Silver is the whitest of all the metals, very ductile, but less so than gold; the thinnest leaves of it being one third thicker than those of gold. It is not calcined in the heat of a common furnace, but partially so by repeated fusion, or a strong burning lens.
Sulphureous fumes unite with silver, and tinge it black. The nitrous acid dissolves it, and will hold more than half its weight of it in solution. When fully saturated, this solution deposits crystals, which are called lunar nitre, or nitre of silver. When these crystals are melted, and the water they contain driven off, a black substance, called lapis infernalis, or lunar caustic, is formed. This is used as a cautery in surgery. A strong heat will decompose this lunar nitre, and recover the silver.
Though the nitrous acid dissolves silver the most readily, the marine acid will deprive the nitrous of it, and form a substance called luna cornea, because, when it is melted and cold, it becomes a transparent mass something resembling horn. From this luna cornea the purest silver may be obtained. The vitriolic acid will likewise deprive the nitrous of the silver contained in it, and form a white powder, not easily soluble in water.
A fulminating silver may be made by the following process: the silver must first be dissolved in pale nitrous acid, then precipitated by lime-water, dried, and exposed to the air three days. It must then be washed in caustic volatile alkali, after which the fluid must be decanted, and the black powder left to dry in the air. The slightest friction will cause this powder to fulminate. It is said, that even a drop of water falling upon it will produce this effect; so that it ought to be made only in very small quantities, and managed with the greatest caution.
Most of the metals precipitate silver. That by mercury may be made to assume the form of a tree, called arbor Dianæ.
Silver is found native in Peru; and the ores frequently contain sulphur, or arsenic, or both.
Platina is a metal lately discovered in the gold mines of Mexico, where it is found in small particles, never exceeding the size of a pea, mixed with ferruginous sand and quartz.
The strongest fire will not melt these grains, though it will make them cohere; but they may be melted by a burning lens, or a blow-pipe supplied with dephlogisticated air.
Pure platina is the heaviest body in nature, its specific gravity exceeding twenty-two. It is very malleable, though considerably harder than gold or silver, and has the property of welding in common with iron. This metal is not affected by exposure to the air, or by any simple acid, though concentrated and hot; but it is dissolved by dephlogisticated marine acid, and by aqua regia, in which a little nitrous air is procured. The solution is brown, and when diluted yellow. This liquor is very corrosive, and tinges animal substances of a blackish brown colour. Platina is precipitated from a solution in aqua regia by sal-ammoniac, as gold is by martial vitriol. Iron is precipitated from this solution by the Prussian alkali. Also most of the metals precipitate platina, but not in its metallic state.
Arsenic facilitates the solution of platina; and by melting it with equal parts of arsenic and vegetable alkali, and then reducing the mass to a powder, it may be made to take any form; and a strong heat will dissipate the arsenic and the alkali, leaving the platina in the shape required, not fusible by any heat in a common furnace.
Platina does not readily combine with gold or silver, and it resists the action of mercury as much as iron; but it mixes well with lead, making it less ductile, and even brittle, according to the proportion of the platina. With copper it forms a compound which takes a beautiful polish, not liable to tarnish, and is therefore used with advantage for mirrors of reflecting telescopes. It unites easily with tin, and also with bismuth, antimony, and zinc.
Mercury is the most fusible of all the metals, not becoming solid but in 40° below 0 in Fahrenheit's thermometer. It is then malleable. It is heavier than any other metal except gold or platina. It is volatile in a temperature much lower than that of boiling water, and in vacuo in the common temperature of the atmosphere; and at six hundred it boils.
In a degree of heat in which it would rise easily in vapour, mercury imbibes pure air, and becomes a red calx, called precipitate per se. At a greater degree of heat it parts with that air, and is running mercury again.
Mercury is not perceptibly altered by exposure to the air.
Mercury is acted upon by the vitriolic acid when hot. In this process vitriolic acid air is procured, and the mercury is converted into a white substance, which being dipped in water becomes yellow, called turbith mineral, one third heavier than the mercury from which it was made. By heat this substance parts with its pure air, and becomes running mercury; but if the process be made in a clean earthen vessel, there will remain a portion of red calx, which cannot be reduced by any degree of heat, except in contact with some substance containing phlogiston. If this be done with a burning lens, in inflammable air, much of the air will be absorbed.
Mercury is dissolved most readily in the nitrous acid, when the purest nitrous air is procured; and there remains a substance which is first yellow, and by continuance red, called red precipitate. In a greater degree of heat the dephlogisticated air will be recovered, and the mercury be revived; but the substance yields nitrous air after it becomes solid, and till it changes from yellow to red.
The precipitates of mercury from acids by means of alkalies possess the property of exploding, when they are exposed to a gradual heat in an iron spoon, after having been triturated with one sixth of their weight of the flowers of sulphur. The residuum consists of a violet-coloured powder, which, by sublimation, is converted into cinnabar.
It seems, therefore, as if the sulphur combined suddenly with the mercury, and expelled the dephlogisticated air in an elastic state.
The marine acid seizes upon mercury dissolved in nitrous acid, and if the acid be dephlogisticated, the precipitate is corrosive sublimate; but with common marine acid, it is called calomel, or mercurius dulcis. This preparation is generally made in the dry way, by triturating equal parts of mercury, common salt and vitriol, and exposing the whole to a moderate heat; when the corrosive sublimate rises, and adheres to the upper part of the glass vessel in which the process is made.
