4 is obvious, require different degrees of heat for this purpose. Thus, the cohesive force of such bodies as are called liquids, is so counteracted by the heat of ordinary temperatures, as to make their particles easily moveable among each other, a circumstance on which their liquidity depends. But many of these substances, such as water and oil, by the abstraction of heat, become solids, because then the repulsive force of caloric becomes less than the attractive force of cohesion. On the contrary, in bodies which we term solids, the attract- ive force of cohesion is greater than the repulsive power of caloric, and hence at all ordinary temperatures, their parti- cles are fixed and immoveable among themselves, a circum- stance on which their solidity depends We have stated that the exercise of affinity depends on the state of the substances concerned, and that in general, one of them must be in a fluid state. In most instances, solution is effected in some liquid, as an acid, alcohol, or water. But to produce metallic alloys, the metals must be brought to a liquid state without changing their properties, and this can be effected only by means of caloric. For this purpose, it is only necessary that one of the metals, viz. that requiring tne highest degree of heat, should be melted, and the other thrown into this in small pieces. Quaiitity of matter. Experiment teaches that quantity of Why will the same substance in powder enter into solution more readily than when in the mass? What is the opposing force to cohesion? What is the cause of fluidity in bodies? How might all bodies be made fluid ? Why does water become solid when cal- oric is abstracted from it ? On what does the solidity of bodies depend? What io toe only means by which metallic alloys can be produced? 7* 78 COHESION. matter exerts an important influence over chemical decom- positions and solutions. Thus, we know precisely how much sulphuric acid, for instance, will neutralize a given quantity of potash, when in a free state. But if the same quantity of potash be first combined with nitric acid, forming nitrate of potash, or saltpetre, then more of the sulphuric acid is re- quired to detach this quantity than before, probably because some force is employed to destroy the union previously exist- ing between the nitric acid and the potash, and also because the affinity of the two substances for each other diminishes when both are nearly saturated. In making a solution of a metal in an acid, it may be ob- served, that the chemical action is much more energetic at the beginning of the process then afterwards, and that if no more acid be added, than is just sufficient to dissolve the me- tal, the action finally becomes so feeble as to require a day or two to complete the combination. But if, in this state, more acid be added, the action again becomes brisk, and the metal is soon dissolved. Elasticity. Cohesion being found an obstacle to the exer- cise of affinity, it might be expected that the contrary state, that is, the absence of cohesion, would facilitate chemical combinations ; but experiment determines otherwise. In the elastic fluids, such as the gases, and common air, cohesion may be considered as entirely wanting. But bodies of this kind, though having a strong affinity to each other, show little disposition, under ordinary circumstances, to combine. Thus, oxygen and hydrogen, though in different electrical states, may be mixed together in the same vessel for any pe- riod of time, without the least symptom of combination. The reason of this, is probably owing to the distance of their par- ticles, w r hich prevents that near approach to each other, requi- red to come within the sphere of mutual attraction; for if the two gases be subjected to pressure by means of the little in- strument called a fire pump, Fig. 11, they unite with explo- sive energy. The elastic property not only opposes the chemical union of bodies, but is often an agent by which their decomposition What is said of the influence of quantity of matter on chemical combinations 1 Ex- plain how quantity of matter is illustrated by the solution of a metal in an acid. Does the elastic state facilitate chemical combinations 1 What is the most probable reasons tha gases having an affinity for each other do not unite, when mixed under ordinary circum etances 7 How may oxygen and hydrogen be made to combine 7 CHEMICAL CHANGES. 79 is effected when exposed to the influence of caloric. Thus, substances containing a volatile and fixed principle, are sometimes decomposed by heat alon\ because the repulsive force of caloric 'removes the elern ?he compound be- yond the influence of mutual attraction, and the volatile ele- ment makes its escape in consequence.) Many of the salts, composed of an alkali, or a meial, and an acid, and water, are readily decomposed by heat alone. The water is first turned to steam, and escapes by its elasticity, leaving the salt opake, and as the heat is raised, the acid is converted into vapour, and escapes in the same manner. On the same principle, oxygen ts ,'Wiined from manga- nese, from nitre, and several other compounds, where it exists as a principle. Gravity. When the difference between the weight of the two bodies is great, this circumstance opposes their chemical combination. Thus, when common salt is thrown into water, it sinks to the bottom, where the water soon becomes satura- ted, and will dissolve no more; br water be agitated, the whole will soon dissolve... -It i- found, also, that metals differing widely in their specific gravities, when melted to- gether, do not rnix equally, unless tb..y are stirred, because the heavier metal settles to the bottom. ; _ Changes produced by Chcm ibinations. By chemical combination is mea" f i < : aion between two or more substances of different kinds, so hit i mate that they can- not again be separated by median u us. Thus, if clay or chalk and water be mixed, the rviaure will for a time be turbid, or opake, but if suffered to s . r a day or two, the clay or chalk will settle to the boil lie vessel, and the water above will become transparent. J >ut if water be mixed with an acid, or with a salt, or with Mi^ar, the union becomes permanent, nor will rest, or filtration, or ;my other mechani- cal means, separate either of these hu roclients from the wa- *er. Hence, the distinction between mechanical mixture and How does caloric act to separate a volatile from a fi.\ ' n;;iple 1 How ia the decom- position of a fluid effected by heat? What is said 01 gravity in opposing chemical union 1 How does common salt, in water, illustrate tiiu principle 1 What is said of the combination of metals in this respect 1 What is meant, by chemical combination 1 What is the distinction between mechanical mixture ami chemical union 1 Why will not chalk and water combine permanently? When vat-r and sugar are mixed, why does not the sugar settle to the bottom of the vessel ? 80 CHEMICAL CHANGES. chemical union. In the first, no affinity between the sub stances exists, and therefore no union takes place, and the chalk or clay falls to the bottom of the vessel. In the second, there is a combination between the particles of which the substances are composed, owing to the affinity existing be- tween them, and hence they are not separated, except by a stronger force than that of the existing affinity. The changes that accompany chemical action, are in some proportion to its intensity. In the instances above named, where water is mixed with a small quantity of acid or salt, this action is feeble, and the sensible changes produced in- considerable, being only a slightly acidulous, or saline taste, given to the water. But in cases where the chemical action is intense, the changes produced in the combining substances are often great in proportion. . Thus, -when the tw r o gases, oxygen and hydrogen, are burned together, their combination is attended with most intense chemical action, by which the highest degrees of heat are evolved, and at the same time the change produced is no less than the condensation of two elastic gases into the fluid water. Many substances which are highly corrosive, in a sepa rate state, become mil^ and lose all their acrid qualities by combination with each other. Sulphuric acid and potash, for example, are highly caustic substances. They both act with great energy on animal and vegetable bodies, producing decomposition and total destruction of texture. The acid turns the blue colors of vegetables to red, and the alkali turns these colors' to green. But on mixing these substances to- gether, they entirely destroy the caustic qualities of each other, and there results a solid compound, called sulphate oj potash, which is mild to the taste, and neither acts on animal or vegetable bodies, nor changes the colors of the latter. This is called a neutral salt, because the substances of which it is composed, thus neutralize the active properties of each other. When the opposing properties of chemical agents are thus destroyed by combination, they are said to saturate each other, and it is found that the acrid and caustic qualities of all Is there any proportion between the intensity of chemical action and the changes pro duced thereby 1 What illustrations of this law are given 7 What effect does combina- tion sometimes have on the corrosive properties of bodies 1 Give an illustration of thia eflect ? What is the composition of sulphate of potash ? What is a neutral salt ? When arc substances said to saturate each other ? AFFINITY. 8-1 the acids and alkalies are weakened in proportion as one is added to the other, until the point of saturation is attained, when the compound becomes neutral, and is not affected by a further addition of the acid or alkali, which forms a part of its^ composition. A change of bulk is also in many instances the result of chemical union, so that the two bodies after combination, do not occupy the same space as before. 11 Thus, when a pint of sulphuric acid is mixed with a pint of water, the chemical action is so great as to raise the thermometer above the boil- ing point, and the resulting compound will not measure two pints as before the mixture, but considerably less. When zinc and copper are fused together, the resulting al- loy has a specific gravity greater than the medium specific gravities of the two metals, showing that their bulks are di- minished by the union. The same happens when alcohol and water are mixed ; and in general it is foun$ that the re- sulting body after chemical combination has a greater speci- fic gravity than the mean of its components. Another change often produced by the exercise of affinity, is that of colour. The alloys of any two metals do not ex- hibit the medium of their two colours. Thus the white me- tal, zinc, and the red one, copper, when melted together, form the yellow compound, brass. The colours of the metallic ox- ides differ according to the quantities of oxygen they contain. The black oxide of mercury contains 200 parts of the meta) and 8 parts of oxygen, while the same quantity of the metal combined with 16 parts of oxygen, forms the red oxide of mercury. We have already had occasion to notice, that blue vegetable colours are changed to red by acids, and to green Dy alkalies ; and in addition to this, we may state generally, that all vegetable colours are changed, more or less, by the application of these agents. There is still another change, which is the effect of chemi- cal affinity, and is often highly important ; this is the change of form. Of this change chemistry exhibits a great variety of examples, many of which are highly curious and interest- What is said of change of bulk as a result of chemical action 1 Suppose a quantity o< water and sulphuric acid are mixed, will they occupy the same bulk that they did before he mixture ? Will the bulk be greater or less than before 1 In chemical combinations, s the resulting body more or less dense than the medium density of its components 1 What is said of the change of colour produced by chemical combinations ? Is change of form ever effected by chemical combinations ? 82 AFFINITY. ing-. Thus, if a saturated solution of muriate of lime in wa- ter, be mixed with a small quantity of sulphuric acid, the two fluids immediately become a solid. This change is pro- duced by the exercise of affinity. The muriate of lime is composed of lime and muriatic acid, and of this salt, water will dissolve a large quantity and still remain fluid. The sulphu- ric acid has a stronger attraction for lime than the muriatic has, and the sulphate of lime is nearly insoluble in water. When therefore the former acid is added to the solution, a sulphate of lime is formed, which in a spongy form occupies the whole vessel. On the contrary, if equal parts of alum and acetate, or sugar of lead, be rubbed forcibly together in a mortar, they form a compound mass which is nearly fluid. The cause of this change from the solid to the semi-fluid state, is also easily explained. The alum and sugar of lead contain a quantity of water, called the water of crystallization. When they are forcibly rubbed together, the elements of which they are composed, unite in consequence of mutual affinity, and thus the water of crystallization is set free, and occasions the partial fluidity of the mixture. The great changes which the two gases undergo in the formation of water, have al- ready been mentioned. Similar changes, so far as respects the condensation of elastic fluids and liquids, are phenomena which are frequently witnessed in experimental chemistry. Thus, water absorbs about 500 time its own bulk of the gas, called ammonia, which is in this manner condensed, and forms a part of the liquid. The compound thus formed is known by the name of spirit of hartshorn. Quicklime, in the process of slacking, absorbs a large quantity of water, which by this combination becomes solid, and forms a part of the dry lime. In the formation of the gases, on the contrary, there is an immense increase of bulk. When water is decomposed and made to assume its elementary gaseous form, there is an in- crease of bulk nearly equal to '2000 volumes: That is, a cubic inch of water contains 662 cubic inches of oxygen, and 1325 cubic inches of hydrogen; thus the volume is in- creased 1987 times by the decomposition. The explosion How is the change of form accounted for when sulphuric acid and muriate of lime are mixed ? How is the change of form explained, when alum and acetate of lead are for- cibly mixed 7 What is said of the condensation of ammonia by water, and the conden- eation of water by slacking lime 1 How many times more bulky are the gases of which water is composed, than water itself 1 AFFINITY. 83 of gun powder is another example of the vast increase of volume by chemical decomposition. Force of Chemical Affinity. Although it is ascertained, by means already described, that the affinity of one body for a number of others, is not of equal force, yet we are ignorant how much difference there is in the forces of these different degrees of affinity. The only means of deciding this question is to observe the tendency which several substances have to unite with the same substance, under similar circumstances.'- Oxygen, for instance, as a universal agent, might be selected as a stand- ard, and the force of affinity between this and other bodies be estimated by their degrees of oxidation under the same circumstances. We know that there is an immense differ- ence between the forces with which different bodies attract (his principle. Some of the metals, for instance, absorb oxygen with such avidity, that they cannot be preserved in their metallic state when exposed to the atmosphere, even for a short time; while others have so little affinity for this principle, that they cannot be oxidated without the most ener getic means. Thus, potassium (see this word) attracts oxy gen with such force as to decompose water, at common tem- peratures, by absorbing it from the hydrogen ; while the affinity of platina or gold for this principle is so weak as not 10 attract it at all, except at the highest degrees of heat, or from acids which impart it most easily. We may constantly observe the effect of the different forces with which several metals attract oxygen in the com- mon affairs of life. Thus, iron and lead, when exposed to the moisture of the atmosphere, soon tarnish, and after a time, by the absorption of oxygen, their surfaces become covered with rust, or the oxides of iron and lead. But silver and gold when exposed in the same manner, continue bright and untarnished for years, as may be observed in the points of lightning rods, and the gilded vanes and balls of church steeples. This difference can only arise from the different forces \yith which these metals attract the oxygen of the at- mosphere, There is no department in chemistry, either as a science. Hew might the force of affinity be ascertained 7 How do we know that there is o great difference between the forces with which bodies attract oxygen? How is this difference illustrated ? How is it shown that iron and lead attract oxygen with greater force than silver and gold 1 84 PROPORTIONS. >r an art, which so much needs the investigation of able men as this. Tables of affinity, showing at once the force of at- traction between different chemical elements, would enable the inquirer, without further experiment, to decide what sub- stance would decompose any given compound, and therefore how to separate, or combine, the different principles of bodies for a vast variety of purposes. Tables to a very limited ex- tent have already been constructed for such purposes, but the difficulty and magnitude of this subject seems to -have deter- red the more modern chemists from engaging in this . exten- sive department of the science. Indefinite and Definite Proportions. It is ascertained by experiment that some bodies unite in unlimited, or indefinite proportions, while others combine in proportions which are always limited, or. definite. The discovery of the laws of definite proportions is one of the most important and wonderful among the great and bril- liant achievements in modern chemistry. It is sufficient of itself to convince any reasoning mind, that order and system pervade the universe, and that the minutest atoms of matter, and the vast orbs that move round the heavens, are equally under the control of the invariable laws of the Creator. Indefinite proportions. When we mix water and alcohol, or water and any of the acids, they unite in any proportion. Thus, a drop of acid will combine with any quantity of water, ind water will unite in the same manner with alcohol, or acid. This principle may be tested by direct experiment ; for if a gallon of water be tinged blue by a vegetable colour, a few drops of sulphuric acid will turn every drop in the gallon to a red colour, thus proving, that this small quantity of acid has diffused itself through the whole mass. By similar experi- ment it can be shown that a small quantity of water will dif- fuse itself through a large quantity of acid. These examples prove that some bodies combine in unlimited proportions on both sides. Other combinations appear to be limited on one side, and unlimited on the other. Thus, common salt, and other saline substances, will dissolve in water in any proportion short of What would be the use of tables, showing the force of attraction between different chemical elements ? What is said of the discovery of the laws of definite proportions 7 What substances are mentioned, which combine in unlimited proportions? PROPORTIONS. 85 tne point of saturation, after which, if more be added, it will fall to the bottom of the vessel and remain solid] The great- est proportions in which water and common salt combine, are those of 100 of the former, with 40 of the latter ; but the smallest quantity of salt will diffuse itself through the largest quantity of water, and the probable reason why salt does not unite with water in every proportion, is, that its cohesion resists the feeble affinity of the fluid after it becomes satura- ted. In all cases where bodies combine with each other in eve- ry proportion, or where the proportions are limited on one side, and indefinite on the other, the force of affinity by which such compounds are formed is feeble, and the compounds themselves often differ but little from the original ingredients. Thus, alcohol and water combine in all proportions, but the union produces only a modification of the qualities of each, the degrees of which depend on the proportions of the mix- ture, and the force of affinity between them is so weak, that distillation, by a gentle heat, entirely destroys their union. Solutions of the salts, sugar, acids, and many other princi- ples, are examples of the same kind ; a moderate heat, and sometimes evaporation, without heat, will dissipate the water and leave the other ingredients in their former state. In these, and a great variety of other instances, although the force of affinity is slight, still there is u wide difference between such compounds, and .mere mechanical mixtures, since the latter are separated by rest, while the ingredients of the former are not separated by rest, filtration, or any other mechanical means. These solutions, or combinations, formed by feeble affini- ties, resemble mixturesr'in respect to the slight changes which their ingredients undergo by uniting!) while they resemble chemical compounds in respect to the inseparable nature of che union, by mechanical means/ The writer of the article Chemistry, in the Library of How is it proved that a few drops of acid will diffuse itself through a large quantity erf j definite, what would be the effect of chang- ing these proportions 1 PROPORTIONS. 87 known to have been formed by any two substances, within the limits of definite proportions. The proportions of any given compound being invariably the same, it follows that its characteristic properties depend on these proportions, and that if these proportions are changed, the compound will contain new properties, and therefore a new substance is formed:* As an example of the change produced on the compound, by a different proportion of one of its constituents, we will cite mercury and chlorine, (see chlorine.) These two substances unite in two proportions, the first of which is composed of mercury 200, and chlorine 36. This forms the well known medicine called calomel, and is sometimes given in doses of a tea-spoonful at a time, with- out injury. The other is composed of mercury 200, and chlorine 72, being one more proportion of chlorine, than is contained in the calomel. But the two compounds in their sensible qualities are entirely different, the latter being one of the most active and fatal of poisons, and is known by the name of corrosive sublimate. Thus two substances uniting in one proportion, form a compound which is comparatively inert, while in another proportion they form one of the most virulent^poisons known. Nor is there any medium, or half way union between these bodies ; they combine in these two proportions or not at all. For, suppose 200 parts of mercury should be exposed to the action of 40 parts, by weight, of chlorine, then the mercury would combine with 36 parts of the gas, and no more, leaving the other 4 parts remaining un- touched. And so, on the contrary, if 210 parts of the meta. be exposed to the action of 36 parts of the gas, then the gas will combine with 200 parts of the mercury, while the 10 parts would remain uncombined. In all energetic combinations the proportions of the com- bining substances are limited in the same manner, though the proportions themselves are exceedingly various. Indeed, it appears that the law of limited proportions, is as universal and as permanent as the law of gravitation itself, and that its doctrines, so far from being founded on the theoretical opinions of men, "are in truth based on a general, but more recently discovered law of nature. What example is given of the difference between compounds formed of one and two proportions of the same elements 1 What is said concerning the combination of mercury and chlorine in other proportions 1 Will 40 parts of chlorine unite with 200 parts of mercury ? On what is it said the truth of the law of definite proportions is founded 1 88 PROPORTIONS. Second. When two substances unite in more than one pro- portion, the second or third proportions are multiples of the first, by a whole number. This very remarkable law applies in every case where bodies unite with each other in more than one definite pro- portion. The expression of the law, simply means, that the first proportion in which two bodies unite, is in the lowest or smallest proportion in which the two constituents are capable of uniting with each other, and that the other proportions are double, triple, or quadruple, this lowest proportion. For example, the several compounds of nitrogen and oxy- gen are in the following proportions to each other, viz. : Nitrogen. Oxygen. Nitrous oxide, consists of 14 parts, and 8 parts. Nitric oxide, " 14 16 " Hyponitrous acid, " 14 24 " Nitrous acid, " 14 " 32 " Nitric acid, " 14 40 " Thus the lowest proportions in which oxygen and nitrogen combine, being to each other as the numbers 8 and 14, all the other proportions of oxygen are multiples of this first number, while the proportion of nitrogen remains the same. The se- cond number is the first multiplied by 2 ; the third, the first multiplied by 3; and so on. These proportions are therefore to each other, as the numbers 1, 2, 3, 4, and 5. Illustrations of this law can be observed throughout every department of chemistry, where the analysis of chemical com- pounds are given, and with a single exception, or two, where it is most probable the fault is either in the analysis or the want of knowledge, the same principle is found to be exactly true. One of these exceptions is found in an oxide of man- ganese, and will be pointed out hereafter. On these discoveries is founded the law, called the law of multiple proportions, a phrase which is often repeated in all the late works on Chemistry, and of its general truth, as already observed, there can be no doubt. In the above ex- ample, all the succeeding proportions of oxygen are multi- ples of the first. What is the second law of definite proportions 7 What explanations are given of this Jaw ? Suppose the smallest proportions in which nitrogen and oxygen combine are 14 ol the first, and eight of the last by weight, what then will be the second proportion in which oxygen combines with nitrogen 1 What the third, what the fourth, and what t&e fifth? PROPORTIONS. 89 The third law of combination is nearly connected with the .ast, though the difference of expression and of meaning will be obvious. This law is not less extraordinary than that of multiple proportions, and may be understood by the following examples given by Dr. Turner. Water, we have already seen, is composed of 8 oxygen and 1 hydrogen: hyposulphurous acid is composed of 8 oxygen and 16 sulphur. Now it is a curious fact, that the gas, called sulphuretted hydrogen, is constituted of 1 hydrogen and 16 sulphur ; that is, the quantities of hydrogen and of sulphur which combine with the same quantity of oxygen, combine with each other. Again, 36 parts of chlorine and 8 of oxygen constitute the oxide of chlorine, and with 1 of hydrogen, form muriatic acid gas: also 16 parts of sulphur combine with 36 of chlorine to form the chloride of sulphur. Hence bodies unite in proportional numbers, as in the above instances the proportion of hydrogen is 1, that of oxygen 8, that of sulphur 16, and that of chlorine 36. But this law not only applies to the elementary parts of substances, such as hydrogen, oxygen, chlorine,, and sulphur, but also to compound bodies ; whose combining proportions may likewise be expressed by numbers. Now the proportions of any compound being expressed by the numbers attached to each element of which it is compo- sed, the number representing the compounds, is composed of the -sum of its parts, or elements. Thus water is composed of oxygen 8, hydrogen being 1, and its combining proportion will therefore be 8-j-l=9. When one element combines with another in several proportions, the number representing the single proportion, arid those representing the several other proportions, are added together to make up the combining number of the compound. Thus, sulphuric acid is composed of one proportion of sulphur 16, and three proportions of oxygen ; and as one proportion of oxygen is 8, so the whole number representing the oxygen in this acid is 24; to which 16 being added, makes the number representing sulphuric acid to b p - 40. What is the third law of definite proportions? Explain this law. Suppose 64 represents the metal, and 8 the oxygen, in an oxide of copper, and suppose there is a second oxide, what would be the numbers representing the metal and the oxygen 1 Does this law of numbers apply 'to the elements of bodies only, or to the compounds also ? When the numbers for the elements of a compound are known, how may the number for the compound be found? What are the numbers for hydrogen and oxvgen in water? 90 DEFINITE PROPORTIONS. It must be remembered that the smallest proportion, by weight, in which an element is found to combine, is the fixed number by which that element is always represented. Oxygen is invariably represented by 8, because this is the smallest proportion in which it is known to combine with any other substance. Thus, also, water is composed of oxy- gen 8, and hydrogen 1 ; potash of oxygen 8, and the metal, potassium, 40. The lowest proportion in which sulphur is known to combine with any other substance is 16, and there- fore sulphur is always represented by this number. ^Thus sulphuret of lead is composed of 1 proportion of sulphur 16, and one of lead, whose combining number is 10-O Its num- ber therefore is 16+104=120. We have just mentioned that the combining number of any compound is represented by the sum of its simple, or elementary parts. This will now be understood 5 for by adding the numbers representing the elements in each of the above examples, we shall have those by which the compounds are represented. The number for water, as already shown, is 9 ; the number for potash is 48, viz. 8 oxygen an<3 40 potassium; that for sulphuret of lead is 120, viz. sulphur 16, and lead 104. By remembering the combining weights of the elements of any compound, the number representing that compound may at once be known. For example, hydrate of potash is composed of water and potash; water is composed of oxy- gen 8, and hydrogen 1=9. Potash is composed of potas- sium 40, and oxygen 8=48. These two sums being added, viz. N 9-f 48=57. Thus the number for hydrate of potash is 57. Again, the salt called sulphate of potash is compounded of sulphuric acid and potash. Now to find the number re- presenting its combining proportion, we have only to remem- ber that sulphuric acid is composed of one proportional of sulphur 16, and 3 proportionals of oxygen 24, and that the sums of these two numbers are 40. The number for potash, as above seen, is 48; therefore the number for sulphate ot potash, being the sum of these two numbers, is 40-j-48=88. What then is the number for water? How does it appear that 40 is the number lor sulphuric acid? Are the numbers for each element and compound invariable ? On what circumstance is the number for an element founded ? What is the number for sulphu- ret of lead? What other number is this number composed of? Hydrate of potash is composed of water and potash, how will you find the number which represents hydrate of potash ? What is the composition of sulphate of potash ? How may the number re- presenting this compound be found ? DEFINITE PROPORTIONS. 91 It is unnecessary to adduce further examples, since the in- telligent student will be able to understand from the above epitome, not only on what kind of facts the laws of definite proportions are founded, but will also, it is hoped, be able to arpply the above principles to the proportional numbers of the most common substances to be mentioned hereafter. Combination by Volumes. The doctrine of definite pro- portions was founded on the suggestions of Mr. Higgins, of Glasgow, published in 1789. But it was Mr. Dalton, of Man- chester, in England, who established the laws of chemical combinations, and w r ho has the merit, of not only discovering almost all that is known in the details of this subject, but also of having brought it distinctly before the world. Mr. Dalton published "his views of the doctrine of definite proportions, in 1808, soon after which, Gay Lussac, a French chemist, pro- ved by a publication in one of the journals/' that gases unite in simple and definite proportions, and among other instan- ces, showed that water is composed precisely of 100 volumes of oxygen, and 200 volumes of hydrogen. It was afterwards shown by the same author, that other gaseous substances, which are capable of a chemical union with each other, unite in definite proportions, by measure, or volume, and that these proportions are in the simple ratio of 1 to 1, 1 to 2, 1 to 3, and so on, as above stated. These observations have since been confirmed by nume- rous experiments, instituted by the first chemists of the age, and at present it is as fully established, that the law of defi- nite proportions extends to the volumes of gases, as it does to their weights and to those of solids. As an illustration of the truth of this law, we adduce the condensation of hydrogen and oxygen by combustion, because these gases are more generally known than any others, and because their combi- nation is* also one of the most familiar examples of definite proportions by weight. The apparatus for this purpose it is unnecessary to describe, it being sufficient for our present purpose, to state that the experiment has often been made with the most infallible accuracy. The invariable proportions in which oxygen and hydrogen Who first suggested the doctrine of definite proportions 1 Who extended this sub- ject, and brought it before the public 1 What is said relative to the union of the gases by volume? In what ratio do the gases combine by volume? What illus> tration is given of the union of the gases by volume? What are the proportions in which hydrogen and oxygen combine by volume, and what are these proportions by weight ? 92 DEFINITE PROPORTIONS. combine, are by volume 1 of the first and 2 of the last, and by weight 16 of oxygen to 1 of hydrogen. Thus the speci- fic gravities of these two gases are to each other as the num- bers 1 and 16, that is, a cubic foot of oxygen is just 16 times as heavy as the same bulk of hydrogen. The reason why hydrogen is represented by 1, as its combining proportion, by weight, while its combining volume is double that of the oxy gen, will be seen hereafter. I The mode of ascertaining the comparative volumes in which these two gases combine, is to measure them carefully, and having introduced them into a glass tube, the mixture is inflamed by an electric spark ; and in every instance it has been found, that whatever the propor- tions of the mixture might be in respect to each other, the ra- tio of combination is always the same, and consists of two parts of hydrogen, and one of oxygen, by volume. When one measure of oxygen is mixed with three of hydrogen, there will remain in the vessel one measure of hydrogen un- combined and pure, and no continuance of the electricity will in the least change this proportion ; and so, two measures of oxygen and two of hydrogen, leave one measure of oxygen in the same manner. When other gases unite merely in consequence of being brought into contact, and without combustion, the same law applies, that is, if the volume of one be greater than its com- bining proportion, the excess remains pure and untouched. We give a few examples of the proportions in which ga- ses unite by volume. Volumes. Volumes. 100 muriatic acid gas combine with 100 ammoniacal gas, 100 oxygen gas " 200 hydrogen gas, 100 hydrogen gas " 50 oxygen gas, 100 nitrogen gas " 200 oxygen gas, 100 chlorine gas " 100 hydrogen gas, 100 nitrogen gas " 300 hydrogen gas. Another curious fact concerning the union of the gases is, that many of them suffer a diminution of bulk, which is also in a simple ratio to the volume of the one or both. Thus, when 3 volumes of hydrogen and 1 of nitrogen combine, tkey in- WV-'. are the relative specific gravities of these two gases 1 What is the mode of as- certaining the volumes of these gases? Suppose one measure of oxygen is mixed with three of hydrogen, and inflamed, what will become of the third measure of hydrogen 7 Does the same law apply when two gases combine without combustion 7 What illus rations are given of the combination of gases by volume? CHEMICAL EQUIVALENTS. 93 stantly contract into 2 volumes, or one half their former bulk, and form gaseous ammonia. A similar condensation takes place when several of the other gases combine. Chemical Equivalents. It was long since proved by Wen- zel, a German chemist, that when two neutral salts decom- pose each other, the. resulting compounds are likewise neu- tral. That is, the acid of one will exactly neutralize the alkali of the other ; and although two new salts are formed by this mutual decomposition, they will both, like the original com- pounds, be equally neutral. If one of the salts be in quan- tity too large for the combining proportions, then the excess of that salt will remain undecomposed in the solution, and only such a portion of it will be decomposed as is just suffi- cient to neutralize the constituents of the other salt. Hence, Chemical Equivalents are those definite propor- tions of one subst nice, which neutralize definite proportions of another substance. The truth of this law may be demonstrated by setting down the combining numbers of two salts, and the number repre- senting the two new compounds, and then by exchanging the numbers representing the combining parts, the numbers for each compound will be found to represent the number for the new compound, and the combined numbers of the old and new compounds will be equal to each other. Thus, the num- ber for sulphuric acid is 40, and the combining proportion of potash is 48, and therefore the number for ,sulphate of po task is 88. The combining proportion of nitric acid is 54, and that of baryta 78, and the sum of these two numbers is 132, which represents the nitrate of baryta. Now when these two salts are mingled together in solution, both are decom- posed ; the 54 pans of nitric acid of the nitrate of baryta will saturate the 48 parts of potash of the sulphate of potash, ma- king a new salt, -nitrate af potash, whose combining number is 102. At the s-'ine time, the 40 parts of sulphuric acid of the sulphate of potash, will combine with, and saturate, the 78 parts of the baryta of the nitrate of baryta, forming another new salt, "'sulphate of baryta, whose number will therefore be 40 added to 78=118. What is meant by chemical equivalents? How may it be proved that when two salts decompose each other, the acid of one exactly neutralizes the alkali of the other? What number represents nitrate of baryta? What number represents sulphate of potash? When these two salts decompose each other, what are the names of the new salts formed, and what is the number for each ? 94 CHEMICAL EQUIVALENTS. Now it may be observed that the sums of the proportional numbers of the old and new compounds are equal, and the same, and therefore that there can be no excess in either ol the alkalies or acids. This may be shown thus : Sulphuric acid 40 and potash 48, form sulph. potash, 88 Nitric acid 54 and baryta 78, form nitrate baryta, 132 Sum of the old compound, 220 Sulph. acid 40 and baryta 78, form sulph. of baryta, 1 1 8 Nitric acid 54 and potash 48, form nitrate of potash, 102 Sum of the new compound, 220 The utility of being acquainted with these important laws, says Mr. Turner, is -almost too manifest to require notice. Through their aid, and by remembering the proportional num- bers of a few elementary substances, the composition of an extensive range of compound bodies may be calculated with facility^ By knowing that 6 is the combining proportion of carbon, r;ad 8 of oxygen, it is easy to recollect the composi- tion of carbonic oxide, and carbonic acid ; the first being composed of 6 carbon and 8 oxygen, and the second of 6 carbon and 16 oxygen. By simply remembering, therefore, that carbonic oxide is composed of one proportion of carbon, and 1 proportion of oxygen, and knowing that carbon is represented by 6 and oxygen by 8, we at once arrive at its composition. And by recollecting that carbonic acid has 1 proportion of carbon, and 2 of oxygen, the composition of this is also known. It may be remembered that the number for potassium is 40, and tnat when combined with one pro- portion of oxygen, 8, it forms potash, 48. Now by remem- bering these clata, we know without "further trouble the com- position of the carbonate and bicarbonate of potash. The car- bonate being composed of one proportion of carbonic acid, 22, (that is 6 carbon and 16 oxygen,) and one proportion of potash, 48, (that is, potassium 40 and 8 oxygen,) is represent ed by 70. The bicarbonate is composed of one proportion What is the sum of the numbers of the old salts, and what the sum of the numbers of the two new salts 1 What is the equivalent number for carbon? What is the equi- valent number for oxygen ? ' Carbonic aci:l is composed of 1 equivalent of carbon, and 2 equivalents of oxygen now what is the number for carbonic acid 1 Why is the numbeti AT equivalent, of carbonate of potash 70 ? CHEMICAL EQUIVALENTS. 95 of potash, 48, and two of carbonic acid, 44, and its number is therefore 92. Again, having in the memory the numbers representing carbonic acid, we can readily apply them to the composition of other compounds, with which this acid is united. Thus, the number for carbonate of soda, is 54, and we know from its name (see Nomenclature,) that it contains only one pro- portion of carbonic acid. Now by recollecting the combin- ing proportion of sodium, "we know, in # moment, the compo- sition of the carbonate of soda. The combining number for carbonic acid being 22, this substracted from 54, leaves 32, for the other combining proportion, and knowing thai 24 is the number for sodium, and that soda is composed of sodium and oxygen, and that the combining number of oxygen is 8, we ascertain the composition of the salt in question, viz. sodium '24, oxygen 8,=32 soda ; carbonic acid 22=54, carbonate of soda. By the same law of proportions, suppose it is required td find the composition of sulphate of soda. The composition and number of soda oeing known, we have only to remember that the combining proportion of sulphur is 16, and that sul- phuric acid is composed of one proportion of sulphur and 3 of oxygen, and the composition of this salt and its number is ascertained. Soda 32, sulphur 16; oxygen 3 proportions, 24, 16=40 added to 32=72. Therefore' the number for sul- phate of soda is 72, and its composition 32 of soda and 40 of sulphuric acid. Thus by the application of this law to the combining num- bers, or the equivalents of chemical bodies, a table of which may be found at the end of this work, the composition of most compounds may be readily ascertained. Method of ascertaining the proportional numbers of compounds. The combining numbers of all the elementary bodies, as already stated, represent the smallest proportions in which they are severally found in union with any other body. ' But it is obvious that all these numbers must have one common smit from which they are calculated, otherwise there would exist no proportions between them. For this purpose, hydro- why is bi-carbonate of potash represented by 92 1 Why is catbonate of soda represent- *d by 54 f By the same law of proportion, show why the equivalent for sulphate of soda is 72 ? What are the units or data from which the combining numbers, or equivalent* are calculated 1 96 CHEMICAL EQUIVALENTS. gen, as uniting- in the lowest possible proportion, is employ ed. Thus, hydrogen unites with oxygen in one proportion, by weight to form water, and the weight of hydrogen being 1 , the weight of oxygen in water is 8, which is also the small est proportion in which the latter body is found in union. fThese two elements having an extensive range of affinity and therefore bein^ found in combination with a great variety of other substances, are made the data, or points of compa- rison from which all the other numbers are calculated. Afterwards, other compounds were examined which con- tained the smallest proportions of these elements united to other substances. Among these "it was found that the gas called carbonic oxide, contained the smallest combining pro- portion of carbon, united with the smallest proportion of oxy- gen, these proportions being as 6 to 8. And also, that the gas called sulphuretted hydrogen, contained the smallest pro Dortion of hydrogen united to the smallest of sulphur, these proportions being 1 of hydrogen and 16 of sulphur. Thus, the numbers for carbon and sulphur were found to be 6 for the former and 16 for the latter, the numbers for hydrogen and oxygen being 1 and 8. On examination of the different oxides of iron, it was found that the least proportion with which that metal combined with oxygen, was that of 28 of the former, and 8 of the latter. The number for iron is therefore 28, and that of this oxide of iron 32. In this manner the proportional numbers of each compound has been ascertained, and from these, tables of chemical equi valents have been constructed. Wollastoris scale of Chemical Equivalents. Dr. Ure says, that this scale of chemical equivalents has contributed more to facilitate the general study and practice of chemistry than any other invention of man. The descrip- tion of this instrument was published by the inventor in 1814. It consists of a piece of mahogany board two or three inches wide, and of a length proportionate to the extent of the scale it contains, or of the size of the type in which it is printed. Running through the middle of the board there is a sliding Having the numbers for hydrogen and oxygen as data, how are the numbers for other bodies found 1 What are the equivalent numbers for carbon and sulphur 7 Explain low the number for iron was found. Describe the construction of Wollaston's scale of shemical equivalents ? CHEMICAL EQUIVALENTS. 97 rule, containing the proportionate numbers of all the most common chemical compounds, and on each side of the rule are printed the names of the compounds corresponding with these numbers. The divisions of this scale are laid out logo- metrically, after the manner of the common Gunter's scale, and consequently the ratios between the numbers are found, by the juxtaposition of the several lines, on the sliding and fixed parts, with the greatest accuracy. The arrangement of this instrument is such, that the weigh of any ingredient in a compound, or its definite proportion, and also the equivalents of the acids and alkalies, may be at once seen by merely moving the sliding part. On this scale, instead of taking hydrogen for unity, Dr. Wollaston has taken oxygen, which he calls 10; but if we slide down the middle rule so that 10 on it stands opposite to 10 hydrogen on the left hand, then every thing on the scale will be in accordance with Sir H. Davy's system of proportions, taking hydrogen for unity, and also in accord- ance with the theory of definite gaseous combination, by volume. The principle on which this instrument works, may be learned in a few minutes ; and after a little practice, it be- comes one of the most efficient and beautiful of labor-saving machines, to both the practical and theoretical chemist} Nothing but actual practice with the instrument, will con vey to the mind of the learner a knowledge of its practical usefulness ; we will however give an example, by which the principle of its construction may perhaps be comprehended. We have already stated, that on this scale oxygen is the unit from which all the other proportions are calculated, and that this element is marked 10. When therefore, 10 on the sliding rule is against this number, the weights of -the other bodies are in due proportion to this number. Thus carbonic acid being 27.54, and lime 35.46, carbonate of lime being the sum of these numbers, is placed at 62. Then if the sli- ding rule be drawn upwards, so that the number 1 00, on it, corresponds with carbonate of lime, the other numbers will correspond with carbonic acid and lime, and will show the oroportions in which these ingredients unite to form 100 What principle does Dr. Wollaston call unity, and what is its number on the scale fM chemical equivalents'} On what evidence is the truth of the doctrine of definite propcw ;ons founded 1 9 98 ATOMS. parts of carbonate of lime. Thus, the number 56 corres ponds with lime, while 44 corresponds with carbonic acid, these two numbers making 100. Theory of Atoms. That chemical bodies unite in definite proportions, by weight, arid also by volume, and that where one body unites with, another in more than one proportion, the second is a multiple of the first, are facts resting on the evidence of experiment alone. These facts, in themselves so wonderful, and in their relation to science so important, excited the inquiry and speculations of many philosophic minds, as to their cause. Among these inquirers, Mr. Dai- ton, of Manchester, seems to have "been the most successful, having proposed a theory which accounts, with few, if any exceptions, for all the phenomena observed, and which therefore explains satisfactorily, the reasons why bodies com- bine in such proportions.'" As the basis of this theory, Mr. Dalton assumes that the union of bodies" in their smallest pro- portions, always takes place between the atoms of which they are composed ; that is, one atom of one body combines with one atom of the other body. Thus, water is formed by the combination (of one atom or particle of oxygen combined with one particle or atom of hydrogen. (This theory sup- poses also that the ultimate atoms of matter are indivisible : that they are always of the same shape and size in the same body, and that their weights are different in the different bodies. Thus, the weight of an atom of oxygen is 8 times that of an atom of hydrogen, these being the proportions in which these gases form water. But when bodies unite in several proportions, then it is 2 or 3 atoms of one, to one atom of the other. Thus, sulphurous acid is composed of 2 atoms of oxygen united to 1 atom of sulphur, and sul- phuric acid is composed of 1 atom of sulphur and 3 atoms of oxygen, these being the relative weights of their elements. But as it is found that the lowest proportion in which sul- phur unites with any other body, is in the proportion of 1 6 by What is said of Mr. Dalton's theory of atoms 1 What does Mr. Dalton assume as the basis of his theory of atoms? On this theory what is water composed of? What does this theory suppose, in respect to the divisibility, shape, and weight, of the atoms of bodies 1 Why is an atom of oxygen supposed to be eight times as heavy as one of hydrogen ? Why is an atom of sulphur supposed to be twice as heavy as one of oxygen? Why is it supposed that sulphurous acid contains 1 alum of sulphur united to two atoms of oxygen ? That sulphuric acid is composed of 1 atom of sulphur and 3 atoms of oxygon 1 Why is the equivalent number of oxygen 8 1 Why is that for sulphur 16 ? ATOMS. 99 weight, hydrogen being 1 , so it is assumed that a particle of sul- phur is sixteen times as heavy as one of hydrogen, and twice as heavy as one of oxygen. And as in sulphurous acid the weight 01 oxygen is found to be exactly double that in water, it is reasonable to suppose that sulphurous acid consists of 1 atom of sulphur united to 2 atoms of oxygen, and for the same reason, since sulphuric acid contains three times the weight of oxygen that water does, that this acid is com- posed of 1 atom of sulphur and 3 atoms of oxygen. All this, whether true or false, exnlams in the most satisfac- tory manner, why bodies combine with each other in definite proportions, and why these proportions are expressed by the numbers attached to each. Thus, hydrogen is unity, or the prime equivalent, and is expressed by 1, because by weight this gas is found to form water by uniting with 8 parts of oxy- gen. Oxygen is expressed by 8, because its proportion in water weighs eight time as much as the hydrogen. The number for sulphur is 1 6, because this is the smallest propor- tion in which it unites with any substance, and the number for the oxygen in sulphurous acid is 16, because in this acid the sulphur and oxygen are of equal weights, and therefore iust twice the weight of the oxygen in water 5 and the num- ber for the oxygen in sulphuric acid is 24, because its weight is three times that in water. Now by supposing that one atom of oxygen is 8 times as heavy as one of hydrogen, and that an atom of sulphur is twice as heavy as one of oxygen, or 16, times as heavy as one of hydrogen, the whole mystery of the law of definite proportions is reduced to simple arithmetical calculation, for the proportional numbers are in fact nothing more than the relative weights of the atoms of which the several bodies are composed. In respect to the truth or falsity of this theory, it is obvi- ously without the bounds of demonstration, for we never can ascertain whether the proportions on which it is founded are the smallest in which bodies combine, nor whether, if so, they combine atom to atom, as is supposed. But whether it be true or false, it does not in the least affect the truth of the law of definite proportions, which, as already stated, is found- ed on experiment alone, and is therefore purely an expression Why is the number of oxygen in sulphuric acid 24 1 What is said of the proportionate numbers in relation to the weights of the atoms of bodies 7 What is said in respect W the truth of this theory 1 too CHEMICAL APPARATUS. of facts. The atomic theory, however, must always be con- sidered an elegant and probable hypothesis, and while it dis- plays uncommon ingenuity, and great chemical research, has the advantage of agreeing, in general, perfectly with the facts obtained by analysis. Chemical Apparatus. Before proceeding to treat of ponderable bodies, and the description of particular agents, it is proposed to describe some of the most common, and necessary utensils, used in the manipulations of chemistry. Fig. 29. A crucible, Fig. 29, is a deep conical cup, of a tri- shape at the top, and round at the bottom./ Crucibles are made of this shape for the conve- Unience of pouring out their fluid contents at either an- gle. They are made of clay and sand baked hard, and will withstand. very high degrees of heat without melting, but are liable, to crack when suddenly cooled. They are chiefly manufactured at Hesse, in Germany, and hence are called Hessian crucibles. Fig. 30. A melting pot, Fig. 30. These pots are made of various sizes and materials. Those used in glass houses are made of clay, and are of large size. Chemists employ those made of silver or platina, as well as of black lead, but of small dimensions. Metallic crucibles are used for particular purposes, when the substance to be experimented on would destroy the common crucible, in consequence of its Fig. 31. corrosive quality. A matrass, Fig. 31, is a glass vessel, in the shape of an egg, with a long neck. It is employed in ef- 1 \ fecting the solution of such substances as require / \ heat, and long continued digestion, for that purpose. / \ When used, they are commonly placed in a sand J bath, that is, in sand moderately heated. Whether it is true or false, does it in the least affect the truth of the doctrine o f ie- finite and multiple proportions 1 What is a crucible, and for what purpose is it v*d 1 Of what are crucibles made 1 How do melting pots differ from crucibles? Of wha> *ub stances are melting pots made ? Of what are matrasses made ? For what purpose- *e these vessels used ? CHEMICAL APPARATUS. 101 Pig. 32. A retort and receiver is repre- sented at Fig. 32. Retorts, a, ,are egg shaped vessels, with I the neck turned on one side. These vessels are of various capacities, from a gill to a bar- rel, or more. They are made of glass, metal, or earthen ware, but most commonly of glass. No vessel is so much used in experimental chemistry as the retort. In the process of distillation, in collecting the gases, in concentrating the acids, and in a great variety of other operations, this vessel is universally employed. The receiver, b, is a necessary appendage to the retort, and is destined to receive whatever comes over from it, during the process of distillation. For common purposes, these ves- sels are made of glass, but in the manufacture of various articles they are made of wood or metal. Fig. 33. Fig. 33, represents a tubulated retort. It differs from the plain retort, figured above, in having a Jubulure, or opening, as seen in the figure, to which is fitted a glass ground stopper. This opening saves the trouble of detaching the retort from the receiver when any additions are to bo- made to its contents, after they are con- nected, as in Fig. 32. It is also necessary for the introduc- tion of a safety tube, a part of this apparatus, absolutely necessary in some processes, and which will be described in another place. The alembic, Fig. 34, is used for the distil- lation or svMimation of solid, volatile substan- ces. It consists of two parts, the head a t which is ground on, so as to be perfectly tight, and the body b, which is set into a sand bath, when in use. The product of sublima- tion rises into the head, where it is condens- ed, and then runs down the spout into a re^ ceiver. -What is a retort ? How large are retorts ? Of what are retorts made ? What are the uses of retorts ? What is a receiver, and what is its use 1 Of what are receivers made 7 How does a tubulated, differ from a plain retort 7 What is the use of the tubulure, of opening, in this retort ? What is an alembic "\ What is the use of the alembic ? 9* Fig. 34. 102 CHEMICAL APPARATUS. Pig. 35. Evaporating dish, Fig. 35. Every cnemi cal apparatus must have among its utensils shallow dishes for evaporating fluids., The best are made of Wedgewood's ware, and com* 1 packed in nests containing several sizes each. The heat is applied by means of heated sand or ashes, and these vessels are used to evaporate solutions of salts, in order to obtain crystals, and for various other purposes. Ftg. 36. . Fig. 36, a Florence flask, furnished with a tube, to be used instead of a retort. Students will save considerable expense, by employing these flasks in the room of retorts:. The cork is pierced with a burning iron, and through the aperture is passed a tube of glass or lead, bent as in the figure. In obtaining oxygen, by means of oxide of manganese and sulphuric acid, and for many other purposes, this arrangement will serve instead of the best retort, while, if broken, the expense is only a few cents. Fig. 37, The common blow pipe, Fig. 37, is a little instru- ment by means of which the most violent heat of a furnace may be produced. It is a pipe of brass, about the third of an inch in diameter at the largest end, and thence tapering, gradually, to a point, and b^nt, as in the figure. To use it, place the curved end in the flame of a lamp, or candle, and apply the lips to the other end, then blow gently and steadily, giving the jet of flame a horizontal direction. To keep up a constant stream of diT for a length of time, the inspiration must be T^ mode by the nostrils, while the cheeks are used as bellows.". The art of doing this is soon learned by practice. The small fragments of ore, or other substance, on which the is thrown, must be laid on a piece of charcoal, which is held by small foreceps. When a very intense heat is re- quired, and the fragment is so light as to be blown away by the air, it may be confined by making a small cavity in the charcoal support, into which the substance is put, and anothei piece of charcoal is placed partly over this. Of how many parts does the alembic consist 1 For what purposes are evaporation dishes employed ? What does Fig. 36 represent! What are the advantages of usinj Florence flasks instead of retorts ? What is the common blow pipe 1 What is the use of this instrument 7 Describe the mode of using it. CHEMICAL APPARATUS. 103 Fig. 38. Gahn's Blowpipe, Fig. 38, is a much more con- venient form than the common one above descri- bed. In the common form, the flame is sometimes nearly extinguished, and the process stopped, by the condensed moisture from the breath. In Gahn's instrument this is prevented by the cham- ber a, which retains the condensed moisture, and which may be taken off from the main pipe for its removal. The tip of the sm&ll pipe through which the air passes to the flame, fits to a socket, so that those of different sized orifices can be used. The dropping tube, Fig. 39, is a small glass tube, blown into a ball in the middle, and ending with a fine orifice at the lower end. It is filled by dipping the small end into the fluid, and exhaust- ing the air by sucking at the upper end with the mouth. The thumb is then placed on the upper end, which keeps the liquid from running out. On 39. raising the thumb, the contents will descend in drops, but is instantly restrained on replacing it. This little instrument is highly useful for various purposes^ arid particularly when it is required to intro- duce one fluid under another, as w r ater under alcohol, or sulphuric acid under water.) The simple arrangement, Fig. 40, is designed to col- lect and retain for the purpose of temporary examina- tion, such gases as are lighter than the atmosphere, 40. and at the same time are absorbable by water. These gases, for more thorough examination, re- quire the aid of a mercurial bath, but most of their properties may be examined by the apparatus re- presented by the figure. The flask a, is to contain the materials for extri- cating the gas, and into the mouth of this, there is inserted a tube a foot or more long. The tall bell glass b, or a large tube closed at the upper end, is inverted over this tube, as seen in the figure. As an example of the use of this apparatus, sup- pose we desire to make some experiments on am- monia, a gas which is rapidly absorbed by water, and specifically lighter than atmospheric air. The materials for separating this gas are muriate of am How does Gahn's blowpipe differ from the common one ? What arc the peculiar ad 104 CHEMICAL APPARATUS. monia, called also sal ammoniac, and slacked quick-lime. {'These being separately reduced to powder, equal parts are then mixed, and introduced into the flask a, and the tube put into its place. On application of a gentle heat, the gas will be set free in consequence of the combination which takes place between the lime and the muriatic acid of the muriate of ammonia) The ammonia is thus set at liberty, and being lighter than the air, ascends and gradually displaces the air from the vessel b, and takes its place. This experiment affords an instance of the chemical action of two solids on each other. Fig- 41. Fig. 41 is designed as a simple illustration of a 'gas apparatu^: The me- thod of making experi- ments with the perma- nently elastic fluids, such as common air, and the gases, and of transferring them from one vessel to another, though sufficient- ly simple, requires some directions for the beginner. The gases are none of them sufficiently dense, to be retained in vessels open to the air for any considerable time; and some of them being lighter than the atmosphere, instantly ascend, and are lost, when the vessels containing them are opened. All the gases, therefore, when open to the air, mix with it more or less rapidly, according to their densities, and thus escape us entirely, being diffused in the atmosphere. Hence, to re- tain a gas in a state of purity, it must be kept from contact with the atmosphere, and hence also the necessity of first fill- ing the vessel with a fluid instead of air, before the gas is in- troduced, and of transferring it under a fluid from one vessel to another. The figure represents a wooden vessel or tub, a, with a shelf k, k, fixed a few inches from the brim. When the ap- paratus is to be used, the tub is to be filled with water, vantages of this blowpipe ? Describe the construction of Gahn'a blowpipe. What is the ehape of the dropping tube? What is the use of this instrument ? Describe the manner gf using the dropping tube. For what purposes is the dropping tube useful 7 What \a the use of the apparatus represented by Fig. 40 1 Describe Fig. 40, and explain an ex- ample of its use. How may ammonia be obtained and examined by means of this appa- ratus ? What is represented by Fig. 41 ? Why cannot the gas be poured from one vea- id to another, and be retained in an open vessel like water 1 CHEMICAL APPARATUS. 105 so as to rise a few inches above the shelf. Now when a glass jar, or any other vessel, open only at one end, is filled with water, by being plunged into the fluid, it will retain its contents when raised above the fluid, provided its mouth be kept under it ; for the water is sustained in the vessel by the pressure of the atmosphere, on the same principle that the mercury is sustained in the barometer tube. (See Barometer in Natural Philosophy.) The vessels b, g, /, represent jars filled with water, and inverted on the shelf, their necks pass- ing through an aperture in it, so as to preserve their uprigh 1 , positions. The vessels e, c, and i, are retorts, with their necks inserted into the mouths of the inverted jars. _ Now when common air, or any gas, is introduced into the mouth of a vessel so inverted, the air will rise to the upper part of the vessel, and will displace the water, and occupy its place. If a tumbler, or cup, in the state which we usually call empty, but which is really full of air, be plunged into water with its mouth downwards, very little water will enter it, because the admission of the fluid is opposed by the in- cluded air ; but if the mouth of the vessel be turned upwards, it immediately fills with water, while the air is displaced, and rises to the surface of the fluid in one or more bubbles. Suppose this is done under the mouth of a jar filled with wa- ter, the air will ascend as before, but instead of escaping, it will be detained in the upper part of the jar. In this man- ner, therefore, air may be transferred from one vessel into another, by an inverted pouring, and the first portions, in- stead of occupying the bottom of the vessels, like water, as- cend to the top, the air, instead of running from a higher to a lower vessel, rising from the lower to the higher one. This is owing to the pressure of the water on the air, or to the lightness of air when compared with water. For the same reason, lead being lighter than quicksilver, if a bullet of the former be sunk in a vessel of the latter, it will rise to the surface. On this principle balloons ascend ; the hydrogen with which they are charged being 13 times lighter than the Explain the reason why a vessel filled with water may be raised above the fluid, pro- vided its mouth be kept under it. When a tumbler is forced into the water with its mouth downwards, why does not the fluid rise in if? When air is introduced under a vessel, inverted and filled with water, why does it rise to the highest part of the vessel How does the rise ot a balloon illustrate this principle 7 106 CHEMICAL APPARATUS. atmosphere, the former is forced upwards by the pressure of Che latter. A bell glass receiver, Fig. 42, is employed in making experiments on air, or the gases. It is a glass vessel, of the shape represented in the figure, and of various sizes, from the capacity of a pint to that of several gallons. The knob at the upper part, is the handle by which, it is moved. It is used for the temporary confine- ment of elastic fluids, on which experiments are to be made. Large tumblers are good substi- tutes for bell glasses. A lamp furnace, Fig. 43, is one of the most indispensable articles in a chemical apparatus. It consists of a rod of brass, or iron, about half an inch in diameter, and three or four feet long, screwed to a foot of the same metal, or to a heavy piece of wood. On this rod, slide three or four metallic sockets, into which are screwed straight arms terminated with brass or iron rings of different diameters. The screws cut on the ends of the arms where they enter the sockets are all of the same size, so that the rings may be changed from one socket to another, as con- venience requires. These rings are for the support of retorts, receivers, evaporating dishes, &c., as repre- t ented in the figure, and may be moved up, or down, or turned aside, and then fixed in their places, by means of thumb screws passing through the sockets and act- ing on the rod. The lamp by which the heat is given for dis- tillation, or other purposes, is also fixed with a thumb screw, so that the heat can be regulated by moving it up or down. Specific Gravity. The specific gravity of a body is its re- What does Fig. 42 represent ? What is the use of the bell glass receiver 1 Describe Hkc lamp furnace, Fig. 43. What are the uses of the rings on the ends of the arms! What are the uses of the thumb screws with which the sockets and lamp are furnished 1 What is the specific gravity of a body ? CHEMICAL APPARATUS. 107 iative weight when compared with the same bulk of another body. For solids and liquids, water is the substance to which the weight of other bodies are compared ; and for elastic fluids, the atmosphere is the standard of comparison. When a body weighs twice as much as the same bulk of water, it is said to have the specific gravity of 2 ; and if it weighs three, four, or five times as much as the same bulk of water, it has the specific gravity of 3, 4, or 5. Water, there- fore, is the unit, or standard of comparison, and has in this respect the specific gravity of 1. When a body is weighed in water, its weight will be di- minished by exactly the weight of a quantity of water equal to its own bulk, and thus the difference between its weight in air and in water being known, its specific gravity is readily found. The most simple mode of taking the specific gra vity f a solid, is by means of Nicholsons Portable Balance, represented by Fig. 44. The body is a hol- low cylinder of tinned iron, terminated at each end by a cone. From the vertex of the upper cone rises the small stem a, of copper or brass, bearing a small tin cup. This cup slips on, and may be removed when the instrument is not in use. From the point of the lower cone is suspended the tin cup e, at the bot- tom of which is attached a cone of lead so heavy as to sink the whole instrument in water nearly to the base of the upper cone. Before this balance is used, it is placed in a vessel of water, and the upper cup loaded with weights until it sinks so far that a mark on the stem at a, coincides exactly with the surface of the water. The weights so added are called the balance weights, and their amount may be marked on the cup as a given quantity for future use : suppose this is 900 grains. The specific gravity of a solid may then.be taken as fol- lows. First place it in the upper cup, and add weights until the mark on the stem coincides with the water ; suppose this With what substance are solids and liquids compared to find their specific gravities ? What is the standard of comparison for elastic fluids! Suppose a body weighs twice aa much as the same bulk of water, what is its specific gravity 1 What does Fig. 44 repre- sent ? Describe this balance. What preparation is necessary before the balance is ueed* What are the balance weights? After the balance ^weight is known, how will you pro- ceed \o find the specific gravity of a body ? 108 CHEMICAL APPARATUS. to be 400 grains ; subtract this from the balance weight, and we have 500 grains for its weight in air. Then remove the subject of experiment to the lower cup, and the stem will rise above the mark, because it weighs less in water than in air ; weights must therefore be placed in the upper cup until the mark again coincides with the surface of the water ; sup pose this to be 100 grains, which will be exactly the weight of the water displaced by the mineral or other solid. The specific gravity is now found by a very simple rule, namely, Divide the weight in air by the loss in water, and the quotient will be the specific gravity.', In the present instance, we have 500 grains for the weight m air, and 100 for the loss in water; therefore 100 : : 500=- 5, the specific gravity. The most simple method of taking the specific gravity of liquids, is by means of a graduated bottle holding 1000 grains of water, which is taken as the unit or standard for other liquids. Fig. 45. Take a small bottle with a long narrow neck, as represented by Fig. 45, and having weighed it accu- rately, introduce into it exactly 1000 grains of pure water, and mark the level of the water with a file on the neck of the bottle. The bottle thus prepared will serve to ascertain the specific gravity of any fluid, for since water is the standard by which the comparative weights of all other fluids are known, the same bulk of any other fliiid, weighed at the same temperature, will be its specific gravity. Thus, suppose that when the bottle is filled with sulphu- ric acid up to the mark at which the Water weighed 1000 grains, it should be found to weigh 1800 grains ; then the specific gravity of the acid would be 1800, water bein 1000. If filled to the same mark with alcohol it might weigh 800 grains. The specific gravity of alcohol would therefore be 800, water being 1000. But as it is understood that water is the standard of comparison, the specif^ gravities of bodies are expressed merely by the numbers i-~ signifying their relation to this standard. Thus the specific gravity of After finding the weight of a body in air, and its weight in water, what is the rule for finding its specific gravity 1 What are the most simple means of finding the specific gravity of a liquid ? How does a bottle filled with 1000 grains of water, become the standard for other liquids? Suppose a given bulk of water weighs 1000 grains, and the same bulk of another fluid 1600 grains, what would be the specific gravity of the alter 1 CHEMICAL APPARATUS. 109 lead is 1 1, that is, it is 11 times as heavy as water, bulk for bulk; while the specific gravity of ether is 750, that is, a given bulk of ether will weigh 750 grains, ounces, or pounds, while the same bulk of water weighs 1000 grains, ounces, or pounds. (See spec. grav. in Nat. Philosophy.) To determine accurately the specific gravity of the gases, is an operation of great delicacy, and requires not only very nice apparatus, but much experience. The method by which it is done is, however, easily explained, and will be readil understood. We have already said that atmospheric air is the standard of comparison for the gases. In the first place, therefore, it is necessary to ascertain the weight of a given volume of air. This is done by weighing very accurately, a light glass ves- sel furnished with a good stop-cock, when full of air, or in its ordinary state. Then having withdrawn the air, by means of an air pump, and closed the stop-cock, the vessel is again weighed, and the difference will show the weight of air which the vessel contained. On making this experiment^ it is found that 100 cubic inches of air weigh 30.5 grains, and by the same method, the weight of a given portion of any elastic fluid may be ascertained. In all these experiments, it is understood that the thermometer stands at 60 and the barometer at 30. Fig. 46. Suppose, then, that the glass globe a, Fig. 46, is of sufficient capacity fo contain 100 cubic \g inches of air weighing 30.5 grains, and it is found on filling it with oxygen that the same quantity of this gas weighs 34 grains. Then to find the specific gravity of the latter gas we say, "as the weight of the air is to- that of the oxygen, so is unity, or the specific gravity of the atmosphere to the specific gravity of oxygen." Thus, 30.5 34: : 1=1.1147. gives 1.1147 for the specific gravity of oxygen gas. But since it is inconvenient in practice to ex- periment on just 100 cubic inches of gas, the graduated vessel b, has been invented, to show ^at once what quantity of gas in cubic inches is weighed in the globe a. The globe being first exhausted of air, and its stop-cock closed, is then connected with the re- ceiver b, containing the gas, and both cocks ~ Howls the specific gravity of a gas ascertained 1 10 110 NOMENCLATURE. being opened, the gas passes from the receiver to the globe The receiver being open at the bottom, and set over water, or mercury, the rise of the fluid will show the quantity of gas which passes into the globe, and on weighing the globe both before and after connecting it with the receiver, the differ ence will show the weight of the air thus transferred. Nomenclature. The nomenclature of Chemistry, now universally employ- ed, was invented by the French chemists about 1784. Be- fore that period, the names of chemical substances were en- tirely arbitrary, that is, each substance had an independent name, the signification of which had nothing to do with its composition, or often gave an erroneous idea concerning it. Thus, solution of muriate of lime was called liquid shell, and afterwards oil of lime. Liquid ammonia was called bone spirit, and sulphuric acid was called oil df vitriol. It is true, at that time the substances known to chemists were few in number, when compared with the immense list of the present day. But even then, their number was such as to make it difficult for the memory to retain them, and at the same time to remember their origin or composition, when this was known. At present, were the substances mentioned in any chemical book merely designated by arbitrary names, or names inexpressive of their composition, the student would necessarily spent more time in learning and remembering them, than is now required to obtain a knowledge of the whole science of Chemistry. The general diffusion of chemical knowledge, therefore, is in a great measure owing to the present nomenclature, its perfect simplicity, its co- piousness of meaning, and the ease with which it is learned and retained. Each term in this nomenclature designates the composi- tion of the compound substance to which it is applied ; and What is the weight of 100 cubic inches of common air ? Suppose it is found that 100 cubic inches of oxygen gas weighs 34 grains, how is its specific gravity found ? Explain Fig. 46, and show the design of each vessel, and the manner of using them. When was the chemical nomenclature invented, and by whom? Before this invention, how were chemical substances designated 1 What is said concerning improper names before this invention? At present, were the substances known to chemists designated only by arbi- trary names, what would be the consequence to the learner'? What effect has this no menclature had on the diffusion of chemical knowledge? By this nomenclature what do the names of the substances designate? NOMENCLATURE. Ill as the simple substances are comparatively few, the compo- sition of most chemical substances are known only by these names. The names of the acids are derived from those of their bases, that is, from the names of the substances to which oxygen unites in such proportions as to form acids. \ Thus, sulphur is the base of sulphuric acid, and carbon is the base of carbonic acidT' Some of these bases unite with several proportions of oxygen, and form acids of different degrees of strength. These proportions are designatec], by the differ- ent terminations of the name of the acid, the smaller pro- portion being signifiedrby ous and the larger by ic^ , Thus, sulphurous and sulphuric, and nitrous and nitric acids, mean that these acids contain single and double proportions of oxy- gen. The salts, that is, the compounds which the acids form with alkalies, earths, and metallic oxides, also indicate by their names the substances they Contain. Thus, the salts ending in ite consist of a base, united to an acid ending in ous ; and a salt ending in ate contains an acid ending in ic Sulphite and phosphide of potash are formed of potash and sulphuro?/s and phosphorous acids, while sulph^e and phos- phate of potash denote compounds of sulphuric and phos- phoric acids, united to the same base. The names of all the salts, of which there are nearly 2000, denote their com- position in the same manner, and thus we know the ingredi- ents of their compositions by merely seeing their names. The termination uret denotes the union of simple non-metal- lic bodies with a metal, a metallic oxide, or with each other. Thus, sulphuret and awkuret of iron, indicate a combination between sulphur or carbon with iron. As oxygen combines with several of the metals in different proportions, but not al- ways sufficient in quantity to form acids, the compounds so formed, though derived from the same metal, differ from each other. These compounds are called oxides, and are distin- guished from each other by the Greek derivatives, prot, deut, From what are the names of the acids derived ? What is the base of sulphuric acid T What is the base of carbonic acid ? By what termination in the word is a weak acid de- signated 7 By what termination is the strong acid indicated ? What are the compounds called which the acids form with different bases? If an acid ends in ous, what is the termination of the salt of which it composes a part? If the acid ends in ic, how does the salt end ? How will you know the composition of a salt by merely hearing its name 1 What does the termination uret denote 1 What is the composition of a carburet ol sulphur 1 What are oxides t 112 NOMENCLATURE. trit Y and per. Protoxide signifies the first degree of oxida tion; dioxide, the second; /ritoxide, the third ; and peroxide, the highest. In some of the salts, it was formerly supposed that the acid prevailed, or that more acid was present than necessary to saturate the alkali, and in others that the alkali prevailed. The first of these were called supersets, and the second s&6salts, while those in which the acid and alkali were in due proportion, were called neutral salts. These names are now regulated by the atomic constitution of the salt. If it is a compound of one atom of acid and one of al- kali, 'the generic name is employed, as carbonate of potash. But if two or more atoms of the acid be combined with the same base, a numeral is prefixed to indicate its composition in this respect. Thus, when the acid is in two proportions, or there are two atoms of acid to one of potash, it is called it-carbonate of potash. The three salts of oxalic acid and potash are called the oxalate, 6moxalate 1 and guadroxalaie of potash, the first consisting of one atom of each, the second of two atoms of acid to one of potash, and the third of four atoms of acid to one of potash. PART II. PONDERABLE BODIES. Explanations. A ponderable body, is one which has ap preciable weight. A simple body, is one which has not been decomposed These are also called elements, or elementary bodies. It is possible that all the substances now called elementary, may still be in reality compounds, for our knowledge on this subject is entirely negative, that is, all bodies which the art of chemistry has been unable to separate into parts, or to de- compose, are called simple, in order to distinguish them from By what terms are the different oxides denoted ? What is a deutox\de 1 What is a fritoxide 1 What is a peroxide 1 What is said of swpersalts and subsalts 1 What are carbonate and A/carbonate of potash? What is a ponderable body? What is a simple body ? What is the difference between a simple and an elementary body ? When do chemists call a body simple 1 PONDERABLE BODIES. 1 13 known compounds. Before the refinements of chemical analysis were known, it was believed that nature afforded only four elements, viz. fire, air, earth, and water. Analysis has however shown, that fire, or heat, is the result of chemi- cal union ; that air is a compound of nitrogen and oxygen ; that there are many earths, and that water is composed of hydrogen and oxygen. The number of simple bodies now enumerated amount to about fifty, or perhaps fifty-two. They consist of about 40 metals, three, or perhaps four supporters of combustion, viz. oxygen, chlorine, and iodine, ancf probably also bromine, and seven non-metallic combustibles, viz. phosphorus, carbon, hydrogen, sulphur, boron, selenium, and nitrogen. Only a few years since, potash, soda, and several other substances, no\v found to be compounds, were supposed to be elementary bodies ; and it is highly probable, that many sub- stances, now arranged as simple, will soon be found to be compounds. Before proceeding to describe the properties of the gases, it might be thought necessary to detail more particularly than has been done, the modes of confining and transferring them from one vessel to another. But it is thought that such di- rections are better understood by the student, and much more readily followed when given in connexion with the particu- lar subjects or cases, to which they immediately apply. The method, for instance, of transferring the nitrous oxide from the retort to the gasometer, and from the gasometer to the gas bag, will be best understood if given in connexion with an account of the properties of the gas, or immediately after it. The same, it is thought, may be said of confining and transferring the other gases. As several different methods are required, depending on the nature of the gas, its absorp- tion by water, its specific gravity, and other properties, these different modes can be best explained and understood in im- mediate connexion with the description of the peculiar pro- perties of each gas. As the doctrine of definite proportions is not only highly interesting as a subject of philosophy, but is also intimately connected with chemistry, both as a science, and a practical How many elements were formerly supposed to exist 7 What is said concerning flre, air, earth, and water 1 How manv elements are now supposed to exist, and what are they ? What is said of the probability that some bodies now arranged as elements will be found to be compounds? 10* 114 PONDERABLE BODIES. art, we shall attach to the name of each substance at the head of sections, its equivalent number, so that the reader may at once observe its combining proportion. And it is earnestly recommended to the pupil, that he should not only regar*d this subject as one of great importance in a scientific relation, but also, when viewed in a different light, as one that tends directly to impress the mind with the most serious conviction, that nothing in nature has been left to chance, but that the Almighty Creator has left a witness of himself, even in the proportions, and arrangement of the atoms of matter. No- thing, perhaps, even the sublimest works of nature, are more calculated to elicit the wonder and astonishment of a reflect- ing mind, than the fact that substances combine with each other in exact, and definite quantities, and that these quanti- ties or proportions, are the same in relation to the same sub- stance throughout the world, and have been so ever since the creation. This discovery may be considered as anew proof, directed expressly to the present age, that the most minute works of what we call nature, do indeed bear the most indu- bitable marks of divine agency and design. But while the discovery itself is an evidence of the profound philosophy of the present age, the developement of its prin- ciples, by the constant accession of new ideas, is calculated rather to humble the pride of human knowledge, by as con- stant a conviction, that after all our acquirements, we know comparatively nothing of the laws and operations of nature. The very fact, that the laws of proportions, now comparatively just known to man, have existed ever since the creation of matter, and Rave been in perpetual exercise all over the uni- verse, without a suspicion of their existence, is of itself a suf- ficient proof of the almost entire ignorance of man even of the phenomena of nature, and^a still stronger proof of his igno- rance of her laws, j And if facts, in themselves so simple, yej. so wonderful, and when once known, so obvious, have esca ped the observation of man for thousands of years, is it not What is said of the doctrine of definite proportions, in relation to philosophy and che- mistry? In what other respects is this subject recommended to the particular attention of the pupil 7 What is said of divine agency and design in the minute works of nature 1 Afwr all human acquirements, how much do we know of the laws and operations of na- ture 7 What improved hy the fact, that the law of definite proportions, though existing ever since the creation of matter, have, until lately, remained unknown 7 What is said of the probability that wonderful phenomena are constantly going on before our eyes? INORGANIC CHEMISTRY. 115 probable that phenomena are constantly going on before our eyes, which, could we understand them, would astonish us still more, and at the same time afford a still stronger convic- tion of our ignorance, and want of penetration ? These considerations, while they are calculated to humble the pride of human intellect, by showing how little we know of the laws which govern even the ordinary operations of nature, ought, by the conviction of ignorance, to prove an in- centive to constant observation on natural phenomena, that, if possible, we might arrive at the knowledge of their true causes. INORGANIC CHEMISTRY. NON-METALLIC SUBSTANCES. Oxygen 8. The name oxygen is derived from two Greek words, and signifies the former, or generator of acids, because it enters into the composition of most acid substances, and was for- merly considered the universal and only acidifying principle in nature. It was discovered by Dr. Priestley in 1774, and named by him dephlogisticated air. Its specific gravity is 1.11, air being 1. It is a non-conductor of electricity, like common air. It's electrical state is always negative, and when sud- denly and forcibly compressed, as in the fire-pump, already described, it emits light and heat. Oxygen may be obtained from many substances. The peroxides of lead, or manganese, and the nitrate and chlorate of potash, all yield it in abundance, when merely exposed to a dull red heat. The cheapest and most convenient substance for this pur- pose is black, or peroxide of manganese, in the state of fine powder. This, when heated in an iron bottle or gun-bar- rel, will yield upwards of 120 cubic inches of the gas to an ounce of the oxide. For small experiments, a gun-barrel may be used ; but where considerable quantities are wanted, a wrought iron bottle, with a neck 18 inches long, is the best instrument. Wliat does the term oxygen signify 7 Who discovered this gas 1 What is the specific gravity of oxygen gas "? What are the substances from which it can be obtained 1 What is the cheapest and most convenient mode of obtaining ill How many cubic inches of this gas will an ounce of the black oxide of manganese yield 1 What are the methods described of extricating this gas from manganese 1 116 OXYGEN. Fig. 47. The shape is represented at Fig. 47, with the addi- tion of a piece of gun-barrel, fitted to the mouth of the bottle by grinding. A tube, leading from the gun-barrel to the gas holder, conveys away the oxy- gen as it is extricated from the manganese. In the absence of such a bottle, oxygen may be convenient- ly obtained by mixing, in a proper vessel, one part of sulphuric acid, and two parts of the oxide of manga- nese, and applying the heat of a lamp. The cheap- est and most convenient vessels for this purpose are Florence flasks, fitted with corks and tubes, as rep- resented by Fig. 36. This, and the lamp furnace, 'Fig. 43, together with an inverted vessel filled with water, constitute the apparatus necessary for the extrication and confinement of oxygen. With respect to the theory of these processes, it is neces- sary to state, that there are three oxides of manganese, each of course containing different proportions of oxygen. These oxides are thus constituted, the combining proportion of man ganese being 28, and that of oxygen 8. Protoxide manganese, '28, added to oxygen, 8=36 Deutoxide 28, " " 12=40 Peroxide 28, " " 16=44 When the peroxide is exposed to a red heat, it parts with half a proportion of oxygen, that is, 4 parts, the number for oxygen being 8, and is therefore reduced to a deutoxide, whose number, it will be observed, is 40. The number for the peroxide being 44, and the loss by a red heat being 4, we obtain 4 grains of oxygen for every 44 grains of the oxide, which in bulk is nearly 12 cubic inches, making about 128 cubic inches for each ounce of the oxide. When oxygen is obtained by means of sulphuric acid, the theoretical expression is different. In this case the peroxide loses a whole proportion of oxyg'en, and is thus conveited into a protoxide, which then combines with the acid, forming What apparatus is necessary for obtaining this gas from manganese by means of sul- phuric acid ? How many oxides of manganese are there, and what are the proportions of oxygen in each? What proportion of oxygen does the peroxide part with at a red heat? To what oxide is the peroxide reduced by parting with a portion of its oxygen? What does deutoxide mean ? Explain the chemical cha/iges which take place when the oxygen is obtained by means of sulphuric acid. OXYGEN. 117 a sulphate of manganese, which remains in the retort. By this process, therefore, the peroxide yields 8 grains of oxy- gen to every 44 grains employed ; but in practice it is found that the first method is the best and cheapest. It will be observed, that the weight of oxygen for the deut- oxide, expressed above, is only 12, being a proportion and a half, instead of 2 proportions of that element; The oxides of lead and iron afford examples of precisely the same kind. These facts were at first supposed to afford exceptions to the law of definite proportions, or rather to the atomic theory by which the cause of definite quantities is explained. But it will be remembered, as already stated, that the smallest pro- portions in which bodies have been found to combine by weight, are those by which they are represented in numbers. Now the smallest proportion in which oxygen 'ias hitherto been known to combine, is in water, this proportion being as 8 to 1. The number, therefore, for oxygen is 8. But if it should be hereafter found, in the course of analysis, that oxy- gen unites in half this proportion, in any instance, then this apparent anomaly will be completely explained, for then its union with hydrogen, to form water, will be in two propor- tions, and its union with manganese, forming the deutoxide, will be in three proportions, &c. The fact, therefore, that oxygen unites in the proportion of 12 is not considered a valid objection to the universality of the law of definite and multiple proportions, but only a proof that the smallest combi- ning proportion of oxygen may not yet have been discovered. This digression seemed necessary, in order to explain, once for all, this apparent anomaly. Oxygen gas is an invisible transparent fluid, like common air, and has neither taste nor smell. It is sparingly absorbed by water/ 100 cubic inches of which, take up three or four cubic inches of the gas. Oxygen has the most universal affinity of any known sub- stance, there being not one of the simple substances with which it may not be made to combine. It unites with all the metals, forming a very extensive class of compounds, known under the name of oxides. With some of them it combines What is said concerning the weight of oxygen for the deutoxide of manganese ? Why does not ihe discovery, that oxygen sometimes combines in the proportion of 12, tend to invalidate the atomic theory ? What is said of the taste and smell of oxygen ? In whal proportion is this gas absorbed by water 1 What is said concerning the extensive affinity of oxygen ? 118 OXYGEN in such proportions as to form acids. Such is tne case with arsenic, molybdena, and others. With the simple combusti- bles, sulphur, carbon, &c., it also combines in various pro- portions, forming oxides and acids. With the metals sodium and potassium, it enters into combination to form the alkalies soda and potash. Thus the acids and alkalies, though in most of their properties so entirely opposed to each other, are composed of oxygen united to different bases, the base of sulphuric acid being sulphur, and that of potash being po- tassium. The process of oxidation sometimes takes place very slow- ly, as in the rusting of iron exposed to the atmosphere. In this case, the affinity of the iron for the oxygen contained in the atmosphere, though constantly exerted, produces its ef- fects very gradually, particularly if the iron is kept in a dry state ; but the oxidation is greatly facilitated if .the iron is moistened with water, since then the metal absorbs oxygen from the water, as well as from the air. In ordinary combustion, which is nothing more than a rapid oxidation, with the extrication of heat and light, the strong affinity between the combustible and the oxygen 'is caused by the great elevation of temperature. The combustible re- quires, in the first place, to be heated to a certain degree, before it will attract oxygen with sufficient force to emit heat and light, after which, the elevation of its temperature is con- tinued by the absorption of oxygen, and thus the combination of one portion of oxygen with the burning body causes the absorption of another. A combustible is any substance, capable of uniting with oxygen, or any other supporter of combustion, with such ra- pidity, as to cause the disengagement of heat and light. In this sense, iron, steel, and many other bodies, though they will not burn in the open air, are strictly combustibles, as they conform to the 'above definition, when heated in oxygen gas. In this gas, all combustibles burn with greatly increais. d What are the compounds of oxygen and the metals called ? Does it ever form acid* by combining with the metals? When combined with the metals potassium and sodium, what are formed 1 What is said of the spontaneous oxidation, or rusting of iron ? Wfcat la ordinary combustion? In combustion what causes the strong affinity between th burning body and oxygen ? In kindling a fire, why is it necessary to raise the tempera- ture of the wood, in order to make it burn? What is a combustible body? In wbai seaaa are iron, steel, and other metals, combustibles 7 OXYGEN. 119 splendor ; and many substances which, before the discovery of this gas, could not, in any sense, belong- to this class, are now strictly combustibles. The combustion of various substances in oxygen gas, affords experiments of the most brilliant and instructive kind. Among these, the combustion of iron, steel, and zinc, are highly interesting, not only because we are not in the habit of seeing metals burn, but because the first give out the most splendid corruscations of light, while the zinc burns with a light peculiar to itself. To exhibit the combustion of iron or steel, in this gas, procure a piece of wire of small size, or what is better, a watch spring, and wind it round a slender rod of wood, so as to coil it in a spiral form, the turns of the wire being about the fourth of an inch apart. Then withdraw the rod, and fix to the lower end of the qpil a small piece of thread dipped in melted bees-wax, or sulphur, or what is better, a little piece of spunk. . The otner end of the wire, for a few inches, is to be left straight, and fixed to the cork fitting the mouth of the bottle in which the experiment is to be made. Next, fill a clear glass bottle of a quart or more capacity with oxygen gas, and having set it upright, cover the mouth with a plate of glass, or otherwise. Then inflame the com- bustible on the end of the wire, and having removed the cov- er from the bottle, introduce the coil, and fix the cork in its place, as represented by Fig. 47. p- 47 The wire will burn with a light too vivid for the eyes to bear, throwing out the most brilliant corruscations in every direction. Now and then a globule of the melted metal will fall, and if the vessel contains water, it will leap on its surface for an instant or two, being thrown up by the steam into which it converts the fluid. If the vessel contains no water, the intense heat of the globule will cause it to melt the glass and ?sink into its substance, and if the glass be thin, it will fuse a path quite through it, without caus- the least fracture. What is said of the brilliancy of the combustion of some of the metals 1 How is tht iron wire prepared for combustion in oxygen gas 1 Describe Fig. 47. What causes th* globules of melted iron to leap on the surface of the water 1 What is said of the action of the globules of metal on the glass '{ 120 OXYGEN. To witness the combustion of zinc in oxygen, first prepare the metal by melting, and pouring it while fluid into the water. Then place some thin pieces in a spoon prepared with a cork on its handle, as represented by Fig. 48, and put in the Fig 49 m ^ st f ^ e zmc a sma U piece of phosphorus. Hav- ' ' 'ing a bottle of the gas prepared as in the last experi- ment, inflame the phosphorus by holding the spoon over a lamp, and instantly introduce it into the bot- tle, fixing the cork in its place. The metal will burn with a beautiful white light, often tinged with green, owing to a small quantity of copper which the zinc contains. If a lighted candle be blown out' and then plunged into a vessel of this gas, while a spark of fire remains in the wick, it will be relighted with a slight explosion. The best way of making, this experiment, is, to place a short piece of candle in a socket, fixed to a wire, as in Fig. 49. In this manner a candle may be blown out and again set on fire by dipping it into a bottle of oxygen, twenty or thirty times, and perhaps oftener. During combustion in oxygen gas, the oxygen corn- bines with the burning body, and produces remarka- ble changes, not only on the combustible, but also on the gas. The combustible, on examination, will be found to have sensibly increased in weight, by the combination, while the oxygen entirely loses the pow- er of again supporting combustion, so that if a lighted candle be plunged into it, instead of burning with splendor as before, it is now instantly extinguished. These changes are readily explained by the analysis of the body burned, and of the gas. The iron loses its brillian- cy, and is converted into a dark brittle substance, easily pul- verised in a mortar. This is an oxide of iron, and consists of the iron itself united to the ponderable portion of the gas. If the iron is weighed before the combustion, and afterwards, it will be found to have increased in weight in the proportion of 8 parts to the 28. Describe the method of preparing and burning zinc in oxygen gas. What is the effect when a candle is blown out, and then instantly plunged into the gas 7 What eSect does combustion produce on oxygen gas 1 What change is produced on the iron burned in it ? Why does the oxide of iron weigh more than the metal before it was burned 1 Suppose ihe iron and oxygen are both accurately weighed before and after the experiment, what effect on their weights will be produced by the combustion! OXYGEN, 121 The gas on the contrary loses in weight what is gained by (he iron, and if the vessel in which the experiment is made, be open at the bottom, and stands in a dish of water, the di- minution of the gas in volume will be indicated by the rise of the water in the vessel. If the gas and iron are both accu rately weighed before the experiment and afterwards, the sum of their weights will be found precisely the same, proving that nothing has escaped, and that what has been lost by the oxygen has been gained by the iron. When other combusti- bles are submitted to the action of this gas, though they may entirely change their appearance by the process, or seem to be dissipated and consumed,! yet nothing is lost by the burn ing^here being in all such instances merely a change of form. Thus, when charcoal or diamond is burned in a confined por- tion of this gas,' instead of losing as in the former experiment, the gas increases in weight', that is, it is converted into car- bonic acid gas, by a union between the oxygen of the gas, and the carbon of the diamond or charcoal, so that what is lost by the charcoal is gained by the gas. In every instance, the gaseous matter which remains in the vessel after combustion, is unfit to support animal life. If a bird or any other animal be confined in a limited portion of atmospheric air, it soon dies, because it destroys the oxy- gen the air contains, by converting it into carbonic acid, thus leaving another portion of the atmosphere called nitrogen, both of which are destructive to life. (See Nitrogen.) If a bird be confined in a portion of oxygen, it will live longer than in the same quantity of atmospheric air, because it is the oxygen alone which supports the respiration ; but it dies when the oxygen is consumed, or converted into carbonic acid. But if any animal be introduced into a portion of air after its oxygen has been destroyed, or absorbed by a burn- ing body, it dies in a few seconds, unless like the frog it has the power of suspending its respiration. Finally, it is proper to remember, that no animal can live, in an atmosphere which will not support combustion. Is any thing lost by combustion ? When charcoal is burned in a confined portion of oxygen gas, what effect is produced on each 1 Into what gas is the oxygen con- verted by the process ? Will the gas left after combustion ever sustain animal life? Why will a bird or any other animal soon die when confined in a limited portion of common air 1 Why will an animal live longer in oxygen gas, than in the same portion of common air ? Will an animal live in air which will not support com- bustion 1 11 122 HYDROGEN. Were this fact more generally known and remembered, we should not every year hear of instances where lives are lost by descending into old wells or cisterns. The cause of such accidents is the presence of carbonic acid, in the bot- toms of such cavities ; and were the precaution taken to let down a burning candle, before the descent of the person, all danger might be avoided ; for if the flame is extinguished, the air will not support animal life. It, has been recently reported, that throwing buckets of wa- ter into a well, where two persons had fallen down'by suffo- cation with carbonic acid gas, had been the means of saving their lives. (See Carbonic Acid.) Hydrogen. 1. The name of this gas is derived from two Greek words, signifying the generator of water, because it enters largely into the composition of that fluid. It was discovered by Mr. Cavendish in 1766. Its specific gravity is 0.694, air being 1. A 00 cubic inches weigh 2.11 grains) while the same bulk of air weighs 30.5 grains; it is therefore about "14 times lighter than atmospheric air. Com- pared with oxygen, it is just i 6 times lighter than that gas; being indeed the lightest of all known ponderable bodies. It refracts light more powerfully than any other body, Nits re- fraction being in the ratio of 6.6, air being 1. Its electricity is positive. Hydrogen may be obtained by several processes, but in no instance without the presence of water, it being evolved only by the decomposition of that fluid. The most convenient method, is to put fragments of iron or zinc into a proper vessel, and pour on them two parts by weight of sulphuric' acid, diluted with 5 or 6 parts of water. The hydrogen will immediately ascend through the water in abundance. Will air which is unfit for respiration support combustion? What precaution ought always to be taken, before a person goes into a well rr old cistern 7 What is the derivation of the word hydrogen? What is the weigfit of 100 cubic inches ol this eas? What is its weight when compared with air? How much lighter is hy- drogen than oxygen ? What substance is lighter than hydrogen gas ? What is said of its power to refract light ? What is the electrical state of this gas ? Can this gas be obtained without the presence of water! Why 1 ? What is the best method of obtaining this gas ? \ HYDROGEN. 123 Pig. 50. Where only small quantities of the gas are wanted, the simple ap- paratus represented at Fig. 50, is all that is required. It consists of a Florence flask into which the zinc and acid are put, with a tube lead- ing under a bell glass, or large tumbler filled with water, and in- verted in a dish of the same fluid, c for this purpose is better than iron, and is easily prepared by melting, and while fluid, pour- ing it into .water. The production of the hydrogen depends on the decompo- sition of the water which "is effected by the united action of the metal and acid.. The metal having an attraction for oxy- gen, obtains it from the water; this forms an oxide of the metal which is instantly dissolved by the acid ; the surface o the metal is thus left clean, and exposed to the water, from which it attracts another portion of oxygen, which is dissol- ved as before. Meanwhile the hydrogen being thus detacheo. from the oxygen, absorbs caloric, and is evolved in the form of hydrogen gas^ Hydrogen may also be obtained by passing the vapor o water through a hot iron tube. In this case, the oxygen of the water combines with the iron, while the hydrogen is set free. (Place a gun barrel across a* furnace so as to heat it red hot. Connect to one end of the barrel, by means of a tube, a re- tort containing water, and placed over an Argand lamp : and to the other end of the barrel fix a tube, leading under a ves- sel of water, inverted in a water bath. Then make the water the retort boil, so that its steam may pass into the gun bar- 1, and hydrogen will be evolved, and will pass into the inverted vessel.' Hydrogen, when obtained by either of these methods, is not quite pure, but contains a little sulphur or carbon. For par- ticular purposes it may be purified by passing it through a solution of pure potash in water. In this state hydrogen is without colour, taste, or smell. It On what does the production of hydrogen depend! Explain the chemical changes which take place during the production of this gas. By what other method may this gas be obtained 1 How does the red hot gun barrel decompose the water? Is hydrogen a compound or an elementary bodv 124 HYDROGEN. 'S, so far as is known, an elementary body, having resisted all attempts to resolve it into more simple parts. It is inflammable, but not a supporter of combustion. If a lighted candle be introduced into a vessel of this gas, the flame is-instantly extinguish ed| but in passing into the gas, it inflames that portion which is in contact with the atmosphere. This shows that the combustion of hydrogen requires the aid of oxygen which it absorbs from the atmosphere as a supporter. IThis experiment may be made by inverting the vessel con- taining the hydrogen in the open air, its levity preventing it from escaping downwards. In this state it will be seen to burn only on the lowest surface. But if the vessel contain- ing it be turned upright, the whole will escape in a volume of flame. 'N Hydrogen is the gas with which balloons are charged, and being about fourteen times lighter than common air, if the balloon is large, it ascends with great force. The principle on which balloons ascend, is the difference of specific gravity between the balloon as a whole, consisting of hydrogen, and the apparatus containing it, and the same bulk of atmosphe- ric air. ill is the same principle that makes a cork rise through water, or a leaden bullet through quicksilver. The principle of balloons may be illustrated thus. Fill a bladder, or a gas bag, furnished with a stop-cock, with hy- drogen gas ; attach to the stop-cock a tobacco pipe, or what is better, one of metal. Then dip the bowl of the pipe into a solution of soap, and form bubbles by pressing the bladder. These bubbles being detached from the pipe, Avill rise rapidly through the air. When hydrogen is mixed with oxygen and inflamed, the mixture detonates violently: The best proportions are two parts of the hydrogen and one of oxygen by volume. If soag, bubbles of this mixture are touched with a candle when float- ing in the air, they give a report as'lqud as a pistol, but much more sharp and stunning. A loud report is also given when the hydrogen is mixed When a lighted candle is plunged inlo this gas, does it continue to burn, or is it extin- guished 7 As the candle passes into the gas, what part of it is set on fire 1 How is this experiment best made 7 Why does the hydrogen burn only on the surface 7 With what gas are balloons filled 1 On wha' principle do balloons ascend 1 How may the principle of balloons be illustrated 1 What is the consequence of firing a mixture of hydrogen and oxygen 7 What proportions of each make the loudest report 7 HYDROGEN. 125 with common air, instead of oxygen. The best proportions are about three of the air to one of the hydrogen. Fig.5\. This experiment may be varied by means of the hydrogen .gun, Fig. 51. It consists of a tin vessel, holding about a pint, the lower end being closed, and the upper end left open and fitted with a cork, a small | orifice being made toward the lower end, as seen in [the figure. Having filled this vessel about one third with water 'close the small orifice with the thumb, and let in hy- drogen until the water is displaced. Thus, the vessel will contain three parts of air, arid one of hydrogen. The cork being put rather loosely in its place, the mixture is fired by raising the thumb, and applying a lighted taper to the orifice. The cork will be driven out with violence, at- tended with a loud report. When a jet of hydrogen is burned at the end of a tube with a fine bore, and with a large tube of glass, porcelain, or metal, musical tones are produced, which are grave or acute in proportion to the size or kind of tube employed, Fig;J)'2. This pleasing experiment may be performed by placing the materials for making hydrogen, in a convenient vessel, furnished with a tube, as in Fig. 52. Or the tube may be connected with a reser- voir of gas already collected. The manner of hold- ing the large tube to produce the musical tones is shpwn in the figure. Hydrogen cannot be breathed without deleterious effects, though it is not immediately fatal to animal life. The action of platinum sponge on hydrogen is singular, and highly curious. ^When a jet of this gas is directed on a few grains of the sponge, both being cold, and in the open air, the latter immediately be- comes hot, and in a moment glows with a red heat, setting fire to the hydrogen. Platinum sponge 'is prepared by dissolving the metal m What are the best proportions for mixing hydrogen and air for the same purpose ? Describe the method of using the hydrogen gun, Fig. 51. How are musical tones pro- duces! by the burning of hydrogen 1 Explain Fig. 52. Is hydrogen a respirable gas ? What effects does it produce \\ hen breathed ? What phenomena are produced when hy drogen is thrown in a stream upon platina sponge ? How is platina sponge prepared ? 