Mercury combines readily with sulphur by trituration, and with it forms a black powder called Ethiops mineral. A more intimate combination of mercury and sulphur is made by means of fire. This is called cinnabar, about one third of which is sulphur. Vermillion is cinnabar reduced to powder.
Mercury readily unites with oil, and with it forms a deep black or blue compound, used in medicine.
It readily combines with most of the metals, and when it is used in a sufficient quantity to make them soft, the mixture is called an amalgam. It combines most readily with gold, silver, lead, tin, bismuth, and zinc. Looking-glasses are covered on the back with an amalgam of mercury and tin.
When mercury is united with lead or other metals, it is rendered less brilliant and less fluid; but agitation in pure air converts the impure metal into a calx, together with much of the mercury, in the form of a black powder.
Heat recovers the pure air, and the mercury, leaving the calx of the impure metal.
Much mercury is found native in a slaty kind of earth, or in masses of clay or stone; but the greatest quantity is found combined with sulphur in native cinnabar.
Lead is a metal of a bluish tinge, of no great tenacity, but very considerable specific gravity, being heavier than silver. It melts long before it is red hot, and is then calcined, if it be in contact with respirable air. When boiling it emits fumes, and calcines very rapidly. It may be granulated by being poured into a wooden box, and agitated. During congelation it is brittle, so that the parts will separate by the stroke of a hammer; and by this means the form of its crystals may be discovered.
In the progress of calcination it first becomes a dusky grey powder, then yellow, when it is called massicot; then, by imbibing pure air, it becomes red, and is called minium, or red lead. In a greater degree of heat it becomes massicot again, having parted with its pure air. If the heat be too great, and applied rapidly, it becomes a flaky substance, called litharge; and with more heat it becomes a glass, which readily unites with metallic calces and earths, and is a principal ingredient in the manufacture of flint glass, giving it its peculiar density and refractive power.
Though lead soon tarnishes, the imperfect calx thus made does not separate from the rest of the metal, and therefore protects it from any farther action of the air, by which means it is very useful for the covering of houses, and other similar purposes. All acids act upon lead, and form with it different saline substances. White-lead consists of its union with vinegar and pure air. Also dissolved in vinegar, and crystallized, it becomes sugar of lead, which, like all the other preparations of this metal, is a deadly poison.
Oils dissolve the calces of lead, which, by this means, is the basis of paints, plaisters, &c.
By means of heat litharge decomposes common salt, the lead uniting with the marine acid, and forming a yellow substance, used in painting, and by this means the fossil alkali is separated.
Lead unites with most metals, though not with iron. Two parts of lead and one of tin make a solder, which melts with less heat than either of the metals separately; but a composition of eight parts of bismuth, five of lead, and three of tin, makes a metal which melts in boiling water.
This metal will be dissolved by water if it contain any saline matter, and the drinking of it occasions a peculiar kind of cholic.
Lead is sometimes found native, but generally minerally mineralized with sulphur or arsenic, and often mixed with a small quantity of silver.
Copper is a metal of a reddish or brownish colour, considerably sonorous, and very malleable.
At a heat far below ignition, the surface, of copper becomes covered with a range of prismatic colours, the commencement of its calcination; and with more heat a black scale is formed, which easily separates from the metal, and in a strong heat it melts, and burns with a bluish green flame.
Copper rusts by exposure to the air; but the partially-calcined surface adheres to the metal, as in the case of lead, and thus preserves it from farther corrosion.
Copper dissolved in the vitriolic acid forms crystals of a blot colour, called blue copperas. From this solution it is precipitated by iron, which by this means becomes coated with copper. The nitrous acid dissolves copper with most rapidity, producing nitrous air. If the solution be distilled, almost all the acid will be retained in the residuum, which is white; but more heat will expel the acid, chiefly in the form of dephlogisticated air, and the remainder will be a black substance, consisting of the pure calx of copper. The vegetable acids dissolve copper as well as the mineral ones, which makes the use of this metal for culinary purposes in some cases dangerous. To prevent this they give it a coat of tin. The solution of copper in the vegetable acid is called verdigris.
Alkalies dissolve copper as well as acids. With the volatile alkali a blue liquor is formed, but in some cases it becomes colourless. All the circumstances of this change of colour have not yet been examined. Both oil and sulphur will dissolve copper, and with the latter it forms a blackish grey compound, used by dyers.
Copper readily unites with melted tin, at a temperature much lower than that which is necessary to melt the copper; by which means copper vessels are easily covered with a coating of tin. A mixture of copper and tin, called bronze, the specific gravity of which is greater than that of the medium of the two metals, is used in casting statues, cannon, and bells; and in a certain proportion this mixture is excellent for the purpose of mirrors of reflecting telescopes, receiving a fine polish, and not being apt to tarnish. Copper and arsenic make a brittle compound called tombach; and with zinc it makes the useful compound commonly called brass, in which zinc is about one third of its weight.
Copper is sometimes found native; but commonly mixed with sulphur, in ores of a red, green, or blue colour.
Copper being an earlier discovery than that of iron, was formerly used for weapons and the shoeing of horses; and the ancients had a method, with which we are not well acquainted, of giving it a considerable degree of hardness, so that a sword made of it might have a pretty good edge.