11* 126 HYDROGEN. nitro-muriatic acid, that is, a mixture of one part of nitric to 2 parts of muriatic acid. v > Ammonia, or muriate of ammonia, is added to this solution, which produces a yellow precipitate When this precipitate is exposed to a red heat in a crucible the acids and ammonia are driven off, and there remains pure platinum, in the form of a delicate spongy mass. Another method of obtaining- the sponge, is to throw the yellow pre- cipitate on filtering paper, and when the liquid has passed through, to dry the paper, and introduce it, with the adhering precipitate, into the crucible. This curious effect of the action between platina sponge and hydrogen, was discovered by Professor Dobereiner, of Jena, who invented the following method of producing an instantaneous light by its means, *. Fig. 53. The two vessels, a and b, Fig. 53, are of glass ; a is prolong- ed in the form of. a tube, and is fitted to the mouth of b, by grinding, or cement, so as to be air tight. The lower part of a reaches nearly to the bot- tom of b, and is encompassed with a strip of zinc. Sulphuric acid, diluted with five or six parts of water, being placed in b, a is fixed in its place, as seen in the figure. Hydrogen is evolved by the action of the acid on the zinc, and pressing upon the fluid, (which must fill only about one half of b,) drives it up the tube into a. The stopper of a, is conical, and rises to let the air from that vessel escape. When so much gas has been evolved as to press most of the acid up into a, and consequently to remove it from the zinc, the chemical process will cease, leaving b nearly filled with hydrogen. The brass tube d, is cemented to the neck c, and furnished with a stop-cock. The box e, contains the platina sponge at the end of the tube. When a light is wanted, nothing more is necessary than to Explain Fig. 63, and show how hydrogen is produced, and in what manner it is throwr upon the sponge. Why does not the acid constantly act upon the zinc 1 HYDROGEN. l27 open the stop cock d, and let a jet of the gas blow upon the sponge, which becoming immediately red hot, a match, and then a candle may be lighted. By permitting the hydrogen to escape, the acid again comes in contact with the zinc, and thus another portion of the gas is formed, and retained until wanted/ Protoxide of Hydrogen 9. 1 p. Oxygen 8-f 1 p. Hydrogen 1. Water. It is only necessary to remark in respect to the above ab- breviations, that the number for water, as already explained, is , being composed of 1 proportion of oxygen 8, and 1 propor- tion of hydrogen 1. The same method being observed with respect to the other substances to be described, the student has only to notice the numbers affixed to the names of each substance, and he at once becomes acquainted with the pro- portions and composition of each compound, and the number by which the compound itself is represented. This method, it is thought will not only be found highly convenient, but will also greatly facilitate the acquirement of a proper know- ledge of chemical equivalents, a subject, as formerly remark- ed, of great importance to the student in the present state of the science. It has been stated that water, by analysis, is composed of two parts of hydrogen, and one of oxygen, by volume, and 1 part hydrogen, and 8 oxygen by weight. Having described the properties of these two gases sepa- rately, it now remains to demonstrate by synthesis, that is, by the combination of these gases, that water is the product. It may be seen by a very simple experiment, that when hydrogen is burned, water is formed. When one portion of the gas escapes, in what manner is another portion generated 7 What is signified by the numbers affixed to water, oxygen and hydrogen 1 With what does the student become acquainted by observing the numbers affixed to names of the elements, and of their compounds? By analysis, what is the composition of water, by weight and measure ? By what einiple experiment may be shown that when hydrogen is burned, water is formed ? 128 WATER. Fill with hydrogen a blad- der, furnished with a stop- cock, and small tube. In- flame the hydrogen at the end of the tube, and intro- duce the flame into a dry glass globe with two open- ings, as represented at Fig. 54. As the gas burns, the rarefied and vitiated air will pass off at one of the openings, while the other admits fresh air to support the combustion. In a few minutes the inside of the globe will be covered with moisture, and by continuing the experiment, water will run down its sides, which may be tasted or otherwise examined. The same experiment may be made with a large glass tube instead of a globe. In this experiment, it is supposed that the combustion of the hydro- gen is supported by the oxygen of the atmosphere, and there- fore nothing can be known of the proportions in which they unite. Nor would it be absolutely certain by this experiment that it was the oxygen of the atmosphere which combined with the hydrogen, and supported its combustion. But when the two gases are confined, each in a separate gasometer, and burned 1 - together in an exhausted vessel, the result will not only demonstrate to the senses that water is the product, but will also show the exact proportions of each ele* ment by weight and measure. For this purpose two graduated gasometers contain the two gases, each being furnished with a tube, leading to the glass globe, Fig. 55. Before the experiment begins, this globe is connected with an air pump by the screw c, and completely exhausted of air, and then accurately weighed. It is then connected with the two g'asometers which contain the gases by the pipes d and e. When every thing is thus prepared, the stop-cock d is opened, and a small stream _of hydrogen let in, which is instantly in- "flanied by an electrical spark from the conductor a, this being of course connected with an electrical Is it absolutely certain by this experiment, that it is the oxygen of the atmosphere which unites with the hydrogen to form water 7 How may it be demonstrated that the combustion of hydrogen and oxygen form water ? Describe the apparatus represented 6y Fig. 55, and explain how the two gases are brought together, and how inflamed? WATER. machine. The oxygen is then admitted, by turning the stop- cock, e, and thus the combustion of the hydrogen is supported. At the end of the process, the graduated gasometers show exactly the volume of each gas consumed, and as the weight of 100 cubic inches of these gases are known, it is easy to compute the weight of the volumes consumed, and by weigh- ing the globe to compare it with the weight of water produced. By such experiments made with every attention to accura- cy, together with that before described, of weighing the gases by means of exhausted vessels, Fig. 45, it is proved, that hydrogen and oxygen unite in the proportions of two of the first, to one of the last, by volume ; and in the proportions of 1 and 8, by weight ;) that the sole product of the combustion of the two gases is water, and that the weight of the water is just equal to the combined weights of the two gases. In this manner has the constitution of water been demonstrated beyond all doubt or controversy. Compound Blowpipe. When hydrogen and oxygen are burned together, in the proportions in which they form water, a most intense heat is produced. The compound blowpipe, the instrument by means of which the combustion of the two gases is regulated for this purpose, was invented by Professor Hare, of Philadelphia, in 1801. The apparatus consists of two pipes, which convey the gases from two gas-holders, to another pipe, at the end of which their combustion takes place. Fig. 56. The principle of the com- pound blowpipe will be under- stood by Fig. 56. The two brass pipes c and d, are con- nected with the gas-holders a and b, by coupling screws, which fix their lower ends to short tubes furnished with stop- cocks, as seen in the figure. These stop-cocks are for the convenience of confining the gas in the gas-holders, when the blowpipe is not in use, and At the end of the process, how ia it ascertained what proportion of each gas has been consumed, and how much water formed 1 What has been proved hy such experiments in respect to the quantities and proportions of the gases consumed, and quantity of water formed ? What is said of the intense heat produced by the combustion of hydrogen and oxygen 1 What is the instrument called by which the combustion of the two gaees i 130 COMPOUND BLOWPIPE. for other purposes connected with the pneumatic cistern. The two upper stop-cocks are designed to regulate the quan- tity of gas from each pipe, so as to produce the greatest heat, and also to stop it entirely while making experiments. The gas-holden . a and b, are two boxes of painted tin, open nt the bottom, and :nade to fit a cistern of wood, about five feet long, containing 1 water. These boxes are fixed in their places, at each end of the cistern, by buttons, so that they can- not rise when filled with gas. They maybe two and a half, or three feet deep, and two feet wide, or of any other size, according to the extent of the experiments proposed. The cistern must be several inches deeper than the boxes, so that the water will rise above them. The two pipes convey the two gases separately to the point t, where they are soldered together, and on their united points is screwed a platina or silver tip, having a single orifice, at the end of which their combustion is effected. If the tip is of silver, it should be large, and care taken not to include it in the cavity of the charcoal support, while making experi- ments, otherwise it will be melted. Having such an apparatus ready, the gas-holders are put in their places, (the blowpipe being removed, until every thing is prepared for experiment,) and water is poured into the cistern, the stop-cocks being open for the escape of the air. When the cistern and boxes are full of \vater, the stop-cocks are closed, the blowpipe screwed on, and^the two gases are conveyed under the boxes by tubes, coming from the vessels where the gases are evolved. One of the boxes being filled with hydrogen and the other with oxygen, the blowpipe is set in action by turning the stop-cock connected with the hydro- gen, and setting' the gas on fire as it issues from the tip. The oxygen is then admitted, when the flame of the hydrogen will become less, being reduced to a small blue flame, which gives little light, and to the eye appears insignificant, and regulated for this purpose 1 Explain Fig. 56, and show the uses of the two tubes, the atop-cocksy and the platina tip, &c. In filling the cistern, why are the stop-cocks left Open ? What is said of the smallness of the flame, and the intensely heating powei of this blowpipe 1 PROPERTIES OF WATER. 131 totally incapable of the calorific effects attributed to this cete" brated machine. But the student who had never witnessed its powers, will 'be struck with astonishment, when he finds that a piece of iron, or copper wire, held in this little flame, burns with nearly the same facility, that a cotton thread con- sumes in a candle 5 and that a piece of tobacco pipe not larger than a kernel of corn, will give a light, from which he will instantly be forced to cover his eyes. The compound blowpipe melts the most refractory substan- ces, and even dissipates in vapor those which are infusible by the best furnaces. No means hitherto discovered, with the exception of the galvanic battery, produce calorific effects so intense as this blowpipe. Fig. 57. The pneumatic cistern above described is represent- ed at Fig. 57, with the blow- pipe in its place. For schools or private experiments, per- haps this is as cheap and convenient a form as can be constructed ; since it serves the purpose of gasometers for the blowpipe, and a cistern for experiments on all the gases where a water bath is employed. It is believed, after having had occasion to direct the construction of several cisterns for the above named purposes, that the following dimensions are sufficient. Length of the cistern, 5-J- feet ; depth, 2j- or 3 feet; width, 2 feet; gas-holders or boxes, 2 feet square. The cistern to be made of pine boards, and well painted on both sides before it is used. The frame and legs on which it stands, must be separate from the cistern, about 18 inches high, and furnished with rollers. Such an apparatus, including the blowpipe and boxes, costs about 14 dollars. Properties of Water. It is unnecessary to describe the common properties of a fluid which is so universally knowu, that neither man nor animal can exist without it. The purest water not having ui> dergone distillation, is that which falls from the clouds. It la there any means of producing a more intense heat than that produced by the coo* pound blowpipe 1 Explain Fig. 57. What water is purest without distillation? 130 COMPOUND BLOWPIPE. for other purposes connected with the pneumatic cistern. The two upper stop-cocks are designed to regulate the quan- tity of gas from each pipe, so as to produce the greatest heat, and also to stop it entirely while making experiments. The gas-holden . a- and b, are two boxes of painted tin, open .at the bottom, and .n'ade to fit a cistern of wood, about five feet long, containing 1 water. These boxes are fixed in their places, at each end of the cistern, by buttons, so that they can- not rise when filled with gas. They maybe two and a half, or three feet deep, and two feet wide, or of any other size, according to the extent of the experiments proposed. The cistern must be several inches deeper than the boxes, so that the water will rise above them. The two pipes convey the two gases separately to the point e, where they are soldered together, and on their united points is screwed a platina or silver tip, having a single orifice, at the end of which their combustion is effected. If the tip is of silver, it should be large, and care taken not to include it in the cavity of the charcoal support, while making experi- ments, otherwise it will be melted. Having such an apparatus ready, the gas-holders are put in their places, (the blowpipe being removed, until every- thing is prepared for experiment,) and water is poured into the cistern, the stop-cocks being open for the escape of the air. When the cistern and boxes are full of water, the stop-cocks are closed, the blowpipe screwed on, and^the two gases are conveyed under the boxes by tubes, coming from the vessels where the gases are evolved. One of the boxes being filled with hydrogen and the other with oxygen, the blowpipe is set in action by turning the stop-cock connected with the hydro- gen, and setting the gas on fire as it issues from the tip. The oxygen is then admitted, when the flame of the hydrogen will become less, being reduced to a small blue flame, which gives little light, and to the eye appears insignificant, and regulated for this purpose ? Explain Fig. 56, and show the uses of the two tubes, the Btop-cock.s, and the platina tip, &c. In filling the cistern, why are the Btop-cocks left open 1 What is said of the smallness of the flame, and the intensely heating powei of this blowpipe ? PROPERTIES OF WATER. 131 lotally incapable of the calorific effects attributed to this cefe^ brated machine. But the student who had never witnessed its powers, willbe struck with astonishment, when he finds that a piece of iron, or copper wire, held in this little flame, burns with nearly the same facility, that a cotton thread con- sumes in a candle ; and that a piece of tobacco pipe not larger than a kernel of corn, will give a light, from which he will instantly be forced to cover his eyes. The compound blowpipe melts the most refractory substan- ces t and even dissipates in vapor those which are infusible by the best furnaces. No means hitherto discovered, with the exception of the galvanic battery, produce calorific effects so intense as this blowpipe. Fig. 57. The pneumatic cistern above described is represent- ed at Fig. 57, with the blow- pipe in its place. For schools or private experiments, per- haps this is as cheap and convenient a form as can be constructed ; since it serves -the purpose of gasometers for the blowpipe, and a cistern for experiments on all the gases where a water bath is employed. It is believed, after having had occasion to direct the construction of several cisterns for the above named purposes, that the following dimensions are sufficient. Length of the cistern, 5-J- feet ; depth, 2 j- or 3 feet; width, 2 feet; gas-holders or boxes, 2 feet square. The cistern to be made of pine boards, and well painted on both sides before it is used. The frame and legs on which it stands, must be separate from the cistern, about 18 inches high, and furnished with rollers. Such an apparatus, including the blowpipe and boxes, costs about 14 dollars. Properties of Water. It is unnecessary to describe the common properties of a fluid which is so universally knowu, that neither man no* animal can exist without it. The purest water not having un- dergone distillation, is that which falls from the clouds. It la there any means of producing a more intense heat than that produced by the COB* pound blowpipe 1 Explain Fig. 57. What water is purest without distillation? 132 PROPERTIES OF WATER. is transparent, and without either taste or smell ; and being perfectly bland and neutral, it is to all animals, whose tastes have not been vitiated, the most agreeable of drinks. The weight of water, as already shown, is the standard by which the weight or gravities of all solids and liquids are es- timated. The weight of a cubic foot of pure water is 1000 avoirdupois ounces. A cubic inch of this fluid weighs, at the temperature of 60, 252.52 grains, and consists of 28.00 grains of hydrogen, and 224.46 grains of oxygen. By divi- ding 224.46 by 28.06, it maybe seen how nearly these gases unite in the proportions of 1 and 8 to form water. The weight of water, when compared with that of air, is as 828 to 1. The effect of temperature upon liquid water is distinguished by a peculiarity of a very striking kind, and exhibits a departure from the general laws of nature, for a purpose so obviously wise and beneficent, as to afford one of the strongest and most impressive of those endless proofs of design and omniscience in the frame of creation, which it is the most exalted plea- sure of the chemist, no less than of the naturalist, to trace and admire. " All liquids, except water, contract in volume, as they cool down to their points of congelation ; ( but the point of the greatest density in water is about 40, its freez- ing point being 32." As its temperature deviates from this point, either upwards or downwards, its density diminishes ; or in other words, its volume increases. This peculiar law is of much greater importance in the economy of nature than might at first be supposed. The cold air which rushes from the polar regions progressively abstracts the heat from the great natural basins of water, or lakes, till the whole mass is reduced to 40 ; but at this point, by a wise Providence, the influence of the atmosphere no longer has this effect ; for the superficial stratum, by farther cooling, becomes specifi- cally lighter, and instead of sinking to the bottom, as before, and displacing the warmer water, it now remains at the sur- face, becomes converted into a cake of ice, and thus preserves the water under it from the influence of farther cold. I To what animals is water the most agreeable of all drinks 7 What is the weight of a Cjlbic foot of pure water ? What is the weight of a cubic inch of water 1 How may it be proved that the weights of hydrogen and oxygen in water are in the proportions of 1 to 8 1 What is the weight of water when compared to that of air ? At what tempera- ture is water at its greatest density? When water is above or below the temperature of 40 degrees, how is its bulk affected ? In what respect is the expansion of water ii> freezing, of great consequence to man 7 OXYGENIZED WATER. 133 If, like mercury, water continued to increase in density to its freezing point, the cold air would continue to rob the mass of water of its heat, until the whole sunk to 32, when it would immediately congeal into a solid mass of ice to the bot- tom, and thus every living animal it contained would perish. In the northern or southern temperate zones, such masses of ice would never again be liquefied ; a striking proof of the beneficence and design of the Creator in forming water with such an exception to the ordinary laws of nature. Water, in its natural state, always contains a quantity o* air. This may be shown by placing it under the receiver of an air pump, for as the air is removed from the receiver, bub- bles will be seen to rise from the water. The air in water is found to contain a larger proportion of oxygen than the com- mon air of the atmosphere. The lives of all such fishes as live entirely under the water, depend on the quantity of oxy- gen it contains, for no animal can live and move where oxy- gen does not exist. Deutoxide of Hydrogen. 17. - 2 p. Oxygen 16+1 p. Hydrogen, L Oxygenized Water. Water, in the scientific language of chemistry/, is the prot- oxide of hydrogen? being composed of hydrogen, with one proportion of oxygen. (See Nomenclature.) It was supposed that hydrogen was incapable of a farther degree of oxygen- ation, until 1818, when Thenard, a French chemist, showed that by a certain intricate process, hydrogen could be made to combine with another dose of oxygen, and thus a new compound was formed, called deuloxide of hydrogen. This compound is formed in precise accordance to the law of definite and multiple proportions, and consists of 2 propor- tions of oxygen and 1 of hydrogen, as stated at the head of this section. It is a highly curious and interesting compound. In some of its properties, it exactly resembles water, being inodorous and colourless ; but in others, it is remarkably differ- ent. It is corrosive to the skin, which it turns white, and to If water, like mercury, had its density increased by cold to 32 degrees, what would be the consequence, on large bodies of this fluid? What is said of the beneficence and de- eign of forming water with this exception to the ordinary laws of nature 1 How is it shown that water always contains air 1 How does the air in water difler from common air? What is the scientific name of water? What is deutoxide of hydrogen? What are the properties of oxygenized water ? How does this compound differ from common water 1 134 NITROGEN. the tongue it is sharp and biting, and leaves a peculiar me- tallic taste in the mouth. At the temperature of 58, it is decomposed, oxygen ga& being evolved in abundance. It is therefore necessary, in the summer season, to keep it surrounded with ice. f It is also decomposed and turned into common water by nearly all the metals, and most rapidly by those which have the strongest attraction for oxygen. Some of the metallic oxides produce the same effect, without passing into a higher degree of oxi- dation, a fact which has not been satisfactorily explained. The metals, silver and platinum, in a state of fine division, decompose this water, when thrown into it, with such energy as to produce explosions. The same effect is produced by the oxides of silver, gold, mercury, manganese, and several other metals. Nitrogen. 14. This gas was formerly called azote, which signifies life destroyer, because no animal can live when confined in it. But the same epithet might be applied to several other gases, with equal propriety; and therefore, -being the basis of nitric acid, it is more properly called nitrogen. As the atmosphere is composed of fourfifths of nitrogen, this gas may be obtained by placing a mixture of iron filings and sulphur, a little moistened, in a confined portion of air, as under a bell glass, over water. The mixture will absorb the oxygen from the air, and leave the nitrogen nearly pure. It may also be ob- tained by burning a piece of phosphorus in a vessel of air, inverted over water. The phosphorus forms phosphoric acid with the oxygen of the air, which acid is absorbed by the water, thus leaving the nitrogen remaining in the vessel. Nitrogen is transparent, and without taste or smell, like common air. It is arranged as a simple body, though there are reasons for believing that it is a compound. It is destructive to animal life, and is a non-supporter of combustion. A lighted candle plunged into it, is instantly extinguished, and any animal soon dies when confined in it. At what temperature is this compound decomposed ? Why do the metals decompose this kind of water ; and what do they absorb from it 1 What was the former name of .nitrogen 1 What does azote signify 7 Why is it now called nitrogen 1 How may nitro- gen be obtained? How is gas obtained by means of iron filings and sulphur? How ia nitrogen obtained by means of phosphorus ? What are the properties of this gas 1 ATMOSPHERE. 135 Yet it exerts no injurious influence on the lungs, the priva- tion of oxygen being the sole cause of death. Its specific gravity is a little less than that of atmospheric air, nitrogen being 0.9722, air being 1000. One hundred cubic inches weigh 29.7 grains. When combined with oxygen in certain proportions, it forms nitric acid. Nitrogen exists in all animal substances, and in such plants as putrefy with an animal odour, as cab- bage and mushrooms. The Atmosphere. The air w r hich we breathe is composed of 20 parts of oxy- gen, and 80 parts of nitrogen, to every 100 by volume. TKese proportions are found never to vary, except from local causes. Gay Lussac, in an aerial voyage, carried with him an exhausted bottle, closely corked, and when at the height of nearly 22,000 feet from the earth, he uncorked his bottle, and let in the air. It was then closely corked again, and brought to the earth. On examination, this air was found to contain precisely the same proportions of the two elements as that taken from the surface of the earth. Speci- mens of air have also been brought from Chimborazo, Mount Blanc, from the deserts of Africa, and from the midst of the oceans, and on analysis, they have all been found to contain the same proportions of the two 'gases. These proportions are found by experiment to form the most agreeable air for respiration, and to be best fitted for the support of animal life. Animals confined in air, contain- ing more than the ordinary proportion of oxygen, have their respiration hurried, and become feverish, by over excitement : while those confined to air which contains a less proportion of that gas, become languid and faint, from the want of its stimulating effects. Besides these two gases, the atmosphere contains variable portions of carbonic acid gas, and aqueous vapor. The car- In what manner does nitrogen destroy life? Is the specific gravity of nitrogen greater, or less, than that of atmospheric air? With what substance does nitrogen form nitric acid ? In what vegetables is this gas found ? What is the composition of atmospheric air ? What is said of the constancy of these proportions ? From what parts of the world have specimens of air been analysed, and found to contain the same proportions of the two gases 1 What is the effect of a greater proportion of oxy- gen than common air contains on the animal system ? What is the effect of a less pro- portion on the system ? Does the atmosphere contain other gases besides oxygen and trogen? 136 ATMOSPHERE. bonic acid seems always to be present, since Saussure found it in the air of Mount Blanc, taken from the height of 16,000 feet above the level of the sea. Its proportion never exceeds one part in a 100, in freely circulating air ; and it generally amounts to only 1,1000th or 1,2000th part of the whole. The proportion of aqueous vapor is also exceedingly variable, but seldom exceeds 1 part in 100. The air of particular situations, is also found to contain small quantities of carburetted hydrogen, or inflammable gas, and of ammonia ; but these are not constant. It has been a question among chemists, whether the two gases composing the atmosphere are simply in a state of mix- ture, or whether they exist in a state of chemical combina- tion. Mixture has commonly been distinguished from com- bination, by the spontaneous separation of the ingredients oi the former. But, although oxygen is specifically heavier than nitrogen, no such instance has been found to occur. Air, confined in a long tube standing vertically for many months, was found to contain the usual proportion of oxygen in its upper part. The proportions of its constituents are also definite, like those of energetic combinations. By weight, there are two proportions of nitrogen 28, with 1 of oxygen 8. And by volume 4 parts of the first, 80, to one of the latter, 20, in the 100, thus making the simple proportions of 4 to 1. It has, however, been found that other gases of different specific gravities mix with entire uniformity where it is known that no^chemical union exists between them. Thus, if one ves- sel be filled with carbonic acid gas, and another with hydro- gen gas, the latter being placed over the former, with a tube communicating between them, the two gases will mix with per- fect uniformity in a few hours. In this instance, a part of the carbonic acid, though 22 times as heavy as the hydrogen, is found to have ascended into the upper vessel, while a part ol the hydrogen, though 22 times lighter than the acid gas, de- scends into the lower one. The cause of such an intimate mixture, under such circumstances, and without the influence What other gas is always found in the air ? What gases are occasionally found, their presence depending on local circumstances ? What reasons are there to believe that air is a chemical compound 1 What singular fact is mentioned in respect to the mixture ol carbonic acid and hydrogen, through a tube ? What does this fact show with respect to the uniform mixture of the elements of the atmosphere without a chemical union ? What " ises the facility with which oxygen is abstracted from the atmosphere tend to show ia woect to this chemica. anion? ATMOSPHERE. 137 of chemical attraction, has not been explained. But the fact is sufficient to show, that the uniform mixture of the consti- tuents of the atmosphere may be accounted for, without a chemical union. The facility, also, with which oxygen is abstracted from the atmosphere is against a chemical union. Thus, rain water contains a considerable portion of oxygen, besides a portion of atmospheric air. But the attraction of water for oxygen, is not supposed sufficient to overcome a chemical combination, and therefore did such a combination exist in the atmosphere, oxygen would not be found in water under such circumstances. On the whole, it is most probable, that the constituents of the atmosphere exist in a state of mixture, and not in a state of chemical union. The oxygen of the atmosphere being the principle which supports life, and flame, it is obvious that large quantities of this gas must be consumed every day, and therefore that its quantity must diminish, unless there exists some source from which it is replaced. The quantity consumed, however, must be exceedingly small, in a definite period of time, when compared with the whole ; for the atmosphere not only en- tirely surrounds the earth, but extends above it, at every point, about 45 miles. Now, when we consider how small a pro- portion of this immense mass, comes into contact with ani mals or fires at any one time, and that it is only these small portions that become vitiated, we may suppose that ages would elapse before any difference could be detected in the quantity of oxygen, even were there no means of replenish- ment provided. But the wisdom and design of Deity which the study of nature every where detects, and which as constantly seems ordained for the benefit and comfort of man, has not left so important a principle as that of vital air to be consumed, with- out a source of regeneration. It appears from experiments, that vegetation is the source from which the atmosphere is replenished with oxygen, and so far as is known, this is the only source. Growing plants, during the day, absorb carbonic acid from the atmosphere, On the whole, is it most probable that the elements of the atmosphere exist in a state of mixture, or in that of a chemical union 7 What is said of the quantity of oxygen consumed by animals, and flame, when compared with the whole which exists in the atmosphere ? From what source is the atmosphere replenished with oxygen 7 38 ATMOSPHERE. decompose the gas, emit the oxygen of which it is in part composed, and retain the carbon to increase their growth. (See Vegetation.) We have seen, under the article Oxygen, that when wood or carbon is burned, that oxygen is thereby converted into carbonic acid gas, and a greater or less proportion of this gas contained in the atmosphere may be attributed to this source. Here, then, we are able to trace another instance of the won- derful order and design of Omnipotence. The destruction of plants by burning, while the process absorbs the oxygen from the air, furnishes carbonic acid, which in its turn, is de- composed by growing vegetables, the carbon being again converted into wood, while the oxygen goes to replenish the loss created by the burning, and to purify the atmosphere for the use of man. NITROGEN AND OXYGEN. In addition to the reasons formerly assigned for supposing the atmosphere not to be a chemical compound, may be ad- duced the fact, that most other combinations of nitrogen and oxygen produce corrosive or noxious substances. Five such compounds are known to chemists, and they all admirably illustrate the changes produced by chemical com- binations, as already noticed under the article Affinity. They also confirm the truth of the doctrine of multiple proportions, having been adduced, as illustrations of this principle, under the same article. Some of the most material properties of each of these compounds will be stated, beginning with that containing the least proportion of oxygen, and ending with that containing the most. Protoxide of Nitrogen. 22. 1 p. Nitrogen 14X1 p. Oxygen 8. Nitrous Oxide. The best method of obtaining this gas is by fusing a salt called nitrate of ammonia. This salt may readily be formed How do plants obtain the oxygen which they emit ? Whence comes the carbonic acid gaa which plants decompose 1 What is said of the wonderful order and evident design of Providence, in making the destruction of plants the means of replenishing the air with oxygen ? What is said of the compounds of nitrogen and oxygen in reference to the chemical nature of the atmosphere? What do these compounds illustrate? What is the signification of protoxide ? What other name is there for protoxide of nitr igen 7 How is this gas obtained ? NITROGEN AND OXYGEN. f39 t-y mixing carbonate of ammonia with nitric acid (aqua fortis) diluted with four or five parts of water, and then evapora- ting- the solution by a gentle heat. The ammonia should be added in small lumps until the effervescence ceases ; and the evaporation continued until a drop of it, placed on glass, con- cretes. Having prepared the salt, the nitrous oxide or exhilarating gas may be procured from it, and its effects 'by respiration tried by the following simple means, when no better appara- tus can be obtained/ Prepare a Florence flask, as shown at Fig. 36, and into this put four or five ounces of the nitrate of ammonia. For a gas holder, fit to a large stoneware jug a cork pierced with two apertures with a burning iron; into one of the apertures pass a tube of glass or tin, so that it shall reach nearly to the bottom when the cork is in its place, and stop the other ori- fice with a cork. For a pneumatic cistern, take a common wash tub, and fit to it a strip of board passing through the middle, and about four inches from the top, so that Avhen the tub is filled with water, the board will be covered. Through the board cut a hole to receive the neck of the jug, so that it will stand in- verted. Having prepared things in this manner, fill the jug with water, and invert it in the tub, also previously filled with wa- ter. Then bend the tube belonging to the flask, so that it will enter the mouth of the jug, while the flask itself stands on a ring of the lamp furnace, and apply a gentle heat. If no lamp furnace is at hand, the flask may be suspended by a wire or string, and heated by a common lamp, or a few coals. The salt will soon melt and become fluid and trans- parent, when the gas will be extricated in abundance. When the jug is nearly full, which will appear by the sound of the bubbles, slip the hand under its mouth, and having set it up- right, immediately put the cork with the tube through it, in its place. As the nitrous oxide sometimes contains a mix- ture of iiitric oxide, or deutoxide of nitrogen, which is danger- ous to respire, but which is absorbed by water, it is safest Hdw is nitrate of ammonia formed ? Having prepared the salt, in what manner is th* gas extracted from it ? In what manner may a temporary gas holder and water bath be prepared ? Having prepared the gas holder, or jug, and the water bath, or tut, how will you proceed to fill the jug with gas 7 How will you know when the jug is full of gas 'J What gas is sometimes raided with the nitrous oxide 7 140 NITROGEN A.ND OXYGEN. before the gas is respired to let it stand an hour or two, with the water remaining in the jug. To respire the gas, prepare a bladder, or oiled silk bag, by attaching, to it a tube which fits closely to the second aper- ture in the large cork, and having squeezed all the air out o, the bladder, or bag, remove the small cork and pass in the tube. Next pour .such a quantity of water into the jug through the long tube as it is desired to obtain gas in the bag. Now the gas cannot escape through the long tube, because its lower end is in the water, nor can it escape through the mouth of the jug, this being closed by the cork ; it therefore passes into the bag. When this is full, withdraw the tube from the jug, and having expired, or thrown the air from the lungs, close the nose with one hand, and with the other apply the tube to the lips and breathe the gas from, the bag into the lungs, and from the lungs to the bag. Sir H. Davy respired 12 quarts, but the medium dose is from 4 to 8 quarts for an adult. On some persons this gas has a highly exhilarating or in- toxicating effect, and produces the most agreeable sensations, often attended by momentary mental hallucinations, and cor- responding actions. On others it produces mental depression, and melancholy forebodings. Its action commonly continues only for a few moments, and its effects seldom or never pro- duce a state of languor or debility, which might be expected to follow such a degree of excitement. The composition of the protoxide of nitrogen by volume, is nitrogen 100, and oxygen 50. 100 cubic inches of this gas weighs 46.5 grains, 'and its specific gravity is therefor 1.5, air being 1. It is transparent,, and colorless, has a sweet- ish taste, and an agreeable aromatic smell. It is a supporter of combustion, and many substances burn in it with far greater energy than in atmospheric air. The burning body absorbs the oxygen from the nitrous oxide and thus the nitro- gen remains in the vessel Why is it safest to let the gas stand over water awhile before it is breathed 1 After hay- ing prepared a bladder, or gas bag, how is this filled with the gas from the jug 7 How is the gas respired 1 What is the medium dose for an adult ? What effect is the respira- tion of this gas said to produce on the human feelings 1 What is the composition of th? n.j-ous oxide ? What is its specific gravity 1 Does this gas support combustion ? NITROGEN AND OXYGEN. 141 Deutoxide of Nitrogen. 30. 1 p. Nitrogen 14+2 p. Oxygen 16. Nitric Oxide. Nitrous Gas. Deutoxide of nitrogen, as expressed above, and as its name signifies, contains two proportions of oxygen to one of nitro- gen. It was formerly called nitric oxide, and nitrous gas, but analysis having shown its composition, its name is fixed in accordance. This gas is formed by the action of nitric acid on copper. Having introduced some copper turnings or filings into a retort, pour on them a quantity of strong nitric acid or aqua fortis. A violent effervescence will ensue, and the gas will escape in abundance. At first it will appear of a deep red colour, which is owing to the presence of atmos- pheric air in the retort ; but on passing it through water the red fumes are absorbed, and the nitrous gas remains pure and colorless. To understand the chemical changes by which this gas is formed, it is necessary to state that nitric acid is composed of 40 parts of oxygen and 14 parts of nitrogen, and that this acid is decomposed by the process. A part of the oxygen of the acid unites with the copper, and forms an oxide of the metal, while another part of the oxygen continues in union with the nitrogen, forming a deutoxide of nitrogen, which, as already seen, contains only 16 parts of oxygen. The gaseous form of the deutoxide is owing to the absorption of a quantity of caloric at the instant of its formation. The evolution of this gas is therefore owing to the abstraction of a part of the oxygen from nitric acid, by the copper. Other metals, and particularly quicksilver, will produce the same effect. Nitrous gas, when pure, is sparingly absorbed by water. It .is a little heavier than atmospheric air, 100 cubic inches weighing 31.7 grains, while the same quantity of air weighs 30.5 grains. It cannot be respired, even in small quantity, without a sense of suffocation, and violent coughing. It in- stantly extinguishes the flame of most substances, when plunged into it, but if charcoal, or phosphorus, in a state of What does deutoxide signify ? What is the composition, and what the equivalent numbers for deutoxide of nitrogen 1 What was the former name of this gas ? How is nitric oxide obtained 1 Why do the first portions of this gas appear red 1 What are the chemical changes by which this gas is formed 1 What causes the gaseous form of thia acid? To what is the evolution of this gas owing 1 ? What is the weight of this gas? What are its effects on respiration and flame ? 142 NITROGEN AND OXYGEN. vivid combustion, be immersed in it, its oxygen is absorbed and they burn with increased energy. When mixed with atmospheric air, red fumes are genera- ted, as already noticed. This is owing to the union of the oxygen of the atmosphere with the nitrous gas. When pure oxygen is added to a portion of this gas, the red becomes still deeper, and there is formed nitrous acid, which is entirely ab- sorbed by water. Thus these two gases, nitrous gas and oxy- gen, are a delicate test for each other, the smallest quantity of the one being detected by introducing a quantity o"f the other. From, the property of the nitrous gas above stated, it has been employed in Eudiometry, that is, to ascertain the purity of the atmosphere, or the quantity of oxygen it contains. The method by which this is done, is to confine a certain portion "of air in a graduated tube, and then to introduce into the tube, a sufficient quantity of the gas to unite with all the oxygen it contains. Then as the compound formed between the oxygen and the nitrous gas is entirely absorbed by water, it is readily seen by the graduated tube what proportion of air has disappeared, after agitating the mixture with w 7 ater, and consequently how much oxygen it contained. The composition of deutoxide of nitrogen has been accu- rately ascertained by burning charcoal in it, which absorbs all the oxygen, amounting to exactly one half the volume of the whole, and leaves the nitrogen, which amounts to the other half. By this analysis, it is found that 100 parts of this gas lose 50 parts of oxygen, and that 50 parts of nitroger remain. 50 cubic inches of oxygen weigh 16.8 grains, 50 cubic inches of nitrogen weigh 14.9 grains, The 100 parts therefore weigh 31.7 grains. The equivalent composition therefore is 1 atom, or equivalent of nitrogen 14 2 do. do. oxygen 16 30 What acid is formed when this gas combines with an additional portion of oxygen gas ? By what fluid is this gas absorbed ? In what manner is the nitrous gas employed to as- certain the quantity of oxygen in the atmosphere 1 In what manner has the composition Of this gas been ascertained ? What is the composition of this gas 'I What ia its equi Talent number 1 What are the equivalent numbers of its elements ? NITROGEN AND OXYGEN. 143 Nitrous Acid 46. 1 p. Nitrogen 14-f 4 p. Oxygen 32. The next compound of nitrogen and oxygen which we shall notice is nitrous acid. This acid is formed by adding oxygen to the compound last described, in consequence of which, the nitrogen of that compound combines with another portion of oxygen equal to that which it before contained. The deutoxide contained 2 proportionals of oxygen, 16. The nitrous acid contains 4 proportionals of oxygen, 32. Between these, there is a hy- pothetical compound, containing 3 proportions of oxygen, but which has not been obtained in a free state. This is called hyponitrous acid, and by some subnitrous acid, because it contains less oxygen than nitrous acid. Nitrous acid may also be obtained by the distillation of nitrate of lead, in a retort. (See Nitrate of Lead.} During the distillation, the receiver should be kept cold, by surround ing it with ice. By either of these methods, there is obtained a vapour, or gas, of a deep orange red colour, which is the nitric acid in a gaseous state. To obtain it pure, it is, however, necessary that the receiver should be first exhausted by the air pump, because the gas is instantly absorbed by water, and a mercu- rial bath cannot be employed, because the gas acts upon that metal. By volume this acid is composed of, Nitrogen 100 By weight, Nitrogen 14 Oxygen 200 Oxygen 32 300 46 Nitrous acid, in its fuming state, is totally irrespirable ; but supports the combustion of phosphorus or charcoal, when these are introduced into it in a state of combustion. Water absorbs this gas in large quantities, and acquires thereby, first a green and afterwards a blue tint. If still more be added, it becomes yellow, or colourless, and forms a solution of nitrous acid in water. What are the processes by which nitrous acid may be, obtained! What is the compo- sition of this acidl In what does this acid occur, and what is its colour? How is this acid obtained in its pure state 1 Why cannot a mercuiial or water bath be employed ID confine this gas? What are the definite proportions of the elements of this acid by volume anu weight 1 Does this gas support combustion or animal life ? What is said rf its absorption by water and the colours produced thereby 1 144 NITRIC ACID. Nitric Acid 54. 1 p. Nitrogen 14-f5 p. Oxygen 40. Aqua Fortis If a mixture of oxygen and nitrogen be confined in a glasa tube containing a little water, and powerful electrical shocks be passed through this mixture, the water, after a continued succession of such shocks, will possess acid properties. By this process, the two gases are made to combine, and form nitric acid, which is absorbed by the water. This experiment is designed merely to prove that the acid in question is formed of oxygen and nitrogen. The usual mode of forming this acid, is by the distillation of the nitrate of potash, more commonly called nitre, or salt- petre, with sulphuric acid. The proportions are four parts of nitre, in coarse powder, with three parts of the acid by weight The receiver must be large, and kept cold, otherwise much of the acid will escape before it is condensed. The strongest acid is formed when no water is placed in the receiver, that already combined with the sulphuric acid being sufficient to condense the nitric acid vapor as it is formed. The strongest nitric, acid is without color, and has a spe- cific gravity of 1.5, that is, this acid is by one half heavier than water. In this state it contains 25 per cent, of water. The dry nitric acid, which is formed by the condensation of its constituent gases, contains no water, and is composed, as stated at the head of this section, of 1 proportion of nitro- gen, 14, arid 5 proportions of oxygen, 40. The combining number of the dry acid is, therefore, 54. The acid obtained by distillation contains the same ele- ments as the dry acid, and in the same proportions, but with the addition of two proportions of water. Now, the combi- ning proportion of water being 9, that is, oxygen 8 and hy- drogen 1, it is easy, by the above data, to find the combining or equivalent number for liquid nitric acid. It may be stated thus : What is the composition of nitric acid, and what its combining number ? What ex periment shows that this acid is formed of nitrogen and oxygen ? What is the usual mode of obtaining this acid? In what manner is the strongest nitric acid formed? Whence comes the water to absorb the acid vapor when none is placed in the receiver ? What is the specific gravity of the strongest acid ? What proportion of water does H contain? How is the dry nitric acid formed? Does the acid obtained by distillation contain he same elements as the dry ? NITfcIC ACID. 145 1 prop, of Nitrogen 14 5 prop, of Oxygen 40 54 dry acid. 2 prop, water 18 72 liquid acid. The acid in this state is called hydro nitric acid, from Greek word signifying water, to denote its combination with chat fluid. When this acid combines with other substances it abandons *he water, which therefore is not reckoned in its equivalent number. In this state it is called anhydrous nitric acid, denoting that it contains no water. Nitric acid is an exceedingly acrid and corrosive substance. It stains the skin and nails of a permanent yellow, and is an active poison when swallowed. It parts with its oxygen with great facility, and hence is decomposed by nearly every combustible body. It combines with most of the metals, and decomposes all vegetable and animal substances. As a proof of the slight degree of force with which this acid retains its oxygen, take some warm, dry, and finely pow- dered charcoal, and pour on it a few drachms of strong nitric acid. The charcoal will be ignited, with the emission of im- mense volumes of red fumes. By this process the acid is decomposed, and parts with 2 or 3 portions of its oxygen to the charcoal, in consequence of which it is converted into nitrous acid, and deutoxide of nitrogen, which pass off in the form of red fumes. If an ounce of the spirit of turpentine be placed in a cup, and on it there be poured suddenly, about half an ounce of this acid, the turpentine will be inflamed with an explosion, sending forth a great quantity of black smoke, and often throwing the acid and fire to a considerable distance. In both these cases, the acid parts with its oxygen with so What are the constituents of liquid nitric acid? What is the chemical name for the liquid nitric acid 1 When this acid combines with other substances, what becomes of its water ? What is the chemical name for the dry acid ? What are the properties of nitric acid ? How is it shown that this acid holds its oxygen with a slight force 1 What effect does the action of the charcoal have on this acid? What are the red fumes which pass off during this experiment 1 How may spirit of turpentine be inflamed by this acid 1 Why are the combustibles set on fire by this acid 1 13 146 AMMONIA. much freedom, aud the combustibles absorb it with such avi- dity, as to set them on fire. In making the latter experiment, the vial containing tne acid should be tied to a long stick, otherwise the operator will be in danger from the explosion. Nitric acid forms a great number and variety of salts, when combined with the different metals, earths, and alkalies. Most of these salts scintillate when thrown on burning char- coal This is in consequence of the oxygen which the salt emits when exposed to heat, and by which the combustion of the charcoal is rendered moje vivid. This scintillation i: a sure proof that the salt is a nitrate. All the nitrates are soluble in water, and many of them furnish oxygen gas of more or less purity when heated in a retort. NITROGEN AND HYDROGEN. Ammonia 17. 1 p. Nitrogen 14-J-3 p. Hydrogen 3. Hartshorn. There is a substance well known to artists, and others, by the name of sal-ammoniac. In chemistry its name is muriate of ammonia. If some of this substance be pulverized by itself, and then mixed with an equal portion of unslaked quicklime, also in powder, and then introduced into a retort, -upon the application of a gentle heat, there will arise an ex- tremely pungent gas, which is ammonia. Water absorbs this gas with great avidity, and in large quantities, and consequently it cannot be collected like most other gases, by means of the water bath. In the absence of a mercurial bath, therefore, its proper- ties can be examined by receiving it in a bladder attached to the retort, or by means of a tall bell glass, and the appa- ratus described at Fig. 40. This gas is transparent, and co- lorless. In its pure state it cannot be respired. An animal cannot live in it, and it extinguishes the flame of burning bodies. What is said of the salts formed by the combinations of nitric acid 1 Why do the nalts of this acid scintillate when thrown on burning charcoal 1 What is said of the solubility of the nitrates? How is ammonia obtained ? Why cannot this gas be collected under water 1 How may its properties be examined without a mercurial bath? CARBON. 14T This gas is composed of 1 equivalent or atom of nitrogen 14 3 do. do. hydrogen 3 Its combining weight is therefore 17 It is much lighter than atmospheric air, 100 cubic inches weighing only 18 grains. When this gas is absorbed by water, which will take up more than 500 times its own bulk of it, there is formed the well known pung'ent liquid called spirit of sal ammoniac, or spirit of hartshorn, and by the apothecaries, liquid ammonia. When ammoniacal gas is submitted to the pressure of 6 or 7 atmospheres, equal in the whole to about 100 or 120 pounds to the square inch, it is condensed into a clear colorless liquid, but when the pressure is removed, it again expands, and assumes its former gaseous state. Ammonia is called the volatile alkali, by which it is distin- guished from the fixed alkalies, soda and potash. It possesses, fully, all the properties of an alkali, having an acrid taste, a strong affinity for water, and being capable of neutralizing the corrosive qualities of the acids. The article used in smelling bottles, and called volatile salts, and salt of hartshorn, is a carbonate of ammonia. The salts of ammonia, and particularly the muriate and carbonate, are articles of considerable importance in com- merce, in the arts, and in medicine. Carbon. 6. Nature furnishes carbon in its purest state, in the form ol that precious gem, the diamond. That the diamond is nothing but pure carbon, is proved by direct analysis. If in a glass vessel containing oxygen gas, a piece of diamond be placed, and then exposed to the intense heat of a large convex lens, or burning glass, the diamond entirely disappears, and there remains in the vessel carbonic acid, instead of oxygen. Thus the diamond, like other com- What are the most obvious properties of ammonia 1 What is the composition of am- monia, and what is its equivalent number ? What is the weight of 100 cubic inches ol this gas? How is liquid ammonia form/d 7 What quantity of this gas will water ab eorb? What is said of the condensation of ammonia into a liquid 1 What is the article called volatile salts 7 What is said of the alkaline properties of ammonia 1 How is it proved that the diamond is composed of pure carbon 1 148 CARBON. bustibles, forms carbonic acid by being burned, or by uniting with oxygen. When charcoal, or carbon from wood, is burned in pure oxygen gas, exactly the same result is produced, the charcoal entirely disappears, and the oxygen is converted into carbonic acid.^. * Charcoal may be obtained for experiments, by burying wood under sand, in a crucible, and exposing it to an intense heat for an hour or two. By this process, tj^water and other ingredients of which wood is composed are driven off, and the carbon remains. Both diamond and charcoal sustain the most intense de grees of heat, without change, provided oxygen is entirely excluded from them. Charcoal, when newly prepared, pos- sesses the property of absorbing large quantities of air, or other gases, at common temperatures, and of yielding the greater part of them again when heated. There is, however. a great difference in respect to the quantity absorbed, depend- ing on the kind of gas with which the experiment is made. Ammoniacal gas is taken up in the largest quantity, this be- ing 90 times the bulk of. the charcoal. Muriatic acid gas is absorbed in the proportion of 85 -times the bulk of the char- coal. Other gases are absorbed only in small proportions, nitrogen being only 7 then converted into phosphoric acid. Indeed the acid form- ed by this method, is probably always mixed with the phos- phoric acid. There are several other compounds of phosphorus and oxygen, but these are the most important. The phosphates will be described in their proper place. When phosphorus is thrown into nitric acid, what are the chemical changes which ensue 1 In what manner does charcoal convert phosphoric acid into phosphorus'.' Whal is the composition and what the combining number of this acid 1 How is phosphorous acid obtained 7 What are the salts called which this acid forms with the different baseo 7 BORON 163 BORON 8. There is a solid substance, resembling alum in appearance, which is used in medicine and the arts, under the name of borax. From borax there is extracted an acid, called the boracic acid. When boracic acid is heated in contact with the metal called potassium, the metal, having a strong affinity for oxygen, deprives the acid of that principle, and thus its base, called boron, is set free. This, so far as is known, is an element. Boron is insoluble in water, alcohol, or oil. It may be exposed to the strongest heat in a close vessel, with- out change, but when heated to about 600 in the open air, it takes fire, burns vividly, and by the absorption of oxygen, is again converted into boracic acid. Boracic Acid. This is the only known compound of boron and oxygen. It is a natural product, occasionally found in springs, and also in several salts, of which borax, or the bo- rate of soda is the principal. The acid may be obtained from the borate of soda, by dis- solving that substance in hot water, and then adding sulphuric acid until the solution becomes sour. Sulphuric acid com- bines with the soda, forming sulphate of soda, or Glauber's salt, while the boracic acid thus set free, is formed when the water cools, in small crystals. It is not readily soluble in water, but alcohol dissolves it freely, which being set on fire, burns with a beautiful green flame. This green flame is a good test of the presence of boracic acid in any composition. This acid is composed, of Boron 1 proportion Oxygen 2 do. 16 The combining p. of this acid is therefore t 24 CHLORINE 36. Oxymuriatic Acid. This highly important and useful gas is obtained by the action of muriatic acid on black, or peroxide of manganese. The most convenient mode of preparing it is by mixing strong How is boron obtained 1 Is boron a compound, or an elementary body 7 What are. Jie properties of boron? What is boracic acid 1 How may boracic acid be obtained! What is the common name for borate of soda ? What is the best test for the presence of boracic acid 1 What are the elements of boracic acid, and what is its combining num- ber 1 How is chlorine obtained 1 164 CHIORINE. muriatic acid, contained in a retort, with half its weight of the black oxide of manganese in fine powder, and then ap- plying a gentle heat. ) The gas may be received in glass bot- tles filled with water, and inverted in the pneumatic cistern, m the usual way. The water should be warmed, to prevent absorption. A cheaper mode of obtaining this gas, is to mix three parts of sea-salt, powdered with one of the manganese, in a tubu- lated retort, (Fig. 33,) and then to pour in two parts of sul- phuric acid, diluted with an equal quantity of water.; By the heat of a lamp, the gas will be extricated in abunda'nce. This gas is of a yellowish green color, the name, chlorine, in Greek, signifying green. It has an astringent taste, and is so exceedingly suffocating, that a bubble or two let loose in a room, will excite coughing and a sense of strangulation. Gold water, recently boiled, will absorb twice its volume of chlorine, which it gives out again on being heated. The specific gravity of this gas is 2.5, -so that it is more than twice as heavy as atmospheric air. 100 cubic inches weigh 76.25 grains, while the same quantity of common air weighs only 30.5 grains. Chlorine was formerly called oxymuriatic acid, from the opinion that it was composed of muriatic acid and oxygen. But according to thte logic of chemistry, it is now universally considered a simple body, having never been decomposed, though repeatedly submitted to the most active decomposing agents known to chemists. Sir H. Davy submitted it to the most powerful effects of galvanism, and to charcoal heated to whiteness, without decomposition, and without separating the least trace of oxygen from it. Hence, according to the pre- sent state of knowledge, it is an elementary body. Chlorine is a supporter of combustion. When a lighted taper is plunged into this gas, it burns with a small red flame, emitting a large quantity of smoke. Phosphorus takes fire in it spontaneously, and so do several of the metals. Fill a deep bottle, or large tube, with this gas, and set it upright, with the mouth covered by a plate of glass. Have some antimony prepared, by being pounded in a mortar ; What are the two processes, described, of obtaining it? What is said of the co- lor and suffocating effects of this gas? What is it3 specific gravity ? What was ihe former name of this gas? Does this gas contain any oxygen? What is said of the experiments of Sir H. Davy on chlorine ? Is this an elementary, or a compound body 1 Is chlorine a supporter of combustion ? What substances take fire in this gas spontane- ously? CHLORINE AND HYDROGEN. 165 then slide off the cover and pour in the metal. It will take fire before it reaches the bottom, and afford a beautiful show- er of white flame. This affords an elegant and striking ex- periment. The metals, tin, zinc, copper, arsenic, and even gold, when in the state of powder, or thin leaves, will be in- flamed in the same manner. Chlorine, has a very strong attraction for hydrogen, but it is through the mysterious influence of light that the combi- nation between the two substances seems spontaneously to be effected. Thus, when a mixture of these two gases is kept in the dark, no combination ensues, but if exposed to the direct light of the sun, they combine suddenly, and with- a violent detonation. This gas, though formerly called an acid, does not appear to possess any acid properties. It is not sour to the taste, nor does it redden vegetable blue colors, properties nearly universal in the acids. But the most important property of chlorine, is its bleach- ; ng power, all vegetable and animal colors being discharged by its action. For this purpose, it is combined with quick- lime, forming chloride of lime, or bleaching powder, an arti- cle very extensively employed at the present time, and which will be described, and its properties examined, in its proper place. Another very important property of chlorine is its disin- fecting power, any infectious or disagreeable odor being al- most instantly destroyed by it. For this purpose, the chloride of lime is also chiefly employed. The compounds of chlo- rine which are not acid, are called chlorides, or chloiurets. When chlorine, united to oxygen, combines with a base, and forms a salt, it is called a chlorate. These were formerly called hyperoxymuriates. They possess no bleaching proper- ties. In what manner may a shower of flame be made by this gas and a metal ? What is said of the union between this gas and hydrogen? Does chlorine contak) any of the pro- perties of an acid ? What is the most important property of chlorine ? What does chlo rine form, when combined with quicklime ? What other important and useful property lias this gas? What are the compounds of chlorine, which are not acid, called? 166 CHLORINE AND HYDROGEX. CHLORINE AND HYDROGEN. Muriatic Acid 37. 1 p. Chlorine 36+ 1 p. Hydrogen 1. We have just seen that chlorine has a strong affinity for hydrogen, hut that no union takes place between them, with- out the influence of light. When the light is entirely exclu- ded, a mixture of these -gases remains without change. When the mixture is made in a glass vessel, and exposed to the light of day in the shade, the gases, if of equal volumes, slowly combine, and form muriatic acid gas. But when the mixture is exposed to the direct rays of the sun, the union is sudden, and attended by an explosion. This combination does not change the volume of the origi- nal mixture, but the properties of the two gases are greatly changed. If the vessel in which the experiment has been made is unstopped under water, the fluid will in a few mo- ments entirely absorb its contents, and fill the vessel in its place, while the two gases, before combination, were absorbed by water only in small proportions. The peculiar odor oi chlorine, and its prompt bleaching property, are also destroy- ed, and other change of properties will become apparent on further examination. The compound formed by the union of chlorine and hy- drogen is called muriatic acid gas. This gas is composed by weight of 1 equivalent of chlorine 36 1 do. of hydrogen 1 Combining weight of muriatic acid gas 37 The production of muriatic acid by the combination of its elements, is designed to prove its constitution, and combining proportions. This acid is, however, much more readily pre- pared, by the action of sulphuric acid on common salt. If the salt be pulverized and mixed with an equal weight of the acid, and then the heat of a lamp applied, muriatic acid When a mixture of hydrogen and chlorine is kept in the dark, what change takes place ? When placed in the shade, what is the effect 1 When the mixture is placed in the sun, what effect is produced ? What are the changes produced on these gases by this Combination ? What is the name of the new gas? What is said of the absorption by water of chlorine, and hydrogen, and also of muriatic acid gas ? What is the composition of muriatic acid gas, and what is its combining number? How is this gas most readily arid conveniently prepared ? CHLORINE AND OXYGEN. 167 gas will be disengaged. But it must not be received over water, which will absorb several hundred times its own bulk of this gas. Muriatic acid gas is a transparent, elastic fluid, of a very pungent smell, and intensely acid taste. Its attraction for water is so great, that when it escapes in the open air, even in the dryest season, it instantly forms a white cloud, in con- sequence of combining with the moisture of the atmosphere. Water, at the temperature of 40, absorbs 480 times its bulk of this gas, and the solution is known under the name of muriatic acid, or spirit of sea salt, and is largely employ- ed for chemical and manufacturing purposes. This acid is prepared, in the large way, by extricating the gas from sea salt, by sulphuric acid, as above described, and then passing a current of it into water, as long as any is absorbed. It forms, with the different bases, a class of salts, called muriates. When this gas, in a pure state, is submitted to the pressure of 40 atmospheres, that is, 600 pounds to the square inch, it is condensed into a liquid. CHLORINE AND OXYGEN. There are four compounds of chlorine and oxygen, formed by the union of as many different proportions of the oxygen to the same proportions of chlorine. These compounds are known only to chemists, and with the exception, perhaps, of chloric acid, possess no value in the art. They are all form- ed by the action of an acid on the chlorate of potash, or ths chlorate of barytes. The chief interest which these sub- stances possess, in a chemical relation, is their strict con- formity to the laws of definite and multiple proportions. Their names and constituents are as follow : Protoxide of chlorine, 36 chlorine + 8 oxygen. Peroxide of chlorine, 36 " +32 " Chloric acid, 36 " +40 " Perchloric acid, 36 " +56 " Why does muriatic acid gas fcrm a white cloud in the open air 1 How many times its own bulk of this gas will water absorb ? Under what name is this solution of gas in vvater known ? How is the muriatic acid of commerce prepared 1 Under what pressure is this gas condensed into a liquid ? How many compounds of chlorine and oxygen ai known 1 Do the compounds of chlorine and oxygen possess any value in the arts! In what relation are the ivirn pounds of chlorine and oxygen interesting 1 168 CHLORINE AND NITROGEN. T* us, the first is composed of 1 proportion of chlorine combined to 1 of oxygen. The second, 1 of chlorine and 4 of oxygen. The third, 1 of chlorine and 5 of oxygen. The fourth, 1 of chlorine and 7 of oxygen. The equivalent numbers, therefore, for the first, is 36-j-8= 44 ; the second, 36-}-32=68 ; for the third, 36-f40=76; and for the fourth, 36+56=92. CHLORINE AND NITROGEN. Chloride of Nitrogen 158. 4 p. Chlorine 144-j-l p. Nitrogen 14. This curious compound was discovered by Dulong, a French chemist, in 1811. Chlorine and nitrogen have but a very slight affinity for each other, but they may be made to combine, by passing a current of the first through a solution of nitrate of ammonia. (Nitric acid, it may be remembered, consists of the two elements, oxygen and nitrogen, and am- monia is composed of hydrogen and nitrogen. By the union of these two compounds, nitrate of ammonia is formed.) To prepare chloride of nitrogen, dissolve an ounce or two of the nitrate of ammonia, in 1 4 or 16 ounces of hot water, and when the solution has cooled to about 90 degrees, invert in the solu- tion a glass jar, with a wide mouth, filled with chlorine. The solution gradually absorbs the chlorine, and consequently, rises in the jar, at the same time acquiring a yellow color. In about half an hour, minute globules, of a yellow fluid, like oil, are seen floating on- its surface. These, by uniting, ac- quire the size of small peas, when they sink to the bottom of the vessel. These globules are the chloride of nitrogen. They are formed by the decomposition of the ammonia, in the solution 5 the chlorine combining with its nitrogen, and thus forming the compound in question. A cup of lead, or glass, should be placed at the bottom of the solution, and under the mouth of the jar, to receive the product. The chloride of nitrogen is the most violently explosive substance yet discovered, and should not be experimented What is, the atomic weight, or chemical equivalent of chlorine ? What are the names, and what the combining numbers, of the four compounds of chlorine and oxygen 1 What is said of the affinity between chlorine and nitrogen ] What is the composition of nitrate of ammonia ? How is the chloride of nitrogen prepared ? What chemical changes take place in the formation of chloride of nitrogen ? What cautions are given with respect to wcperimentins on this compound? IODINE. 169 upon by the student, in quantities larger than a mustard-seed at a time, and even in this quantity, with great caution. Both its discoverer and Sir H. Davy, notwithstanding their expe rience and caution as chemical experimenters, were serious }y injured hy its violence. At the temperature of about 200 de- grees, it explodes, and at common temperatures, when thrown on some combustible. When a small globule is thrown into olive oil, or spirit of turpentine, it explodes with such vio- lence as to shatter any vessel of glass in pieces. The violence of its detonation is owing to the great vo lame of the products \yJWeh are formed at the instant. The compound consists wholly of the two gases, chlorine and ni- trogen, condensed, and combined with each other. When, therefore, the explosion takes place, these two elements as- sume their gaseous forms, thus, in an instant, occupying a yast space, when compared to their former state. Chloride of nitrogen consists of 1 equivalent of nitrogen 14 4 do. of chlorine 144 Making its number, 158 IODINE 124. The next simple substance we shall examine, is iodine. Its name signifies, in Greek, "violet colored," because, when in the state of vapor, it is of a most beautiful violet color. Iodine was discovered at Paris by a manufacturer of nitre, in 1812. This substance is obtained from the ley made of the ashes of marine vegetables, or from the substance called kelp or barilla, which is an impure alkali, made during the manufacture of soda. The process is as follows : Dissolve the soluble part of kelp, or the ashes of sea-weeds in water ; concentrate the solution by evaporation, when crys- tals of carbonate of soda will appear, which must be sepa- rated. Then pour the remaining liquor into a clean vessel, and mix with it an excess of sulphuric acid. Boil this liquid for some time, and then strain it through a cloth. Put this At what temperature does this compound explode? What combustible substances cause it to explode at common temperatures 1 Explain the cause of its violent explosion. .What are the combining numbers for its constituents, and also for the compound! What does the name iodine signify, and from what circumstance has it derived ita name? By what process is iodine prepared ? What is the appearance of iodine 1 15 170 IODINE. liquid into a small flask, and mix with it as much black OX' ide of manganese by weight, as there was sulphuric acid ; then attach to the mouth of the flask a glass tube, closed at the upper end, and apply the heat of a lamp to the flask. The iodine will be sublimed, and will attach itself to the tube in small brilliant scales resembling black lead. Iodine thus obtained is a friable solid, with a brilliant me- tallic lustre, and bluish gray color. Its taste is hot and acrid, and it is sparingly soluble in water. It corrodes the cork of the vial in which it is kept, and escapes is a strong poison when taken in large doses : but in solution with alcohol, which dissolves it freely, has been considerably used as a medicine. When heated in a retort to about 250 degrees, it evaporates, and fills the vessel with an exceedingly rich violet colored gas. As the retort cools, it again. condenses in fine brilliant points resembling frost on the glass. If exposed to the open air it slowly evaporates, and if handled, it leaves a brown stain on the fingers. Iodine resembles chlorine in smell, and in some of its pro- perties, particularly in destroying vegetable colors. Like oxygen and chlorine, it is a non-conductor of electricity, and is a negative electric. So far as is known it is a simple body. It has a strong attraction for the pure metals, and the simple non-metallic substances, such as sulphur and phosphorus. These compounds are called iodides. From experiments made by Dr. Thompson, the atomic weight of iodine is 124. The best test for iodine in its free state is starch, with which it forms an insoluble compound in water, of a deep blue co- lor. This test is so delicate as to indicate the most minute portion of starch in solution. Iodine combines with hydrogen, oxygen, and chlorine, forming hydriodic acid, iodic acid, and chloriodic acid. Among these, the hydriodic acid, only, is of any importance or use. What are its sensible properties ? What are its uses! What is the effect when it is heated in a retort ? When exposed to the open air what is the consequence ? In what respects does iodine resemble chlorine ? What is its electrical state ? Is iodine a simple or a compound body ? For what substances has iodine a strong attraction 1 What U the atomic weight of iodine 1 What is the most delicate test for iodin* 1 IODINE AND HYDROGEN. 171 IODINE AND HYDROGEN. Hydriodic Acid 125. 1 p. Iqdine 124+1 p. Hydrogen 1. When iodine is heated in a porcelain tube with hydrogen gas, the two substances combine and form a compound in the form of a gas, which has acid properties, and which is rapidly absorbed by water. This is the hydriodic acid. This gas is without color, is very sour to the taste, reddens the blue colors of vegetables, and has an odor similar to muriatic acid gas. It combines with alkalies, forming salts, called hydriodates. The discovery of iodine was one of the means of subvert- ing the former doctrine, that oxygen was the universal acidi- fying principle, the above instance showing that compounds, having all the properties of acids, are formed by the combi- nation of hydrogen with iodine. Several other instances of similar nature have been discovered, as in the case of mu- riatic acid. These instances appear, however, to be only ex- ceptions to a universal principle, oxygen being still the ac- knowledged agent by which most acids are formed. Hydriodate of Pdtask. This is given a place here, instead of among the salts, because it is the only salt of the kind to be described, and because, in manufacturing this compound, the method of obtaining the hydriodic acid is different from. that stated above. It is the only hydriodate of any use or importance, and does not exist as a salt in a separate state, but only in solution. In preparing hydriodate of potash for medicinal use, the preliminary labor of forming the acid may be dispensed with, and the salt in solution, may be formed by a very simple process, as follows : Add to a hot solution of pure caustic potash in water, as much iodine as it is capable of dissolving. This will form a solution of a reddish brown color, consisting of the iodate How may hydriodic acid be formed 1 What are its sensible properties ? What are th wlta called which.this acid forms with alkalies 1 How does this acid demonstrate that oxygen is not the universal acidifying principle ? Are there any other instances in which an acid is formed without oxygen 7 What is said relative to these exceptions to a general principle ? How is the hydriodate of potash formed ? What does the reddish brown eolu lion conflict of 1 172 BROMINE. and hydriodate of potash, together with an excess of free iodine. Through this solution, a current of sulphuretted hydrogen gas is transmitted, until the free iodine and iodic acid are converted into hydriodic acid, changes which may be known to be accomplished by the appearance of the liquid, which will gradually lose its brown color, and become colorless and transparent. The solution is then heated to expel the re- maining sulphuretted hydrogen, and after being filtered, is pure hydriodate of potash, in aqueous solution. .This solu- tion is considerably employed, as a medicine, in scrofula, and other glandular diseases. BROMINE 75. The name bromine is from the Greek, and signifies a " strong, or rank odor." Bromine, after undergoing various and multiplied tortures, by means of the most powerful decomposing agents, is ar- ranged as an elementary body, having endured fire, galva- nism, &c., without loss of integrity. It was discovered by Balard, of Montpelier, in 1826, and like iodine, exists in the ashes of marine vegetables, and also in sea water. The process of extricating it is too intricate to be detailed in this work, nor would it ever be undertaken by pupils in chemistry, for which this book is designed. Bromine is a fluid of a hyacinth red color, when viewed by transmitted light ; but of a blackish red, when seen in the ordinary manner, or by reflected light. Its odor resembles that of chlorine, but is much more disagreeable. Like iodine, it corrodes wood or cork, and stains the fingers of a yellow- ish hue. Its specific gravity is 3. It is a strong poison. It is volatile at common temperatures, and emits red vapors similar to those of nitrous acid. A lighted taper is soon extinguished by it, but before going out it burns with a flame which is green at the base and red at the top. How ia it known when a sufficient quantity of sulphuretted hydrogen has been passed through the solution of iodine 7 What is the use of the hydriodate of potash ? What floes the name bromine signify ? la it an element, or a compound ? In what substanca doea it exist ? What is the appearance of bromine 1 In what respects is it similar to iodine? FLUORIC ACID. 173 Bromine does not turn blue vegetable colours red, but like chlorine, destroys them. From these properties it will be observed, that this new substance has many characters in common with iodine and chlorine. Bromine combines with oxygen, hydrogen, and chlorine, but these compounds are little known, and of no interest ex- cept to professed chemists. Its .equivalent number, as seen at the head of this section is 75. Fluoric Acid 10. It is a singular circumstance in chemistry, that the base of the fluoric acid (has never been detached from the acid itself, notwithstanding every effort has been made on the part of the chemists to effect a separation^ It will be re- membered, that all the other acids consist of a base united to an acidifying principle, and that the two elements have been examined in separate states. Thus, sulphuric acid consists of sulphur and oxygen ; carbonic acid, of carbon and oxy- gen, &c. The base of this acid, however, has been named fluorine, but whether this is united to oxygen, as the acidifying prin- ciple, or whether such a base exists or not, is unknown. Flu- oric acid must, therefore, at present, be examined as a simple body, or in connection with substances to which it unites. This acid exists in nature in considerable quantities, being found combined with lime, forming the salt called fluate of llme\~b\it more commonly known under the name of Derbyshire spar. This latter substance is found crystallized, and of va- rious colors intermixed, forming, when polished, one of the most beautiful productions r of the mineral kingdom. It is in common use, for vases, candlesticks, snuff-boxes, &c. To obtain fluoric acid, a quantity of fluate of lime is pow- dered, and submitted to the action of twice its weight of strong sulphuric acid, in a retort of lead. On the application of a gentle heat to the retort, the acid distils over, and must be received in a leaden vessel. In what respect does it resemble chlorine in properties ? What is the equivalent num- ber of bromine ? Has the base of fluoric acid ever been detached from the acid itself! Is the same true of any of the other acids? What is the base of fluoric acid called 1 la it known that any such bare exists ? What natural substance contains fluoric acid 7 How is fluoric acid obtained from fluate of lime'* 15* 1T4 FLUORIC ACII7 The retort, and receiver, Fig 59, made of sheet lead, and soldered together on the edges, and the juncture between them stopped with a lute of clay, will answer very well. The white fluor must be selected for this purpose, as being most pure. It is first put into the retort, the acid poured in, and then connected with the receiver, which must be surrounded with a mixture of common salt and snow, or powdered ice. Fluoric acid, at the temperature of 32, or, the freezing point, is a colourless liquid, and will retain its liquid state, if preserved in well stopped vessels, when the temperature is 60. But if exposed to the air when the temperature is above 32, it flies off in dense white fumes, which consist of the acid, and the moisture of the air with which it com- bines. No substance with which we are acquainted has so strong an affinity for water as fluoric acid. Its liquid state appears to be owing to the water which is distilled over from the sul- phuric acid during the process of obtaining it, and no process yet devised has succeeded in freeing it entirely from mois- ture. When a single drop is let fall into water, a hissing noise is produced, like that occasioned by the plunging of a red hot iron into the same fluid, such is the heat produced by its combination with water. In experimenting with this fluid, the utmost caution is ne- cessary ; for no substance so instantly and effectually disor- ganizes the flesh, and produces such deep and obstinate ulcers, as this. The least particle would inevitably destroy an eye, or create an obstinate ulcer on any other part. Fluoric acid has the singular property of corroding glass, and may be used for this purpose in the fluid state, as above described, or in the gaseous form, the latter of which is com- monly the most convenient. Any design may be etched on glass, by the folio wing sim- ple method : First, cover the glass with a coat of bees wax. or engravers' What is the appearance of fluoric acid at the temperature of 32 degrees 7 What is it* appearance when exposed to the open air, at a tpmperature above 32 degrees 7 What is said of the affinity of this singular acid for water 7 Wha r is said of the action of this acid on the flesh 7 What is said of the action 3f fluoric acid on glass 7 Describe the method of making designs on glass. CARBON AND HYDROGEN. 175 varnish. If wax is used, it must be spread over the surface as thin as possible. This is done by heating the glass over a lamp, and at the same time rubbing it with wax. A thin and even coat may thus be obtained. Next draw the design by cutting the wax with a sharp pointed instrument, quite down to the glass, so that every line may leave its surface naked ; otherwise the design will be spoiled, since the acid will not act through the thinnest film of the wax. A large needle answers for a graver for this purpose. Having made the design, the etching is done by placing the glass in a horizontal position and pouring on the liquid acid. But a simpler method is the temporary extrication of the gas from the fluor spar, for the occasion. For this pur- pose, take a lead or tin cup, large enough to include the figures on the glass, the lower the better, and having placed on its bottom a table spoonful of powered* spar, pour on it a quantity of strong sulphuric acid sufficient to form a paste. Then place the glass on the cup, as a cover, with the etching downwards, and set the cup in a dish of hot water, or apply to it the gentle heat of a lamp, taking care not to melt the wax. In twenty or thirty minutes the etching will be finished, and the wax may be removed with a little spirit of turpen- tine. In this manner, figures of any kind may be perma- nently and beautifully done on glass. COMBINATIONS OF SIMPLE NON-METALLIC COMBUSTIBLES WITH EACH OTHER. CARBON AND HYDROGEN. Carburetted Hydrogen 8 1 p. Carbon 6-f 2 p. Hydrogen 2. Light Carburetted Hydrogen. This gas has also been called hydro-carburet, and heavy inflammable air. It exists in every stagnant pool of water, especially during he warm season, being generated by the decomposition of vegetable products. To obtain it from such places, fill a glass jar with water, * ~" After the design is formed, in what manner is the etching done ? What are the names under which Carburetted hydrogen has been known 1 In what place has this gas been formed by the operation of nature? 176 CARBON AND HYDROGEN. and invert it in a stagnant pool or ditch; then stir the mud under it with a stick, and the gas will rise and displace the water in the jar. To preserve it for examination, slide a dish under the mouth of the jar while in the water, and then carefully raise, and carry the whole to the place of experi- ment. The gas so obtained is found to contain a proportion of carbonic acid gas, which may be removed by passing it through lime water. This gas is composed by weight of 1 equivalent of carbon 6 2 do. of hydrogen 2 8 It is immediately destructive to animal life, and will not support combustion. It is highly inflammable, and burns with a yellowish* blue flame, but owing to the carbon it con- tains, it gives considerably more light than pure hydrogen. Mixed with atmospheric air, like hydrogen, it detonates powerfully when inflamed. When burned with oxygen, the product of the combustion is water and carbonic acid. There appears to be several varieties of light carburetted hydrogen, or perhaps the difference may depend on a mixture of the light and heavy kinds. If a volume of steam be sent through a red hot gun barrel filled with charcoal, the gas obtained differs little in its illuminating powers from that ob- tained from stagnant pools. Nor is there any material dif- ference between these and that evolved by the burning of common wood, such as maple or beech, in a gun barrel. But if pine wood containing turpentine, be heated in the same manner, the gas obtained has much greater illuminating pow- ers, the brilliancy of the flame being nearly equal to that of oil gas. Now as by analysis there appears to be only two kinds, or varieties, of carburetted hydrogen ; in the first of which there is but one proportion, and in the second two proportions of carbon, it is most probable that these different powers of illumination depend on a mixture of the two gases. How may it he obtained from stagnant pools of water ? What gas is commonly found Blixed with this 1 What is the atomatic composition of carburetted hydrogen"? How does it affect animal life and combustion ? When burned, why does this gas give a gtronger light than pure hydrogen ? What-is said concerning the several varieties of ca- Curetted hydrogen. CARBON AND HYDROGEN. 177 This gas sometimes exists in large quantities in coal mines, and is known by the miners under the name of fire-damp. The most shocking accidents have often occurred in conse- quence of the explosion of this gas in the mines, when mixed with atmospheric air. In some mines, this gas flows from the coal beds in vast quantities, being obviously the product of the decomposition of water by the coal. But in what manner the water is decomposed, is unexplained. Did the process consist in the formation of sulphuric acid, in consequence of the oxygenation of the sulphur, and the subsequent action of this acid on the iron, of the sulphuret of iron, there would be formed sulphuretted, instead of carburetted hydrogen. There are no facts, it is believed, which warrant the suppo- sition, that in ordinary cases, the decomposition is consequent upon the heat, or ignition of the coal. Possibly in such vast bpdies of coal as are found to exist in some mines, the water is slowly decomposed, by gradually imparting its oxygen to the carbon, without the aid of heat. We have already stated, that when carburetted hydrogen is mixed with atmospheric air, and inflamed, a violent explosion is the consequence. In the coal mines of England, the mix- ture of atmospheric air and the gas in question, often produ- ces such an exp.osive compound. It appears that the miners have no certain means of ascertaining the presence of this gas, probably because, being much lighter than the atmos- pheric air, it at first rises to the roof of the mine, and then gradually descends towards the floor. As the miners work entirely by the light of lamps, one of which is sufficient to set fire to the explosive compound existing throughout the whole cavern, it is obvious, that as soon as the hydrogen has mixed with the air near the floor of the mine in the explod- ing proportions, it must inevitably take fire. It can readily be imagined, particularly by those who have witnessed the detonation of a pint or two of this compound, that a quantity covering many acres of surface, and extending upwards in some places, at least, several hundred feet, must produce the most awful consequences. Under what name is this gas known, when it occurs in coal mines 1 In what manner ia this gas formed in coal beds 1 What are the remarks on this subject 1 What is the consequence, when this gas is mixed with atmospheric air and inflamed '.' In what situa- tions is it said that explosive compounds are thus formed 1 What is the reason that th miners are not aware of the existance of this compound until the whole takes fire! 178 CARBON AND HYDROGEN. Such explosions have often taken place in the coal-mines in different parts of England. That which happened in a mine called Felling colliery, in Northumberland, on the 25th of May, 1812, was attended with the loss of 92 lives, and spread poverty and wretchedness throughout the whole dis- trict. Most of these men had wives and children, who de- pended entirely on their daily labor for support, and who, in addition to the loss of their husbands and fathers, by so sudden and awful a death, were in a moment deprived of the means of subsistence. This mine had been wrought a century or more, and only a single accident from fire-damp had before happened, and this was so trifling, as only to slightly burn two or three workmen. Twenty-five acres of coal had been excavated in this mine, and the number of men employed under ground, at the time of the accident, was 128. The explosion took place between the hours of 11 and 12 in the morning. The fire was seen to issue from two shafts leading to the mine, and called William and John, and at the same instant, the noise of the explosion, which was heard three or four miles, and the trembling of the earth, showed that an awful acci- dent had happened there. The force of the expanded gas was such as to throw from the two shafts immense clouds of dust, and small coal, which rose high in the air, and also pieces of wood and working implements, which fell back near the shafts. As soon as the explosion was heard, the wives and children of the colliers came by hundreds to the place. But not a single person who was in the mine during the accident, was to be seen. Terror and dismay was pictured on every countenance; some were crying out for a father, some for a son, and others for a husband. The machinery for entering the mine, being shattered by the blast, it was at first impossible to go down, but the urgency of the occasion soon impelled those present to find the means of entering the shaft ; and in about half an hour from the time of the explosion, 32 persons, all who remained alive out of 121, who were in the mine, were brought out. It appear- ed that of the whole number of the workmen, seven had come up, on different occasions, before the explosion, and were unhurt. The wives and children of those who were What number of lives were destroyed by uch an explosion at Fllin colliery in 18121 CARBON AND HYDROGEN. 179 known to be still in the mine, waited in a most heart-rending state of anxiety, and those who had their friends restored, seemed to suffer nearly as much from excess of joy, as they had before done from suspense and grief. These hurried away with their friends from the dismal scene, while those who were still in suspense, or whose hopes ended in the dreadful certainty that their husbands or fathers were indeed among the dead, still lingered about the place, silently endu- ring the torture of a forlorn hope, and uttering cries of agony and despair. As the fate of many of the men was still uncertain, because they were in different parts of the mine r from those who had been found alive, the exertions of those above were unremit- ted, and in the course of an hour or two, many hundred peo- ple had collected around the shafts, all anxious to do every thing in their power for the sufferers. But it was soon found that the pit in some places was still on fire, the gas probably continuing to burn as it was extricated from the coal. It was also found by those who attempted to descend, that where the mine was not on fire, it was filled with carbonic acid gas, the product of combustion, and that therefore it was impossi- ble for any person to make further examination without in- evitable death. Consequently all hope of finding any of the unfortunate persons alive, who were still in the mine, was abandoned, and it was proposed that the shafts should be closed, in order to extinguish the fire. But the wives and children of the sufferers, distracted at the idea of seeing their friends buried alive, and still entertaining hopes of their re- covery, made the most pitiful importunities against such a course, while others became frantic with rage, and accused those of murder who proposed it. The owners of the mine, therefore, in mercy to the feelings of these distracted widows and orphans, waited until all were satisfied that no hopes re- mained of ever again seeing their friends alive, when the two shafts were closed with earth. To insure the extinguishment of the fire, the mine was kept dosed from the 27th of May until the 8th of July, on which day it was again opened and ventilated. On this occasion, the lamentations of the widows and orphans was again re- newed, and such was the crowd of people that assembled on the spot, some urged by feeling, and others by curiosity, thai constables were in attendance to preserve order. Those who descended to search for the remains of these unfortunate suf- ferers, found no difficulty in breathing the air of the mine, 180 SAFETY LAMP. but were struck with horror at the scene of destruction and mutilation which the explosion had occasioned. The search continued until the 19th of September, when 91 bodies had been found, brought up, and interred, but the 92d never was found. We have been thus particular in describing a single in- stance of the awful effects of the fire damp in mines, that the reader might fully appreciate the safety-lamp, an invention made by Sir Humphrey Davy, expressly for the purpose of preventing such explosions, and which has proved completely successful. Before the invention of this lamp, such explosions were more or less common, and all the mines were subject to them, though none has been attended with such destruction to hu- man life, as that of Felling colliery. In 1815, such an oc- currence happened in a mine at Durham, and destroyed 57 persons, and in another mine, 22 persons were killed in the same manner. The invention of the safety-lamp was not owing to accident, but is the result of inquiries undertaken and pursued expressly for the purpose of protecting the miners from such horrible accidents as we have described above. Sir Humphrey Davy commenced his inquiries, by deter- mining the proportions in which carburetted hydrogen and atmospheric -air, in mixture, produce explosions ; and found, that when the gas is mixed with three or four times its vol- ume of air, it does not explode at all. When mixed with five or six times its bulk of air, it detonates, feebly, but when the air is in the proportion of seven or eight times the bulk of the gas, the explosion is most powerful ; and with fourteen times its volume of air, it still explodes, though slightly. He also found that the strongest explosive mixture would not take fire when in contact with iron heated to redness, or even to white- ness ; while the smallest point of flame, owing to its higher temperature, caused an instant explosion. What other accidents of the same kind are noticed ? Does it appear that all excavated eoal mines are liable to such accidents ? Who invented the safety-lamp, which protects the miners from such accidents 1 Was this invention accidental, or was the safety-lamp the result of inquiry and experiment 7 In what proportions did Sir H. Davy find that carburetted hydrogen and common air exploded with the least force, and in what pro- portions with the greatest force ? What did Sir H. Davy discover in respect to the com- munication of flame through narrow tubes 1 SAFETY LAMP. 18* But the most important step in this inquiry was deduced from the fact that flame cannot be communicated through a narrow tube. The fact itself was known before, but Sir H. Davy discovered, that the power of tubes, in this respect, is not necessarily connected with their lengths, and that a short one is as efficacious in preventing the transmission of flame, as a long one, provided its aperture be reduced in proportion to its length. Pursuing this principle, he found that fine wire gauze, which may be considered as an assemblage o exceedingly short tubes, was totally impermeable to flame ; and on making the experiment, it was found that a lighted lamp, when completely surrounded with such gauze, might be introduced into an explosive mixture, without setting it on fire. Thus the means of preserving the miners, a most useful and laborious class of people, from the dreadful effects of the fire-damp, was at once developed. It only became necessary to surround their lamps with a fine net work of brass wire, to insure their safety from explosion. This lamp also indicates the existence of danger ; for when the fire-damp in the mine is in a highly explosive state, it takes fire within the gauze, and burns there, while the light of the lamp itself is unseen. When the miners observe this indication of danger, they in- stantly leave the mine, for although the flame within the gauze will not communicate with the explosive mixture on the outside, while the gauze is entire, yet as a high degree of Fig. 60. heat would be kept up by the combustion within the lamp, the wire would soon be- come oxidated, and perhaps fall in pieces, when an instant explosion would be the consequence. The safety lamp is represented by Fig. 60. The cistern a holds the oil, and is in all respects a complete lamp, with a spout at the side, for feeding it. On the top of this is set the cylinder of wire gauze, b, sup- ported by three iron or brass rods, to which is connected the disc, or cover c, and to the cover, the ring, or handle by which the whole is carried. The drawing d, is a On pursuing this inquiry, what did Sir H. Davy discover with respect to wiw gauze 7 3n this principle, how was it discovered that the miners might be protected from explo- none ? In what manntV do these lamps indicate the presence of danger 1 16 182 GAS LIGHTS. piece of wire passing through a tube, showing the manner in which the lamp is trimmed, and the wick raised, without making any dangerous communication between the outside and inside of the lamp. This tube passes through the cis- tern containing the oil. The reason why the wire gauze obstructs the communi- cation of flame is easily explained. We have already stated, that according to the experiments of Sir H. Davy, the heat of flame is greater than that of a metal heated to whiteness, for the former occasioned a mixture of air antl gas instantly to explode, while the iron, though white hot, produced no effect. Now the metals are all rapid conductors of heat ; when, there- fore, the flame comes in contact with the wire, its tempera- ture is so reduced by the conducting power of the metal, as to be incapable of setting fire to the gas which is on the Out- side. Any one may illustrate this, principle, by holding a piece of wire gauze over the flame of a lamp, and" then bring- ing his hand over this, as near the lamp as he can bear. Now on removing the gauze, he will find that he cannot for an in stant bear the additional heat. Bicarburetted Hydrogen 14. 2 p. Carbon 12-}- 2 p. Hydrogen 2. Olefiant Gas. - To prepare this gas, mix in a capacious tubulated retort, three measures of alcohol, with eight measures of undiluted sulphuric acid, and then apply the heat of a lamp. .This mixture turns black, swells, and emits bubbles of gas in abun- dance, which may be collected over water, in the same man- ner as described for hydrogen. Alcohol is composed of carbon, hydrogen, and oxygen. During this process, the oxygen of the sulphuric acid appears to combine with a part of the carbon of the alcohol, in con- sequence of which, sulphurous acid gas is evolved, and the hydrogen is set free. At the same time, the hydrogen com- bines with another portion of the carbon, and escapes in the Why does it become necessary for the men to leave the mine, when the explosive mi*- twre burns within the gauze ? Describe the safety lamp, as represented at Fig. 60, and point cmt the uses of its several parts. Explain ths reason why the flame is not commu- nicated through the wire gauze. How may this principle be illustrated by holding a piec# of wire gauze and the hand over a candle 1 How is (defiant, or bicarburetted hydroge* gas obtained 1 What is the composition of alcohol 7 GAS LIGHTS. 183 form of bicarburetted hydrogen. Or perhaps the evolution of the olefiant gas is owing to the strong attraction which the sulphuric acid has for the water which the alcohol contains, and by combining with which, the hydrogen and carbon are liberated. Olefiant gas is colorless and elastic. It possesses no taste, and when pure, little smell, though, when not purified, it has a faint odor of ether. When mixed with oxygen and in- flamed, it explodes with violence. This gas is a little lighter than atmospheric air, 100 cubic inches weighing 29.64 grains. The weight of carbon in this composition is 25.41 grains, and the weight of hydrogen 4.23 grains. Olefiant gas, therefore, consists of Grains. Carbon, by weight 24.31, or two atoms, 12 Hydrogen, do 4.23, or two atoms, 2 29.64 14 This gas may be decomposed, by passing it through a red hot porcelain tube, one proportion of carbon being deposited, in consequence of which, it is converted into light carburetted hydrogen, which, as we have already seen, contains only 1 proportion of carbon to 2 of hydrogen. Gas Lights. The olefiant gas, when pure, (with perhaps a single ex- ception) gives the most brilliant and intensely luminous flame of any known substance. The illuminating powers of other gases depend chiefly, if not entirely, on the olefiant gas they contain. In all cases, the light of any inflammable gas is in exact proportion to the quantity of carbon it contains. The flame of pure hydrogen scarcely gives sufficient light Jo show the hour on a watch dial. When combined with one proportion of carbon, forming carburetted hydrogen, its light is greatly increased, and when combined with another pro- \\hat are the chemical changes which take place during the production of olefiant gas? What are the sensible properties of this gas? Does it explode when mixed with oxygen and inflamed 7 What is the weight of carbon, and what the weight of hydrogen, in thks gas 1 What is the atomic composition and what the combining number of this gaa ? How is olefiant gas decomposed and resolved into carburetted hydrogen 1 What is said of Ihe brilliaat light of the olefiant gas 1 On what does the brilliancy of gas lights depend? 184 GAS LIGHTS. portion, its light becomes perfectly fitted for the purposes of illumination. Gas light, for the purpose of illumination, was first made and employed by Dr. Clayton, an Englishman, in 1739, but from some unknown cause, was given up, and neglected for sixty years afterwards. At length, Mr. Murdock instituted a series of experiments on the subject, and the gas distilled from coal, began to be used, on a small scale, for lighting different factories in the vicinity of London. From that period, which was about 30 years since, gas lights obtained from coal, or oil, have gradually come into use, for the purpose of lighting streets, shops, and manufactories, in all parts of Great Britain, and is, at the present time, in common use on the continent of Europe, and in several parts of America. For many years, the gas lights of London, and other parts of England, were supplied entirely by the distillation of bitu- minous coal ; but more recently, many of the gas works, in different parts of that kingdom, obtain their lights from oil. In this country, also, oil gas is chiefly employed. In respect to the advantages of gas, on the morals of soci- ety, in great cities, Mr. Gray, in his Operative Chemist, says, "From the more brilliant manner in which our streets (those of London) are lighted by gas, than they ever were or could be, by oil or tallow, there is a greater degree of security, both in person and property, for every class of honest men. Crimes cannot now be committed in darkness and secrecy: and as the risk of detection increases, the temptation to guilt is di- minished, and thus coal gas, by the brilliant light it sheds on our streets, has worked, and is now working, a moral reform- ation. The house-breakers and pick-pockets dread the lamps more than the watchmen, and a more efficacious measure of police was never introduced into society, than that from gas lights." Oil gas is obtained by distilling impure whale or other oil, in large cylindrical cast iron retorts. From four to six such retorts, which, in appearance, resemble 24 pound cannon, are placed across a furnace built of brick, and are all heated by When were gas lights, for the purpose of illumination, first employed ? From whsL substance was gas lights first obtained ) What is the substance now employed in this country, and in some parts of England, for this purpose 1 What is said of the influence of gas lights on the morals of London 7 How is oil gas manufactured 1 Describe the furnace and retorts. GAS LIGHTS. 185 ihe same fire. These are half filled with pieces of brick, or iron, in order to increase the surface, and thus to effect the decomposition of a greater proportion of the oil. The oil is contained in a reservoir placed so high as to run to the re- torts through a tube, of which each retort has a separate branch. The oil is admitted into the retorts on the outside of the furnace, the quantity being regulated by a stop-cock, with which each is furnished. On the opposite side of the furnace, the gas is conducted from each retort by separate tubes, which afterwards join in a common tube of larger size, and thence is conveyed to the gasometer. The oil is admitted into the retorts in a very small stream, or sometimes only by drops, and is decomposed, and converted into gas as fast as it runs in. In large works, the gasometer is of immense size, being 30 or 40 feet in diameter, and 15 or 20 feet high, and capa- ble of containing from 12, to 20,000 cubic feet of gas. This is made of sheet iron, suspended by a chain, over a pulley, and counterbalanced by weights on the other side. This falls into a tank, or cistern, held together by iron hoops, which are drawn with great force around it by means of screws. The tank being filled with water, the gasometer is let down into it, while the air escapes by opening a valve in its top. When the air is all excluded the gas is conducted into the gasometer by a pipe coming from the retorts, and opening under the water. As the gas rises through the water, the gasometer is buoyed up, and rises also, and thus the vessel is filled with in flammable gas instead of air. From the gasometer, which is the great fountain, the gas is conducted by one large iron pipe, laid under ground to the place or street where it is burnt. It is then conducted in smaller pipes through the different streets, and from these pipes it is conveyed to the houses and shops by small tubes ; and tubes of still smaller size convey it to the burners where the lights are wanted.' Rosin has lately been used instead of oil, and is said to yield a gas fully equal in quality to that of oil, and at a much less expense. As the burners are stationary, in the ordinary mode of light- How la the oil admitted into the retorts ? In large works, what is the size of the gaso- meter t How is the gas conveyed into the gasometer ? How is the gas conveyed from the gasometers to the gas burners ? What inconvenience in experienced in the use -f ordinary gas lights? 16* .86 GAS LIGHTS. ing with jgas, there exists an inconvenience in its employment for the purpose of common household illumination, where the lights are often necessarily carried to different parts of a room, or from one room to another. There is also another inconvenience, which arises from the expense of laying con- ductors through streets where the houses are scattered, and consequently, where but a small quantity of the gas is want- ed. To remedy these defects in the ordinary method of light- ing with gas, it has, within a feAv years been proposed to con- dense the gas in strong copper, or brass lamps, at the gas works, and then transport them thus filled, to the, houses, to supply the place of common lamps. This is distinguished by the name portable gas, and has been, and it is believed is still extensively, employed in London and its vicinity. To fill these lamps, there is provided a long iron pipe, at one end of which is a forcing pump, which is also connected with another pipe leading from the gasometer, to the pump through which the gas is conveyed. The long pipe is fur- nished with short tubes placed at convenient distances apart, and communicating with its inside. These tubes are cut with screw threads, which fit the screws at the bottoms of the lamps, and on which these vessels are screwed, to be filled. TJius by working the forcing-pump, the gas is brought from the gasometer, forced into the pipe, and from the pipe into the lamps, so that many are filled at the same time. There is a mercurial gauge connected with the pump, by which its pressure is shown, and consequently by which the amount of condensation of the gas in the lamps is indicated. The flame, in burning the gas, is regulated by turning a small screw, and the gas is prevented from escape at the bottom by a valve, and another screw. The gas obtained from oil, is much purer than that obtain- ed from coal. The latter cannot be burned until it is purified by being passed through lime water, in order to deprive it of the carbonic acid, and other impurities ; but the oil gas does not require any such process, being fit for use as it passes from the retort. The illuminating power of the oil gas is also much greater How has it been proposed to remedy this defec( ? Under what name is this condensed gas Iwiown ? In what manner are the portable gas lamps filled 1 How is it ascertained with what degree of force the gas is condensed in the lamps ? Which is most pure, the gas obtained from oil, or that from coal? Which gas has the greatest illuminating power, (hat from the coal, or that from oil 1 HYDROGEN AND SULPHUR. 