Iron is a metal of a bluish colour, of the greatest hardness, the most variable in its properties, and the most useful of all the metals; so that without it it is hardly possible for any people to make great advances in arts and civilization.
This metal readily parts with its phlogiston, so as to be very subject to calcine, or rust, by exposure to the air. The same is evident by the colours which appear on its surface when exposed to heat, and also when it is struck with flint; the particles that fly from it being iron partially calcined. In consequence of its readily parting with its phlogiston, it is capable of burning, like wood or other fuel, in pure air.
Iron and platina have the property of welding when very hot, so that two pieces may be joined without any solder.
When iron is heated in contact with steam, part of the water takes the place of the phlogiston, while the rest unites with it, and makes inflammable air. By this means the iron acquires one third more weight, and becomes what is called finery cinder. This substance, heated in inflammable air, imbibes it, parts with its water, and becomes perfect iron again. If the iron be heated in pure air, it also imbibes the water, of which that air chiefly consists, and also a portion of the peculiar element of the pure air.
The solution of iron in spirit of vitriol produces green copperas; which being calcined, becomes a red substance, called colcothar.
The precipitate of iron, by an infusion of galls, is the colouring matter in ink, which is kept suspended by means of gum. The precipitate from the same solution by phlogisticated alkali, is Prussian blue.
Water saturated with fixed air dissolves iron, and makes a pleasant chalybeat.
The calx of iron gives a green colour to glass.
Iron readily combines with sulphur. When they are found combined by nature, the substance is called pyrites.
The union of phosphoric acid with iron makes it brittle when cold, commonly called cold short; and the union of arsenic makes it brittle when hot, thence called red short.
Iron unites with gold, silver, and platina, and plunged in a white heat into mercury, it becomes coated with it; and if the process be frequently repeated, it will become brittle, which shews that there is some mutual action between them.
Iron readily unites with tin; and by dipping thin plates of iron into melted tin, they get a complete coating of it, and make the tinned plates in common use.
When crude iron comes from the smelting furnace it is brittle; and when it is white within, it is extremely hard; but when it has a black grain, owing to its having more phlogiston, it is softer, and may be filed and bored.
Cast iron becomes malleable by being exposed to a blast of air when nearly melting; the consequence of which is a discharge of inflammable air, and the separation of a liquid substance, which, when concreted, is called finery cinder. The iron generally loses one fourth of its weight in the process. Crude iron contains much plumbago, and the access of pure air probably assists in discharging it, by converting it into air, chiefly inflammable.
Malleable iron, exposed to a red heat in contact with charcoal, called cementation, converts it into steel, which has the properties of becoming much harder than iron, and very elastic, by being first made very hot, and then suddenly cooled, by plunging it in cold water. By first making it very hard, and then giving different degrees of heat, and cooling it in those different degrees, it is capable of a great variety of tempers, proper for different uses. Of the degrees of heat workmen judge by the change of colour on its surface. Steel, like crude iron, is capable of being melted without losing its properties. It is then called cast steel, and is of a more uniform texture. Iron acquires some little weight by being converted into steel; and when dissolved in acid, it yields more plumbago. Steel has something less specific gravity than iron. If the cementation be continued too long, the steel acquires a darkish fracture, it is more fusible, and incapable of welding. Steel heated in contact with earthy matters, is reduced to iron.
Iron is the only substance capable of magnetism; and hardened steel alone is capable of retaining magnetism. The loadstone is an ore of iron.
Tin is a metal of a slightly yellowish cast, though harder than lead, very malleable, but of no great tenacity; so that wires cannot be made of it. It easily extends under the hammer, and plates of it, called tinfoil, are made only one thousandth part of an inch thick, and might be made as thin again.
Tin has less specific gravity than any other metal. It melts long before ignition, at 410 of Fahrenheit, and by the continuance of heat is slowly converted into a white powder, which is the chief ingredient in putty, used in polishing, &c. Like lead, it is brittle when heated little short of fusion, and may be reduced into grains by agitation as it passes from a fluid to a solid state.
The calx of tin resists fusion more than that of any other metal, which makes it useful in making an opaque white enamel.
Tin loses its bright surface when exposed to the air, but is not properly subject to rust; so that it is useful in protecting iron and other metals from the effects of the atmosphere.
Concentrated vitriolic acid, assisted by heat, dissolves half its weight of tin, and yields vitriolic acid air. With more water it yields inflammable air. During the solution the phlogiston of the tin uniting with the acid, forms sulphur, which makes it turbid. By long standing, or the addition of water, the calx of tin is precipitated from the solution. The nitrous acid dissolves tin very rapidly without heat, and yields but little nitrous air. With marine acid this metal yields inflammable air. With aqua regia it assumes the form of a gelatinous substance used by dyers to heighten the colour of some red tinctures, so as to produce a bright scarlet in dying wool.
A transparent liquor, which emits very copious fumes, called, from the inventor, the smoking liquor of Libavius, is made by distilling equal parts of amalgam of tin and mercury with corrosive sublimate, triturated together. A colourless liquor comes over first, and then a thick white fume, which condenses into the transparent liquor above mentioned. Mr. Adet has shewn, that this liquor bears the same relation to the common solution of tin, that corrosive sublimate does to calomel, and has given an ingenious solution of many of its properties.