187 than that of coal gas. According to the experiments of Mr. Accum, two cubic feet of coal gas will burn one hour, and give a quantity of light equal to three tallow candles, eight of which weigh a pound. But according to the experiments of Mr. Dewey, superintendent of the gas works of New- York, one cubic foot of oil gas will give light for one hour, equal to 8 candles, 6 to the pound. This agrees very nearly with the result of Mr. Ricardo's experiments, who found that a given quantity of oil gas was equal in illuminating power to four times the same quantity of coal gas. One gallon of clean whale oil will make 100 cubic feet of gas, which, ac- cording to the above statement will burn 100 hours, and give as much light as 8 mould candles, 6 weighing a pound. Such an immense difference between the cost of gas, and other lights, would seem to indicate the propriety of establishing gas works in every village. But the expenses of erecting and tending small establishments of this kind, are such as not to yield any considerable profit to the owners. In this coun- try, where 2,000, or 2,500 lights are wanted in a compact town, perhaps gas works, might be maintained. The ex- penses of erecting such works would be not far from the fol- lowing, viz. 2i miles, 3 inch main pipe, $ 7,500 Gasometer and tank, 3,000 Refrigerator and connections, 1,500 One bench retorts, 6 in number, 3,000 Labour to erect the works 3,000 17,500 HYDROGEN AND SULPHUR. Sulphuretted Hydrogen. 17. 1 p. Sulphur 16-J-l p. Hydrogen 1. This gas may be procured by placing in a retort some sul- phuret of antimony, or iron, and pouring on it sulphuric or muriatic acid. The sulphurets of these metals may be pre- pared by heating either of them, in filings or powder, with What is said to be the comparative difference between the illuminating power of coal and oil gas ? What quantity of gas is it said one gallon of oil will make, and how long will this gas burn 1 The cost of oil gas being much less than other lights, why are they not universally used 1 How may sulphuretted hydrogen be procured 1 188 HYDROGEN AND SULPHUR. sulphur; or the natural sulphurets may be employed. The chemical changes concerned in the formation of this gas, are as follows. The oxygen of the water which the acid con- tains unites with the metal of the sulphuret, which metal is then dissolved by the acid. Thus, the hydrogen of the water, and the sulphur of the sulphuret, are both set at liberty, and having an affinity for each other, they combine, and escape in the form of sulphuretted hydrogen. Sulphuretted hydrogen, is a transparent, elastic gas, which both to the taste and smell, is exceedingly unpleasant and nauseous, its odor being similar to that of putrefying eggs. Under a pressure of 17 atmospheres, that is, under a weight equal to 255 pounds to the square inch, this gas is condensed into a colorless liquid, but again assumes its gaseous form, when the pressure is removed. This gas is instantly fatal to animal life, when pure, and even when diluted with 1500 times its bulk of air, has been found so poisonous as to destroy a bird in a few seconds. Like hydrogen, it instantly extinguishes flame, but is itself inflammable and burns with a pale blue flame. The products of its combustion are water and sulphuric acid. The compo- sition of this gas being hydrogen and sulphur, the water form- ed during its combustion is the product of the union between the hydrogen, and the oxygen of the atmosphere, during the act of combustion ; while the sulphuric acid is formed, by the union of the oxygen of combustion with the sulphur. Sulphuretted hydrogen tarnishes silver, and even gold, and blackens paint, made with preparations of lead. This gas is often generated curing the decomposition of animal products, in sink drains and ditches, and hence the paint of white lead, about such places often becomes black in consequence. Eggs contain a small quantity of sulphur, which on boiling is converted into sulphuretted* hydrogen, and hence a silver spoon is instantly tarnished by coming in contract with a boiled egg. What chemical changes take place by which this gas is evolved ? What are the oen- rtble properties of this gas? Under what piessure may this gas be condensed into a liquid ? Does it remain liquid when the pressure is removed 7 What is said of the pot Bonous effects of this gas 7 What are the effects of plunging a burning candle into thja gad? When this gas is burned, what are the products of combustion? Whence come the water and sulphuric acid ? What is its effects on the metals 7 HYDROGEN AND PHOSPHORUS. 189 The composition of sulphuretted hydrogen by weight, is as follows : 100 cubic inches of this gas weigh 36 grains. This is composed of sulphur, 33.89 do. do. do. of hydrogen, 2.11 do. 36.00 HYDROGEN AND PHOSPHORUS. Phosphuretted Hydrogen 13. 1 p. Phosphorus 12-}-l p. Hydrogen 1. This compound consists of hydrogen, in which is dissolved a small quantity of phosphorus. It may be formed in several ways. One of the most simple is the following : Into five parts of water put 15 or 20 grains of phosphorus, cut into small pieces. It must be cut under water to prevent its tak- ing fire. Then add one part of granulated zinc, and pour in three parts of sulphuric acid. The gas will instantly rise through the water in small bub- bles, and will take fire spontaneously on coming in contact with the air. Each bubble as it takes fire will form a hori- zontal ring of white smoke, which will gradually enlarge as it rises, until lost in the air. The cause of this curious ap- pearance is owing to the formation of a small quantity of phos- phoric acid by the combustion of the phosphorus, and which having a strong affinity for moisture, attracts it from the at- mosphere, and thus forms a little ring of dew, which is visi- ble to the eye. Phosphuretted hydrogen may also be obtained by placing some pieces of phosphuret of lime in water, when the gas will be extricated, and will rise through the water as above de- scribed. [See Phosphuret of Lime.] This gas detonates with great violence when mixed with oxygen, and forms a dangerous explosive compound with at- mospheric air ; consequently much caution is required in making experiments with it. When a bubble of phosphuretted hydrogen is allowed to mix with oxygen, a flash of the most vivid light is spontane- What is the composition of 100 cubic inches of this gas by weight 1 How is phos- phuretted hydrogen formed 1 What singular property does this gas possess 1 How is the ring of white smoke accounted for, which rises after the combustion of a bubble of this gas 1 With what substances does phosohuretted hydrogen afford dangerous detona Ung compounds ? 190 NITROGEN AND CARBON. ously produced, which, in a darkened room, resembles light- ning. The safest method of performing this beautiful ex- periment, is to let up into a small strong bell glass, or a thick glass tube, a few ounces of oxygen gas. Then, having col- lected a little of the phosphuretted hydrogen in a small vial, Ixold the bell glass in the left hand, with its mouth underwa- ter, and with the right hand manage the vial, so as to let only a single bubble at a time escape into the oxygen. The deto- nation of each bubble will product- a considerable reaction on the bell glass, which will be felt by the hand. But if the ex- periment be performed as described, there will be no danger of an explosion. The gas above described is called per-phosphuretted hydro- gen, denoting, as already explained, the highest degree with which one body unites with anoiher. It is,so called to dis- tinguish it from the prolo-phospkv retted hydrogen, which con- tains only half the quantity of phosphorus, and is a much less interesting compound. Per-phosphuretted hydrogen consists of 1 equivalent of phosphorus, 12 1 do. hydrogen, 1 13 NITROGEN AND CARBON. Carburet of Nitrogen 26. 2 p. Carbon 12+1 p. Nitrogen 14. Cyanogen. By boiling together red oxide of mercury and prussian blue in powder, with a sufficient quantity of water, there may be obtained a compound which shoots into crystals, and which was formerly called prussiate of mercury, but is now known by the name of cyanuret of mercury. When this salt is heated in a retort, jt turns black, the cy- anogen passes over in the form of a gas, and the mercury is revived, or assumes its metallic form. This gas has a pungent, disagreeable odor, burns with a purplish blue flame, extinguishes burning bodies, and is re- duced to a liquid under the pressure of about three and a half atmospheres. This gas must be collected over mercury. What directions are given for admitting bubbles of this gas into oxygen 1 What to the equivalent composition of per-phosphuretted hydrogen? How may cyanurel of mercury be formed ? How is cyanogen procured 1 What are the properties . oi PRUSSIC ACID. 191 100 cubic inches of this gas weigh 55 grains, and is found to be composed of 2 equivalents of carbon, 12 1 do. nitrogen, 14 26 its combining number. Cyanogen, though a compound gas, has the singular pro- perty of combining with other substances, in a manner per- fectly similar to the simple gases, such as oxygen and hy> drogen. The term cyanogen, comes from two Greek words signify- ing to form blue, because it is an ingredient in Prussian blue. Hydrocyanic Acid 27. 1 p. Cyanogen 26-f-l p. Hydrogen 1. Prussic Acid. Cyanogen is obtained by simply heating cyanuret, or prus- siate of mercury, as above described. Hydrocyanic, or prus- sic acid, is composed of cyanogen and hydrogen. It may be obtained, by heating in a retort a quantity of prussiate of mer- cury with two thirds of its weight of muriatic acid. During this process, there takes place an interchange of elements. -The cyanogen of the cyanuret of mercury unites with the hydrogen, forming hydrocyanic acid, while a muriate of the peroxide of mercury remains in the retort. But a more common method of making prussic acid is the following : Mix together, in a convenient vessel, four ounces of finely powdered Prussian blue, two and a half ounces of red oxide of mercury, and twelve ounces of water. Boil the mixture for half an hour, now and then stirring it. The blue color will disappear, and the solution will become yellowish green. Filter the solution, and wash the residuum, by pouring on boiling water, in quantities sufficient, to make up the loss by evaporation, and let this also pass through the filter. Put this solution, which is a prussiate of mercury, into a retort containing two ounces of clean iron filings, then con- nect the retort with a receiver, and place them on a lamp fu- What is the equivalent composition of this gas, and what is its combining number* Whence comes the name of this gas? How may hydrocyanic, or prussic acid, be formed by means of prussiate of mercury and muriatic acid? What are the interchanges of element* which take place during this process ? What is the more common method de- cr.bed for making Pruesic acid 1 192 PRUSSIC ACID. nace, as represented by Fig. 61, taking care that the juncture Fig. 61. b e made air tight, which may be done by winding a wet rag around the neck of the retort. Next, pour into the retort one ounce of sulphuric acid, diluted with three or four parts of water, and stop its tubulure by pass- ing in a straight glass tube, which had been ready prepared by being passed through a cork. Then light the lamp, and distil with a slow heat, until three ounces of prussic acid is obtained. The receiver must be kept cold, and also from the light, by being covered with a wet cloth. The fumes of this acid are exceedingly poisonous, and therefore the lamp furnace should be set in a fi re-place during the process, so that they may escape up the chimney. There is a complicated inter- change of principles which take place in this process, which Scheele explained thus. In prussian blue the prussic acid exists in combination with iron. The red oxide of mercury, having a stronger attraction for this acid than the iron has, the prussian blue is decomposed, and a prussiate of mercury is formed, which is soluble in water. On the addition of the iron filings and sulphuric acid to this solution, the iron ab- sorbs the oxygen from the mercury, which is then precipita- ted in the metallic form, and at trie same instant the iron is thus oxidized, it is dissolved by the sulphuric acid forming the sulphate of iron. Thus, the prussic acid is liberated, because it does not combine with the metals, but only with their ox- ides, and as the iron deprives the prussiate of mercury of its oxygen, the prussic acid remains free in the solution of the sulphate of iron, and being volatile, readily passes over into the receiver, by a gentle heat. The hydrocyanic acid thus obtained, is a perfectly color- less, limpid fluid, and cannot be distinguished by the eye from distilled water. It has a strong odor, resembling that ol peach blossoms, and when much diluted has the taste of bit- ter almonds. Prussic acid is the most active and powerful of all known What is said of the poisonous quality of the fumes of this acid, and of the precaution* to avoid them ? Explain carefully the complicated interchange of chemical principles (hat take place by this process. What is the appearance of the acid thus obtained) Wbat \ the smell of this acid ? What cases are mentioned of its poisonous effects 7 pnrssic ACID. 193 poisons. A single drop placed on the tongue of a dog causes his death in a few seconds, and a servant girl who swallow ed a small glass of it, diluted with alcohol, fell down instant ly, as though struck with apoplexy, and died in two minutes. A professor at Vienna, having prepared some of this acid in its most concentrated state, by way of experiment, diffused some of it on his naked arm, and was killed thereby in a short time. These instances not only show the terrific and mysterious effect which this substance has on (.he animal economy, but they also show what extreme caution is necessary in prepar- ing and using it. When much diluted, it has, however, been considerably employed as a medicine, in cases of consump- tion, and often with good effect. Although the investigations of chemistry have developed this substance, than which, even lightning itself is scarcely more prompt, or sure, in destruction, still the wisdom of Om- niscience has connected circumstances w r ith its production and nature, which, in a great measure, will always prevent its employment for criminal purposes. The process by which it is made, requires more chemical skill than generally falls to the lot of unprincipled and vicious persons ; and when obtained, its active properties are so evanescent, as never to remain more than a week or two, without peculiar treatment, and sometimes it becomes nearly inert in a few days. The odor, also, which is distinguished in animals destroyed by it, is often the sure means of detection. The commencement of its decomposition is marked by the reddish brown color of the liquid, and, in a short time after, it becomes black, and deposits a thick carbonaceous substance, at the same time it loses its peculiar smell, and emits that of ammonia." In this state, the prussic acid has none of its for- mer properties, but becomes entirely inert and worthless. This substance possesses the sensible qualities of an acid only in a very slight degree, being hardly sour to the taste, and producing but very little change in the blue colors of vegetables. It however performs the office of an acid in For what purposes is this acid employed when much diluted ? What circumstances are connected with the production and nature of this acid, which it is said will prevent its employment for wicked purposes 1 How does the acid appear while decomposing ? Does this substance possess the sensible qualities of an acid? In what respect does it perform the office of an acid ? 17 194 PRUSSIC ACID. combining with alkaline bases, forming salts, called prussiates or hydrocyanates. The following is an example, by which the composition of a substance may be found, when one of its elements can be made to combine with a third body, in a known proportion. By a previous experiment it was ascertained how much cya- nogen would combine with a given portion of potassium, the basis of potash. Then, Gay Lussac exposed to the action of 100 measures of prussic acid, heated so as to be in the state of vapor, a quantity of potassium precisely sufficient to absorb 50 measures of cyanogen. By this process, cyanuret of potassium was formed, and exactly 50 measures of the vapor of prussic acid was absorbed, leaving 50 measures of pure hydrogen remaining in the vessel in which the experiment was made. From this experiment, it appears that prussic acid is com- posed of equal volumes of cyanogen and hydrogen, and there'' fore that they combine in the ratio of their specific gravities, that is, the weight of the vapor of prussic acid must be the combined weights of cyanogen and hydrogen, of an equal bulk. Now the specific gravity of hydrogen is known to be 0.0694, and cyanogen gas, 1.8044, air being 1000. Cyano- gen, therefore, is 26 times as heavy, bulk for bulk, as hydro- gen, and since they combine in equal proportions, by volume, to form prussic acid, it follows that this acid consists of an atom of hydrogen united to an atom of cyanogen, and there- fore, that an atom of cyanogen gas is 26 times as heavy as an atom of hydrogen. Thus, the atomic weight of cyano- gen is' 26, that of hydrogen being 1, and the specific gravity of the vapor of prussic acid being the medium between them, is 0.9369, because 0.0694, the specific gravity of hydrogen, added to 1,8044, the specific gravity of cyanogen, makes How did Gay Lussac know that exactly 50 measures of cyanogen were absorbed by the potasskim ? [Cyanogen combines with metals in the same manner that oxygen does. See Cyanogen.] What was the quantity of hydrogen which remained after this absorp- tion ? From tliis experiment, what appears to be the coin position of prussic acid, by vo- lume ; and therefore, the vapor of prussic acid consists of the combined weights of what ? How docs it appear that cyanogen is 26 times as heavy as hydrogen ? Multiply 0.0694 by 26. How does it appear that an atom of cyanogen is 26 times as heavy as one of hy- drogen 1 [Because they combine in equal volumes, but cyanogen weighs 26 times the most.] What then is the weight of an atom of cyanogen, that of hydrogen being 7 CARBON AND SULPHUR. 195 1.8738, the medium, or half of which is 0.9369, the specific gravity of the vapor of prussic acid. The composition of prussic acid may therefore be stated thus: By volume. By weight. Cyanogen 50 1.8044 26, one atom, Hydrogen 50 0.0694 1, one atom. 100 acid vapor. 27 atomic weight. Thus the atomic weight, or equivalent number for cyano- gen is 26, and that for prussic acid is 27. The above will serve as a practical example of the method of finding the atomic weight of a constituent, under similar circumstances. CARBON AND SULPHUR. Sulphuret of Carbon 38. 1 p. Carbon 6+2 p. Sulphur 32. This singular compound may be made by the following process. Place an earthen tube, of about an inch and a half in diameter, a little inclined across a chaffing dish, previous- ly nearly filled with small pieces of newly burned charcoal. To the higher end of this tub ' adapt another tube of glass, filled with small pieces of sulphur. The end of this tube, not connected with the one of earthen, must be stopped with a cork, through which passes a wire, the whole being made air tight. To the opposite end of the earthen tube, another glass tube must be connected, and so bent as to pass under the surface of some water, contained in a bottle. When every thing is thus prepared, the charcoal in the chaffing- dish is set on fire, and when the centre of the tube becomes red hot, the sulphur must be pushed forward with the wire, so as to come in contact with the charcoal. The combination instantly ensues, and the vapor of sulphuret of carbon will condense under the water in the vessel. In this state it is of a yellowish color, but may be purified by redistilling in a What is the specific gravity of the vapor of prussic acid, it being the medium between those of cyanogen and hydrogen 1 From these data, what is the composition of prussic acid, by volume and weight 1 What is the equivalent number for prussic acid 1 Describe the process for making sulphuret of carbon. What is the color of the compound so pre- pared 7 How may it be purified, so as to become colorless and transparent ? 196 METALS. retort containing a little muriate of lime, to absorb the water. The heat, during this process, must not be over 110, and therefore, is best applied by a vessel of water over a lamp, in which the retort is placed. The neck of the retort is dipped under water, as before. The compound, thus obtained from two solids, the one black and the other yellow, is a perfectly transparent and color- less liquid. Its taste is acrid and pungent, and its smell ex- ceedingly fetid and disagreeable. Its specific gravity is 1.27, water being 1.00. It does not mix with water, but sinks through that fluid, as water does through the lightest oil. It possesses very high refractive powers, (see Nat. Philoso- phy,) and is so volatile as to produce an intense degree of cold by evaporation, when exposed to the open air. It is high- ly inflammable, and burns with a blue flame, emitting copious fumes of sulphuric acid. It dissolves phosphorus and iodine, the solution of the latter being of a beautiful pink color. It was stated a year or two since in Paris, and re published in the journals of this country, that when this substance is mixed with phosphorus, and allowed to stand under water for six or eight months, the phosphorus combines with the sul- phur, thus, leaving the carbon to crystallize, and form real diamonds. Having left such a mixture, undisturbed, for a much longer period than the recipe directs, we have as yet discovered no appearance of this precious gem. Sulphuret of carbon is composed of 1 equivalent, or atom, of carbon, 6 2 do. do. sulphur, 32 Its combining number, 38 METALS. The metals form the most numerous class of undecomposed, or elementary bodies. They possess a peculiar lustre, called the metallic, which continues in the streak, or when they are In what respect does this compound show the mysterious effects of chemical combina- tion'? What are the sensible properties of sulphuret of carbon! What is its specific gravity ? What is said of its refractive powers, its volatility, and its inflammability 1 What has been published concerning the method of making diamonds from this sub- stance 1 What is the equivalent composition of sulphuret of carbon^ What is its equi valent number ? Have any of the metals been decomposed "? What is the peculiar lu tre of the metals called 1 METALS. 197 reduced to small fragments. They are all conductors of electricity and caloric. They are fusible, at different tem- peratures, and in fusion retain their lustre and opacity. They are, in general, good reflectors of light, and with the excep- 'tionof gold, which, in the thinnest leaves transmits a green light, they are perfectly opaque. Many of the metals may be extended under the hammer, and are hence called malleable, or under the rolling press, and are called laminable, or may be drawn into wire, and are called ductile. Others can neither be drawn into wire, nor hammered into plates, but may be ground to powder in a mortar ; these are called brittle metals. The metals are capable of combining with each other, in any proportion, when melted together, and such compounds are called alloys. With a few exceptions, the metals have the greatest spe- cific gravity of all bodies. Potassium and sodium swim on water, but with these exceptions, the lightest among them, cerium, is about 5 2 L times the weight of water; platinum is more than 20 times heavier than the same bulk of water. The metals differ in respect to brilliancy, color, density, hardness, elasticity, ductility, tenacity, conductility for caloric and electricity, fusibility, expansibility by heat, stability, odor, and taste. When combined with oxygen, chlorine, iodine, or sulphur, and the resulting compounds submitted to the action of gal- vanism, the metals without exception are revived, and appear at the negative side of the battery, hence 'all the metals are positive electrics. The malleable metals, such as gold, silver, and iron, in whatever manner their surfaces are increased, if this is done rapidly, grow hot, and crumble under the hammer, or press, and finally refuse to be extended any further. It then be- comes necessary, if their surfaces are to be farther extended, to anneal them, which is done by exposure to a red heat, when they become soft and malleable as before. It is pro- What imponderable agents do all the metals conduct? Are all the metals opaque? What are malleable, laminable, and ductile metals ? What are brittle metals ? What Is an alloy 1 What is said of the specific gravity of the metals ? What are the proper- ties in respect to which the metals differ ? What is the electrical state of the metals? When the surfaces of the malleable metals are suddenly increased, what effect is thereby produced on their temperature 1 When is it necessary to anneal a metal 7 17* 198 METALS. bable that this change is produced by a quantity of caloric which the metal retains in its latent state, and by which its particles are prevented from forming so compact a mass as before. When the metal is again drawn under the hammer or press, it grows hot, and at the same time is increased in density and specific gravity, the caloric before absorbed be- ing given out, and the metal is again rendered brittle by the process. All the metals are converted into a fluid state by sufficient degrees of heat. In this respect there is a vast difference in the different metals. Mercury is a fluid at all common tem- peratures, and does not assume the solid form uniess exposed to a temperature nearly 40 below the freezing point, while platina and columbium continue solid under the highest heat of a smith's forge, and only become fluid under the heat of the compound blowpipe, or the action of the most powerful galvanic battery. With several exceptions, these bodies suffer a singular change on exposure to air and moisture, or on exposure to air and heat. They lose their tenacity, brilliancy, and other qualities peculiar to the metals, soil the fingers, and crumble to powder, but at the same time increase in weight. This change is termed oxidation, and in this state they are termed metallic oxides. This increase in weight and loss of metallic splendor, does not happen when the metal is placed in a vacuum, or when it is protected from the air by varnish or other means, but is found to be the consequence of the union between the metal and the oxygen of the air, or water, or both. Thus, iron, when exposed to air and moisture, spontaneously absorbs oxygen and is converted into a brown friable matter called rust. "This is an oxide of iron. The increase of weight is caused by the solid oxygen which thus combines with the metal. Metals, in the language of chemistry, are termed combus- tibles, because they are capable of combining with oxygen, How is the process of annealing supposed to affect the metal, so as to restore its raallea- oility ? By what means may all the metals be rendered fluid 1 What is said of the dif- ferent temperatures at which the metals become fluid 1 The metals, with the exception of platina, gold, and silver, are said to suffer a peculiar change, when exposed to heat, or to air and moisture. To what is this change owing, and what are the resulting com- pounds called 1 What causes iron arid other metals to rust, when exposed to the air? Why are the metals termed combustible in the language of chemistry ? METALS. 199 and thus passing through the process of oxidation, or com- bustion. In ordinary combustion there is an extrication of heat and light, and under favorable circumstances, several of the metals exhibit these phenomena. Zinc burns with a brilliant flame when heated, and exposed to the open air ; and iron, when heated in oxygen gas, emits the most vivid scin- tillations, attended with intense heat. Gold and platina, the metals which have the least affinity for oxygen, are still ca- pable of uniting with it so rapidly, as to produce scintillations when heated with the flame of the compound blowpipe. In all cases the metals combine with oxygen most rapidly when exposed to the highest degrees of heat. Hence, at common temperatures, their oxidation proceeds so slowly as not to emit sensible light or heat ; and some of them, such as gold, silver, and platina, do not combine with it at all at such tem- peratures. Some of the metals combine with oxygen in only one pro- portion, while others combine with it in three or four pro- portions. Thus, there is only a single oxide of zinc, but there are three or four oxides of iron. After the metals are converted into oxides, they may again be reduced, that is, brought back to their metallic states, by depriving them of their oxygen. This may be done by se- veral methods, depending on the nature of the metal, or the force by which it retains the oxygen. The reduction of many of the metals from their ores, is nothing more than depriving them of their oxygen. For this purpose, a common method is to heat the oxide with some combustible, which has a stronger affinity for the oxygen than the metal has. Thus, the oxide parts with its oxygen, and assumes the metallic form, while the combusti- ble absorbs that which the oxide before contained, and is itself consumed or converted into an oxide. As an example, carbon when heated has a stronger affinity for oxygen than iron, and therefore,, when carbon and oxide of iron are strongly heated together, the iron is reduced while the char- Under what circumstances do several of the metals exhibit the ordinary pheno- mena of combustion 7 Under what circumstances do all the metals combine most rapidly with oxygen 1 What metals do not combine at all with oxygen at common temperatures ? Do the metals all combine with the same proportion of oxygen 1 After a metal has been converted into an oxide, how may it again be reduced, or brought again to its metallic state? By what method can the metals be deprived ol their oxygen ? What is one of the most common methods of reducing iron from its ores 'I 200 METALS. coal is converted into an oxide, or an acid, and passes aw*ay into the air, or in common language, is burned up. This is the method of reducing iron from its ores. In some instances, heat alone drives away the oxygen and reduces the metal ; but in such cases the metal has only a weak affinity for oxygen. The oxides of gold, mercury, and platina, are thus reduced. Metals having stronger affinities for oxygen, resist such methods of redaction, and require the more powerful agency of galvanism. When metallic oxides are exposed to this influence, the reduced metal is found at the negative side of the battery, while the oxygen rises through the water at the positive side. None of the metals are soluble in an acid, in their metallic states, but when first combined with oxygen they are readily dissolved. Gold will not dissolve in muriatic acid alone, because this acid does not part with its oxygen with such facility as to form an oxide of the metal. But if a quantity of nitrip acid be added to the muriatic, the gold instantly be- gins to enter into solution, and a chloride of the metal is formed. If a piece of zinc be thrown into sulphuric acid, it will remain undissolved, but if three or four parts of water be poured in, the metal is attacked with great violence, and soon dissolved. In this case the water furnishes the oxygen, by which the zinc is oxydized, and it is then dissolved by the acid. By this method hydrogen is obtained ; the metal de- composing the water by absorbing its oxygen, w r hile the hy- drogen is set at liberty. The metals combine with phosphorus, sulphur, and car- bon, forming compounds called phosphurets, sulphurets, and carburets. Of all the inflammable bases, sulphur appears to possess When iron is reduced by heating its oxide with charcoal, what becomes of the oxy gen! In what instances does heat alone reduce the metallic oxides? When me- tallic oxides are reduced by means of galvanism, at which pole of the battery is the oxygen extricated ? Are any of the metals soluble in the acids, while in their metallic states ? Why is it necessary to add nitric acid to the muriatic acid before it will dissolve gold 1 Why does not zinc dissolve in strong sulphuric acid 1 Why is hydrogen evolved when the zinc is dissolved in diluted sulphuric acid ? When a metal combines with phosphorus, what is the resulting compound called ? What is the composition of a sul- phuret ? What is the composition of a carburet? What combustible body appears to possess the strongest affinity for the metals ? METALS. 201 the strongest affinity for the metals, and its combination with some of them is attended with remarkable phenomena. This affinity is shown by the following- interesting experiment. Introduce into a Florence flask, three parts of iron, or cop- per filings, and one part flowers of sulphur, well mixed to- gether. Then stop the flask with a cork, and place it over a lamp, so as to heat it slowly, and as soon as any redness appears, remove the flask from the fire. The chemical ac- tion thus begun, will be continued by the heat evolved by the combination between the sulphur and the metal, and the whole mass in succession will become red hot, which, in the dark, will produce a very beautiful appearance. We have stated, in a former part of this work, that when bodies pass from a rarer to a denser state, caloric is evolved. The heat and light, in this experiment, seems to be the consequence of this general law of condensation, for the sul- phuret, formed by the union of the two bodies, occupies much less space than the metal and sulphur did before. Many of the metallic sulphurets are very abundant in na- ture, forming the ores of the metals. Several metals are extracted entirely from such ores. The most abundant sul- phurets are those of lead, antimony, copper, iron, and zinc. The phosphurets are seldom found as natural products, but may be formed, by bringing phosphorus into contact with the metal, at a high temperature. Carbon unites with iron in several proportions. Unrefined iron, steel, and black lead, are all carburets of iron, the latter containing 95 per cent, of carbon. When the oxide of a metal is dissolved in an acid, there is a compound formed, which differs entirely from either of these two substances, and when the liquor is evaporated there remains a crystalline solid, called a metallic salt. These salts differ materially from each other, according to the kind of acid and metal of which they are composed. Some of them, such as the sulphate of iron, and acetate of lead, are of great importance to the arts. The oxides of the metals readily unite by fusion with glass, What experiment is stated,|illustrating the affinity between iron and sulphur? Whence does the heat arise in this experiment 1 What are the most abundant sulphurets in na- ture 1 Are the phosphurets often found native 1 What carburets are mentioned 1 What is a metallic salt 7 What particular salts are mentioned, as being of great importance to the arts 7 What is said of the union between the metallic oxides and glass 7 202 METALS. and it is by such means that this substance is made to re- semble gems and precious stones. The stained glass, so celebrated among the ancients, and used in the windows oj churches, was prepared in this manner. This art was said to have been lost, but stained glass is still made in many parts of Europe, and in this country. (See Glass.) Compounds, made by fusing two or more metals together, are called alloys. In these cases there is a chemical union between the metals ; and hence such compounds differ great- ly from the metals of which they are composed. In general, the specific gravity of the alloy is greater than the medium specific gravity of tbe two metals, and of consequence, the bulk of the alloy is less than that of the two metals taken separately. As an example, if two bullets of copper and two of tin, of equal bulk, be melted "together, they will form little more than three bullets of the same size. This diminution of bulk is accounted for, by supposing that the particles of the two metals enter into a closer union with each other, when combined, than those of either did in a separate state. The alloys of the metals are also more easily fusible than the metals of which they are composed ; that is, the melting point of an alloy is below the medium temperature at which the metals composing it are fusible. An alloy, made of 8 parts bismuth, 5 lead, and 3 tin, is a curious instance of this fact. In a separate state, the melting point of lead is 500, bismuth, 490, and tin, 430, and yet, when these are fused together, the compound melts at 212. Amusing toys, in the form of tea-spoons, have been made of this alloy. Such spoons, in the hand of those who know no- thing of their composition, have excited great astonishment, by coming out of a cup of hot tea with their bowls melted off. The number of metals, and the variety of properties which they possess, render it necessary to throw them into classes and orders, that a knowledge of these properties may be more easily obtained. The following arrangement is that originally proposed by Thenard, and adopted by Henry and others. We have already stated, that some of the metals are redu- ced from the state of oxides by heat alone, such metals hav- What are alloys 1 In what respect do alloys differ from the metals of which they are composed 7 How is the increased specific gravity of the alloys accounted for ? What if aid of the fusibility of alloys? What curious illustration of the fusibility of an alloy made of bismuth, lead, and tin, is given ? METALS. 203 ing- only a slight affinity for oxygen. Others, it was also sta- ted, have so strong an attraction for oxygen, that they cannot be reduced by this method, but require the presence of a con> bustible, or some other means, for their reduction. The ar- rangement into classes is founded on this distinctive difference. The orders of the second class are founded on the powers of tne metals to decompose water. CLASS I. Metals, the oxides of which are reducible to the metallic state, by heat alone. These are Mercury, Platinum, Osmium, Silver, Palladium, and Gold, Rhodium, Iridium. CLASS II. Metals, the oxides of which are not reducible to the metallic state by the action of heat alone. Order 1. Metals which decompose water at common tem- peratures. These are, Potassium, Lithium, Strontium, Sodium, Barium, Calcium. Order 2. Metals which are supposed to be analogous to Order 1, but whose properties are but little known. These are, Magnesium, Ittrium, Zirconium, Glucinum, Aluminum Silicium. Order 3. Metals which decompose water at a red heat These are, Manganese Iron, and Zinc, Tin, Cadmium. Order 4. Metals which do not decompose water at any temperature. These are, Arsenic, Uranium, Titanium, Molybdenum, Columbium, Bismuth, Chromium, Nickel, Copper, Tungsten, Cobalt, Tellurium, Antimony, Cerium, Lead. Of the first class, there are 8 metals ; of the second, there are 32 ; making 40 in all. What is the distinctive difference between the metals, on which is founded the arrange- ment into classes 1 What are the peculiar properties on which the orders of the second clase are founded ? How are the classes and orders defined, and what are the names of the metals belonging to each? How many metals belong to the first class and how many to the second. 204 MERCURY. CLASS I. Metals, the oxides of which are decomposed by the actioi of heat alone. MERCURY 200. Mercury, or quicksilver, is found native, or in its pure state, only in small quantities, the mercury of commerce being chiefly extracted from cinnabar, which is a sulphuret of the metal. The metal is extracted from this ore, by heating it in iron retorts, mixed with iron filings or lime. By this process, the sulphur combines with the lime or iron, forming a sul- phuret of lime or iron, while the mercury is volatilized, and is distilled into a receiver, where it condenses in its pure form. This metal is distinguished from all others by preserving its fluidity at common temperatures. Its specific gravity is 13.5. At the temperature of 660 it boils, rises in vapor, and may be distilled from one vessel into another. At 40 below zero it becomes solid, and is then malleable, and may be ham- mered into thin plates. When pure, this metal is not readily oxidized in the open air at common temperatures, but when mixed with other me- tals, such as tin, or zinc, there is commonly a film of oxide oil its surface ; hence this is an indication that the mercury is impure. When mercury is triturated with an equal quantity of sulphur, there is formed a black powder, called etkiop* mineral, Mercury readily combines with gold, silver, tin, bismuth, and zinc ; but not so readily with copper, arsenic, and anti mony, and with platina and iron scarcely at all. The result- ing compounds between mercury and the other metals, are called amalgams. Mercury has such an affinity for gold and tin as to dissolve these metals in small pieces, at common temperatures. In the mines of South America, a great proportion of the gold What is the definition of class first? From what substance is the mercury of com- merce extracted? What is the composition of cinnabar, and what its chemical name! What is the method of obtaining the mercury from its sulphuret ? What striking dis- tinction is there between mercury and other metals? What is the specific gravity of mercury ? At what temperature does mercury boil, and at what temperature does U freeze ? When solid, what property common to many other metals does it possess * What are the obvious indications of impurity in this metal ? What is ethiops mineral 1 When mercury combines with other metals, what is the compound called ? MERCURY. 205 was formerly procured by amalgamation. Sand containing particles of gold, was agitated in a close vessel with mercury, and the two metals thus brought in contact, united and formed an amalgam. This was then distilled in an iron vessel, by which the mercury was driven away, while the gold remained. At the present time, the gold-beaters make use of the same means to obtain the small particles of the metal contained in the sweepings of their shops. The sweepings being placed in a close vessel, and agitated with mercury, an amalgam i formed. The gold is then separated by pressing the amal- gam in a buckskin bag, which forces the mercury through the pores of the leather, while the gold is retained. Mercury is applied to many other uses in the arts, and is a constituent in several important medicines. The silvering on the backs of looking-glasses, is an amai gam of tin, and is put on in the following manner: A sheet of tin foil is laid perfectly smooth on a slab of marble, and on the tin foil, mercury is poured', until it is about the eighth of an inch thick ; the attraction of the metals for each other, keep- ing the mercury from running off When the mercury is spread equally over the surface, the glass plate is run or slid on. This is so managed, by partly immersing the end of the plate in the edge of the mercury, and pushing it forward, a? to entirely exclude the air from between the metal and the glass. Weights are then laid on the plate, to press out the mercury which does not amalgamate with the tin. In about 24 or 36 hours, the amalgam adheres to the. plate in the manner we see it on looking-glasses. The glass, therefore, merely serves to keep the amalgam in its place, and being transparent, to transmit the image which is reflected from the surface of the metal. Could the mercury be kept from oxy- dation, and be retained in its place without the glass plate, such mirrors would be much more perfect, since the glass prevents some of the rays of light from passing to and from the metal. How is gold obtained by mercury 1 How do gold-beaters obtain the small particles of gold from among the sweepings of tneir shops 7 What is the composition called the sil- vering, on the backs of looking-glasses? Describe the process of silvering a plate of glass. In forming a looking-glass, what is the use of the glass plate 1 18 206 MERCURY MERCURY AND OXYGEN. Peroxide of Mercury 216. 1 p. Mercury 200-f 2 p. Oxygen 16 Red Precipitate. This compound is commonly formed by dissolving 1 mercury in nitric acid, and then exposing the nitrate to such a degree of heat as to expel all the acid. It is in the form of small, shining crystalline scales, of a red color. When exposed to a red heat, this oxide is reduced, and converted into oxygen, and metallic mercury, a circumstance on which its arrange- ment in the present class depends. When long "exposed to the action of light, the same effect is produced. Red pre- cipitate is employed in medicine chiefly as an escharotic. It will be observed at the head of this section, that the per- oxide of mercury is composed of 200 parts of the metal com- bined with 16 parts or two equivalents of oxygen. The prot- oxide of this metal consists of 200 mercury, and 8 oxygen, these compounds conforming precisely to the doctrine of defi- nite and multiple proportions, as formerly explained. The reason why so large a number as 200 is taken for the equi- valent of mercury, arid some other metals, will be understood, when it is recollected, that the data from which all the pro- portional numbers are estimated, is the proportions of hydro- gen and oxygen forming water. The proportion of oxygen in this compound being 8, and this number for oxygen being fixed, that for mercury is 200, because it is found by experi- ment, that these are the smallest proportions in which thesf wo bodies combine. MERCURY AND CHLORINE. Protochloride of Mercury 236. I p. Mercury 200-f 1 p. Chlorine 36. Calomel. When chlorine, a gas formerly described, is brought in contact with mercury, at common temperatures, a combina- tion takes place between them, amounting to one proportion of each, forming a protochloride of the metal. This, how- evei, is not the common method of preparing calomel; the What is the composition of peroxide of mercury? By what simple process i it ob Uined ? How may this oxide be decomposed 1 What is the use of red precipitate 7 ET plain the reason why the combining number for mercury is 200. MERCURY. 207 two constituents being more conveniently combined in their proper proportions, by mixing the bichloride of this metal with an additional quantity of mercury. The bichloride of mercury contains, as its name signifies, two proportions of chlorine and one of the metal. This compound is known un- der the name of corrosive sublimate. It contains mercury 200, and chlorine 72 parts by weight. When this salt is triturated with mercury, the metal absorbs a part of the chlorine, and the whole is converted into a protochloride, or calomel. The proportions are 272 parts, or 1 equivalent of the corrosive sublimate, and 200 parts, or I equivalent of the mercury. This process affords a beautiful illustration of the truth of the doctrine of definite proportions ; for when these equivalents are mixed in a mortar, and then sublimed by heat, 36 parts, or 1 proportion of the chlorine is transferred from the bi- chloride to the metallic mercury, thus converting the w r hole into 472 parts of protochloride of mercury, or calomel. This process also shows, in a striking manner, the effects of different proportions of the same principles, on the quali- ties of bodies. Corrosive sublimate is one of the most active and virulent, of all metallic poisons, and in doses of only a few grains, occasions the most agonizing symptoms, which com- monly end in death. But calomel is a mild and safe medi- cine, which maybe taken in doses of 60, or even 100 grains, without injury. And yet the only chemical difference between these two substances is, that the calomel is a compound of 1 atom, of chlorine combined with one of mercury, while corro- sive sublimate consists of 2 atoms of the first and 1 of the metal. MERCURY AND SULPHUR, Sulphur et of Mercury 216. 1 p. Mercury 200+1 p. Sulphur 16. Cinnabar. Cinnabar is prepared by fusing mercury and sulphur to- gether, and afterwards subliming the compound. When this compound is reduced to a fine powder, it forms the well What is said of the combination between mercury and the gas chlorine, at common temperatures? What common name has the protochloride of mercury ? How does the protochloride differ from the bichloride of mercury ? What is the common name for the bichloride of mercury? What is the common mode of making calomel? What pro- portions of corrosive sublimate and mercury combine and form calomel? What two principles are strikingly illustrated by this combination ? What is the composition of ulphuret of mercury ? 208 SILVER. known pigment vermilion. Cinnabar occurs in nature, in large quantities, and is the substance, as already stated, from which mercury is chiefly obtained. SILVER 110. Silver is found native in small quantities. It also occurs mixed with several other metals, as copper, antimony, arse- nic, and sometimes with gold, but is chiefly found in combi- nation with sulphur, forming a sulphuret of silver. This metal, when pure, admits of a lustre only inferior to that of polished steel. Its specific gravity is 11, being about half that of platina. In malleability and ductility it excels all the other metals except gold and platina. Silver is fused by the heat of a common furnace, and by a long continued and high degree of heat it may be volatili- zed, or turned into vapor. By slow cooling, this metal may be obtained in regular crystals. It is not oxidated by expo- sure to the combined action of heat and moisture, but is readily tarnished by sulphureous vapor. Sulphuric acid dis- solves this metal, when assisted by heat, but its proper solvent us nitric acid, with which it readily combines, and when the solution is evaporated, forms nitrate of silver, a substance known under the name of lunar caustic. Silver is precipitated from its solutions, by several of the ather metals, in its metallic form. This happens when any other metal, having a stronger affinity for oxygen than silver, is placed in a solution of this metal. If a quantity of nitrate of silver, or lunar caustic, be dis- solved in water, and a slip of clean polished copper be dip- ped into it, the copper will be covered with a coat of silver. Diana's silver tree is made by precipitating silver from its solution by means of mercury. This interesting experiment may be performed in the following manner. Mix together six parts of a solution of nitrate of silver, and four parts of a solution of nitrate of mercury, both completely saturated, Add a small quantity of rain water, and put the mixture into What is the more common name for this compound 1 What is vermilion ? In what elates does silver occur 1 What is the substances with which it is chiefly found combined? What is its specific gravity 1 What is said of its malleability and ductility 1 How may miver be obtained in crystals? What vapor readily tarnishes silver ? What is the pro- pec solvent of this metal? What is the salt formed when silver is dissolved in nitric acid ? How is lunar caustic formed ? How may silver be precipitated in its metallic form ? What is the process for forming Diana's silver tree ? SILVER. 200 a glass decanter, containing six parts of amalgam, made of seven parts of mercury, by weight, and six parts of silver leaf. In the course of some hours, there will appear small shining scales of metallic silver on the amalgam, which will increase, and shoot out in the form of a silver tree, producing a very beautiful appearance. Silvering powder may be prepared in the following man- ner. 1 Precipitate silver from its solution in nitric acid, by dropping into it some plates of clean copper. Take 20 grains of this powder, and mix with it two drachms of cream of tar tar, the same quantity of common salt, and half a drachm of alum. These articles must be finely pulverized, and intimately mixed in a mortar. If a little of this powder be moistened, and rubbed on a clean surface of brass or cop- per, the^ silver Avill be precipitated, and the surface of the metal will be covered with it. In this way the silvering of candlesticks, or other articles, where it is worn off, may be replaced. The addition of the other articles to the precipi- tated silver, probably serves no other purpose than to keep the surface of the brass perfectly clean, and free from oxide, as the powder is rubbed on. Silver may also be precipitated on ivory, and then revived by the action of solar light. Into a dilute solution of nitrate of silver immerse a slip of polished ivory, and let it remain until it acquires a yellow color, then place it in a tumbler of pure water, and expose it to the direct rays of the sun for a few hours, or until it turns black. If now, it be gently rub- bed, the surface will be changed into' a bright metallic one, and the slip of ivory will, in appearance, be transmuted into one of silver. This change is caused by the deoxidizing power of the solar rays, in consequence of which, the oxy- gen is separated from the silver, and the metal reduced to its former state. A very useful solvent of silver is made by dissolving one part of nitre with about eight parts of strong sulphuric acid. This solvent, when heated to about the temperature of boil- ing water, will dissolve silver, without acting on gold, copper, How may silvering powder be prepared 1 What is the use of the silvering powder? Of what use are the other ingredients in this powder besides the precipitated silver* What is the process for silvering ivory 1 How do you account for the return of the sil- ver lo its metallic state by being placed in the sun ? What is the composition of a solvent for silver, which does not act upon other metals? 18* 210 GOLD. lead, or iron, and hence may be conveniently used to extract the silver from old plated goods, &c. The combining number for silver is 110, it having been found that the oxide of this metal contains 110 silver, and 8 oxygen. The sulphuret of silver is composed of 110 of the metal, and 16 sulphur. GOLD 200. This well known precious metal is found only in the me- tallic state, either alone, or mixed with other metals. Con- sequently, there is no such thing as an ore of gold.) "Gold is sometimes found disseminated in rocks, but always in its metallic state, and never mineralized by sulphur, oxygen, or any other substance. Its specific gravity is 19, It is the most malleable of all the metals, and in ductility is only ex- celled by platina. The extent to which a given portion of this metal may be spread, and still continue a perfectly unbroken surface, is truly astonishing. A single grain of the best wrought gold leaf is found to cover fifty-six square inches, and it would take near- ly 282,000 such leaves to make an inch in thickness. This, however, is not the utmost limit to which its tenuity may be extended, for the Avire used by lace makers is drawn from an ingot of silver gilded with this leaf, and from the diameter of the ingot, compared with that of the wire, it has been found that the covering of gold on the latter is only a twelfth part of the thickness of gold leaf Supposing the leaf, when first placed on the silver, to have been the 30 thousandth part of an inch in thickness, the covering on the wire would require 360,000 times its own thickness to make an inch ; and still this covering is so entire that, even with a microscope, the silver is not to be seen. Gold is the only metal which can be made so thin as to transmit the rays of light, and the rays so transmitted, instead of being of the same color with the metal, are green. This metal, when pure, is not oxidated, or otherwise alter- ed, by being kept in fusion, in the highest heat of a furnace What is the equivalent number for silver? In what state is gold always found ? Are there any ores of gold 1 What is the specific gravity of gold ? What illustrations are given of the malleability of gold? What is said of the thickness of -this metal on the wrre used by lace makers ? What is said of the light seen through gold leaf? How is jold affected by continued fusion at the highest degrees of heat 1 GOLD. 211 for any length of time. Sulphuric, nitric, or muriatic acid, do not alone produce the least action on gold ; but when two parts of nitric and one of muriatic acid are mixed, forming aqua regia, the mixture dissolves this metal with facility. Put some nitric acid into one vessel, and some muriatic acid into another, and throw a little gold leaf into each. Not the least effect on either will be produced ; but if the contents of one vessel be poured into the other, immediate action will ensue, and the metal will soon be dissolved. The solution of gold is decomposed by many substances which have a stronger attraction for oxygen than this metal has, and by absorbing the oxygen, restores the gold to its metallic state. If a piece of ribbon, or other substance, be moistened with some dilute solution of gold, and exposed to the action of a current of hydrogen, the gold will be revived, and the rib- bon, or other substance, will be covered with a film of gold. By means of a camel hair pencil, the solution may be applied to the ribbon in regular figures, and as the appearance of the ribbon is not changed by the application, until the hydrogen is thrown upon it, a striking experiment may be made in this way. The hydrogen must be applied while the ribbon is moist, and may be blown on, through a tube attached to a bladder containing it. Sulphuric ether precipitates gold, but instantly dissolves the precipitate, forming an etherial solution of the metal. This solution is sometimes employed to gild lancets, scissors, and other instruments, in order to preserve them from rust. This is readily done by the following method. Into a given quantity, say an ounce of the nitro-muriatic solution of gold, pour twice as much sulphuric ether ; shake the vessel, and let it stand t\vo or three minutes, and then pour into another ves- sel about one third of the mixture. The acid does "not mix with the ether, but settles to the bottom of the vessel, leaving the ether in possession of the gold on its surface ; the por- tion decanted into the other vessel, therefore, is an etherial solution of gold. Any perfectly clean and polished steel in- strument, will be covered with a coat of gold, if dipped for a moment into this solution. When taken from the ether, it What acids dissol ye gold? How may the solutions of gold be decomposed 1 In what manner may figures of gold be made on ribbon 1 What are the directions for making an etherial solution of gold 7 In what manner may steel instruments be gilded with an etherial solution of gold 1 212 PLATINUM. should be instantly plunged into pure water, to wash off any particles of acid, which may be retained in the solution. The instrument may afterwards be burnished, when it will have all the appearance of the best gilding. In this case the gold appears to be in its metallic state, and to be retained on the surface of the steel by the attraction of cohesion, while the ether evaporates. PLATINUM 96. Platinum is a white metal, resembling silver in color, but a little darker. It is the heaviest of all known bodies, having a specific gravity of 22, This metal comes chiefly from several parts of South Ame- rica, where it is found in small grains, or scales, exceedingly heavy, and nearly the color of wrought iron. In this state it is alloyed by several other metals, and requires to be puri- fied before it is malleable. It was first discovered in 1741, but has not been applied to any considerable use until within the last twenty years. This metal has lately been discovered in considerable quantities in Russia, and is employed for the purposes of coin, for which it is well adapted. Platina, like iron, may be welded, and like gold, suffers no change from the combined agencies of air and moisture, or by long continued heat. For many purposes, therefore, it is the most valuable of all the metals. This metal is so difficult of fusion, as to undergo the great- est heat of a smith's forge without the least change. None of the acids act on it, except the nitro-muriatic, the solvent of gold. Platinum is purified and obtained in a malleable state by dissolving the grains in 8 times their weight of aqua regia, assisted by heat. The acid only dissolves the platinum, leaving the iridium and osmium, the metals with which it is alloyed, in the form of a precipitate at the bottom of the vessel. The acid solution is then evaporated, and the metal precipitated by mu- riate of ammonia. The precipitate thus obtained, is heated in a crucible, lined with a mixture of clay and charcoal, to the utmost degree that can be attained in a blast furnace, What is the color of platinum? What is its specific gravity? Is there any known vxly of greater specific gravity than platina ? In what countries is platina found ? Whea \ as this metal discovered ? In what respect does platina possess the property of iron* l When heated in oxygen, it burns with a deep red light, and when thrown into water, the fluid is decomposed, hydrogen being extricated. BARIUM AND OXYGEN. Protoxide of Barium 78. 1 p. Barium 70-f-l p. Oxygen 8. Barytes. When the metal barium, is exposed to the air, it falls into a powder, which was formerly called pure barytes, or baryta, but which Sir H. Davy has proved by the above stated ex- What is known concerning the metallic base of this alkali 7 What are the equivalent numbers of lithium, and lithia ? How is baryta obtained 1 By what process is barium separated from baryta 7 What is the color of barium ? At what temperature is barium fuaiblc 1 What is the specific gravity of barium 7 When barium is exposed to the air, what compound is formed 1 226 METALS. periment, to consist of a metal and oxygen. This substance is therefore called oxide of barium. Oxide of barium may also be obtained by a different pro- cess from that above described, viz. by exposing the carbon- ate of baryta to an intense heat, mixed Avith charcoal. The carbonate of barytes is found native in small quantities, but maybe obtained from the sulphate of barytes by a simple process. Mix sulphate of barytes in fine powder, with three times its weight of carbonate of potash, (pearlash), and a pro- per quantity of water. Let the mixture boil for an hour, now and then breaking the lumps into Avhich it is apt to run, with a pestle. By this means the two salts will decompose each other, and there will be formed carbonate of barytes, and sul- phate of potash. The carbonate may now be exposed to a high heat, or it may be dissolved in -nitric acid, and this de- composed, which is effected by a moderate heat, when prot- oxide of barium, or barytes, will be obtained. This substance is of a white color, has a sharp caustic taste ; changes vege- table blue colors to green ; neutralizes acids, with which it forms salts, and is a strong poison. When water is thrown on it, it falls into fine powder, like quicklime, but with a greater evolution of heat. Barytes is composed of 1 equivalent, or atom of barium, 70 1 do. of oxygen, 8 The equivalent combining number for barytes, 78 Barytes is soluble in about twenty parts of water, at com- mon temperatures, and this solution forms a delicate test for the presence of carbonic acid. The carbonate of barytes being insoluble in water, a white cloud is instantly formed by the union. STRONTIUM 44. The -sulphate and carbonate of strontian, or strontia, are native salts. They consist of pure strontian, combined with sulphuric and carbonic acids. From the sulphate, the car- When thrown into water, what effects are produced ? By what process may barium be obtained without the agency of galvanism ? How may carbonate of barytes be ex- tracted from the sulphate ? What are the properties of barytes, or protoxide of barium 1 What is the composition of barytes 1 In what quantity of water is barytes soluble 1 ? Why is barytes a test for carbonic acid 1 How is the carbonate of strontian produced from the sulphate 1 METALS. 227 Donate may be procured by precisely the same means as al- ready described for barytes, and the pure oxide may also be obtained, and the metal strontium separated from it, by the same process as that described for barytes. Strontia resembles baryta in most respects. It slakes in water, causing an intense heat, and possesses distinct alkaline properties. The metal strontium is similar to barium in appearance, and when exposed to the air quickly attracts oxygen, and is converted into strontia. Perhaps the principal difference be- tween these two substances, which has been detected, is their different combining proportions with oxygen, and the inertness of the oxide of strontium on animals. The protoxide of strontium connsists of Strontium, 1 equivalent 44 Oxygen, 1 do. 8 52 The oxides of barium, as already stated, are strong poi- sons, but those of strontium are inert. CALCIUM 20.;v When carbonate of lime, or white marble, is exposed to a ..ed heat, the carbonic acid is expelled, and there remains a /vhite caustic substance, well known under the name of quick- lime. When this substance is exposed to the action of galva- nism, in the same manner as already described for the decom- position of barytes, calcium, the metallic base of lime, is sepa- rated. This metal is of a whiter color than barium, and has a lustre like silver. When exposed to the air, it absorbs oxy- gen, and is converted into quicklime, and when thrown into water, the fluid is decomposed, its oxygen being absorbed, while hydrogen is given off, and a solution of lime remains. How is the pure earth strontia obtained from the carbonate 7 By what process is the Metal strontium separated from strontia 7 What is the appearance of this metal 7 What is the composition of strontia, or the protoxide of strontium 7 What is the combining number of strontia 7 What is the difference between strontia and baryta 1 What is quick- lime 1 How may quicklime be decomposed, and calcium, its metallic base, be separated? What is the appearance of calcium 7 How is calcium converted into quicklime 7 What effect is produced when calcium is thrown into water 1 228 METALS. CALCIUM AND OXYGEN. Oxide of Calcium 28. 1 p. Calcium 20+1 p. Oxygen 8. Quicklime. From the quantity of hydrogen evolved by the action of calcium on water, it has been determined that lime is com posed of Calcium, 1 equivalent 20 Oxygen, 1 do. 8 * ~"~"~""" Making the equivalent for lime, 28 Carbonate of lime exists in great abundance as a natural product, under the names of limestone, marble, and chalk. Quicklime, the pure earth, is obtained by exposing the car- bonate to heat, and is a substance of great importance in the arts, and particularly in building. Mortar is composed of this substance combined with water, and mixed with a proportion of sand. Quicklime absorbs water with remarkable avidity, and at the same time a high degree of heat is produced. This pro- cess is called slaking, and the heat is caused by the conden- sation of the water into a solid state, in consequence of which caloric is evolved. The lime will remain perfectly dry after having absorbed one third of its weight of water, which there- fore forms a part of the slaked lime, or hydrate of lime. Hydrate of lime is composed of 28 parts or 1 proportion of lime 9 parts, or 1 do. of water 37 is therefore its combining number. Lime is very sparingly soluble in water, and it is a singular fact, that it is more soluble in cold, than in hot water. Thus, Mr. Dalton found that one grain of lime, at the temperature of 212 required 1270 grains of water for its solution, while at the temperature of 60, the same quantity was dissolved in How is the combining proportion of oxygen with calcium determined 1 What is the composition of lime, or oxide of calcium ? ' What is the equivalent number for 1-ime ? What causes the heat, when water is thrown on quicklime 1 What is the scientific name for slaked quicklime? What is the composition of hydrate of lime? What singular foot \e mentioned concerning the solubility of lime in cold, and hot water ? CHLORIDE OP LIME, T78 grains of water. By other experiments, it has been found that water, at the freezing- point, will take up just twice the quantity of lime that it will at the boiling- point Conse* quently, on heating lime water, which has been prepared in the cold, a deposition of the lime will ensue. Lime water therefore, when used for medicinal purposes, should be pre- pared in cold, instead of hot water, as commonly directed, and should also be kept in a cool place. It should likewise be closely stopped from the air, for, as the lime has a strong attraction for carbonic acid, of which the atmosphere always contains a small portion, if left open, it is soon converted into carbonate of lime, as shown by the production of a thin pelli- cle on its surface. Lime water is a delicate test for the presence of carbonic ucid, with which it forms a white insoluble compound, the carbonate of lime. The air from the lungs contains a small quantity of carbonic acid, and hence, on blowing into a vessel air at a temperature far below a red heat, and burned with : bright flame. The product of the combustion was zirconia But whether this base is of a metallic nature, has not been decided. It is wanting in one property common to all metals, being a non-conductor of electricity. Silica,, or. Oxide of Silicium. Sir H. Davy's experiments In what minerals does the oxide of glucina exist 1 What is the meaning of the word glucina, and why is this earth so named 1 How does ittria differ from alumina and glu- cina 1 In what minerals has the earth zirconia been found 1 How are the salts of zjrco- nia distinguished 1 What is said of the metallic base of zirconia 1 What is said of trw metallic base of silica I METALS. 239 on silica lead him to suppose, that in common with the earths ahove described, it had a metallic base, and it was arranged \vith them, in conformity to this opinion. But more recently, Berzelius has succeeded in decomposing this earth, and has given an account of the properties of its base. From this we learn that silicium is of a dark brown color without the least trace of metallic lustre. That it is incombustible in the open air or in oxygen gas, and that it may even be exposed to the flame of the blowpipe without fusion, and without suffering the least change. It is not dissolved by any of the acids, ex- cept a mixture of the nitric and fluoric, with which it readily enters into solution. It is not a conductor of electricity. These properties, and particularly its want of metallic lustre, and of power to conduct electricity, prove that the base of silica is not of a metallic nature. Silica, or silex, is a very abundant natural product. It forms a large part of all granitic, or primitive rocks, and moun- tains, and is the chief ingredient in sandstones, and earthy formations. Rock crystal, or quartz, flint, chalcedony, agate, cornelian, and all other substances of this kind, are composed almost entirely of silex. Silica maybe obtained in sufficient purity, for most purpo- ses by heating transparent rock crystal to redness and plung- ing it into water while hot, and then reducing it to powder. In this state, silex is a white powder, which feels harsh when rubbed between the fingers, and has neither tastenor smell. It is exceedingly infusible, but may be melted with the compound blowpipe. It resists the action of all the acids, except the fluoric, which dissolves it with considerable faci- lity. It is dissolved by the fixed alkalies, and hence it would appear that its properties are rather of an acid, than of an al- kaline nature. On this account several chemists have called silica an acid, and the compounds which it forms with the alkalies, have been termed silicates. From what has been said, the student will infer that there is yet considerable doubt and uncertainty, in respect to the real nature of silica. Dr. Thompson, being convinced of its non-metallic nature, Is the base of silica of a metallic nature ? What substances are mentioned of which silica forms the principal parti How may pure silica be obtained? What are the pro- perties of silica 1 What is said of the compound nature of silica? 240 METALS. arranges it with the simple bodies carbon and boron. There is no doubt, however, from the experiments of Davy and Ber- zelius, of its compound nature ; and that it consists of a base combined with oxygen, has been proved by direct experiment. But that its base is not a metal is proved from its want of lus- tre, and power to conduct the electric fluid, these two proper- ties being essential to all metallic bodies. Silex in the form of sand, is a principal article in the ma- nufacture of glass. The common dark colored, or green glass, is composed of impure sand, which contains oxide of iron, melted with kelp, wood ashes, or impure potashes. Crown glass, for windows, is composed of white sanu, fused with a purer alkali. Plate glass, for looking glasses, js made of still purer materials; and what is known by the name of flint glass, of which decanters, and other ornamental or cut glassware is made, is composed of the purest sand and al- kali, with the addition of a considerable portion of lead, which is added in the form of litharge, or red lead. This is the softest and heaviest kind of glass. It cuts more easily, and withstands the changes of temperature much better than glass containing no lead. Order 3. Metals which decompose water at a red heat. These are, Manganese, Iron, and Zinc, Tin, Cadmium. The power of a metal to decompose water, depends on its affinity for oxygen. In some instances, as in those of potas- sium and sodium, already given, the metals have so strong an affinity for oxygen, as to absorb it from water, at common temperatures. Other metals do not decompose this fluid at any temperature, such being the 4th order of the present class. Those now to be examined, have an affinity for oxygen, which they slowly absorb from the atmosphere, and a part of which they retain at high degrees of heat. But their attraction for oxygen is not in sufficient force to decompose water, except when heated to redness, when the combination is effected with considerable rapidity. What use is made of silex in the arts 7 Explain the difference between green glass, erjown glass, and plate glass. What is the composition of cut glass 1 What is the defi- nition of order 3d 1 What metals bel->fg to order 3d ? On what property of a metal doea its power to decompose water depend ? METALS. 24. MANGANESE 28. This metal always occurs in nature in combination with oxygen, and which it holds with such force as to require the most intense heat for its removal. The metal may, however, be obtained in a pure state, by exposing the black, or per- oxide, mixed with a combustible, to the highest heat of a smith's forge. The combustible, which may be pitch or powdered charcoal, with which the oxide is mixed, is thus made to 'absorb the oxygen, and the metal is found at the bottom of the crucible. Manganese is of a dusky white color, with a specific gra- vity of 8. When exposed to the air it absorbs oxygen, and soon falls into powder, which afterwards changes its color from gray to brown, and from brown to black, according to its grade of oxidation. When this metal is exposed to a red heat, and the steam of water is passed over it, decomposition takes place, the oxygen of the water combines with the man- ganese, and the hydrogen is disengaged. MANGANESE AND OXYGEN. Peroxide of Manganese 44. 1 p. Manganese 28+2 p. Oxygen 16. Black Oxide of Manganese. This compound occurs abundantly in nature, and is known under the name of black oxide of manganese. It is found in amorphous masses, of a dark gray or nearly black color, and is commonly mixed with various proportions of sand, oxide of iron, carbonate of lime, or other impurities. In its pure state, it occurs in the form of prismatic crystals of a dark color, and slightly metallic lustre. In this state the metal contains its full proportion of oxygen, and undergoes no change on exposure to the air, or to a moderate heat. When heated to redness, it parts with one proportion of oxygen, and is converted into a deutoxide. In this manner oxygen gas may be obtained. The peroxide of manganese is of considerable consequence in the arts, and In what state does manganese occur in nature 1 By what process may metallic man- ganese be obtained from the oxide 1 What is the appearance and specific gravity of manganese 1 Under what circumstances does manganese decompose water 1 What is the scientific name for black oxide of manganese 1 When peroxide of manganese is heated to redness, what chemical change does it undergo? Of what use is peroxide of manganese in the arts 1 2i 242 METALS. rjarticularlv in the formation of chlorine for the manufacture of bleaching powders, and also in furnishing oxygen gas for other chemical uses. The methods for obtaining these gases have already been described. The peroxide of mercury is composed of 1 proportion of manganese, 2 proportions of oxygen, 16 44 There are two other oxides of manganese, viz. the protox- ide and the deutoxide. There is also reason to believe that manganese is capable of combining with such proportions of oxv-en as to form acids; but the subject has not been suffi- ciently investigated to determine the composition or nature of these compounds. . "Manganese combines with the acids/and forms a variety of salts? which are either colorless, or of a reddish or pink hue These salts are found only in the laboratory of the chemist, and are of no use in the arts. At a red heat this metal decomposes water. IRON 28. This well known metal has a gray color, and a strong metallic lustre, which is much improved by burnishing. Iron is at once the most useful, the most abundant and the most universally diffused of all the metals. It is found in the mineral, the vegetable, and the animal kingdoms, and in some countries it exists in such quantities as to form mou tains of considerable size. When heated, it becomes soft and malleable, and in this state two pieces may be incorporated, or 'welded together, by hammering. Its specific gravity is about 8. It is attracted bv the man-net, and may itself be made permanently magnetic. This property is of vast consequence to the world being pos- sessed by no other metals except nickel, and cobalt, and by these ki a much inferior degree. Iron has a strong affinity for oxygen, and when exposed t. air and moisture, soon rusts or oxidates on its surface, perfectly dry atmosphere, however, it undergoes 1 change, a proof that it absorbs oxygen with more facility "l^i^hTc^nposition of the peroxide of manganese 1 What is said of the acids of manganese! What is the combining number for iron? What is said of the abundance and usefulness of iron ? What is said of the affinity of iron for oxygen 7 METALS. 243 from water than from the air. When heated, it attracts oxy- gen both from air and water, with great rapidity. When the steam of water is passed over iron, at a red heat, the wa- ter is decomposed, its oxygen combining with the metal, while the hydrogen is set at liberty. When heated to red- ness, in oxygen gas, it burns with intense brilliancy. Iron is exceedingly ductile, and may be drawn into wire not exceed- ing the thousandth part of an inch in diameter ; but it cannot, like gold and"~silver, be hammered into thin leaves, and there- fore is not highly malleable. The ores of this metal are very numerous, and some of them highly beautiful and interesting. They are chiefly sul- phurets and oxides, but the oxides are the only ores from which the metal is obtained. Iron has, In a few jnstances,(been found in its native state, mixed with lead and copper, or with some earthy substance. It has also been found in large masses, alloyed with five or six other metals, and called meteoric iron, from an opinion that these masses fell from the clouds. Native iron is soft and malleable as it occurs, and does not differ from that which has been reduced from its ores and purified. Cast iron contains variable proportions of carbon and oxy- gen, and in this state it is hard and brittle. These impuri- ties are detached by the process of refining, and then the iron becomes soft and malleable. Steel is made by heating pure iron with carbon, or char- coal, by \vhich it is rendered exceedingly hard and brittle. This change is produced in consequence of the absorption of a portion of carbon by the iron. Steel, therefore, is compo- sed of iron and carbon, and its scientific name is carburet of iron. IRON AND OXYGEN. Oxide of Iron. Rust of Iron. Iron combines with oxygen in two proportions, forming the blue and red oxides of this metal. Under what circumstances does iron decompose water ? In what, does this decomposi- tion consist? What is said of the ductility and malleability of iron 7 In what state does iron occur as a natural product 1 What is the ore from which iron is extracted 7 What is meteoric iron ? What are the impurities contained in cast iron 1 How is steel made 1 What is the composition of steel 1 What is the scientific name of steel ? 242 METALS. particularly in the formation of chlorine for the manufacture of bleaching powders, and also in furnishing oxygen gas for other chemical uses. The methods for obtaining these gases have already been described. The peroxide of mercury is composed of 1 proportion of manganese, 28 2 proportions of oxygen, 16 44 There are two other oxides of manganese, viz. the protox- ide and the deutoxide. There is also reason to believe that mano-anese is capable of combining with such proportions of oxygen as to form acids ; but the subject has not been suffi- ciently investigated to determine the composition or nature of these compounds. Manganese combines with the acids, ;and forms a variety of salts, which are either colorless, or of a reddish or pink hue These salts are found only in the laboratory of the chemist, and are of no use in the arts. At a red heat this metal decomposes water. IRON 28. This well known metal has a gray color, and a strong metallic lustre, which is much improved by burnishing. Iron is at once the most useful, the most abundant, and the most universally diffused of all the metals. It is found in the mineral, the vegetable, and the animal kingdoms, and m some countries it exists in such quantities as to form moun- tains of considerable size. When heated, it becomes soft and malleable, and state two pieces may be incorporated, or welded together, by hammering. Its specific gravity is about 8. It is attracted by the mao-net, and may itself be made permanently magnetic. This property is of vast consequence to the world, being pos- sessed by no other metals except nickel, and cobalt, and by these in a much inferior degree. Iron has a strong affinity for oxygen, and when exposec air and moisture, soon rusts or oxidates on its surface. In a perfectly dry atmosphere, however, it undergoes little or no change, a proof that it absorbs oxygen with more facility What is the composition of the peroxide of manganese 1 What is said of the acids of manganese ? What is the combining number for iron ? What is said of the abundance and usefulness of iron 7 What is said of the affinity of iron for oxygen 7 METALS. 243 from water than from the air. When heated, it attracts oxy- gen both from air and water, with great rapidity. When the steam of water is passed over iron, at a red heat, the wa- ter is decomposed, its oxygen combining with the metal, while the hydrogen is set at liberty. When heated to red- ness, in oxygen gas, it burns with intense brilliancy. Iron is exceedingly ductile, and may be drawn into wire not exceed- ing the thousandth part of an inch in diameter ; but it cannot, like gold and "silver, be hammered into thin leaves, and there- fore is not highly malleable. The ores of this metal are very numerous, and some of them highly beautiful and interesting. They are chiefly sul- phurets and oxides, but the oxides are the only ores from which the metal is obtained.] Iron has, In a few ]nstances,(been found in its native state, mixed with lead and copper, or with some earthy substance. It has also been found in large masses, alloyed with five or six other metals, and called meteoric iron, from an opinion that these masses fell from the clouds. Native iron is soft and malleable as it occurs, and does not differ from that which has been reduced from its ores and purified. Cast iron contains variable proportions of carbon and oxy- gen, and in this state it is hard and brittle. These impuri- ties are detached by the process of refining, and then the iron becomes soft and malJ cable. Steel is made by heating pure iron with carbon, or char- coal, by which it is rendered exceedingly hard and brittle. This change is produced in consequence of the absorption of a portion of carbon by the iron. Steel, therefore, is compo- sed of iron and carbon, and its scientific name is carburet of iron. IRON AND OXYGEN. Oxide of Iron. Rust of Iron. Iron combines with oxygen in two proportions, forming the blue and red oxides of this metal. Under what circumstances does iron decompose water 1 In what does this decomposi- tion consist? What is said of the ductility and malleability of iron ? In what state doea iron occur as a natural product? What is the ore from which iron is extracted? WhaC is meteoric iron ? What are the impurities contained in cast iron ? How is steel made 1 What is the composition of steel? What is the scientific name of steel 1 246 METALS. ZINC 34. Zinc, when pure, is of a bluish white color, and of a stn ated fracture, presenting the result of a confused crystalliza- tion. When rubbed with the fingers it imparts to them a pe- culiar metallic taste and smell. When cold, this metal is not malleable, but when heated to between 200 and 300, it be- comes both malleable and ductile. If its temperature be raised to 400, it becomes so brittle as to be readily reduced to pow- der, in a mortar. Zinc melts at 680 degrees, and if this temperature be in- creased, it burns with a bluish flame in the open air. When melted with copper it forms the alloy, well known under the name of brass. This metal never occurs in the native, or pur^pate, but is always found combined either with sulphur, carbonic acid, or oxygen. The sulphuret of this metal, called zinc ble?ide,and the carbonate, called calamine, are the ores from which zinc is obtained. The sulphuret being roasted, that is, submitted to a low red heat in the open air, to drive off the sul- phur, and oxidize the metal, is then melted with charcoal, by which the oxygen is absorbed, and the metal reduced. The calamine is first roasted to drive off the carbonic acid, and is then distilled in iron retorts, by which means the pure metal is obtained. Tnis latter process is said to have been learned of the Chinese, and that a man was sent from Europe to China on purpose to obtain the secret. Pure zinc, w r hen ex- posed to a white heat in a close vessel, will, in the same man- ner sublime, and again condense, unchanged. ZINC AND OXYGEN. Oxide of Zinc 42. 1 p. Zinc 34-j-l p. Oxygen 8. Flowers of Zinc. When zinc is exposed to a red heat in the open air, it burns with a white flame, and at the same time an oxide of the metal is formed, which rising by the heat, falls around the What is the color of pure zinc? Under what circumstance is zinc malleable? In wha* temperature does zinc melt ? What ia the composition of brass 1 Is zinc ever found ift the native state ? What are the names of the ores of zinc, and of what are they com- posed I How is zinc reduced from its sulphuret ? How is calamine reduced 1 How is th oxide of zinc formed? CADMIUM. 247 place of combustion in the form of white flakes. This sub- stance was formerly called floweis of zinc, and sometimes philosophical wool. It is an oxide of the metal, and the only one known. When this oxide is collected, and again sub- mitted to the fire, it does not rise, as before, but melts into a clear glass. When the vapor of water is brought into contact with metallic zinc at a red heat, the water is decomposed, the zinc combining with its oxygen, and forming an oxide, in the same manner as is done in the open air. Both these, oxides are composed by weight, of 1 atom, or equivalent of zinc, 34 do. do. oxygen, 8 n*m CombminjPbumber for oxide of zinc, 42 CADMIUM 56. Cadmium is one of the new metals, having been discovered in certain ores of zinc, in 1817. This metal in color and lustre resembles tin, but is harder and more tenacious. It is both ductile and malleable to a considerable degree. Its spe- cific gravity is nearly 8.5. It fuses at a. temperature some- what less than 500 degrees, and at a little higher heat it rises in vapor, and condenses in globules like mercury. When cadmium is heated in the open air, like many other metals, it absorbs oxygen, and is converted into an oxide. It is readily dissolved by the nitric acid. When heated in contact with the vapor of water, the fluid is decomposed, and an oxide of the metal is formed. Cadmium combines, so far as is known, with only one pro- portion of oxygen. This oxide is composed of Cadmium, 1 equivalent 56 Oxygen, 1 do. 8 x^ m , 64 Cadmium, like the other metals, forms salts by combina- tion with the acids. But these compounds are little known, and of no value. What was this oxide formerly called ? How may zinc be made to decompose water 7 What is the composition of oxide of zinc, and what is its combining number? What is cadmium 1 What other metals does cadmium resemble ? Is this a brittle or a malleable metal 1 What is the specific gravity of cadmium 1 What is the composition of oxide o/ cadmium? 248 TIN. TIN 59. Tin must be examined in the state of grain, or block tin ; what is commonly called tin, being sheets of iron, merely covered with this metal. Tin is procured from its native oxides, by heat and charcoal, on the same principle that has already been described for iron and several other metals. The ores of tin are only two, viz. an oxide, and a sulphuret. This metal is not readily oxidized by exposure to the atmosphere, though the brilliancy of its surface is soon tarnished. It is highly malleable, but not equally ductile, its tenacity not being sufficient to allow its being drawn into fine wire. Its specific gravity is 8. When heated to whiteness, it takes fire in the' open air, and burns with a white flame, being at the same time co^Berted into an oxide ; at a red heat it decomposes water. Tin is a highly useful metal, being employed for many va- luable purposes in the arts and conveniences of life. Thin sheets of iron, being dipped into melted tin, receive a coat of the metal, and are thus prevented from rusting. This is called sheet tin, and is the article of which the common tin ware is made. Tin foil, that is, tin rolled into thin sheets, is used for many purposes. Electrical jars are coated with it, and the backs of looking-glasses are formed of an amalgam of tin foil and mercury. Block tin forms a part of Britannia ware, of princes' metal, of pewter, speculum metal, &c. TIN AND OXYGEN. Tin combines with oxygen in two proportions : The first, or the protoxide, is formed when the metal is kept for some time in fusion in the open air. At this temperature it absorbs oxygen from the atmosphere, and is converted into a gray powder. This powder is the protoxide, and is composed of 1 equivalent, or atom of tin 59 1 do. do. oxygen 8 67 This oxide is soluble in acids and in ammonia. The se Of what metal is the sheet tin chiefly composed ? How is tin procured from its oxide! What are the only ores of tin 1 Is tin readily oxidized by exposure to the air or not"} What is said of the malleability and ductility of tin ? What is the specific gravity of tin 1 Into what is this metal converted when burned in the open air 1 How is sheet tin made ? What are the principal uses of tin? In how many proportions does tin combine with oxygen ? How is the protoxide of tin formed ? ARSENIC. 249 cond, or peroxide of tin, is prepared by dissolving the metal in nitric acid, slightly diluted with water. It is a powder of a yellow color, and is composed of 1 equivalent of tin, 59 2 -do. of oxygen, 16 75 This oxide, when melted with glass, forms white enamel. Tin combines with sulphur, chlorine, and the acids, form- ing a variety of compounds, some of which are occasionally used in the arts. Order 4. Metals which do not decompose water at any temperature* These are, Arsenic Uranium Titanium Molybdenum Columbium Bismuth Chromium Nickel Copper Tungsten Cobalt Tellurium Antimony Cerium Lead The last order includes all such metals as attract oxygen with sufficient force, when heated to redness, to decompose water. The present division absorb and retain oxygen at high temperatures, but none of them attract that principle, even at the highest temperatures, with sufficient force to de- compose water. ARSENIC 38. There are no mines worked merely for the purpose of ob- taining arsenic, the arsenious acid, the only form in which it is used, being procured by the process of roasting the ores of cobalt. The ores of the latter metal, being heated in furnaces with long chimneys, the acid rises and attaches itself to the sides of the chimney, in layers, or cakes. After a considerable quantity has been accumulated in this manner, it is scraped off, and purified by a second sublimation, when What is the composition of the protoxide of tin? How is the peroxide of this metal prepared ? What is the quantity of oxygen contained in the peroxide of tin 1 What is the definition of order 4th ? What are the names of the metals arranged under the 4th order 1 Are any mines worked merely to obtain arsenic 1 How is the oxide of arsenic procured ? 50 ARSENIC AND OXYGEN. it forms the well known poison, called white arsenic, or oxide of arsenic. From the white oxide the metallic arsenic is procured, by heating- this with a combustible. In legal investigations, where there is a suspicion of poi- soning with arsenic, it sometimes happens that justice will de- pend on the decision of the chemist, whether arsenic might not have been the cause of death. In such cases, very mi- nute portions of arsenic may be detected by means of a com- bustible and a glass tube, in the following manner : Let the matter suspected to contain the poison, be well dried at a low heat ; then mix it with five or six times its weight ol powdered charcoal, and put the mixture into a thin glass tube, closed at one end. If now heat be gradually applied to the tube until it becomes red, the metal, if arsenic be pre- sent, will rise and coat its inside, showing a brilliant metallic lustre, similar to that of steel. If it is found that, on heating a small piece of this metal, it rises in white vapor and gives the smell of garlic, it is arsenic beyond doubt. The structure of metallic arsenic is crystalline, and its spe- cific gravity about 8. When heated to about 360 Q it sublimes, without fusion, its melting point being far above that at which it becomes volatile. If the metal is heated in the open air, it is converted into the arsenious acid, and again becomet poisonous as before ; but, while in the metallic form, arsenic has no action on the system, and, therefore, is not a poison. ARSENIC AND OXYGEN. Arsenious Acid 54. 1 p. Arsenic 38+2 p. Oxygen 16. White Arsenic. Oxide of Arsenic. We have stated above, that when metallic arsenic is healed in the open air, it is converted into a white substance, called oxide of arsenic. This is the arsenious acid of che- mists. It differs from the oxides of metals in possessing acid properties. It is slightly soluble in water, reddens vegeta- ble blue colors, and combines with alkalies, forming salts, How may arsenic be reduced from its oxide to the metallic state? What is the a< pearance of pure arsenic ? What is the specific gravity of arsenic ? Is metallic arser a poison 'I How is arsenious acid formed ? METALS. 251 called arsenites. The arsenite of potash, usually called Fowler's solution of arsenic, has been long employed in medi- cine as a remedy for eruptive, and other diseases. ARSENIC AND SULPHUR. Sulphurets of Arsenic. Sulphur combines with arsenic in two proportions, form- ing compounds which are known by the names of orpiment, and realger. These compounds are both of them natural products, and may also be formed by art. Realger is of a red, or scarlet color, with a shining semi-metallic lustre, and is composed of 38 parts of metallic arsenic, and 16 parts, or one proportion, of sulphur. Orpiment has a rich yellow color, and a foliated structure. Its lustre is shining, and somewhat metallic, and it is readily separated into layers, like mica. This is composed of 38 parts, or one atom of metallic arsenic, and 24 parts, or one atom and a half of sulphur. Orpiment is employed as a paint under the name of King's Yellow. CHROMIUM 28. The metal, chromium, has been detected only in the two native compounds, chromate of lead, and chromate of iron. In these two salts, the metal chrome exists in combination with so much oxygen as to constitute an acid, which is united to the oxides of lead and iron, forming the compounds above named. Arsenic, as shown above, forms an acid with oxy- gen in the same manner, and we shall see presently that several other metals when combined with oxygen perform the office of acids. Chromium has been procured only in very small quanti- ties, by exposing its acid mixed with charcoal, to the highest temperature of a smith's forge. It is a brittle metal, of a What is the common name of this acid 1 What is the form of arsenious acid? What are the salts called which arsenious acid forms with the salifiable bases 1 What use is made of arsenite of potash 1 In how many proportions does sulphur combine with arsenic 1 What is realger 1 What is its composition 1 How does orpiment differ from realger 7 What use is made of orpiment? What is chromium 1 In what native compound is chromium found ? In what state does chromium exist in these compounds 1 How has shromium been procured 7 252 CHROMIUM. grayish white color, and very infusible. Its specific gravity is 6. Chromium combines with oxygen in three proportions, forming the following compounds: Chrome. Oxygen. Protoxide, composed of 28 and 8 Deutoxide, do. 28 do. 16 Chromic acid, do. 28 do. 24 The oxides of chrome are of no importance in the arts, but the chromic acid forms colored salts with the oxides of the metals which are extensively employed in painting and coloring. The chromic acid may be obtained in a separate state, by boiling the native chromate of lead in powder, with twice its weight of carbonate of potash, and afterwards saturating the alkali with dilute sulphuric acid. The sulphate of pot- ash thus formed, will subside, leaving the chromic acid in solution, which on evaporation, will yield crystals of chromic acid. These crystals are of a ruby red color, and when dissolved in water, possess all the properties of an acid. The useful compounds formed by combining chromic acid with salifiable bases, are prepared from chromate of potash in solution. The latter salt is made by heating to redness the native chromate of iron with an equal weight of nitrate of potash. By this process, the chromate which was in the state of an oxide, is converted into chromic acid, by the oxygen of the nitre, the acid at the same time combining with the potash of the nitre. The ignited mass is then dissolved in water, neutralized by nitric, acid, and the solution concen- trated by evaporation, when the chromate of potash shoots into crystals, of a yellow color. The chromate of lead, a beautiful paint, at present largely employed under the name of chrome yellow, is made by mix- ing acetate, or sugar of lead, dissolved in a large quantity of water, with solution of chromate of potash. A double decomposition of these two salts is thus effected, and acetate What is the color and what the properties of chromium 7 In how many proportions doea chromium combine with oxygen ? What are the names of these compounds 1 Of what use is the chromic acid? How may pure chromic acid be obtained 1 ? What is the color and form of this acid ? How is chromate of potash prepared ? How is the chromate of lead made from the chromate of potash 1 What is the color and use of chromate of lead 1 METALS. S53 of potash and chromate of lead are formed. The acetate re- mains in solution, while the chromate being insoluble in water, falls down in form of an orange colored, or yellow powder. This powder being separated from the liquid, and dried, forms the beautiful pigment in question, MOLYBDENUM 48, The native sulphuret of molybdenum is a ponderous mine- ral, which occurs in masses, or is disseminated in othet minerals. Its structure is foliated, and its lustre like that of lead recently cut. When this compound is reduced to fine powder, and digested in nitro-muriatic acid, the sulphur and metal are both acidified by the oxygen imparted to them by the nitro-muriatic acid. On heating the solution, the sulphu- ric acid thus formed is expelled, while the molybdic acid re- mains in the form of a heavy white powder. From this powder the metallic molybdenum may be obtained by expos- dig it, mixed with charcoal, to the strongest heat of a smith's forge.^ This metal has never- been obtained, except in very small quantities, and in the form of brilliant white globules con- tained in a blackish mass. When heated in the open air, it is soon converted into molybdic acid, Molybdic acid is in the form of a white powder, which has a sharp metallic taste, reddens vegetable blues, and forms j?alts with the alkalies, called molybdates. This acid is composed of 1 proportion of molybdenum 48, and 3 proportions of oxygen 24. TUNGSTEN 96. The tungstate of iron, is a brownish black mineral, which is found both massive and crystallized. Its specific gravity is upwards of 7, and when broken it presents a foliated struc ture, and a lustre somewhat metallic. This mineral, by the miners, is called wolfram, and is com- posed of tungstic acid and oxide of iron, with a portion of the oxide of manganese. How is the native sulphuret of molybdenum described ? By what process is molybdic acid procured 1 How is the metal obtained from this acid 1 What is the appearance of molybdenum'? What are the salts called which molybdic acid forms with the salifiablc bases ? What is the appearance of tunsstate of iron ? How is tungstic acid procured ? 22 254 METALS. From this mineral the tungstic acid may be procured by the action of muriatic acid in the form of a yellow powder. When tungstic acid is mixed with charcoal, and exposed to an intense heat, the metal is deprived of its oxygen by the charcoal, and appears in its pure form. Tungsten has a specific gravity of 17.4 being next to pla- tina, gold, and iridium, the most dense body known. It is nearly equal to steel in hardness, and is one of the most infu- sible of the metals. When heated in the open air, it is recon- verted into tungstic acid. This acid is composed of 96 parts of tungsten and 24 parts of oxygen, consequently 96 is the atomic weight of this metal, and 1 20 the equivalent number for tungstic acid. No use has been made of this metal, or any of its compounds. COLUMBIUM- 144. This metal was discovered by Mr. Hatchett of London, in a black mineral, which was sent to the British Museum by Gov. Winthrop, of Connecticut. The mineral came from New London, and is said to have been found near the resi- dence of the governor. Columbium, like tungsten, exists in its natural state, com- bined with so much oxygen as to perform the part of an acid, and is found united to the oxides of iron, or manganese. This metal is of an iron gray color, and considerable me- tallic lustre. Its specific gravity is 5.5 5 Columbic acid is composed of columbium 144, and oxy- gen 8. Its equivalent number, therefore, is 152. ANTIMONY 44. The only ore from which the antimony of commerce is ob- tained, is the sulphuret. From this native compound the pure metal is separated, by heating it with half its weight of iron filings in a covered vessel. By this process the sulphur unites with the iron, while the fused antimony is drawn off at the bottom of the vessel. What is the process for procuring tungsten from tungstic acid 7 What is the specific grayity of tungsten? What ajre the properties of tungsten 1 What is the composition of tungstic acid 7 Whence came the mineral in which columbium was first discovered 1 In what state does columbium exist combined with iron ? What is the specific gravity of columbium 7 What is the ore from which antimony is obtained 7 In what ie this metal obtained from its ore 7 METALS. 255 Antimony is a brittle metal, of a bluish white color, and considerable lustre. Its structure is lamellated, or it consists of layers, which are the result of an imperfect crystallization. It fuses at about 800, and when slowly cooled, may be crys- tallized in octahedrons. By exposure to the air it tarnishes, though not so readily as several other metals. Its specific gravity is about 7. ANTIMONY AND OXYGEN. Oxygen combines with antimony in three proportions, forming the protoxide, composed of antimony 44, and oxygen 8 the deutoxide, consisting of antimony 44, and oxygen 12 and the peroxide, composed of antimony 44, and oxygen 16 The deutoxide combines with alkalies, and forms salts ; it is therefore called antimonious acid, and the salts so formed are antimonitcs. The peroxide also performs the office of an acid, and com- bines with alkalies, forming salts, called antimoniates, the acid itself being the antimonic. Formerly, there were at least forty different preparations of antimony, known and used in medicine. At present this number is reduced to three or four, and of these only one is in general use, viz., the tartrate of antimony and potassa, or tartar emetic, ANTIMONY AND SULPHUR. The native sulphuret of antimony, as stated above, is the only ore from which the metal is extracted. This is gene- rally found in compact masses, though it sometimes occurs in long crystals, interlacing each other. It is of a leaden gray color, with a metallic lustre. The same compound may be formed by fusing antimony and sulphur together, or by transmitting sulphuretted hydro- gen through a solution of tartar emetic. Sulphuret of antimony is composed of Antimony 1 proportion, 44 Sulphur 1 proportion, 16 What is the color and what the specific gravity of antimony 7 In how many propor- tions does oxygen combine with antimony 7 What are the oxides called 1 What w the composition of sulphuret of antimony 7 256 BIETALJS, URANIUM 208. This metal was first detected in a mineral found in Saxony, which, from its black color, was called pitchblende. This ore, now called black oxide of uranium, contains uranium in the state of an oxide, mixed with the oxides of iron and lead. The metal is reduced from its oxide to the metallic state, with great difficulty, even in the laboratory of the chemist. According to Klaproth, who discovered it, uranium' is of a dark gray color, with a metallic lustre, and granular texture. It is soluble in nitric acid, fuses only at the highest tempera- ture, and affords a deep orange color to enamel. Its specific- gravity is about 8. Chemists are acquainted with two oxides of this metal. The protoxide is composed of uranium 208, and oxygen 8. The combining number of the protoxide is therefore 216. The peroxide consists of 1 proportion of uranium 208, and 2 proportions of oxygen 16; so that the equivalent number for the peroxide is 224. The protoxide occurs as a natural product, of a dark eme- rald green color, and shining lustre. li is often found at- tached to other minerals, in the form of scales, or in bundles of crystals, variously grouped, or interlacing each other, af- fording one of the most beautiful products of the mineral king- dom. This oxide is also formed by art, and is employed to give a black color to porcelain, the change from green to black being produced by the heat of the porcelain furnace. CERIUM 50. The chemists have proved that a metal called cerium exists in a reddish brown mineral found in Sweden, and called cerite, or siliceous oxide of cerium ; and also in a mineral found in West Greenland, and called Allanite. The properties of this metal are little known, it having never been obtained, except in minute quantities, not larger than a pin's head. It has, however, been ascertained, that cerium combines with oxygen in two proportions, and that its combining 01 What is the ore of uranium called ? What is the appearance of uranium ? What is its specific gravity ? How many oxides of this metal are known? What is said of the native protoxide of this metal 1 What use is made of this oxide 1 What is said of the existence of the metal cerium ? METALS. 257 equivalent number is 50. These oxides are composed of cerium 50, and oxygen 8, forming- the protoxide, whose equi- valent, therefore, is 58. The deutoxide contains the same quantity of metal, with one and a half proportions of oxygen. Its equivalent is, therefore, 62. COBA.LT. The ore from which this metal is extracted, is called arse- nical cobalt. It is found in primitive rocks, both disseminated and in veins, associated with nickel, silver, bismuth, arsenic, and copper. When this ore of cobalt is heated in contact with the air, the arsenic is expelled in the form of arsenious acid, and the sulphur which it also contains is converted into sulphureous acid gas, and escapes. By this process, the ore commonly loses more than half its weight, and there remains in the fur- nace an impure oxide of cobalt, called zaffree. When zaffree is heated with sand and potash, there is form- ed a glass of a beautiful blue "color, which, when pulverized, is extensively known and used under the name of smalt. The blue color of porcelain and earthenware, is produced entire- ly by this oxide of cobalt. Paper and linen, also, receive their bluish tinge from this oxide. From the oxide of cobalt, or zafFree, the metal may be ob- tained by heating that substance in contact with some carbona- ceous matter. If it is intended to obtain the metal in its pure state, the zaffree must first be purified from the iron, or other metals, which it may contain. Cobalt is a brittle metal, of a reddish brown color, and slightly metallic lustre. It is fused with difficulty. Its spe- cific gravity is 8.5. It is attracted by the magnet, and is ca- pable of being permanently magnetic. Muriatic or sulphu- ric acid acts but slightly on this metal, but it is readily solu- ble in nitric acid. Cobalt does not attract oxygen by exposure to the air, but by a long continued and strong heat, it is converted into an oxide of a deep blue or nearly black color. The atomic weight of cobalt has not been determined. What is said of the oxides of cerium? From what ore is the metal cobalt obtained! What is zaffree ? What is smalt 1 What is the use of oxide of cobalt 1 How may me- tailic cobalt be procured from the oxide ? What is the appearance of cobalt 7 What ifl the specific gravity of eobak '} What is said of the magnetic property of cobalt ? What acid is the proper solvent of cobalt 7 22* 258 METALS. This metal is the base othat curious liquid called sympa thetic ink, and which may be prepared in the following man- ner : Dissolve one part of 6balt, or zafTree, in four parts of nitric acid, and assist the solution by heat. To this solution add one part muriate of soda, and four times as much water as there was acid. Characters written on paper, with this ink, are illegible when the paper is cold, but become plain, and of a beautiful green color, when the paper is warmed. This experiment is rendered still more pleasant by drawing the trunk and branches of a tree, in the ordinary manner, and then tracing the leaves with the solution of cobalt. In winter such a tree wdll appear without leaves, except when warmed, but in the summer, particularly if placed in the sun, it will be covered with beautiful green foilage. -Screens, painted with this so- lution, will show their green when in use, but will immedi- ately begin to fade when carried away from the fire. NICKEL 40. -V Nickel is generally found mineralized by the acids of arsenic. The Saxon ores, among which this metal is found, are mixtures of lead, copper, iron, cobalt, and arsenic, com- bined with sulphur and oxygen. In nearly every instance, where meteoric iron, or other meteoric products, have been analyzed, they have been found to contain this metal. Nickel, being of no use in the arts, is never reduced to its metallic state, except in the laboratories of chemists, as spe- cimens or curiosities. Nickel has a strong metallic lustre, and is nearly the coloi of tin and silver. It is both ductile and malleable, and like iron and cobalt, is attracted by the magnet, and 'may be made permanently magnetic. Its specific gravity, after being ham- mered, is 9. It is exceedingly infusible, and suffers no change at common temperatures, when exposed to the air ; but is slowly oxidized at a red heat. The muriatic and sul- phuric acids do not act on nickel, but it is readily oxidized and dissolved in nitric acid. What is the method of preparing sympathetic ink ? What are the peculiar properties of this ink ? With what is nickel combined in the natural state ? What is said of the existence of nickel in meteoric products 1 Is this metal of any use in the arts ? Whai is the appearance of nickel ? What is said of its magnetic property 1 What is its spe cific gravity 1 In what acid does nickel dissolve 1 METALS. 