Tin detonates with nitre; and if the crystals made by the solution of copper in the nitrous acid be inclosed in tinfoil, nitrous fumes will be emitted, and the whole will become red hot. Also if five times its weight of sulphur be added to melted tin, a black brittle compound, which readily takes fire, will be formed.
Another combination of tin, sulphur, and mercury, makes a light yellow substance called aurum musivum used in painting.
Tin is the principal ingredient in the composition of pewter, the other ingredients being lead, zinc, bismuth, and copper; each pewterer having his peculiar receipt. It is also used in coating copper and iron plates, and in silvering looking-glasses, besides being cast into a variety of forms, when it is called block tin.
Tin is sometimes found native, but is generally mineralized with sulphur and arsenic. The latter is thought to be always contained in tin, and to be the cause of the crackling noise made by bending plates of it.
Bismuth is a semi-metal of a yellowish or reddish cast, but little subject to change in the air; harder than lead, but easily broken, and reducible to powder. When broken it exhibits large shining facets, in a variety of positions. Thin pieces of it are considerably sonorous.
Bismuth melts at about 460° of Fahrenheit. With more heat it ignites, and burns with a slight blue flame, while a yellowish calx, called flowers of bismuth, is produced. With more heat it becomes a greenish glass. In a strong heat, and in close vessels, this metal sublimes.
Vitriolic acid, even concentrated and boiling, has but little effect upon bismuth; but the nitrous acid acts upon it with the greatest rapidity and violence, producing much nitrous air, mixed with phlogisticated nitrous vapour. From the solution of bismuth in this acid, a white substance, called magistery of bismuth, is precipitated by the affusion of water. This has been used as a paint for the skin but has been thought to injure it.
The marine acid does not readily act upon bismuth; but when concentrated, it forms with it a saline combination, which does not easily crystallize, but may be sublimed in the form of a soft fusible salt, called butter of bismuth.
Bismuth unites with most metallic substances, and in general renders them more fusible. When calcined with the imperfect metals, it unites with them, and has the same effect as lead in cupellation.
Bismuth is used in the composition of pewter, in printers' types, and other metallic mixtures.
This metal is sometimes found native, but more commonly mineralized with sulphur.
Nickel is a semi-metal of a reddish cast, of great hardness, and always magnetical; on which account it is supposed to contain iron, though chemists have not yet been able to separate them.
The purest nickel was so infusible as not to run into a mass in the strongest heat of a smith's forge; but then it was in some degree malleable.
Concentrated acid of vitriol only corrodes nickel. Alkalies precipitate it from its solution in the nitrous acid, and dissolve the precipitate. It readily unites with sulphur.
Nickel is found either native or mineralized with several other metals, especially with copper, when it is called kupfer nickel, or false copper, being of a reddish or copper colour.
This semi-metal has not yet been applied to any use.
What is commonly called arsenic is the calx of a semi-metal called the regulus of arsenic. It is a white and brittle substance, expelled from the ores of several metals by heat. It is then refined by a second sublimation, and melted into the masses in which it is commonly sold. This calx is soluble in about eighty times its weight of cold water, or in fifteen times its weight of boiling water. It acts in many respects like an acid, as it decomposes nitre by distillation, when the nitrous acid flies off, and the arsenical salt of Macquer remains behind.
When the calx of arsenic is distilled with sulphur, the vitriolic acid flies off, and a substance of a yellow colour, called orpiment, is produced. This appears to consist of sulphur and the regulus of arsenic; part of the sulphur receiving pure air from the calx, to which it communicates phlogiston; and thus the sulphur becomes converted into vitriolic acid, while the arsenical calx is reduced, and combines with the rest of the sulphur.
The combination of sulphur and arsenic, by melting them together, is of a red colour, known by the name of realgal, or realgar. It is less volatile than orpiment.
The solution of fixed alkali dissolves the calx of arsenic, and by means of heat a brown tenacious mass is produced, and having also a disagreeable smell, it is called liver of arsenic.
The regulus of arsenic is of a yellow colour, subject to tarnish or grow black, by exposure to the air, very brittle, and of a laminated texture. In close vessels it wholly sublimes, but burns with a small flame in pure air.
Vitriolic acid has little action upon this semi-metal, except when hot; but the nitrous acid acts readily upon it, and likewise dissolves the calx, as does boiling marine acid, though it affects it very little when cold.
Most of the metals unite with the regulus of arsenic.
Dephlogisticated marine acid converts the calx of arsenic into arsenical acid by giving it pure air.
The acid of arsenic acts more or less upon all metals, but the phenomena do not appear to be of much importance.
The calx of acid is used in a variety of the arts, especially in the manufactory of glass. Orpiment and realgar are used as pigments. Some attempts have been made to introduce it into medicine, but being dangerous, the experiments should be made with caution.
Cobalt is a semi-metal of a grey or steel colour, of a close-grained fracture, more difficult of fusion than copper, not easily calcined. It soon tarnishes in the air, but water has no effect upon it.
Cobalt, dissolved in aqua regia, makes an excellent sympathetic ink, appearing green when held to the fire, and disappearing when cold, unless it has been heated too much, when it burns the paper.