259 Nickel combines with two proportions of oxygen. The protoxide is composed of nickel 48, and oxygen 8. The per- oxide of nickel 40, and oxygen 16. BISMUTH 72. Bismuth occurs native, and in combination with sulphur, oxygen, and arsenic. That which is employed in the arts and in commerce, is derived chiefly from the native metal. Bismuth has a reddish white color, a brilliant lustre, and a foliated structure. It fuses at 476, being, with the exception of tin, the most fusible of the solid metals. When slowly cooled, this metal may be obtained in octohedral crystals. Its specific gravity is 1C. Bismuth enters into the composition of printing type ; and its oxides are employed as paints, and in medicine. BISMUTH AND OXYGEN. Oxide of Bismuth SO. I p. Bismuth 72 -j-1 P- Oxygen 8. Floiuers of Bismuth. Bismuth combines with oxygen in only one proportion, forming a yellowish white oxide. This may readily be formed by submitting the metal to a strong heat in the open air. It takes fire and burns with a blue flame, while the oxide falls down in the form of powder. Bismuth is not readily soluble in the muriatic or sulphuric acids, but the nitric acid dissolves it with facility, forming nitrate of bismuth. When nitrate of bismuth, either in crystals or in solution, is thrown into water, -a copious precipitate subsides, in the form of a beautifully white powder. This is the subnitrate of bismuth, and was formerly known under the name of magislery of bismuth. This is employed as a cosmetic pow- der for whitening the complexion, but it is a dangerous sub- stance for such a purpose, since, if it happens to be exposed to sulphuretted hydrogen, it turns black, thus exposing the wearer to mortification and detection. What are the states in which bismuth is found ? What is the color of bismuth 7 What are the uses of bismuth 1 In how many proportions does this metal combine with oxygen 1 How may this oxide be formed! What use is made of the subnitrato of bismuiJ 7 260 METALS. TITANIUM. Titanium has hardly been seen in its pure metallic state, but the analysis of its oxides proves that such a metal exists. The ores of this metal are considerably numerous, and are widely disseminated. The native oxides of titanium some- times occur in long striated, acicular crystals, of a reddish brown colo.r, and shining metallic lustre. Such crystals are sometimes contained in transparent pieces of quartz, forming- specimens of singular beauty. The artificial oxides of this metal are white, and are ob- tained by difficult processes. They hold their oxygen with such tenacity that all attempts to reduce them, by means of heat and a combustible, in the usual manner, have failed. The equivalent numbers of these acids have not been deter mined with certainty. TELLURIUM 32. This is an exceedingly rare metal, being hitherto found only in the gold mines of Transylvania, and at Huntington, in Connecticut. It occurs in the metallic state, associated with gold and silver, lead, iron, and sulphur. The color oi tellurium is between these of zinc and lead ; texture lamina- ted, like that of antimony, which it also resembles in some oi its properties. It melts at about 600 ; has a specific gravity of 6.1 1 5 is brittle, and easily reduced to powder. When heated before the blowpipe, it takes fire, burns rapidly with a blue flame, and is dissipated in gray fumes, which are an oxide of the metal. This oxide, which is the only one tellurium forms, is com posed of 32 parts of this metal and 8 parts of oxygen ; so that 32 is the atomic weight of tellurium, and 40 the equivalent of its oxide. COPPER 64. Copper is found native, also combined with sulphur, with oxygen, with carbonic acid, arsenic acid, sulphuric acid, mu riatic acid, and with several of the metals. Its ores are very numerous, and some of them highly beautiful and interesting. What is said of the existence of titanium 1 What is said of the native oxide of tita- nium? Where have the ores of tellurium been found ? In what state does tellurium occur? What is the color of tellurium 1 What is the composition of the oxides of te} hirium ? What are the substances with which copper is found combined ? METALS. 261 The uses of this metal are numerous, and well known. In the metallic state, it forms a part of brass, of pinchbeck, of Dutch gold, and many other alloys. When dissolved in various acids, it forms compounds which are employed for a great variety of useful purposes. The green pigment, verditer, is a nitrate of copper, preci- pitated by carbonate of lime. Verdigris is an acetate of cop- per. Mineral green is a sulphate of copper, precipitated by caustic potash. Copper receives a considerable lustre by polishing, but soon tarnishes when exposed to the open air. Its specific gravity is 8.78, and is increased by hammering. It is mallea- ble and ductile, and its tenacity is inferior only to iron. It hardens when heated and suddenly cooled. At a red heat, with access of air, it absorbs oxygen, and is converted into the peroxide, which appears in the form of black scales. "Nitric acid acts on this metal with vehemence, and it is dissolved slowly in the muriatic and sulphuric acids. The vegetable acids, as vinegar, also dissolve copper when ex- posed to the air, but not otherwise, the oxygen of the atmos- phere assisting in the oxidation of the metal. COPPER AND OXYGEN. Protoxide of Copper 72. 1 p. Copper 64-f-l P- Oxygen 8. Red Oxide of Copper. The red, or protoxide of copper, is found native in the form of regular octohedral crystals, variously truncated, and form- ing specimens of great beauty. It may also be prepared ar- tificially, by mixing 64 parts of copper filings with 80 parts of the peroxide in powder, and heating the mixture to redness in a close vessel. By this process, the copper filings attract one proportion of oxygen from the peroxide, which contains twice ' the quantity of oxygen contained in the protoxide. Thus the quantity of oxygen is equalized, and the whole is converted into the protoxide. This experiment affords a very simple illustration of the law of definite proportions. Eighty parts of the peroxide of What are the principal uses of copper 1 What is the specific gravity of copper? How may copper be convened into a peroxide 1 What acids dissolve this metal ? In whaf form does the protoxide of copper occur? How may the protoxide of copper b prepared by art ? 262 METALS. copper contains 64 parts of the metal, and 16 of oxygen. When this quantity is heated with 64 parts of copper, 1 pro- portion, or 8 parts of oxygen, leaves the peroxide, and unites with the copper, thus making, in the whole, 144 parts of the protoxide, the copper gaining 8, and the peroxide losing 8, the number for each becomes 72, the equivalent for the prot- oxide Peroxide of Copper 80. 1 p. Copper 64+2 p. Oxygen 16. This oxide is said to be found in the native state. By art, it may be formed by keeping thin pieces of copper at a red heat exposed to the air, or by heating the nitrate of copper to redness. This oxide is dark brown, or nearly black. When heated alone, it undergoes no change, but if heated in a close vessel, with charcoal, or other combustible, it parts with the whole of its oxygen, and is reduced to the metallic state. It com- bines with most of the acids, and produces salts of a green or blue color. Copper combines with sulphur, and forms a sulphuret of the metal. This compound occurs native, and may be formed by heating a mixture of copper filings and sulphur. It is composed of 64 parts of the metal and 16 of sulphur. LEAD 104. In a few instances lead has been foun4 in the native state ; but it most commonly occurs combined with sulphur, form- ing the sulphuret, of a bluish gray color, and strong metallic lustre. This compound is known under the name of galena, and is the ore from which the lead of commerce is exclusively obtained. The color and common properties of lead are well known. Its specific gravity is 11. In tenacity, it is inferior to all the ductile metals. It fuses at about 600, and when slowly cooled, may be obtained in octohedral crystals. When newly Explain how the process for forming the protoxide of copper illustrates the law of defi- nite proportions. How may the peroxide of copper be formed 1 How may the peroxide of copper be reduced to the metallic state ? What is the composition of the sulphuret pi copper 1 In what state is lead chiefly found ? What is the common name for sulphuret of lead 7 What is the specific gravity of lead 1 METALS. 263 cut, it has a brilliant metallic lustre, but is soon tarnished by exposure to the air. Lead is not oxidized by moisture without the contact of air, and hence it may be kept under pure water, for any length of time, without change. But if water be placed in an open ves- sel of lead, the metal is slowly oxidized, and a white crust is formed, at the points of contact between the lead, water, and air, which is a carbonate of the protoxide of lead. Hence, as the salts of this metal are poisonous, leaden vessels open to the air, should never be employed to contain water for culinary purposes. The sulphuric and muriatic acids act slowly upon this me- tal. Concentrated sulphuric acid produces so little action on it, that the acid is made in chambers lined with lead. Nitric acid is the proper solvent of this metal. The solution, when evaporated, deposits whitish opaque crystals of nitrate of lead. LEAD AND OXYGEN. There are three oxides of lead, which are thus constituted ; Lead. < )xyf mint and carbonic acid* 296 VEGETATION. out that a small quantity is absolutely necessary to healthftrl vegetation. In Dr. Priestley's experiment, the sprig of mint could not have qualified the air in which it was confined, for the sup- port of combustion, merely by the absorption of the carbonic acid. It must be inferred, therefore, from this experiment, that the plant not only absorbed carbonic acid, but that it gave out oxygen, or that it converted the carbonic acid into oxygen gas^and this inference has been confirmed by experiment. Plants, while growing in the light, absorb carbonic acid from the atmosphere, which they decompose ; the oxygen, of which this acid is in part composed, being emitted, while the carbon is retained by the plant. If a growing plant, as a sprig of mint, be exposed to the sun, in a glass vessel filled with water, it constantly emits from its leaves small bubbles of air, which on examination are found to be oxygen gas. Now water, under ordinary circumstances, always contains a quantity of atmospheric air, and the atmosphere always contains a proportion of carbonic acid, and hence it may be inferred, that the water furnishes the air which the plant decomposes in this experiment ; that this is the case, is proved directly by making the experiment with water, deprived of its air by the air pump, or by boil- ing, when not a particle of oxygen is obtained. That it is the carbonic acid which the plant decomposes, and from which the oxygen is derived, is proved by two facts. The first is, that vegetables are found not to emit oxygen, unless carbonic acid be present. The other is, that if the plant be confined in a mixture of carbonic acid and oxygen, the quantities of which are known, the proportion of oxygen will be increased, -while that- of The acid will be diminished. From these facts we arrive at the wonderful conclusion, that plants absorb carbonic acid from the atmosphere, and that they retain the carbon for their o\vn nourishment, but return the oxygen to purify the air. And from all that is known, it is most probable that a great proportion, if not all In Dr. Priestley's experiment, what change did the mint produce on the carbonic acid 1 When a plant is exposed to the sun in a vessel of water, whence comes the carbonic acid which it decomposes 1 What two facts prove that plants emit oxygen in conse quence of the decomposition of carbonic acid 7 When plants decompose carbonic acid, what becomes of the carbon? From what source is it probable that plants derive moel of their carbon 1 VEGETATION. 297 the carbon which wood contains is derived from the atmos- phere in this manner. On the contrary, during- the night, or when the light of the sun is withdrawn, plants absorb oxygen, and form with it car- bonic acid, a part of which they emit, and a part is retained. It appears from experiment, that vegetables not only cease to thrive, but that they actually die, if deprived of this night- ly inspiration of oxygen. Thus, if a plant be confined du- ring the day in a portion of carbonic acid, it decomposes a part of this gas, which is replaced by the emission of an equal volume of oxygen. But at night a part of this oxygen is absorbed and converted into carbonic acid, which is, again emitted. Thus, ultimately, the plant decomposes all the car- bonic acid, because it emits more oxygen during the day than it absorbs during the night. But if the oxygen which is formed during the day is withdrawn at evening, that is, if the plant has a new supply of pure carbonic acid every day, it soon droops, and dies for the want of its oxypen. The leaves of plants absorb water, as well as carbonic acid and oxygen. The great effect which the dew of night, or sprinkling with water, has on a drooping flower, is a proof that the leaves imbibe moisture. Experiments also prove, that detached leaves often live for weeks when swimming on the water, and that a plant which is dying for want of moisture at the root, will revive and grow, when a branch with its leaves is placed in a ves- sel of water. It is most probable, therefore, that during dry seasons, and when there is a defect of moisture at the root, that the plant is in part sustained by the absorption of water from the air and particularly from the dew as it falls at night. In addition to heat, moisture, oxygen, and carbonic acid, healthy vegetation requires a certain quantity of light. It is well known that plan's which grow in the dark are always nearly colourless, and that "they appear weak and unhealthy. The disposition of plants to enjoy the light is expressed by .neir inclination towards it, when it is stronger in one direc- tion than in another. When do plants absorb oxygen from the amosphere ? How is it shown that giants droop and die, when deprived of oxygen 1 How is it shown that the leaves of plants ab- sorb water ? What agent does healthy vegetation require in addition to heat, oxygen, water, and carbonic acid 1 How do plants show their disposition to enjoy the light ? 298 VEGETATION. Thus, bean, or potato vines growing in a dark cellar, will always run towards the light, and if possible, w r ill creep out into the open air. And flowers, growing in pots placed near a window, will always lean towards the light, so that to keep them i'n a vertical position the pots must often be turned. In thick forests, the trees grow tall for the same reason; they stretch upwards to enjoy the light and heat of the sun. Plants which grow in the dark contain more water, and less carbon, than those which grow in the sun. A plant which grew in the dark, on analysis of one of its branches, was" found to contain only one ninetieth part of carbon ; but on allowing the same plant to stand for thirty days in the sun, it was found to contain one twenty-fourth part of carbon. , This is readily accounted for, by the fact, that plants grow- ing in the dark, emit no oxygen, but give out carbonic acid, and hence the defect of carbonaceous matter which they con- tain. This also accounts for the circumstance, that when a healthy plant is placed in the dark, it not only ceases to form carbon, but actually loses a part of that which it before con tainecl, by the constant emission of carbonic acid. sjr' Recapitulation. 1. Vegetable substances are chiefly composed of carbon, hydrogen, and oxygen, but sometimes contain portions of nitro- gen. '2. During the process of germination, the farinaceous sub- stance of the seed, become sweet, and affords nourishment to the young plant. . 3. Healthy germination does not proceed without the com- bined presence of heat, water, and oxygen. 4. Seeds will not germinate in a vacuum, or in any gas which does not contain oxygen, though heat and moisture be I resent. S Plants receive nourishment from the air, as well as from the earth. G. Plants nourished by pure water, and having access to the air, grow for a time, but do not produce seeds. 7. The nourishment which plants receive by the roots, is probably in a state of solution in water. Why do the trees in thick forests grow tall 7 What is the difference in composition be- tween tlants growing in the dark, and in the light 7 How is the small quantity of carboi* com.i.i.e je in the leaves, where it parts with a portion of water, and is thus fitted to form the various substances found in vegetables. 9. In the day time, plants absorb carbonic acid, retain the carbon, and emit the oxygen. 10. In the night they absorb oxygen, and give out carbonic acid. 11. Plants do not live unless they are permitted to absorb oxygen during the night ; nor will they live unless they ab- sorb a portion of carbonic acid during the day. 12. Vegetation will continue for some time in either car- bonic acid, or oxygen gas ; because when confined in carbo- nic acid, plants emit a quantity of oxygen during the day, which they absorb at night ; and when confined in oxygen, they give out a quantity of carbonic acid at night, which again serves them during the day. 13. Healthy vegetation absolutely requires the agency of light. 14. Plants which grow in the dark, are white. They show their propensity to enjoy the light, by leaning, or creeping to- Avards it. 15. Plants, growing in the dark, do not absorb, and de- compose, but emit carbonic acid, and hence they contain a deficiency of carbon. VEGETABLE ACIDS. The vegetable acids are generally less liable to spontane- ous decomposition than other vegetable products. They form salts when combined with the salifiable bases. Most of them are decomposed; by hot nitric acid,* being converted into carbonic acid and water. All of them suffer decompo- sition when exposed to a red heat. These acids are nume- rous, but a large proportion of them are of little consequence, 'ind therefore we shall describe only the most useful. S Acetic Acid 50. 4 p. Carbon 24. 3 p. Oxygen 24. 2 p. Hydrogen 2. Vinegar. The acetic acid, or vinegar, exists ready formed in the sap What is said of tne tendency of vegetable acids to decomposition 1 How may the vege- table acids be decomposed 1 What is the composition of acetic acid 1 What is the com* mx) same of acetic acid? 300 VEGETABLE ACIDS. of some plants, either in a free state, or combined with lime, or potash. It may be formed artificially either by the ace- tous fermentation, or by the destructive distillation of wood. In the first case, it is made by exposing wine, cider, beer, or any other liquid capable of passing through the acetic fer- mentation, to the action of the air. This last condition is ab- solutely requisite, for no liquid will form vinegar if prevented from the access of air, that is, from the presence of oxygen. The liquid must also be exposed to certain degrees of tem- perature, for the acetic fermentation does not proceed, when the thermometer is at 32 degrees, and but very slowly when it is near this point. In this process, little or no gas is evolved, but on the, con- trary the oxygen of the atmosphere is absorbed, so that the liquid undergoes a slow oxidation. The vinegar obtained by the distillation of wood is called pyroligneous acid, that is, the acid of burned wood. When first made, it is very impure, and of a dark colour, holding in solution carbon, soot, tar, and volatile oil, which gives it a strong smell of smoke. It is purified by a second distilla- tion, and is largely employed for manufacturing purposes, and particularly in the preparation of white lead. The acetic acid is distinguished from all other acids by its peculiar flavor, odor, and volatility. Its salts are called acetates. These salts are all of them decomposed at a rea heat, or by the action of sulphuric acid. Acetate of Lead if 2. 1 p. A. Acid 50+1 p. Oxide Lead 112. Sugar of Lead. This salt is prepared by dissolving either litharge, or white lead, in distilled vinegar. The solution is sweet to the taste, and hence its common name. It occurs in small shining crystals, which contain 27 parts, or 3 atoms of water. This salt is partially decomposed when abandoned to the ac- Is vinegar ever found ready formed in plants? How may this acid be formed by art 1 Wnat liquids form this acid by fermentation 1 What conditions are necessary to I he pro- duction of vinegar by fermentation 1 What gas is absorbed from the air by the forming -vinegar 7 What is the vinegar from distilled wood called ? How is the acetic acid dis- tinguished from all other acids ? What is the composition of acetate of lead 1 What is the common name for acetate of lead ? How is this salt prepared ? In what manner \sih\s salt decomposed when exposed to the air, and what new salt is formed * VEGETABLE ACIDS. 301 tion of the atmosphere. It parts with its water of crystalli- zation, and absorbs carbonic acid from the atmosphere, thus being changed into a carbonate, or into white lead. We have stated in another place, that in the manufacture of white lead, the same change is effected ; the lead being first dis- solved by the acetic acid, and afterwards changed into a car- bonate by the action of the atmosphere. The acetate of lead is largely employed in the process of Colouring, and as a sedative and astringent in surgery. Acetate of Copper 130. 1 p. Acetic Acid 50-j-l p. Oxide of Copper 80. Verdigris. This salt may be prepared by exposing metallic copper to the vapor of vinegar. The process appears to consist in the absorption of oxygen from the atmosphere by the metal, after which it is dissolved in the acetic acid. Verdigris is manufactured largely in the south of France, by placing plates of copper between the refuse of grapes af- fer the juice is pressed out, for the making of wine. The flu- ids which the grapes still contain, pass through the acetic fermentation, by exposure to the atmosphere, and after seve- ral weeks, the plates acquire a coat of the acetate, which being scraped off, they are again exposed to the same pro- cess. The acetate is afterwards purified by solution, and crystallization. Oxalic Acid 36. 2 p. Carbon 12+3 p. Oxygen 24. Acid of Sorrel. The oxalic acid exists ready formed in several plants, and particularly in the oxalis acetosella, or wood sorrel, and also in common sorrel. It is readily prepared artificially, by digest- ing white sugar in five or six times its weight of nitric acid, and evaporating the solution to the consistence of syrup. On cooling, crystals of oxalic acid will be deposited ; but they should be purified by solution in water, and again crystallized by evaporation. What are the uses of acetate of lead ? What is the composition fo acetate of copper 1 What is the common name of this salt 7 By what chemical process is this salt formed 7 How is verdigris made in the large way 1 What is the oxalic acid composed of 1 In what plants is this acid ready formed ? 26 302 VEGETABLE ACIDS. Oxalic acid crystallizes in slender, flat prisms, which have an exceedingly sour taste, and which in solution combine with the salifiable bases, and form a class of salts called oxalates. These crystals contain half their weight of water of crystalli- zation. This acid is easily distinguished from all others, - by the form of its crystals, and by its solution giving with lime water a white precipitate, which is not dissolved by adding in ex- cess of the same acid. Oxalic acid is one of the most prompt and fatal poisons known, when taken in large doses. Fatal accidents have many times happened, in consequence of mis- taking this acid for Epsom salts. This acid is employed by calico printers, for the purpose of discharging certain colors. It is also used in families, for taking out spots of iron mould, and other stains. The oxylates are none of them of much importance. The oxalates of potash, like the acid itself, is sold under the name of essential salt of lemons, for removing stains from linen. Tartaric Acid. 4 p. Carbon 24-f5 p. Oxygen 40+2 p. Hydrogen 2. Tartaric Acid 66. Cream of tartar is the purified lees, or deposits of wine casks. From cream of tartar the tartaric acid is produced, by mixing the former with chalk in fine powder, and throwing the mixture into boiling water, by which the cream of tartar, which is a tartrate of potash, is decomposed, and a tartrate of lime is formed. The tartrate of lime is then washed, and de- composed by dilute sulphuric acid, which, combining with the lime, sets the tartaric acid at liberty, where it remains in so- lution. This solution being evaporated, the tartaric acid is obtained in white crystals. This acid is employed by calico printers, to discharge false prints, and by tallow chandlers to whiten their goods. It is also used, when dissolved in a large quantity of water, as a cooling beverage in the hot season. When mixed with car- How is this acid formed by art? What are the salts called, which the salifiable bases form with oxalic acid 1 He w is this acid distinguished from others ? What is said of its poisonous effects? What are the uses of oxalic acid? What is the tartaric acid composed of? What is the substance from which tartaric acid is obtained ? By what process this acid obtained ? What are the uses of tartaric acid 1 What occasions the efferves- cence of soda powders 1 VEGETABLE ACIDS. 303 bonate of soda in solution, it forms the effervescing draught called soda powder, of which large quantities are prepared and sold during- the summer season. The effervescence, the only property which makes this drink agreeable, is occasioned by the union of the tartaric acid with the soda, in consequence of which the carbonic acid is liberated, and in escaping through the water, causes the effervescence. This acid is remarkable for its power of combining with two bases at the same time, and forming double salts. The most important of these salts is well known under the name of tartar emetic, Tartrate of Antimony and Potash 354. 2 p. Tartaric Acid 132-f-2 p. Protoxide of Antimony 156. 1 p. Potash 48-f2 p. Water 18. Tartar Emetic. This compound, so singular from the number of constitu- ents it contains, is made by boiling the oxide of antimony called crocus mctalloruin, with tartrate of potash, or cream of tartar. This salt crystallizes in transparent prisms, which after- wards grow white and opaque by exposure to the air. It is soluble in about fifteen parts of cold, and three parts of hot water. When dissolved in water, the solution gradually undergoes spontaneous decomposition, and becomes inert as a medicine. This may be prevented by the addition of about one third part alcohol to the aqueous solution. This salt is also decompo- sed by many re-agents, as by all the stronger acids, and seve- ral of the alkalies and alkaline earths, and even by vegeta- ble substances. Infusion of nutgalls causes with it a whitish precipitate, which is considered a compound of tannin and oxide of antimony. This compound is inert, and hence the decoction of chincona bark, as it contains tannin, has been given as an antidote to an over dose of tartar emetic. What w the chemical name of tartar emetic 7 What is the composition of tartar emticl Ho wi tartar emetic prepared? What is said of the decomposition of th aqueous solution of tartar emetic 1 How may this decomposition be prevented ? Ex- plain the principle on which chincona, or Peruvian bark, has been given as an antidoU to tartar emetic. 304 ANALYSIS OF PLANTS. Citric Acid 58. 4 p. Carbon 24-J-4 p. Oxygen 32-f 2 p. Hydrogen 2. Salt of Lemons. This acid is obtained from the juice of lemons, by the same process as that described for tartaric acid. Finely powdered chalk is added to the juice, as long as any effervescence en- sues. The citrate of lime thus formed, is insoluble in water, and sinks to the bottom of the vessel. This being washed, is digested in dilute sulphuric acid, by which ah insoluble sulphate of lime is formed, while the citric acid, being thus set at liberty, remains in the solution, and on evaporation is obtained in crystals. These crystals are large, transparent, and beautiful. (They undergo no change by exposure to the air, are exceedingly sour to the taste, but when dissolved in a large proportion of water, make an agreeable drink, in consequence of retaining the flavor of the lemon. This acid forms salts with the salifiable bases, but none of them are of importance. There is a variety of other vegeta- ble acids, most of which are of no importance in any respect. Some of these have been analyzed, while the composition of others are unknown. We may, however, conclude, by ana- logy, that they are all composed of oxygen, carbon, and hy- drogen, in different proportions. Composition and Analysis of Vegetable Substances. When vegetable substances are submitted to destructive distillation, the carbon, oxygen, and hydrogen, of which they are composed, enter into new combinations, and there is. obtained a variety of products, which differ from each other, according to the nature of the vegetables, and the mode of distillation. In general, these products are water, pyroligne- ous acid, empyreumatic or burnt oil, carbonic acid, and car- buretted hydrogen. If the vegetable contains nitrogen, a quantity of ammonia will be formed, and in either case, there will remain in the retort, a quantity of charcoal, with a small portion of earthy and saline matter. What is citric acid composed of? What is the common name of this acid ? How is citric acid obtained ? What is the use of citric acid ? What are the new products into which vegetables are resolved, by destructive distillation 1 How may these new arrange nxn' c f vegetables be accounted for 7 ANALYSIS OF PLANTS. 305 These several products are all composed of the same ulti- mate principles, but are newly arranged and combined in different proportions. The new arrangements may readily be accounted for, from the circumstance, that the several elements, being in contact with each other in the retort, are at full liberty to exercise their affinities and to combine ac- cordingly. The composition of the new products, named above, will show that they consist only of the old elements differently combined. Thus, icater is composed of oxygen and hydrogen. Pyroligneous acid consists of hydrogen, carbon, and oxygen ; empyreumatic oil of carbon, hydrogen, and oxygen; carbonic acid of carbon and oxygen ; carburetted hydrogen ef carbon and hydrogen ; and ammonia consists of nitrogen and hydro- gen. With the exception of ammonia, therefore, these several products are constituted of only three elements, their differ- ence being the result of the different proportions in which they combine, or, in two instances, ofjhe absence of an ele- ment. On subjecting different vegetables to ultimate analysis, by destructive distillation, it has been found that the products, which result from the different combinations of oxygen and hydrogen are as follows. A vegetable substance is always acid, when the oxygen which it contains is to the hydrogen in a proportion greater than is necessary to form water, or where there is an excess of oxygen. A vegetable substance is resinous, oily, or alcoholic, when the oxygen is to the hydrogen in a less proportion than in water, or where there is an excess of hydrogen. A vegetable substance is neither acid nor resinous, but saccharine or mucilaginous, when the oxygen and hydrogen are in the same relative proportions as in water, or where there is no excess of either oxygen or hydrogen. In oil, resin, alcohol, sugar, and mucilage, there is a quan- tity of carbon, in addition to the oxygen and hydrogen. What are the elements of the several compounds obtained by the destructive distillation of vegetables? In a vegetable acid, is the proportion of oxygen greater or less than ia necessary to form water ? What vegetable substances are formed when there is an ex- cess of hydrogen ? In what proportions are the hydrogen and oxygen in saccharine and mucilaginous substances ? 26* 306 GUM, Ingredients of Plants. The ingredients of plants are distinct substances, formed by their secreting organs, and separable from each other with- out destructive distillation. They are separated by certain solvents, which have the power of dissolving some, but not others. Thus, water dissolves the gum but not the resin, while alcohol takes up the resin and leaves the gum. The solvents employed for these purposes are hot and cold water, ether, alcohol, and some of the acids. The following are the principal ingredients, or what are called the proximate principles of plants ; viz. Gum Fixed oil Sugar Volatile oil Starch Camphor Gluten Resins Extractive Narcotine Lignum Bitumen Tannin Vegetable alkalies Coloring matter Vegetable acids. Wax We shall examine the properties of only the most important of these principles. Gums. Gum Arabic may be taken as an example of pure gum. ft dissolves in water, with which it forms a viscid solution, or mucilage, from which it may be obtained in its original state, by spontaneous evaporation. It is insoluble in alcohol, or ether, the former precipitating it from the watery solution in the form of white flakes. Gum is decomposed by sulphuric and nitric acids. By the former, it is resolved into water, acetous acid, and charcoal: the latter produces with it oxalic and malic acid. When gum is submitted to destructive dis % tillation, it affords water, carbonic acid, carburetted hydro gen, empyreumatic oil, and acetic acid. What are the ingredients of plants 1 How are the ingredients of plants separated from each other ? What are the principal ingredients, or proximate principles, of plants ? In what liquid is gum soluble ? Intt what substances is gum resolved by sulphuric acid! What aw the products of gum, wnen submitted to destructive distillation? SUGAR. 307 Sugar. Sugar is chiefly obtained from the sugar cane, a plant which grows in hot climates, and which yields it in a larger proportion than any other substance. It is also procured from the sugar maple, by boiling down the sap which flows from in- cisions made in the tree ; and from several roots, particularly the beet, from which large quantities are made in France. In the manufacture of sugar from the cane, the first pro- cess consists in obtaining the juice, which is done by grind- ing and pressure. This is then evaporated by a gentle heat, during which a quantity of lime is added, partly for the pur- pose of neutralizing any free acid, and partly for the purpose of separating extractive matter, which unites with the lime, and forms a scum on the surface of the liquid. The evapora- tion is continued until it acquires the consistency of syrup, when it is transferred into wooden coolers, where a portion concretes into a crystalline mass, and in this state forms what is called muscovado or raw sugar. It is then placed in ves- sels with apertures in the bottom, where the more fluid parts drain ofl] and form the well known sweet syrup, molasses. Raw sugar is refined by the following process : The su- gar being dissolved in water, is mixed with the whites of eggs, or the serum of blood, and boiled. The albumen or serum is thus congulated by the heat, and rising to the sur- face, brings with it such impurities as the sugar contained, which are removed by a skimmer. When the syrup is judged to be sufficiently clear, it is placed in smaller pans, and far- ther concentrated by boiling, and then transferred into cool- ers, where it is agitated with wooden oars, until it appears thick and granulated. It now becomes white, and the crystals being broken by the agitation, facilitates the draining off of the colored matter which remains. It is next placed in conical cups of earthenware, of the well known form called sugar loaf. These having aper- tures at the bottom, a portion of molasses drains of leaving the sugar much whiter than before. Lastly, a quantity of pipe clay is mixed with water to the consistency of cream, What are the principal vegetables from which sugar is obtained 1 What is the pro- ms* by which sugar is extracted from sugar cane? Why is lime added to the juice of the cane when boiling! What is muscovado sugar 1 How is molasses obtained ? How ia raw sugar refined ? What is the use of the albumen and serum used in this process 1 808 GLUTEN. and poured on the loaves to the thickness of an inch. The water from this slowly percolates through the loaves, and washes all remains of the coloring matter from the sugar. The loaves are then dried by heat, and put in papers for sale. Refined sugar undergoes no change when exposed to the air, the dampness of raw sugar being caused by impurities. Sugar is decomposed by the sulphuric and nitric acids. By analysis it is resolved into the usual constituents of vege- tables, oxygen, carbon, and hydrogen. Starch. Starch is an abundant principle in the vegetable kingdom, being one of the chief ingredients in most sorts of grain, and in many roots and seeds. The process for obtaining starch consists in diffusing the powdered grain or rasped root in pure cold water, by which the water is rendered white and turbid. After some hours, the grosser parts, which in wheat consists chiefly of gluten, are separated by straining, and the water which passes through, being placed in shallow vessels, deposits the starch, on standing. It is afterwards washed and dried with a gentle heat. If starch be boiled for a considerable time in water con- taining about a twelfth of its weight of sulphuric acid, it is converted into sugar. By careful analysis, it has been found that the only difference between the composition of starch and sugar, is, that the starch contains less hydrogen and oxy- gen, in proportion to the carbon, than sugar. How the acid acts to convert the starch into sugar, has not been satisfacto- rily explained. During the germination of seeds, a similar change is effected, the starch being in part converted into sugar. The principal varieties of starch, are arrow-root, potato starch, sago, tapioca, cassava, salop, and the starch of wheat. Gluten. Gluten may be obtained from wheat flour, by forming it into a paste, with cold water, and continuing to wash this How is the sugar purified and whitened after it is placed in the conical cups 7 What te said of the abundance of starch in the vegetable kingdom 1 What is the process for obtaining starch 1 How may starch be converted into sugar 1 What is the difference between the composition of starch and sugar 7 What are the principal varieties of starch? HQW may gluten be obtained 7 COLORING MATTER. . 309 paste under a stream of the same fluid, as long as any thing" is carried away. The starch being thus removed, a tough elastic substance, of a gray color, will remain, which is gluten. This substance has no taste, and is insoluble in water, alcohol, or ether, but is soluble in alkalies and acids. If left to undergo the putrefactive fermentation, it emits an offensive odor similar to animal substances, and from this circumstance it is apparent that it contains nitrogen, which indeed is proved by its yielding ammonia at a red heat. Of all substances, wheat contains the greatest proportion of gluten, and it is owing to this circumstance, that wheat flour is more nourishing than that of other grain, gluten be- ing the most nutritive of all vegetable substances. It is also owing to the presence of this substance in the flour, that the dough is tenacious, and the bread spongy, or light, the car- bonic acid fornifd during the fermentation of the dough, being detained by the gluten, in consequence of which, the whole mass is distended, with bubbles of air. Wheat contains from 18 to 24 per cent, of gluten, the re- mainder being principally starch. Extractive Matter. Most vegetables, when infused for a time in hot water, impart to it a brown color. When such solutions are evapo- rated, there remains a solid substance, of a brownish, or some- times of a yellowish color, which is extractive matter. Extracts are prepared by apothecaries, as a means of con- centrating the virtues of plants for medicinal purposes. These extracts not only contain the proper extractive matter, but several foreign substances also, such as resin, coloring matter oil, &c. Coloring Matter. The coloring matter of vegetables is chiefly red, blue, green, yellow, or mixtures of these colors. Nearly all vege- table colors are discharged by the continued action of light, What is the appearance of gluten ? What are some of the properties of gluten 1 Why is wheat flour said to he more nourishing than that of other grain? In what manner does the gluten in the dough produce the pponginess of the bread ? What is extractive matter '? What are the principal tints of the coloring matter of vegetables 1 What effect iocs light have on the coloring principle of vegetables 1 SIO TANNIN. and without exception, they are all destroyed by the action of chlorine. Acids and alkalies either destroy, or change the tints of vegetable colors. The extraction of the coloring principles, and the trans- fer of them to different substances, constitutes the art of dye- ing, an art which, in the succession of ages, has been carried to a high degree of perfection. This art has been practised from the remotest antiquity: for the history of man informs us, that from the king on the throne, to the savage in the wilderness, a!l have ever been fond of decorating themselves in a variety of colors. Colors have been divided into substantive, and adjective Substantive colors are such as do not require the interven- tion of any other substance to fix them permanently, their attraction for the cloth bein# sufficiej^ for this purpose. Adjective colors require the intervention of some substance, which has an affinity both for the coloring matter, and the stuff to be dyed. This intervening substance is called a mordant. The mordant generally consists of a metallic salt dissolved in water, with which the cloth is impregnated, after which it is passed through the solution of coloring matter. The mordents most commonly employed, are muriate of tin, sulphate of iron, acetate of iron, and sulphate of alumine. Different mordants are used for different colors, and dif- ferent kinds of cloth. Thus, black is made with sulphate of iron, nutgalls, and logwood. Yellow, with alum, fustic, and saffron ; red, of cochineal, madder, red wood, or archil, with muriate of tin, or sulphate of alumine for a mordant. Blue is made with indigo, v' Tannin ,..* Tannin is the substance, by the absorption of which, the skins of animals are converted into leather. This substance is contained abundantly in nutgalls, in the bark of many trees, particularly the oak, hemlock, and birch, and in most vegetable substances which are astringent to the taste. Tannin may be obtained from any of these substances, by first bruising the article, and then digesting it in a small What are the effects of chlorine on these colors? What constitutes the art of dyeing? How are colors divided? What are substantive colors? What are adjective colors ? What are mordants in coloring? What are the principal substances used as mordants? What is tannin ? What are the principal substances which contain tannin 1 How maj Uuiiin be obtained? VEGETABLE OILS. 31 1 quantity of cold water, and afterwards evaporating the water. This substance is of a yellowish brown color, extremely astringent to the taste, and soluble in water and diluted al- cohol. Tannin is distinguished by its affording an insoluble pre- cipitate with isinglass, or any other animal jelly. It is on this principle that the art of tanning leather is founded. The hides are laid in vats, and between them there is thrown a layer of oak or other bark, which contains tannin, in coarse powder. The tannin of the bark is first dissolved by the water and afterwards combines with the leather, by which it is rendered hard, and nearly impervious to water. Vegetable Oils. The vegetable oils are of two kinds, Fixed andVolatile. Fixed Oils. Thefe are found only in the seeds of plants, and chiefly in such as have two cotyledons, such as almonds, linseed, walnuts, and rapeseed. The oil of olives, however, is extracted from the pulp which surrounds the kernel. The fixed oils are obtained by crushing or bruising the seed, and subsequent pressure. They are viscid, nearly in- sipid, and inodorous, and generally congeal at a temperature considerably higher than 32 degrees. The fixed oils, with a few exceptions, undergo little other change, by exposure to the air, than those of growing more viscid, and acquiring a degree of rancidity. The latter change is owing to the absorption of oxygen, for rancid oils redden vegetable blues, showing that they contain a quantity of free acid. The absorption of oxygen, by some of the fixed oils, and particularly by those of linseed and rapeseed, is sometimes so abundant and rapid, as to set fire to light porous substan- ces ou which they are spread. These are called cases of spontaneous combustion, and in many instances, where these oils have been suffered, either by accident or otherwise, to come in contact with cotton wool, or cotton cloth, destructive fires have been the consequence. The alkalies combine with the fixed oils, and form soap. How is tannin distinguished 1 On what principle is the tanning of leather foundedJ What are the two kinds of vegetable oils ? In what parts of plants are the fixed oito found 7 How are the fixed oils obtained ? What changes do these oils undergo by e* posurc to the air ? What causes oils to become rancid 1 In what manner do theee otto sometimes produce spontaneous combustion 1 312 RESINS. The composition of all these oils is carbon, and hydrogen, and oxygen. Volatile Oils. Plants and flowers owe their odor and fla- vor to volatile or essential oils. These oils are obtained by distilling the plants which contain them with water. The wa- ter prevents the plant from being burned. Both pass into the receiver from the still, where the oil is found either at the bottom, or on the surface, as its density is greater or less than that of water. Some fruits, however, yield essential oil by pressure ; such are the orange, the lemon, and the bergamot, which contain it in vesicles in the rind of the fruit. The odor of the essential oils is aromatic, and their taste penetrating. They consist of the odoriferous principle by which plants are distinguished from each other in a concen- trated state. These oils are soluble in alcohol, and very sparingly so in water. When dissolved in the former, they constitute essences, a great variety of which are manufactur- ed, particularly in Paris, and sold as perfumes in most parts of the world. All the volatile oils, when pure, pass away by evaporation. Hence, a good test of the purity of these oils is to let a drop fall on paper, and if any oily spot is left, after warming the paper, the essential oil has been adulterated by some fixed oil. The essential oils burn with a clear, white light, and the only products of their combustion is water and carbonic acid. Hence, these oils are composed solely of carbon and hydro- gen, the water and carbonic acid being formed by the ab- sorption of oxygen to support the combustion. Resins. The resins are peculiar substances which exude from cer- tain trees, or plants, or are contained in their juices. They commonly contain a portion of the essential oil of the plant. They are solid at common temperatures, and, when rubbed, show signs of electrical excitement. Their colors are yel low, reddish, and white, and most of them are translucent I or transparent. The resins are soluble in alcohol, ether, and the essential What are the resins 1 In what liquids are the resins soluble 1 RESINS. 313 oils, but are precipitated Vy water, in which they are entirely insoluble. They are dissolved, and at the same time decom- posed, by the sulphuric acid, with evolution of sulphuric acid gas, and the deposition of charcoal. The principal resins are, common resin, gum copal, lac, mastic, elemi, and dragon's blood. Common resin, called rosin, is what remains after the distillation of spirit of turpen- tine. The turpentine itself is obtained by making incisions in the fir tree, from which it exudes. This consists of resin, and the oil of turpentine, which are separated by distillation. The use of many of the resins are well known. Sealing wax is made of lac, turpentine, and common resin. Copal and elemi, when dissolved in spirit of turpentine, or alcohol, form varnishes. Fermentation. Fermentation consists in a spontaneous exercise of chemi- cal affinity, in a vegetable substance, or solution, in conse- quence of which its properties are materially or totally changed. There are several kinds of fermentation, the names of which indicate the products formed. These are, the saccharine, the vinous, the acetic, and the putrefactive. The product of the first, is sugar; that of the second, wine ; that of the third, vinegar; while the fourth results in the total decomposition of all vegetable matter, and the destruction of every useful product. Saccharine Ftr mentation. The germination of seeds, and the malting of barley, are instances of the saccharine fermen- tation, the farinaceous being converted into saccharine mat* ter, or sugar. Vinous Fermentation. This, by the generality of mankind, is considered the most important of all fermentations, since, from the days of Noah and Alexander to the present time, its product has been employed, either to heighten the plea- sures, or as an antidote to the cares of this poor life. Wine, as well as other intoxicating liquors, are produced only by the vinous fermentation ; a process by which alcohol Why are the resins precipitated by water 7 What are the names of the principal resins? tn what manner is common resin, or rosin, obtained 1 What are the uses of some of the principal resins ? What is fermentation 1 What are the different kinds of fermentation 7 What is the product of the saccharine fermentation 7 What the product of the vinous ? 27 314 FERMENTATION. is formed. There are four conditions necessary to the suc- cess of this process. These are, the presence of water, sugar, and yeast, in mixture, and a temperature between 60 and 70 degrees. Or, instead of yeast and sugar, saccharine matter, and starch, or the sweet juices of fruits. These conditions, being united, there succeeds a brisk intestine motion, attend- ed with the escape of carbonic acid gas in abundance, and at the same time the transparency of the fluid is diminished by the rising of opaque filaments, the whole being attended with an elevation of temperature. When there phenomena cease, the liquor is found to have lost its sweet, mucilaginous taste, and to have acquired some degree of acidity, with a brisk, pe- netrating flavor, and the power of producing intoxication. In respect to the chemical changes which take place du- ring this process, it is found that after the fermentation, the sugar has entirely disappeared, and that it is replaced by a quantity of alcohol, none of which existed in the liquid before the process. Hence sugar is converted into alcohol by the vinous fermentation. But the weight of the alcohol is never equal to the weight of sugar employed, by nearly one half. This loss is accounted for by the escape of the carbon and oxygen of the sugar, in the form of carbonic acid. When the process is conducted in such a manner that the quantity of carbonic acid can be retained and weighed, it is found to cor- respond nrecisely with the loss of the alcohol 5 that is, the combined weight of the acid and alcohol are equal to that of the sugar. This may be made apparent thus : Sugar and alcohol are composed of Sugar. Alcohol. 3 proportions of carbon 18 2 prop, carbon 12 3 do. of hydrogen 3 3 do. hydrogen 3 3 do. of oxygen 24 1 do. oxygen 8 45 23 This shows a loss of one proportion of carbon and two proportions of oxygen from the sugar, the alcohol contain- What is the product of the acetic ? What are the results of the putrefactive fermenta- tion 1 What changes do seeds and barley undergo by germination and malting ? What are the four conditions necessary to induce the vinous fermentation ? What gas escapes during this fer/nentation ? What becomes of the sugar during the vinous fermentation 1 Is the weight cf alcohol formed, equal to the weight of sugar employed ? What becomes of the deficiency"? What is the composition of sugar ? What is the composition of alco- hol ? How docs it appear that the loss from the sugar escapes in the form of Karbonic acidl ALCOHOL. 315 nig only two parts of carbon and one of oxygen, while the sugar contained three of carbon and three of oxygen, the pro- portion of hydrogen being the same in both. The difference between the number for sugar and that for alcohol is there- fore 22. Now we have seen that carbonic acid is composed of one proportion or atom of carbon 6> and two proportions or atoms of oxygen 16, and these two numbers make the precise quantity of carbon and oxygen lost by the sugar, and which is not contained in the alcohol. Therefore, 45 parts of sugar produce by fermentation, 23 parts of alcohol, which is found in the fermented liquor, and 22 parts of carbonic acid gas, which escape. This investigation, while it affords a beautiful illustration of the doctrine of definite proportions, demonstrates that nothing is lost by a new arrangement, or interchange of ele- ments. It is believed, that the vinous fermentation never takes place without the presence of sugar, the elements of this ingredient, as shown above, furnishing by decomposition those of the alcohol. In cases where substances which con- tain no sugar are known to produce alcohol without the ad- dition of this ingredient, the process is explained by the sup- position that the starch which these substances contain, is converted into sugar by the saccharine fermentation. It is well known that potatoes, which contain little, or no sugar, yield a large quantity of alcohol by fermentation. But po- tatoes contain a large proportion of starch, which entirely disappears during the process, being first converted into su- gar, and then into alcohol. Alcohol. When a liquor which has passed through the vinous fer- mentation is distilled, there rises from it a fluid, having much more highly intoxicating powers than the fermented liquor from which it is obtained. This liquor has a sharp penetra- ting taste, and retains the flavor and odor of the fermented liquor, from which it is distilled. The fluid so obtained is alcohol mixed with water, and containing a portion of the essential oil peculiar to the vegetable which formed the fer- Does the vinous fermentation ever take place without the presence of sugar 1 How is the process explained in cases where alcohol is formed by substances containing no su- ^a 1 -, as in potatoes 7 How are spirituous liquors obtained ? 316 ETHER mentative solution, and which gives it a flavor. Thus, brandy, rum, and whiskey, have each a flavor of their own, which arises from this circumstance. These are called spirituous liquors. When a spirituous liquor is distilled, the alcohol is obtained in a state of much greater purity, the oil which it contained and most of the water being left in the retort, or still. In this state it is colorless, highly inflammable, produces cold by evaporation, and occasions a considerable augmentation of temperature by admixture with water. Common alcohol contains a portion of water, and has a specific gravity of from 850 to 875, water being 1000. It may be further purified, or freed from water, by adding to it warm carbonate of potash, or muriate of lime, which combines with the water, and sinks to the bottom of the vessel, after which the alcohol may be poured off Very pure alcohol may also be procured, by putting it into a bladder, which being sus- pended in a warm place, the water will slowly pass through the coats, while the pure alcohol is retained. The strongest alcohol which can be procured by either of these methods, has a specific gravity of 800, or 796, at the temperature of 60 degrees. Pure alcohol has never been frozen, though exposed to the lowest temperature which art has ever produced. It is a powerful solvent, being capable of dissolving camphor, resins, soap, volatile oils, sugar, balsam, &c. Pure alcohol has precisely the same properties, from what- ever substances it is obtained. Ether. The name ether was originally applied to a highly fragrant and volatile liquid, obtained by the distillation of alcohol with sulphuric acid. But it has been found that the same substance, when distilled with other acids, affords a liquid possessing in some respects similar properties, and therefore these compounds are now distinguished by prefixing the name of the acid employed. What gives the peculiar flavor to distilled Kqtiors, as brandy, rum, and whiskey 1 How is alcohol obtained 7 Do spirituous liquors yield pure alcohol on distillation 1 What is the specific gravity of common alcohol 7 How may pure alcohol be obtained 7 Whal is the specific gravity of the purest alcohol? What is said of the freezing of pure alco bol T What is said of the solvent powers of alcohol 7 How is ether obtained. 1 ETHER. 