The calx of cobalt is of a deep blue colour, which, when fused, makes the blue glass called smalt. The ore of cobalt, called zaffre, is found in several parts of Europe, but chiefly in Saxony. As it is commonly sold, it contains twice or thrice its weight of powder of flints. The smalt is usually composed of one part of calcined cobalt, fused with two parts of powder of flint and one of pot-ash.
The chief use of cobalt is for making smalt; but the powder and the blue-stone used by laundresses is a preparation made by the Dutch of a coarse kind of smalt.
Zinc is a semi-metal of a bluish cast, brighter than lead, and so far malleable as not to be broken by a hammer, though it cannot be much extended. When broken by bending, it appears to consist of cubical grains. If it be heated nearly to melting, it will be sufficiently brittle to be pulverized. It melts long before ignition, and when it is red hot, it burns with a dazzling white flame, and is calcined with such rapidity, that its calx flies up in the form of white flowers, called flowers of zinc, or philosophical wool. In a stronger heat they become a clear yellow glass. Heated in close vessels, this metal rises without decomposition, being the most volatile of all the metals except the regulus of arsenic.
Zinc dissolved in diluted vitriolic acid, yields much inflammable air, and has a residuum, which appears to be plumbago, and the liquor forms crystals, called white copperas. This metals also yields inflammable air when dissolved in the marine acid. Dissolved in the nitrous acid, it yields dephlogisticated nitrous air, with very little proper nitrous air.
The ore of zinc, called calamine, is generally of a white colour; and the chief use of it is to unite it with copper, with which it makes brass and other gold-coloured mixtures of metals. The calx and the salts of this metal are occasionally used in medicine.
The regulus of antimony is of a silvery white colour, of a scaly texture, very brittle, and melts soon after ignition. By continuance of heat it calcines in white fumes, called argentine flowers of antimony, which melt into a hyacinthine glass. In close vessels it rises without decomposition. Its calx is soluble in water, like that of arsenic. This metal tarnishes, but does not properly rust, by exposure to the air.
This metal is soluble in aqua regia. It detonates with nitre, and what remains of equal parts of nitre and regulus of antimony after detonation, in a hot crucible, is called diaphoretic antimony. The water used in this preparation contains a portion of the calx suspended by the alkali, and being precipitated by an acid, is called ceruse of antimony.
When regulus of antimony is pulverized and mixed with twice its weight of corrosive sublimate (which is attended with heat) and then distilled with a gentle fire, a thick fluid comes over, which is congealed in the receiver, or in the neck of the retort, and is called butter of antimony. The residuum consists of revived mercury, with some regulus and calx of antimony. When this butter of antimony is thrown into pure water, there is a white precipitate, called powder of algaroth, a violent emetic. Nitrous acid dissolves the butter of antimony; and when an equal weight of nitrous acid has been three times distilled to dryness from butter of antimony, the residuum, after ignition, is called bezoar mineral, and seems to be little more than a calx of the metal.
Crude antimony, which has been much used in the experiments of alchemists, is a combination of sulphur and regulus of antimony. Heat melts it, and finally converts it into glass, of a dark red colour, called liver of antimony. If antimony be melted or boiled with a fixed alkali, a precipitate is made by cooling, called kermes mineral, formerly used in medicine. The antimonial preparations that are now most in use are antimonial wine and tartar emetic. The wine is made by infusing pulverized glass of antimony in Spanish wine some days, and filtering the clear fluid through paper. The emetic tartar, or antimonial tartar, is a saline substance, composed of acid of tartar, vegetable alkali, and antimony partially calcined. The preparation may be seen in the Dispensaries.
The regulus of antimony is used in the form of pills, which purge more or less in proportion to the acid they meet with; and as they undergo little or no change in passing through the body, they are called perpetual pills.
Manganese is a hard, black mineral, very ponderous, and the regulus of it is a semi-metal of a dull white colour when broken, but soon grows dark by exposure to the air. It is hard and brittle, though not pulverizable, rough in its fracture, and of very difficult fusion. Its calces are white when imperfect, but black, or dark green, when perfect. The white calx is soluble in acids. When broken in pieces, it falls into powder by a spontaneous calcination, and this powder is magnetical, though the mass was not possessed of that property. The black calx of manganese is altogether insoluble in acids. It contains much dephlogisticated air.
The calx of manganese is used in making glass; the glass destroying the colour of that of the other materials, and thereby making the whole mass transparent.
This semi-metal mixes with most of the metals in fusion, but not with mercury.
There is another ore of manganese, called black woad, which inflames spontaneously when mixed with oil.
Wolfram is a mineral of a brownish or black colour, found in the tin mines of Cornwall, of a radiated or foliated texture, shining almost like a metal. It contains much of the calx of manganese, and iron; but when the substance is pulverized, these are easily dissolved, and the calx of wolfram is found to be yellow.
This calx turns blue by exposure to light; and an hundred grains of it heated with charcoal will yield sixty grains of a peculiar metal, in small particles, which, when broken, look like steel. It is soluble in the vitriolic or marine acids, and reduced to a yellow calx by nitrous acid or aqua regia.
Molybdena is a substance which much resembles plumbago; but its texture is scaly, and not easily pulverized, on account of a degree of flexibility which its laminæ possess. With extreme heat, and mixed with charcoal, it yields small particles of a metal that is grey, brittle, and extremely infusible; and uniting with several of the metals, it forms with them brittle or friable compounds. By heat it is converted into a white calx.