317 Sulphuric Ether. To make sulphuric ether, pour into a tubulated retort a certain quantity of alcohol by weight, and add, in small portions at a time, the same weight of strong sulphuric acid, allowing the mixture to cool after each addi- tion. Then connect the retort with a receiver, and, by means of a lamp, make the mixture boil. The receiver must be kept cold by the application of ice, or wet cloths. The ether will pass over and be condensed in the receiver. The ether thus obtained, contains a portion of alcohol, and commonly a little sulphuric acid, from which it is purified by agitation with potash, and redistillation. In respect to the chemical changes which take place be- tween the alcohol and acid, to form the new product ether, it is found, on analysis, that the latter substance is composed of two proportions of olefiant gas, and one proportion of water. The number for olefiant gas being 14, and that for \vater being 9, the equivalent number for ether is 37. Now olefiant gas consists of 2 atoms of carbon 12, and 2 atoms of hydrogen 2=14, to which 1 atom of water 9, being added, makes the composition of ether. Alcohol is composed of, or contains the elements of, 1 atom of olefiant gas, and 1 afom of water, and therefore: alcohol contains double the proportion of water that ether does. Now if 1 proportion or atom of water be abstracted from two of alcohol, the exact proportions constituting ether will re- main. Thus, the number for alcohol being 23, double this number is 46, from which one atom of water, 9, being taken, there remains 37, the number representing ether. It will be seen, on comparing these several numbers, that they ex- actly correspond with the constituents above named, and it is supposed that this is the precise mode in which sulphuric acid operates to convert alcohol into ether. In consequence of the affinity of sulphuric acid for water, it abstracts one atom of that fluid from the alcohol, and thus the elements of ether remain. Sulphuric ether is a light, odorous, transparent fluid, of a hot and pungent taste. Its specific gravity, when most pure, is about 700, water being 1000 ; but that of the shops is 740, or 750, owing to the presence of alcohol. When exposed to What is the process of obtaining sulphuric ether? What is the composition of * phuric ether * Explain the difference between alcohol and ether, and describe the change by which the former is converted into the latter. What is the specific grarity of ether when most pure 7 How does ether occasion an intense degree of cold ? 27* 318 VEGETABLE ALKALIES the open air, it evaporates with great rapidity, and occasions an intense degree of cold. This is in consequence of the principle already explained, that when a substance passes from a denser to a rarer state, caloric is absorbed. Ether is exceedingly combustible, and burns with a blue flame, the product of its combustion being water and car- bonic acid. Ether is employed as a medicine in nervous fevers, and as a solvent in the arts. When pure, or when that of the shops is agitated with water, and, after standing a while, is poured off! it is a solvent of India rubber, one of the most insoluble of vegetable products. Nitrous Ether is prepared by distilling alcohol with nitric acid, in a manner similar to that described for sulphuric ether, to which its leading properties are similar. It is, how- ever, still more volatile, and is subject to decomposition by keeping. Vegetable Alkalies. Potash and soda were formerly called vegetable alkalies, in order to mark their origin, and to distinguish them from the other alkaline substances. These . alkalies, as stated in thsir-proper places, are obtained chiefly by the incineration of land and sea plants, though they both exist ready formed by nature. They are found to be metallic oxides, and have been described under the names of oxide of potassium and oxide of sodium. The vegetable alkalies now to be descri- bed, are strictly vegetable products, and are obtained, not by incineration, but by the digestion,} or maceration, of certain vegetable substances in water. The following is an outline of the method by which tLey are obtained. In the first place, the substance containing the alkali is digested in a large quantity of very pure water, which dissolves the salt, the base of which is the alkali. On adding some salifiable base, such as potash, or ammonia, which has a strong affinity for the acid of the vegetable salt, in the watery solution, this salt is decomposed, its- acid com- bining with the potash, or ammonia, and thus leaving the vegetable alkali in the solution. This being insoluble, while Why does the evaporation of ether occasion cold ? What are the uses of sulphuric ether ? How is nitrous ether procured 7 How does the nitrous difier from the sulphuric ether 7 How do the oxides of potassium arid sodium differ from the vegetable alkalies) How are the vegetable alkalies obtained 1 Give an outline of the process by which these ubstances are procured. MORPHIA. 319 the new salt is soluble in water, is collected and washed on a filter. The vegetable alkali thus obtained, is however im- pure, and requires to be dissolved in alcohol, with the addi- tion of some animal charcoal, which deprives it of its color, then filtered, and the alcohol evaporated, when the pure alkali will be obtained. The most important vegetable alkalies are, Morphia, Cin~ chonia, and Quinia. Morphia. Morphia is the narcotic principle of opium. Opium, be sides morphia, contains meconic acid, narcotine, gum, resin- OTIS, extractive, and colouring matter, and a small quantity of caoutchouc, or India rubber. Morphia exists in the opium, combined with meconic acid, forming meconate of morphia. To obtain it, therefore, it is necessary to decompose this salt, by which the morphia is li- berated, and afterwards obtained by the evaporation of some fluid in which it is soluble. This is done by boiling a solution of opium in water, with magnesia, by which the meconate of morphia is decomposed, and a meconate of magnesia is formed. The morphia being thus precipitated, is obtained in an impure state by filtration, and afterwards purified by solution in alcohol On evapo- rating the alcohol, the pure alkali is deposited in crystals. Pure morphia occurs in sm'all rectangular white prisms, of considerable lustre. It is insoluble in water, but alcohol, especially by the aid of heat, dissolves it freely. "In its pure state, 'this substance is nearly tasteless, owing to its insolubi- lity in water, but when it is rendered soluble by combining with an acid, or when dissolved in alcohol, it is intensely bit- ter. From the same cause, in its pure and solid state, mor- phia is nearly inert on the living system, Orfila having given twelve grains to a dog, without any sensible effects. On -the contrary, when in a state of solution, it acts on the system with great energy, Orfila having seen alarming effects from half a grain. What are the most important vegetable alkalies! What is morphia? What are the ingredients in opium besides morphia? In what state does morphia exist in the opium ? What is the process for obtaining morphia? What is the use of the magnesia in this process ? What arc the solvents of morphia ? In what state is morphia used in medicine I 820 CIXCHONIA AND QUINIA. The best method of using morphia in medicine, is to form with it an acetate, or a citrate, both of which are soluble in water, and alcohol. In either of these states, it is given in those cases where opiates are required, and it produces all the soothing effects of opium, without the disagreeable conse- quences which often follow the administration of that drug. Narcotine, This substance, though not an alkali, is con tained in opium, and is therefore properly noticed here. Narcotine is obtained by digesting opium in water, and evaporating the solution to the consistence of extract, and then digesting this with sulphuric ether. The water, as shown above, will hold in solution meconate of morphia, as well as narcotine, but the meconate is insoluble in ether, which only takes up the narcotine. On evaporation, the ether so treated will deposit small particles of narcotine. This substance is little soluble in water, either cold" or hot, but dissolves in oil and alcohol. The unpleasant properties of opium as a medicine, are at- tributed to this substance, and perhaps the different effects of the salts of morphia from opium, are only owing to their not containing narcotine. Cinchonia and Quinia. It has been fully established, that the efficacy of cinchonia, or Peruvian bark, in the cure of fevers, resides in the alka- lies, called cinchonia and quinia. These two principles, though quite analogous in many respects, are distinct sub- 'stances, and appear to bear the same relation to each other as potash and soda. Cinchonia exists in the pale bark, quinia in the yellow, and both are present in the red bark. They are obtained from these substances by a process similar to that already described for separating morphia from opium. Cinchonia appears in white crystalline grains, which are .nearly insoluble in water, but which are readily taken up by Why is it not used in its pure state ? What advantage has morphia over opium as a medicine? How is narcotine obtained? Is narcotine soluble In water? What are the solvents of narcotine ? What effects of opium are imputed to narcotine ? What is said of the efficacy of cinchonia and quinia in the cure of fevers ? What relation do cincho- uia and quinia appear to bear to each other ? In what species of bark do these alkalies exist ? By what process are these substances obtained ? What is the appearance o Cincbonia ? ANIMAL CHEMISTRY. 321 boiling alcohol. Its alkaline properties are well marked by its power of neutralizing acids. It forms nitrates, muriates, sulphates, acetates, &c., all of which are soluble in water. Quinia is a white, porous substance, of a flocculent ap- pearance. It does not, like cinchonia, form crystals. It is also nearly insoluble in water, but dissolves freely in alcohol, affording an intensely bitter solution. Like cinchonia, it has strong alkaline powers, and forms salts with the several acids. Its febrifuge effects are much more decisive than those of cinchonia, and it is now extensively employed in the practice of medicine, in the form of the sulphate of quinia This salt crystallizes in delicate white needles. It contains 90 parts of the quinia combined with 10 of the acid. The composition of cinchonia and quinia is thus stated by Pelletier and Dumas. JCinchonia. Quinia. Carbon 76.97 Carbon 74.14 Oxygen 7.97 Oxygen 6.77 Hydrogen 6.22 Hydrogen 8.80 Nitrogen 9.02 Nitrogen 10.76 100.18 100.47 The composition of these alkalies, therefore, consist of the ~ame elements, and nearly in the same proportions. ANIMAL CHEMISTRY. In relation to chemistry, the circumstances which distin- guish animal from vegetable substances, are the large quan- tity of nitrogen which the former always contain, their strong tendency to putrefaction, and the offensive products which they exhale during decomposition. Animal substances are essentially composed of carbon, hydrogen, oxygen, and nitrogen ; and in addition to these, they sometimes contain sulphur, phosphorus, iron, and small quantities of saline matter. Fibrin. The lean parts of animals consist chiefly of fibrin. How do the alkaline properties of cinchonia appear? What salts does it form with acids? What is the appearance of quinia? What is the solvent of quinia? In whal form is quinia employed in medicine ? What is the appearance of sulphate of quinia, and what its composition? In relation to chemistry, what are the circumstances which distinguish animal from vegetable substances ? What is the essential composition ol animal substances? 322 ANIMAL CHEMISTRY. This may be separated and observed in its pure s<:ate, by re- moving the soluble parts of lean beef, cut into small pieces, by repeated washing, and digestion in cold water. Fibrin thus obtained, is nearly white, and is insipid and inodorous. It readily passes into the putrefactive fermenta- tion, but in thin pieces, suspended in a dry place, its fluid parts evaporate, and it becomes hard, brittle, and translucent. Alcohol converts fibrin into a fatty substance, which is so- luble in the same fluid and in ether, but is precipitated by the addition of water. This substance is decomposed by all the strong acids, and is dissolved by caustic potash. Fibrin is composed of 18 parts of carbon, 14 of hydrogen, 5 of oxygen, and 3 of nitrogen. Albumen. Albumen enters largely into the composition of animals. Their solid, as well as fluid parts, contain it in greater or less proportion. Liquid albumen is nearly pure in the whites of eggs Its appearance, and many of its pro- perties, in this state, are well known. It is coagulated, and converted into a soft solid, by heat, by alcohol, and by the stronger acids. The character of being coagulated by "heat, distinguishes albumen from all other animal fluids. It is com- pletely soluble in cold water, and it is said that when this fluid contains only^JL^. part of albumen, it becomes opalescent by boiling. On this property is founded the clarifying effect? of albumen. As it coagulates, by the heat of the water, it entangles any insoluble particles the fluid contains, and rises with them to the surface. Gelatine. This substance forms a proportion of all the solid parts of animals, and is particularly abundant in the skin tendons, membranes, and bones. It is soluble in boiling water, and forms a bulky, semi-transparent, tremulous mass, when cold. By evaporation, it becomes a solid, brittle, hard, and semi-transparent substance, known in commerce and the arts, under the name of glue. This is chiefly prepared from the cuttings of skins, and the ears and hoofs of animals. Isin- glass, which is the purest variety of gelatine, is prepared from certain parts of fish, and especially the sturgeon. The gela- What is fibrin ? How may fibrin be obtained? What are the properties of fibrin? What is the composition of fibrin? Where is albumen found nearly in a pure state ? By what agents is albumen coagulated? By what property is albumen dis'inguished from all other animal fluids? How does albumen clarify liquids? In what pans of ani- mals is gelatine most abundant? Under what name is dry gelatine known? What It ANIMAL CHEMISTRY. 323 tine called calves foot jelly, is prepared by boiling the feet of that animal in water. Gelatine is precipitated by tannin. This is so delicate a test for gelatine, that it is' said, an infusion of nut galls, which contains a large quantity of tannin, will show the presence of gelatine when mixed with 5000 times its weight of water. The three ingredients, fibrin, albumen, and gelatine, form the most bulky parts of all animals, that is, the flesh, tendons cartilages, and skin. Oleaginous Substances. The fat of animals is very analogous, in its composition and proportions, to the fixed, vegetable oils, its ultimate prin- ciples being carbon, hydrogen, and nitrogen. There is a considerable variety in the appearance and qualities of the fatty principle contained in different animals. The solid fat of land animals is called tallow, while the cor- responding substance from fish, which is fluid at common temperatures, is called oil. All these substances agree very nearly in respect to com- position, the principal difference being in respect to form and appearance. Their uses, for making soap, giving light, &c are well known. Blood. The blood of animals obviously consists of two parts, called serum and crassamentum. In healthy blood, these two parts se- parate spontaneously on standing. The crassamentum coagu- lates, and forms a red, solid mass, while the serum surrounds it, in form of a yellowish fluid. The serum contains a small quantity of soda in a free state, and is 29 parts in 1000 heavier than water. It consists, in part, of albumen, and is coagulated by heat, acids, and alco- hol. The crassamentum consists of two parts, the fibrin and the colouring matter. The fibrin does not differ, except in form, from that obtained from lean flesh, which has already been described. By what substance is gelatine precipitated from its solutions 1 What parts of animate ore formed by fibrin, albumen, and gelatine 7 What are the ultimate principles of animal fats 7 What difference is there between animal fats and animal oils 7 In blood what is the serum and what the crassamentum 7 What is serum composed of 7 What does crassamemum consist of 7 S24 ANIMAL CHEMISTRY. The coloring matter of the blood consists of distinct par- ticles, which in birds and cold-blooded animals, are elliptical in form, but in man and other mammiferous animals, they are globular. These facts have been acsertained by means of the microscope. The globules are insoluble in the serum, but their color is dissolved by water acids, and alcohol. It has been suppossed that the crassamentum contained a portion of iron, but recent analysis has shown that this metal does not belong to the crassamentum as a whole, but only to the coloring matter ; for when the fibrin is carefully sepa- rated from the coloring principle, it does not contain a trace of iron, while iron is always found in the red glo- bules. From the presence of iron in the globules, and its total absence in the other parts of the blood, it is inferred that the red color of the globules depend on the presence of this rnetal, though its quantity is found to be only half a grain to a hundred grains of the globules. It is found that during the coagulation of blood, heat is evolved, and consequently its temperature is raised. This is owing to its passage from a rarer to a denser state, in con- sequence of which its capacity for caloric is diminished. We have had frequent occasions to refer to this principle. The increase of temperature from this cause, is however very slight, perhaps not more than two or three degrees, but its cooling is considerably retarded by the caloric thus evolved. The blood presents several phenomena, which neither the principles of chemisty nor physiology have been able to ex- plain. The cause of its coagulation, for instance, has never been satisfactorily accounted for. It does not arise for want of heat or motion, for if blood be drawn when the tempe- rature of the air is equal to that of the animal from which it is taken, and then kept constantly in motion, its coagulation is not prevented, or even retarded. Indeed, neither mod- erate heat, nor cold, a vacuum, nor pressure, nor even di- lution with water, seem to have any influence on the coagu- lation of the blood. On the contrary, its coagulation is pre- What does the coloring matter of blood consist of? On what metal does the coloring matter depend 1 What proportion of iron is contained in the red globules of the blood ? What i's said concerning the heat evolved by the coagulation of the blood ? What is said concerning the cause of the blood's coagulation? what circumstances arc raid not to af feet the coagulation of the blood ? CHEMISTRY. 325 vented by certain causes, the effects of which could not be supposed to influence this circumstance. Thus, the blood of persons who have been destroyed by some kinds of poison, and by mental emotions, has been found uncoagulated, and in a fluid state. How causes so unlike should produce the same effects, or why either of them should affect the blood at all, are equally unknown. Respiration Respiration is the act of breathing, and consists in the alternate drawing into, and throwing out of the lungs, a quantity of atmospheric air. And it appears that this pro- cess, or an equivalent one, is necessary to support the lives of all animals. The atmosphere, as formerly shown, is composed of 80 parts of nitrogen, and 20 parts of oxygen, and it is found by experiment, that no other gaseous compound can be substi- tuted for respiration, nor can these proportions be varied with- out injury to its qualities. The immediate effect of respiration, is to produce a change in the color of the blood as it passes through the lungs, thus indicating that it suffers some change in its pro- perties at the same time. The necessity of respiration to all warm blooded animals requires no proof; and the necessity that the blood should be brought into contact with the air inspired, is equally ob- vious from the organization of their lungs. Such animals are provided with two kinds or classes of blood vessels, called veins and arteries. The arteries, particularly the large ones, are deeply seat- ed within the animal, and convey the blood to all parts of the living system. The veins, on the contrary, especially the small ones, are situated near the surface, and are destined to convey the blood back to the heart, which had been thrown sut by the arteries. What circumstances are said to prevent the coagulation of the blood 1 What is respi- ration 7 What is the composition of the atmosphere 7 What effect does a cnange in the omposition or proportion of the elements of the atmosphere produce on respiration Vhat is the immediate effect of respiration on the color of the blood 7 What is said of ne necessity of respiration 7 What are the two kinds of blood vessels called 7 Where ire the veins ard arteries situated with respect to each other 1 What is the use of the ap- eries 7 What part of the circulation do the veins perform 7 28 326 RESPIRATION But besides these two great systems of blood there is another system called the pulmonary, which is des- tined expressly to convey the blood to the lungs, where it undergoes the change above mentioned, and then back again to the heart. The entire circulation will now be readily understood. The blood being thrown to all parts of the body, is returned to the right side of the heart by the great system of veins. From the right side of the heart it is sent to the lungs, by the pulmonary artery, and being there changed into arterial blood, is returned by the pulmonary veins to the left side of the heart. From the left side of the heart, it is thrown^ to all parts of the body by the great system of arteries, to be returned to the right side by the veins, as before. When venous blood, fresh drawn, is suffered to stand a few minutes in a confined portion of atmospheric air, it is found that the air loses a part of its oxygen, which is re- placed by the same volume of carbonic acid gas, and at the same time the color of the blood, from being of a dark pur- ple, becomes florid red. This is the same change of color which the blood undergoes in its passages through the lungs. The cause of the change in the lungs might therefore be inferred to be the absorption of oxygen by the blood, and the subsequent emission of carbonic acid. That this change of colour in venous blood, when out of he lungs, is owing to the contact of oxygen, is shown by the more immediate production of the same effect when oxygen is substituted for atmospheric air, and also by the fact that no change of color is produced when the oxygen is entirely excluded. Hence the inevitable conclusion, that fresh drawn venous blood emits a quantity of carbon in con- sequence of its coming in contact with oxygen, and that its change of color is caused by this emission. The same change thus proved to take place in the atmos- phere, is constantly going on in the lungs. The venous blood, which, as above explained, is sent to the lungs through the pulmonary artery, is charged with carbon, to which it What is the office of the pulmonary system 1 Explain the entire circulation. From whicn Bide of the heart do the great arteries convey the blood to all parts of the body 1 How is the blood conveyed from the right to the left side of the heart ? What effects do the contact of atmospheric air and venous blood produce on each ? How is it proved that the change of color in the blood is produced by the oxygen of the air 1 What is the cause of the change of color in venous blood 1 RESPIRATION. 327 ewes its dark color. The oxygen of the atmosphere, by in- spiration, fills all the air vessels of the lungs, and is thus brought nearly into contact with the blood, being separated from it only by the thinnest membrane. It appears that through this membrane, the oxygen of the atmosphere is absorbed, and having combined with a portion of the carbon of the blood, it is again emitted in the form of carbonic acid gas, and to this process is owing the change "rom venous to arterial blood. In proof of this, experiment shows that when any living inimal is confined in a portion of air containing a known quantity of oxygen gas, the oxygen gradually disappears, tnd is replaced by the same quantity of carbonic acid. In ordinary respiration, the air from our lungs always contains a portion of carbonic acid. This is proved by merely blow- ing into a glass vessel containing a solution of lime in water, or what is commonly called lime water, when the clear water will instantly become turbid, because the carbonic acid from the lungs unites with the lime of the water, and forms an in- soluble carbonate. It does not appear that the oxygen is absorbed, and retain- ed by the blood, for the absolute quantity of air, though anany times respired by a confined animal, remains the same. This also proves that the nitrogen of the atmosphere is not absorbed. It is well known by experiment, that the conver- sion of oxygen gas into carbonic acid, does not in the least change its volume, but only adds to its weight. This ac- counts fer the reason why the volume of air is not changed by respiration, or by convertion into carbonic acid, provided no absorption take place. Thus the change from venous to arterial blood, seems to be produced entirely by the loss of carbon, which the former suffers while passing through the lungs, It appears also, from numerous experiments, that not only \vaim blooded animals, but also fish, and cold blooded reptiles of the lowest order, absolutely require the presence o. To what is the dark colour of venous blood owing 7 What change does the blood undergo in the lungs? How is it proved that oxygen is converted into carbonic acid in the lungs ? How ia it proved that we emit carbonic acid at every expiration 7 In respi- ration, is tho oxygen absorbed and retained by the blood, or not? How does it appear that neither the nitrogen nor the oxygen of the atmosphere is retained in the process o. respiration,? 1 In what does the change from venous to arterial blood consist 7 What if said Qf'JlP necessity of oxygen to support the. lives of cold bloodod reotilcs 1 328 ANIMAL HEAT. oxygen in order to sustain life. Water, it has already Been stated, always contains a portion of this gas in a free state, and although the quantity is small, it is sufficient to sustain the lives of its inhabitants. That fish, frogs, and other animals of this kind, cannot sustain life without oxygen gas, is proved by the fact, that they die in a short time, if the water in which they are placed is covered with a film of oil, so tfyat no oxygen is admitted. Frogs, though capable of suspending their respira- tion for a long time, die in less than an hour, if the small quantity of water in which they are confined is covered with oil. Aquatic insects and worms exhibit the same phenome- na when treated in the same manner. In these cases, ex- periment has shown that oxygen is converted into carbonic acid, the effect being the same as that produced by the re- spiration of warm blooded animals. Indeed, the experiments of Spallanzani prove that ani- mals produce this change by the action of their skin. Thus, serpents, lizards, and frogs, during their torpid state, and when their respiration is suspended, still require small por- tions of oxygen, which they constantly convert into carbonic acid by means of their skin, and it is probable, that in this manner, the blood of these animals parts with a little car- bon. , Animal Heat. During combustion there is an absorption of oxygen, and a suosequent emission of carbonic acid gas, and in the act of respiration, oxygen disappears, and is replaced by the same acid gas. Combustion and respiration are therefore sup- ported by the same principle, and yield the same product. This analogy led Dr. Black to conclude that the changes which take place on the air, and on the blood in tbe lungs, was the cause of animal temperature ; and several circum- stances relative to the structure of animals and the quantity of oxygen they consume by respiration, seem to show that the heat of their blood depends, in a measure at least, on the quantity of this principle thus consumed. Animals having the power to maintain their temperatures above the media in which they live, are provided with capacious lungs, and consume large quantities of oxygen. Birds, the temperature How is it proved that fish and frogs require oxygen ? What effect does the skin of tor pid animals have upon oxygen! What analogy is there between combustion and respi- ration 1 What ia said concerning the quantity of oxygen consumed by warm blooded am mala) ANIMAL HEAT. 329 of whose blood is higher than that of man, and quadrupeds, have lungs still more capacious, according to their size, and consequently, most probably consume more vital air. On the contrary, fish, frogs, and other animal of this tribe, which consume only very minute portions of oxygen, do not, sustain their temperature above the media in which they live. It appears also, that the temperature of an animal, when made to respire pure oxygen gas, is raised above the natural standard, but when the quantity of this gas consumed is small, the temperature of the animal falls, and the circula- tion of the blood is sluggish and languid. From these considerations, it would appear that the heat of the animal is sustained by its respiration, and that its temperature is proportionate, in some degree, to the quantity of oxygen it consumes, or converts into carbonic acid. Dr. Crawford, pursuing this idea, supposed that the car- bonic acid discharged by the breath, being generated in the lungs, and accompanied with the loss of oxygen, extricated heat during its formation, and that the temperature of the animal might thus be explained. But as the heat of the lungs was found to be no greater than that of other internal parts, there must be some mode of accounting for its dis- tribution to other parts of the system, otherwise this theory could not for a moment be supported. It is ob- vious that, in whatever manner this distribution is effected, the heat must be latent, or insensible; for supposing it to be n a free state, the lungs, or part where it is generated, would still be at a higher temperature than the parts to which it is distributed. Accordingly, on comparing the capacities of venous and arterial blood for heat, Dr. Crawford found, that arterial blood had the greatest capacity, and therefore, that at the same temperature, it contained a quantity of latent heat, which the venous blood did not. He therefore supposed that this latent heat was conveyed by the arterial blood, to all parts of the system, and as the arterial is gradually con- verted into venous blood, so the latent heat gradually be- What Is said of the quantity of oxygen consumed by fish and frogs 1 Does it appear lhat there is any proportion between the heat of the animal and the quantity of oxygen it consumes by respiration 7 How did Dr. Crawford explain the cause of animal temper- ature 1 Suppose arterial blood to have a greater capacity for heat than venous blood, en what circumstance could animal temperature be explained t 28* 3<0 ANIMAL HEAT. came sensible, in all parts of the system, and that in this manner, animal ten porature is maintained. This beautiful th eory was supposed to be founded on the true principles of chemistry and physiology, and being so received, it accounts: very satisfactorily for animal tempera- ture. But Dr. Davy has since shown that the principal fact on which it is founded, the difference of the capacities of ve- nous and arterial blood for heat, is not true, but that in this respect there is little or no difference between the two kinds of blood. If Dr. Davy has maintained the truth, it is obvious that Dr. Crawford's theory must fall to the ground. Although the facts stated above, in respect to the capacity of the lungs, in warm blooded animals, and the quantity of oxygen which they consume, when compared with cold blooded animals, would seem to show almost beyond a doubt, that animal temperature is connected with the quantity of oxygen consumed, and the changes which the blood under- goes in the lungs ; still some physiologists deny the agency of either of these causes in producing such effects, and as- cribe the evolution of animal heat entirely to the influence of the nervous system. The foundation of this doctrine, is an experiment of Mr. Brodie, who found that on keeping up an artificial respira- tion in the lungs of a decapitated animal, the colour of the blood was changed from purple to red, and carbonic acid emit- ted as usual ; but that this animal grew cold more rapidly than another decapitated animal of the same kind which lay un- touched. It is obvions that this result would follow unless heat was evolved by the artificial respiration, because the air forced into the lungs would abstract the heat of the ani- mal. "Were these experiments rigidly exact, says Dr. Turner, they would lead to the opinion that no caloric is evolved by the mere process of arterialization. This inference cannot, however, be admitted, for two reasons : First, because other physiologists, in repeating the experiments of Brodie, have found that the process of cooling is retarded by artifi- How did Dr. Da fy show that Dr Crawford's theory was untenable 1 What is the foun dation of the theory that animal h at is evoived by the nervous system 3 If heat were not evolved by artificial respirati- n, why should this process cool tbe animal rapidly 1 What are Dr. Turner's two reasor, for supposing that Mr. Brodie's experiments are not conclusive, that heat is not evolvei by respiration ? ANIMAL HEAT. 331 i'.ial respiration ; and, secondly, because it is difficult tc con- ceive why the formation of carbonic acid, which uniformly gives rise to increase of temperature in other cases, should not be attended within the animal body with similar results. It may hence be inferred, that this is one of the sources of animal heat." In respect to the influence of the nervous system over the development of animal temperature, there is no doubt but considerable effects may be safely attributed to this cause. But in what manner the heat is evolved, is perhaps uncer- tain. In conclusion, we may remark, that the subject of animal temperature has excited the attention, and has been made an object of experiment and research among philosophers and physiologists in all ages, and that many ingenious and some plausible theories have been invented and detailed, in order to give satisfactory explanation of its cause. The theory of Dr. Crawford, among these, was perhaps the most plausi- ble, and certainly the most philosophical and beautiful. But we have seen, that the leading facts on which it was found- ed, have been proved by his successors not to be true, and therefore the theory itself cannot be maintained. That the oxygen of the atmosphere is one of the causes of animal heat cannot be doubted, from the facts, that no animal can live without it, and that the heat of animals is in some propor- tion to the quantity of this principle consumed. But as this principle can have no effect, except through the lungs, if it is admitted that heat is evolved by its action there, there is still much difficulty in explaining either why the lungs are not constantly at a higher temperature than the other parts of the system, or if they were, how the heat could be conveyed to the other parts, from its fountain. On the whole, it appears that the cause of animal heat is one of the arcana of nature, into which man has not yet been permitted to look, and therefore, we must be contented at present to attribute it to the vital principle. Is it probable that the nerves affect the tsmpeiature of the animal 1 What is said in conclusion on this subject ? Has there been A.J/ theory proposed whic^ accounts satis- factorily for the cause of animal heat ? To what is it said must we ai 7*ent avtribute the cause of anirralheat? 332 ANALYSIS OF GASES PART IV. ANALYTICAL CHEMISTRY. To enter into a detailed account of experimental and ana lytical chemistry, is altogether inconsistent with the design and limits of the present work. My sole object in this de- partment is to give a few concise directions for conducting some of the more common analytical processes; and in 01- der to render them more generally useful, I shall give exam pies of the analysis of mixed gases, of minerals, and of mine ral waters. ANALYSIS OF MIXED GASES. Analysis of air, or of gaseous mixtures containing oxygen Of the various processes by which oxygen gas may be with- drawn from gaseous mixtures, and its quantity determined, none are so convenient and precise as the method by means of hydrogen gas. In performing this analysis, a portion of atmospheric air is carefully measured in a graduated tube, and mixed with a quantity of hydrogen, which is rather more than sufficient for uniting with all the oxygen present. The mixture is then introduced into a strong glass tube called Vol- ta's eudiometer, and is inflamed by the electric spark, the aperture of the tube being closed by the thumb at the mo- ment of detonation. The total diminution in volume, divided by three, indicates the quantity of oxygen originally contain ed in the mixture. This operation may be performed in a trough either of water or mercury. Instead of electricity, spongy platinum (page 126) may be employed for causing the union of oxygen and hydrogen gases ; and, while its indications are very precise, it has the advantage of producing the effect gradually and without de- tonation. The most convenient mode of employing it with this intention is the following. A mixutre of spongy plati- num and pipe-clay, in the proportion of about three parts of the former to one of the latter, is made into a paste with water, and then rolled between the fingers into a globular form. In order to preserve the spongy texture of the plati- num, a little muriate of ammonia is mixed with the paste ; and when the ball has become dry, it is cautiously ignited at the flame of a spirit-lamp. The sal-ammoniac, escaping from all parts of the mass, gives it a degree of porosity which is peculiarly favorable to its action. The ball, thus prepared, should be protected from dust, and be heated to redness just ANALYSIS OF GASES. 333 before being used. To insure accuracy, the hydrogen em- ployed should be kept over mercury for a few hours in con- tact with a spongy platinumball and a piece of caustic pot- ash. The first deprives it of traces of oxygen which it commonly contains, and the second of moisture and sulphu- retted hydrogen. The analysis must be performed in a mer- curial trough. The time required for completely removing the oxygen depends on the diameter of the tube. If the mixture is contained in a very narrow tube, the diminution tloes not arrive at its full extent in less than twenty minutes or half an hour ; while in a vessel of an inch in diameter ;he effect is complete in the course of five minutes. Mode of determining the quantity of nitrogen in gaseous mixtures. As atmospheric air, which has been deprived of moisture and carbonic acid, consists of oxygen and nitrogen only, the proportion of the latter is of course known as soon as that of the former is determined. The only method, in- deed, by which chemists are enabled to estimate the quantity of this gas, is by withdrawing the other gaseous substances with which the nitrogen is mixed. Mode of determining the quantity of carbonic acid in gaseous mixtures. When carbonic acid is the only acid gas which is present, as happens in amospheric air, in the ultimate analysis of organic compounds, and in most other analogous researches, the process for determining the quantity of car- bonic acid is exceedingly simple ; for it consists merely in absorbing that gas by lime water or a solution of caustic po- tash. This is easily done in the course of a few minutes in an ordinary graduated tube ; or it may be effected almost in- stantaneously by agitating the gaseous mixture with the alka- line solution in Hope's eudiometer. This apparatus is form- ed of two parts ; a bottle capable of containing about twenty drachms of fluid, and furnished with a well-ground stopper ; and a tube of the capacity of one cubic inch, divided into 100 equal parts, and accurately fitted by grinding to the neck of the bottle. The tube, full of gas, is fixed into the bottle previously filled with lime water, and its contents are briskly agitated. The stopper is then withdrawn under water, when a portion of liquid rushes into the tube, supplying the place of the gas which has disappeared ; and the process is after- wards repeated, as long as any absorption ensues. The eudiometer of Dr. Hope was originally designed for analyzing air or other similar mixtures, the bottle being fi ' 28-}-o. 1B> sulphuret .... 44 44 200 236 272 324 448 208 216 216 232 43 56 64 72 40 76 164 48 56 62 56 14 26 158 386 22 30 8 56 64 12 43 84 18 28 96 132 168 104 112 112 128 40 76 164 48 64 52 56 44 52 60 40 16 ft sulphuret .... bisulphuret .... Cyanogen, (carb. 12-f-nit. 14) Cyanuret of sulphur, (cy. 26-f-s. 32) Ether, (olef. gas. 28-j-wat. vap. 9) Fluorine Glucinum Glucina Gold chloride, (g. 200-j-chl. 36) - bichloride, (g. 200-f-chl. 72) - iodide, (g. 200-f-iod. 124) . oxide, (g. 200-j-o. 8) peroxide, (g. 200-\-o. 24) - sulphuret, (g. 200-j-s. 48) Hydrogen ..... arseniuretted, (a. 38-f-h. 1) - carburetted, (c. 6-f-h. 2) bicarburetted, (olefiant gas) (c. 12-Hi. 2) ... seleniuretted, (s. 40-f-h. 1) sulphuretted, (s. 16-|-h. 1) - bisulphuretted, (s. 32-|-h. 1) - Hydruret of phosphorus Bihydruret of phosphorus Iodine 80 96 26 58 37 18 18 26 200 236 272 324 208 224 248 1 39 8 14 41 17 33 13 14 124 30 28 64 82 152 36 40 44 60 104 140 112 116 120 11C 120 10 46 134 18 26 12 48 20 28 28 64 36 40 chloride, (calomel) (m. 200-j- chl. 36) .... bichloride, (corros. subl.) (m. 200-|-chl. 72) --- 1 iodide, (m. 200-f-iod. 124) - U&iniodide, (m. 200-f-iod. 248) - BRxide, Cm. 200-f-o. 8) - peroxide, (m. 200-(-o. 16) sulphuret .... bisulphuret .... Molybdenum .... mT oxide, (m. 48-f-O- 8) deutoxide, (m. 48-f-o. 16) - Molybdic acid, (m. 48-f-o. 24) - Nickel, (Lassaigne) chloride, (n. 40-f-chl. 36) iodide oxide, (n. 40-j-a 8) peroxide, (n. 40-|-o. 16) phosphuret .... sulphuret .... Nitrogen bicarburet, (cyanogen) - chloride, (n. 14-j-chl. 144) iodide, (n. 14-f-iod. 372) oxide, (n. 14-|-o. 8) deutoxide, (n. 14-f-o. 16) chloride, (i. 28+chl. 36) - perchloride, (i. 28-(-chl. 54) iodide, (i. 28-|-iod. 124) oxide, (i. 28-f-o. 8) - peroxide, (i. 28-|-o. 12) sulphuret, (i. 28-(-s. 16) bisulphuret, (i. 28-f-e. 32) - Lead Phosphorus chloride, (p. 12-j-chl. 36) bichloride .... sulphuret .... chloride. (1. 104-j-chl. 36) . oxide, (1. 104-j-o. 8) deutoxide, (1. 104-f-o. 12) peroxide, (1. 104+O. 16) - phosphuret, (1. 104-(-p. 12) - sulphuret, (1. 104-(-s. 16) Lithium chloride, (p. 96+chl. 36) - bichloride .... Platinum, oxide .... deutoxide .... sulphuret .... bisulphuret .... chloride, (1. 10-{-ch. 36) . iodide chloride, (p. 40-+-chL 36) iodide .... oxide, (potassa) peroxide, (p. 40-j-o. 24) phosphuret .... sulphuret .... oxide, (lithia) .... sulphuret .... chloride, (m. 12-+-chl. 36) - oxide, (magnesia) - sulphuret .... oxide chloride, (m. 28-f-chl. 36) - oxide, (m. 28-f-o. 8) deiitrtYule. (m. 2S-4-O. 12-4 EQUIVALEN 349 chloride (s 110-f-chl. 36) 146 234 oxide, (s. 110-i-o. 8) - phosphuret .... eulphuret .... 118 122 126 24 c. 3 w. - - - - 155 cadmium, (c. 2 w.) - - - 132 copper, (ac. a. 50-[-perox. 80) 130 c 6 w (com verdigris ) - - 184 chloride, (s. 24-{-chl. 36) - J iodide . . . : oxide, (soda) - - -|B 60 148 32 ?fi binacetate .... ISO c. 3 w. (distilled verdigris,) - 207 subacetate, (ac. a. 50-j-perox. 160) 210 36 lead 162 40 " 44 chloride .... iodide ... 80 140 56 magnesia 70 mercury, (protoxide) c. 4 w. 294 phosphuret .... 52 66 silver 163 , B P 10 chloride (s 10-f-chl 36) W iodide, (s. 16+iod. 124) . - - 142 28 Arseniate of lead 174 Sulphuretted hydrogen 17 33 magngsia .... 82 Tellurium, (Berzelius) chloride .... oxide - Tin ...... 32 68 40 58 Binarscniate of potassa, c. 1 w. Arseniate of soda - 94 Bin;>rseniate of soda, c. 5 W. - 201 chloride (t 68-r-chl 36) 94 silver ... 180 bichloride .... 130 66 Arsenite of lime ... - 82 deutoxide .... phosphuret .... eulphuret .... bisulphuret .... Titanium Titanium, oxide 74 70 74 90 32 40 40 Arsenite of soda .... 86 silver 172 Carbonate of ammonia, (carb. a. 22-f- ani. 17) 39 Sesquicarbonate of ammonia, (carb. a. 33-j-am. 17+w. 9) - - 59 96 Carbonate of baryta ... 100 oxide, (brown,) (t. 96-fo. 16) Tungstic acid, (t. 96-fo. 24) - 112 120 208 copper 102 iron, (protoxide) ... 58 lead 134 lime 50 294 g 34 Oxide, (Yttria) .... 42 04 Bicarbonate of potassa c 1 w 101 chloride .... oxide ... 70 49 Carbonate of soda, ... 54 phosphuret .... pulphuret .... 46 50 Bicarbonate of soda, c. 1 w. 85 Carbonate of etrontia 74 Zirconia ... . . SALTS. Acetate of alumina, (ac. a. 50-J-aL 18) c. 1 w 30 48 68 77 Chlorate of baryta, (ch. a. 76-f-b. 78) 154 lead 188 mercury 284 potassa . . . 124 350 EQUIV, Chromate of baryta .... 130 learl * ft/t VLENTS. Binoxalate of strontia ... Phosphate of ammonia, c. 2 w. 134 106 140 66 48 60 168 63 66 118 120 160 250 76 139 152 68 86 67 123 256 296 88 146 72 *62 92 82 145 262 487 178 94 83 .80 .98 an mercury ..... potassa, (chr. a. 52-+-p. 48) - Bichromate of potassa ... Fluate of baryta .... lead 260 100 152 88 122 38 54 124 119 57 161 71 132 161 166 82 74 280 102 172 86 106 53 71 114 150 70 64 84 84 93 120 138 192 255 88 lead .... magnesia .... Muriate of ammonia, (mur. a. 37-f- am. 17) .... Sulphate of alumina .... ammonia, c. 1 w. lime, c. 6 w. maganesia .... strontia, c. 8 w. Nitrate of ammonia, (nit. a. 54-f- am. 17) .... baryta .... bismuth, c. 3 w. Sulphate of copper, (sulph. a. 40-|- perox. 80) .... Bisulphate of copper V-- c. 10 w. (blue vitriol) Sulphate of iron, (protoxide) - c. 7 w. (green vitriol) lead ..... Nitrate of magnesia mercury, (protoxide) c. 2 w. - potassa .... lithia, c. 1 w. - magnesia, c. 7 w. mercury, (sulph. a. 40-f-peror. Bisulphate of mercury, (peroxide) Sulphate of potassa ... Bisulphate of potassa, c. 2 w. Sulphate of soda .... r in w . Oxalate of ammonia, (Ox. a. 36-f- am. 17) - - c.2w. .... strontia zinc > > c. 7w alumina and potassa c. 25 w. (alum) Nitrate of lead Binoxalate of baryta Oxalate of cobalt .... * v 1 potassa .... r 12 w Binoxalate of potassa - Bitartrate oi potassa ... c. 2 w. (cream of tartar) Tartrate of antimony and potassa, c. 3 w. (tartar emetic) Quadroxalate of potassa Oxalate of etrontia .... INDEX. Acetates Acetate of copper of lead - Acid, acetic antimonious - arsenic boracic - carbonic - chloric - chromic - citric - fluoric hydrocyanic - iodic meconic molybdic - muriatic nitric nitrous - nilro-muriatic - oxalic - oxymuriatic phosphoric - phosphorous prussic - pyroligneous sulphurous - sulphuric - tartaric tungstic vegetable - Agents, imponderable Air, atmospheric thermometer - Affinity, - chemical - double elective elective simple - Albumen Alcohol - Alembic Alkali, volatile - vegetable - Allanite - Alloys 300 Alum ----- 273 301 Alumina - - - - 237 300 299 Amalgams - Ammonia - 204 146 255 liquid - 147 250 muriate of - 286 163 149 Analysis of vegetables - of ^minerals 299 335 167 of waters 341 252 304 Animal chemistry oils - 321 323 173 heat - 328 191 Antimony - - - - 254 170 oxides of - 255 319 sulphuret of - 255 253 tartrate of - 302 166 Aqua fortis - - - - 144 144 regia - 211 143 Aqueous fusion - 267 126 Arrow root ... 308 301 Arsenic - 249 163 oxide of - 250 161 sulphurets of 251 162 test of - 250 191 white - - - - 250 300 Arsenites - 251 155 Atmospheric air - 135 157 302 254 composition of Atomic theory - Attraction 135 98 69 299 of cohesion 70 10 chemical 70 135 Azote 238 36 71 Balance, portable - 107 70 Balloons - - - - 124 73 Barium .... 225 73 protoxide of - 225 72 Barytes - 225 322 315 Barley, malting of - Barometer - - - - 313 105 101 thermometric 18 147 Bell glass - 106 318 Bismuth - - - - 259 256 oxide of - 259 202 flowers of 259 352 INDEX. Bismuth, magistery of - - 259 Chlorates - 279 Black lead Black oxide of manganese 245 - 241 Chlorate of potash Chlorides - - - - 280 279 Bleaching powder 229 Chloride of nitrogen 168 Blende - - 246 of calcium 231 Blood 323 of lime 229 Blowpipe, common - 102 Chlorine - 163 Gahn's 103 oxides of 167 compound - 129 Chlorine and oxygen 167 Blue, Prussian - 191 Chromium - 251 Bodies, elementary - 112 Chromate of lead - 252 ponderable 112 of iron 252 Boiling of liquids - Borates - 17,24 282 Chrome yellow - Cinchonia - 252 320 Borax - - 283 Cinnabar .... 204 Boron - 163 Coal gas - 304 Brass - - 246 Cobalt 257 Bromine - 172 oxides of - 256 arsenical - 257 Cadmium - 247 Cohesive attraction - 70 Calamine - - 246 Cold, artificial - 39 Calcium - 227 Colouring matter 309 oxide of - - 228 of the blood - 324 Calomel - 206 art of - 309 Caloric - 11 Colours, primary - 45 conductors of - 22 Columbium - 254 combined - - 13 Combination - 79 free - - 13 by volume 91 equilibrium of - 12 Common salt 223 expansion of - radiation 25 - 29 Combining proportions Combined caloric - 86 13 specific - 32 Combustion - 118 sources of - - 41 in oxygen - 119 of fluidity 13 spontaneous 311 capacity for - 32 Conductors of caloric 22 Canton's phosphorus - 46 Concave mirrors 29 Caoutchouc - 319 Copper - 260 Carbon 147 protoxide of 261 sulphnret of - 195 peroxide of - 262 Carbon and oxygen - Carbonic acid 149 - 149 sulphuret of - Copperas - 262 274 oxide - 154 Corrosive sublimate - 207 Carbonates - - 284 Cream of tartar - 302 Carbonate of potash - of soda - 285 - 285 Cryophorous - Crucible - 20 100 of lead - - 263 Crystallization - 267 Carburetted, hydrogen Caustic, lunar 175 - 278 water of - Cups, galvanic - 267 60 Cerium - 256 Cyanogen - 191 Cistern, pneumatic Chemical affinity - 131 70 Cyanuret of mercury 190 force of - - 83 Decomposition, double 76 combinations 79 Definite proportions 86 apparatus - 100 Decrepitatin - 267 equivalents - 93 Double salts - 269 Chemistry, definition of - 9 i Destructive distillation 304 INDEX. 353 Diamond ... - 147 Galena - - 262 Differential thermometer - 36 Galvanic battei^ ... 61 Dropping tube - 103 circle - 56 Diana's silver tree 208 trough - 59 Dolomite - - 46 poles - 58 cups ... 65 Earths - 236 pile - 57 Efflorescence - 268 Galvanism - 54 Elasticity, affects affinity Elective affinity - - 78 73 chemical effects of heating effects of - 61 68 double - 74 theory of - 55 Electricity - 48 discovery of - 48 conductors of - - 52 Gases, combine by volume - 91 theory of - 51 expand equally - 27 Electrics - - 49 their weight - 109 Electro-chemical theory 66 Gas, oxygen - ... 115 Elements - 9, 112 hydrogen - 122 their number 113 carbonic acid - 149 Emetic tartar - 303 carbonic oxide 154 Epsom salt - 272 chlorine - - - - 163 Equivalents - - 93 muriatic acid 166 scale of, - 96 fluoric acid - 173 Essential oils - 312 lights 183 Ether 316 olefiant - - - - 182 evaporation of - 21 nitrogen - - - 134 Etching on glass 174 nitrous oxide - 138 Eudiometry - - 142 Gas apparatus - 104 Extractive matter 309 Gelatine .... 322 Expansion by heat - 25 Germination - 290 of solids 25 Gilding - 311 of liquids - 27 Glass .... 240 of gases 28 Glauber's salt ... 270 Evaporation - 18 102 Glucina - Gold 238 210 vapoiatmg L\J^f etherial solution of 211 Fermentation - 313 Gravitation - - - - 70 saccharine - - 313 Gravity - - - - 79 vinous - 313 Growth of plants - 294 Fellincr colliery Fibrin - - - - 1 78 1 Gunpowder - 321 Gypsum ... 277 271 Fire damp - - 177 Fixed air - 149 Hartshorn .... 146 Fixed oils ... - 311 Heat ... 11 Florence flask - 102 animal - - - - 328 Friction - - 43 latent- ... 131 Flowers of sulphur - 155 matter of 11 zinc - 246 radiation of 28 Fluidity, caloric of - Fluoric acid - 13 - 173 Hydriodate of potash Hydriodic acid - 171 171 Fulminating powder - Food of plants 277 - 294 Hydro- nitric acid - - - Hydrogen - 145 122 Freezing mixtures 41 carburetted 175 Fluate of lime - 173 sulphuretted 187 Fowler's solution 251 phosphuretted - 189 Fusible alloy - Furnace, lamp - - 202 Hydrosulphurets 106jHydrosulphuretof otash 288 383 30* 354 INDEX. Ice cream - 40 Magnesia - . - 236 Imponderable agents - 10 sulphate of 272 Ink, indelible 278 Manganese ... 241 sympathetic 258 oxides of 241 Inorganic chemistry 1 15 1 Massicot .... 170 Matrass .... 263 100 Iodine - 169 Molasses - 307 lodic acid ... 170 Melting pot - 100 Iodine and hydrogen 171 Mercury 204 Iridium - ... 216 peroxide of 206 Iron 242 protochloride of 206 meteoric - 213 sulphuret of 207 oxides of 243 Metallic compounds - 201 rust of 213 salts 201 carburet of 244 alloys --- 202 sulphate of - 274 Metals 196 sulphuret of - 245 general properties of 197 tinned ... 248 how reduced 199 Isinglass .... 322 arrangement of 203 Ittria .... 000 fVuriVvn "tiViIf* 108 meteoric iron - uo 243 Kelp .... 386 Mineral green - 261 King's yellow ... 251 Mineral waters ... 340 Mirrors, concave - 20 Lamp, furnace ... 106 Mixtures - - - - 85 flameless 213 Mnlybdic acid - 253 safety ... 181 Molybdenum - - - 353 Latent heat - 13 Mordant .... 310 Laws of combination 86 Morphia - ... 319 of proportion 88 1 Mu! ti pie proportions 88 Lead 262 Muriates - 286 oxides of - 263 Muriatic acid ... 166 white - - - . 263 Musical tones ... 125 sulphuret of 264 poisonous 265 Narcotine .... 320 Lemons, salt of - 304 Nickel 258 Liquid ammonia - phosphorus 147 161 Nitrates - Nitric acid ... 275 144 Lio-lit - 44 i -j i ir\ decomposition of 44 aniiyurous . . oxide - L'iO 141 without heat O^ft effects of, on colors , 47 Nitrous acid - 143 effects of, on crystallization Light carburetted hydrogen 47 i oxide - 175 Nitrogen - 138 134 Lime - - ... 229 chloride of 168 chloride of - phosphuret of 229 234 and hydrogen Nomenclature - 146 110 water - 229 Non-metallic bodies - 115 carbonate of - 284 Liquids, expand by heat - conducting powers of 27 24 Oil gas - - - - Oil of vitriol - 184 157 Litharge .... 263 Oils, vegetable - 311 T 1 Lithium - 224 Olefiant gas - 183 Lunar caustic ... 278 Opium - 319 Magistery of bismuth - 259 Organic chemistry - Orpiment - 289 251 INDEX. 355 Osmium - - - - - 216 Respiration - - 325 Oxalates - 301 Receiver ... 101 Oxides, metallic - 198 Retort - - 101 Oxidation 112, 118, 198 Rhodium - 215 Oxygen gas - - 115 Rust of iron - - - - 243 combustion in - 119 Oxymuriatic acid - - 163 Saccharine fermentation - 313 Oxymuriate of potash 280 Safety lamp 181 Oxygenized water - 133 Sal-ammoniac - 286 Salifiable base - 265 Palladium ... - 215 Salt, common - 223 Pearlash - - - - 285 of sorrel 301 Phosphates - - 282 of lemons - 302 Phosphate of soda 282 Salts 265 Phosphoric acid - 161 remarks on - - 265 Phosphorus 160 nomenclature 110 Phosphorescence - - 45 Sap of plants - 296 Phosphuretted hydrogen - 189 Scale of equivalents - - 96, 346 Pile of Volta - 57 Sealing wax - - 318 Plants, growth of 294 Serum ... 323 Plants, food of - 294 Silica - - - - - 239 Plaster of Paris 271 Silicium - 238 Platinum ... - 212 Silver - ... - 208 sponge 126 solvent of - 208 protoxide of - 215 Silver tree - - 209 peroxide of - 215 Silvering powder 209 Pneumatic cistern - - 131 Simple bodies - 113 Plumbago - 245 Smalt ... 257 Ponderable bodies - - 112 Soda .... - 223 Potassa - 220 muriate of - 223 Potassium - - 271 carbonate of - - 285 oxide of - 220 Sodium - 221 Potato starch - 308 protoxide of - 222 Potash, carbonate of - 285 chloride of 223 Precipitate, red Proportions, definite - by volume - 206 86 - 91 Solar spectrum Solids expand by heat Solution ... - 45 25 - 77 how ascertained 95 Sources of caloric 43 Prussic acid - - 191 Spar, Derbyshire - - 284 Pyrites - ... 245 heavy 270 Pyrometer - - 25 Specific gravity of solids - 106 107 Quantity of matter - - 77 of liquids - - 108 Quicklime - 228 of gases 109 Quicksilver - - 204 Spirituous liquors - - 316 Quinia - 321 Sponge, platina 126 sulphate of - - 321 Starch .... - 308 Steam 15 Radiant heat - - 28 latent heat of - 16 Realger - ... 251 Steel - 244 Red oxide of copper - 261 Strontia ... - 227 lead --.. 264 Sugar, how made 307 precipitate - 206 of lead - 300 Reduction of metals - 199 Sulphates 269 Reflectors - - * - - 29 Sulphate of potash - 269 Resins .... 312 of soda 270 356 INDEX. Sulphate of baryta of lime - 270: Vapor 271 ' Van Helmont's willow - 19 294 of magnesia - - 272 Vegetation ... 291 of alumnia - 273, Vegetable acids - 299 of iron - - 274 alkalies 318 of zinc 275 chemistry 291 Sulphur ... - 154 analysis 291 Sulphurets ... Sulphuret of lead, - 201 - 264 ingredients of - Verdigris - 306 301 of arsenic 251 Verditer .... 261 of antimony - - 255 Vermilion ... 208 of iron 245 Vinegar .... 299 of copper - 195 Vinous fermentation - 313 of carbon - 296 Vitriol, green ... 274 Sulphurous acid - 155 white ... 275 Sulphuric acid - - - 157 Volumes, theory of 91 Sulphuretted hydrogen - Supporters of combustion - - 187 113 Volta'spile Volatile salt .... 57 147 Synthesis ... 9, 127 Water, decomposition of 63, 82, 122 Tannin ... - 310 composition of - 128 Tapioca - - - . 308 properties of - 131 Tartar emetic - 203 oxygenized 133 Tartar, cream of 302 weight of 132 Tartaric acid - 302 expands in freezing - 132 Tellurium - 260 of crystallization - 267 Temperature, animal Theory of atoms - 22,328 - 98 boiling temperature of analysis of - - 63, 17 335 Thermometer ... 35 synthesis of 127 differential - - 36 air 36 Wheat flour .... 309 construction of - 37 White arsenic ... 250 Tin 248 Wollaston's scale - - 96, 346 Titanium - 260 Wolfram .... 253 Tones, musical - - - 125 Trough, galvanic - - 59 Zinc .... 246 Tungsten - 253 oxide of ... 246 Tungstic acid - 254 flowers of - 246 Turpentine, oil of 313 alloy of - 246 Zaffree .... 257 Uranium ... - 256 Zirconia .... 23S Vacuum, boiling in - 17 Zero 3S YB 36016 Lih.