There yet remains a class of solid substances, of the combustible kind, but most of them have been already considered under the form of the fluids, from which they are originally formed, as bitumen, pit-coal, and amber; or under the principal ingredients of which they are composed, as sulphur and plumbago.
There only remains to be mentioned the diamond, which is of a nature quite different from that of the other precious stones, the principal ingredient in which is siliceous earth, which renders them not liable to be much affected by heat. On the contrary, the diamond is a combustible substance; for in a degree of heat somewhat greater than that which will melt silver, it burns with a slight flame, diminishes common air, and leaves a soot behind. Also, if diamond powder be triturated with vitriolic acid, it turns it black, which is another proof of its containing phlogiston.
The diamond is valued on account of its extreme hardness, the exquisite polish it is capable of, and its extraordinary refractive power; for light falling on its interior surface with an angle of incidence greater than 24½ will be wholly reflected, whereas in glass it requires an angle of 41 degrees.
It was supposed to be a great discovery of Mr. Stahl, that all inflammable substances, as well as metals, contain a principle, or substance, to which he gave the name of phlogiston, and that the addition or deprivation of this substance makes some of the most remarkable changes in bodies, especially that the union of a metallic calx and this substance makes a metal; and that combustion consists in the separation of phlogiston from the substances that contain it. That it is the same principle, or substance, that enters into all inflammable substances, and metals, is evident, from its being disengaged from any of them, and entering into the composition of any of the others. Thus the phlogiston of charcoal or inflammable air becomes the phlogiston of any of the metals, when the calx is heated in contact with either of them.
On the contrary, Mr. Lavoisier and most of the French chemists, are of opinion, that there is no such principle, or substance, as phlogiston; that metals and other inflammable bodies are simple substances, which have an affinity to pure air; and that combustion consists not in the separation of any thing from the inflammable substance, but in the union of pure air with it.
They moreover say, that water is not, as has been commonly supposed, a simple substance, but that it consists of two elements, viz. pure air, or oxygene, and another, to which they give the name of hydrogene, which, with the principle of heat, called by them calorique, is inflammable air.
The principal fact adduced by them to prove that metals do not lose any thing when they become calces, but only gain something, is, that mercury becomes a calx, called precipitate per se, by imbibing pure air, and that it becomes running mercury again by parting with it.
This is acknowledged: but it is almost the only case of any calx being revived without the help of some known phlogistic substance; and in this particular case it is not absurd to suppose, that the mercury, in becoming precipitate per se, may retain all its phlogiston, as well as imbibe pure air, and therefore be revived by simply parting with that air. In many other cases the same metal, in different states, contains more or less phlogiston, as cast iron, malleable iron, and steel. Also there is a calx of mercury made by the acid of vitriol, which cannot be revived without the help of inflammable air, or some other substance supposed to contain phlogiston: and that the inflammable air is really imbibed in these processes, is evident, from its wholly disappearing, and nothing being left in the vessel in which the process is made beside the metal that is revived by it. If precipitate per se be revived in inflammable air, the air will be imbibed, so that running mercury may contain more or less phlogiston.
The antiphlogistians also say, that the diminution of atmospherical air by the burning of phosphorus is a proof of their theory; the pure air being imbibed by that substance, and nothing emitted from it. But there is the same proof of phosphorus containing phlogiston, that there is of dry flesh containing it; since the produce of the solution of it in nitrous acid, and its effect upon the acid, are the same, viz. the production of phlogisticated air, and the phlogistication of the acid.
Their proof that water is decomposed, is, that in sending steam over hot iron, inflammable air (which they suppose to be one constituent part of it) is procured; while the other part, viz. the oxygene, unites with the iron, and adds to its weight. But it is replied, that the inflammable air may be well supposed to be the phlogiston of the iron, united to part of the water, as its base, while the remainder of the water is imbibed by the calx; and that it is mere water, and not pure air, or oxygene, that is retained in the iron, is evident, from nothing but pure water being recovered when this calx of iron is revived in inflammable air, in which case the inflammable air wholly disappears, taking the place of the water, by which it had been expelled.
In answer to this it is said, that the pure air expelled from the calx uniting with the inflammable air in the vessel, recomposes the water found after this process. But in every other case in which any substance containing pure air is heated in inflammable air, though the inflammable air be in part imbibed, some fixed air is produced, and this fixed air is composed of the pure air in the substance and part of the inflammable air in the vessel. Thus, if minium, which contains pure air, and massicot, which contains none, be heated in inflammable air, in both the cases lead will be revived by the absorption of inflammable air; but in the former case only, and not in the latter, will fixed air be produced. The calx of iron, therefore, having the same effect with massicot, when treated in the same manner, appears to contain no more pure air than massicot does.
Besides this explanation of the facts on which the new theory is founded, which shews it to be unnecessary, the old hypothesis being sufficient for the purpose, some facts are alledged, as inconsistent with the new doctrine.
If the calx of iron made by water, and charcoal made by the greatest degree of heat, be mixed together, a great quantity of inflammable air will be produced; though, according to the new theory, neither of these substances contained any water, which they maintain to be the only origin of it. But this fact is easily explained upon the doctrine of phlogiston; the water in this calx uniting with the phlogiston of the charcoal, and then forming inflammable air; and it is the same kind of inflammable air that is made from charcoal and water.
Also the union of inflammable and pure air, when they are fired together by means of the electric spark, produces not pure water, as, according to the new theory, it ought to do, but nitrous acid.
To this it has been objected, that the acid thus produced came from the decomposition of phlogisticated air, a small portion of which was at first contained in the mixture of the two kinds of air. But when every particle of phlogisticated air is excluded, the strongest acid is procured.
They find, indeed, that by the slow burning of inflammable air in pure air, they get pure water. But then it appears, that whenever this is the case, there is a production of phlogisticated air, which contains the necessary element of nitrous acid; and this is always the case when there is a little surplus of the inflammable air that is fired along with the pure air, as the acid is always procured when there is a redundancy of pure air.
That much water should be procured by the decomposition of these kinds of air, is easily accounted for, by supposing that water, or steam, is the basis of these, as well as of all other kinds of air.
Since air something better than that of the atmosphere is constantly produced from water by converting it into vapour, and also by removing the pressure of the atmosphere, and these processes do not appear to have any limits; it seems probable, that water united to the principle of heat; constitutes atmospherical air; and if so, it must consist of the elements of both dephlogisticated and phlogisticated air; which is a supposition very different from that of the French chemists.
Heat is an affection of bodies well known by the sensation that it excites. It is produced by friction or compression, as by the striking of flint against steel, and the hammering of iron, by the reflection or refraction of light, and by the combustion of inflammable substances.
It has been long disputed, whether the cause of heat be properly a substance, or some particular affection of the particles that compose the substance that is heated. But be it a substance, or a principle of any other kind, it is capable of being transferred from one body to another, and the communication of it is attended with the following circumstances. All substances are expanded by heat, but some in a greater degree than others; as metals more than earthy substances, and charcoal more than wood. Also some receive and transmit heat through their substance more readily than others; metals more so than earths, and of the metals, copper more readily than iron. Instruments contrived to ascertain the expansion of substances by heat, are called pyrometers, and are of various constructions.
As a standard to measure the degrees of heat, mercury is in general preferable to any other substance, on account of its readily receiving, and communicating, heat through its whole mass. Thermometers, therefore, or instruments to measure the degrees of heat, are generally constructed of it, though, as it is subject to become solid in a great degree of cold, ardent spirit, which will not freeze at all, is more proper in that particular case.
The graduation of thermometers is arbitrary. In that of Fahrenheit, which is chiefly used in England, the freezing point of water is 32°, and the boiling point 212°. In that of Reaumur, which is chiefly used abroad, the freezing point of water is 0, and the boiling point 80. To measure the degrees of heat above ignition, Mr. Wedgwood has happily contrived to use pieces of clay, which contract in the fire; and he has also been able to find the coincidence of the degrees in mercurial thermometers with those of his own.
To measure the degrees of heat and cold during a person's absence, Lord George Cavendish contrived an instrument, in which a small bason received the mercury, that was raised higher than the place for which it was regulated by heat or cold, without a power of returning. But Mr. Six has lately hit upon a better method, viz. introducing into the tube of his thermometer a small piece of iron, which is raised by the ascent of the mercury, and prevented from descending by a small spring; but which may be brought back to its former place by a magnet acting through the glass.
Heat, like light, is propagated in right lines; and what is more remarkable, cold observes the same laws. For if the substance emitting heat without light, as iron below ignition, be placed in the focus of a burning mirror, a thermometer in the focus of a similar mirror, placed parallel to it, though at a considerable distance, will be heated by it, and if a piece of ice be placed there, the mercury will fall.
Heat assists the solvent power of almost all menstrua; so that many substances will unite in a certain degree of heat, which will form no union at all without it, as dephlogisticated and inflammable air.
If substances be of the same kind, they will receive heat from one another, in proportion to their masses. Thus, if a quantity of water heated to 40° be mixed with another equal quantity of water heated to 20°, the whole mass will be heated to 30°. But if the substances be of different kinds, they will receive heat from each other in different proportions, according to their capacity (as it is called) of receiving heat. Thus, if a pint of mercury of the temperature of 136 be mixed with a pint of water of the temperature of 50, the temperature of the two after mixture will not be a medium between those two numbers, viz. 93, but 76; consequently the mercury was cooled 60°, while the water was heated only 26; so that 26 degrees of heat in water correspond to 60 in mercury. But mercury is about 13 times specifically heavier than water, so that an equal weight of mercury would contain only one thirtieth part of this heat; and dividing 26 by 13, the quotient is 2. If weight, therefore, be considered, the heat discovered by water should be reckoned as 2 instead of 60; and consequently when water receives 2 degrees of heat, an equal weight of mercury will receive 60°; and dividing both the numbers by 2, if the heat of water be 1, that of the mercury will be 30. Or since they receive equal degrees of heat, whether they discover it or not (and the less they discover, the more they retain in a latent state) a pound of mercury contains no more than one thirtieth part of the heat actually existing in a pound of water of the same temperature. Water, therefore, is said to have a greater capacity for receiving and retaining heat, without discovering it, than mercury, in the proportion of 30 to 1, if weight be considered, or of 60 to 26, that is of 30 to 13; if bulk be the standard, though, according to some, it is as 3 to 2.
The capacity of receiving heat in the substance is greatest in a state of vapour, and least in that of a solid; so that when ice is converted into water, heat is absorbed, and more still when it is converted into vapour; and on the contrary, when vapour is converted into water, it gives out the heat which it had imbibed, and when it becomes ice it gives out still more.
If equal quantities of ice and water be exposed to heat at the temperature of 32°, the ice will only become water, without receiving any additional sensible heat; but an equal quantity of water in the same situation would be raised to 178°, so that 146 degrees of heat will be imbibed, and remain in latent in the water, in consequence of its passing from a state of ice: and heat communicated by a given weight of vapour will raise an equal weight of a nonevaporable substance, of the same capacity with water, 943 degrees; so that much more heat is latent in steam, than in the water from which it was formed.
This doctrine of latent heat explains a great variety of phænomena in nature; as that of cooling bodies by evaporation, the vapour of water, or any other fluid substance, absorbing and carrying off the heat they had before.
Water, perfectly at rest, will fall considerably below the freezing point, and yet continue fluid: but on the slightest agitation, the congelation of the whole, or part of it, takes place instantly, and if the whole be not solid, it will instantly rise to 32°, the freezing point. From whatever cause, some motion seems necessary to the commencement of congelation, at least in a moderate temperature; but whenever any part of the water becomes solid, it gives out some of the heat it had before, and that heat which was before latent becoming sensible, and being diffused through the whole mass, raises its temperature.
On the same principle, when water heated higher than the boiling point in a digester is suddenly permitted to escape in the form of steam, the remainder is instantly reduced to the common boiling point, the heat above that point being carried off in a latent state by the steam.
Had it not been for this wise provision in nature, the whole of any quantity of water would, in all cases of freezing, have become solid at once; and also the whole of any quantity that was heated to the point of boiling, would have been converted into steam at once; circumstances which would have been extremely inconvenient, and often fatal.
This doctrine also explains the effect of freezing mixtures, as that of salt and snow. These solid substances, on being mixed, become fluid, and that fluid absorbing much heat, deprives all the neighbouring bodies of part of what they had. But if the temperature at which the mixture is made be as low as that to which this mixture would have brought it, it has no effect, and in a lower temperature this new fluid would become solid; for that mixture has only a certain determinate capacity for heat, and if the neighbouring bodies have less heat, they will take from it.
It has been observed, that the comparative heat of bodies containing phlogiston is increased by calcination or combustion; so that the calx of iron has a greater capacity for heat, and therefore contains more latent heat, than the metal.
In general it is not found, that the same substances have their capacity for receiving heat increased by an increase of temperature; but this is said to be the case with a mixture of ardent spirit and water, and also that of spirit of vitriol and water.
Since all substances contain a greater or less quantity of heat, and in consequence of being deprived of it become colder and colder, it is a question of some curiosity to determine the extent to which this can go, or at what degree in the scale of a thermometer any substance would be absolutely cold, or deprived of all heat; and an attempt has been made to solve this problem in the following manner. Comparing the capacity of water with that of ice, by means of a third substance, viz. mercury, it has been found, that if that of ice be 9°, that of water is 10°; so that water in becoming ice gives out one tenth part of its whole quantity of heat. But it has been shown, that ice in becoming water absorbs 146 degrees of heat. This, therefore, being one tenth part of the whole heat of water, it must have contained 1460 degrees; so that taking 32 degrees, which is the freezing point, from that number, the point of absolute cold will be 1426 below 0 of Fahrenheit's scale.
By a computation, made by means of the heat of inflammable and dephlogisticated air, at the temperature of 50, Dr. Crawford finds, that it contains nearly 1550 degrees of heat; so that the point of absolute cold will be 1500 below 0. But more experiments are wanted to solve this curious problem to entire satisfaction.
Since all animals, and especially those that have red blood, are much hotter than the medium in which they live, the source of this heat has become the subject of much investigation; and as the most probable theory is that of Dr. Crawford, I shall give a short detail of the reasons on which it is founded.
Having, with the most scrupulous attention, ascertained the latent, or, as he calls it, the absolute heat of blood, and also that of the aliments of which it is composed, he finds that it contains more than could have been derived from them. Also finding that the absolute heat of arterial blood exceeds that of venous blood, in the proportion of 11½ to 10, he concludes that it derives its heat from the air respired in the lungs, and that it parts with this latent heat, so that it becomes sensible, in the course of its circulation, in which it becomes loaded with phlogiston, which it communicates to the air in the lungs.
That this heat is furnished by the air, he proves, by finding, that that which we inspire contains more heat than that which we expire, or than the aqueous humor which we expire along with it, in a very considerable proportion; so that if the heat contained in the pure air did not become latent in the blood, it would raise its temperature higher than that of red-hot iron. And again, if the venous blood, in being converted into arterial blood, did not receive a supply of latent heat from the air, its temperature would fall from 96 to 104 below 0 in Fahrenheit's thermometer.
That the heat procured by combustion has the same source, viz. the dephlogisticated air that is decomposed in the process, is generally allowed; and Dr. Crawford finds, that when equal portions of air are altered by the respiration of a Guinea pig, or by the burning of charcoal, the quantity of heat communicated by the two processes is nearly equal.
The following facts are also alleged in favour of his theory. Whereas animals which have much red blood, and respire much, have the power of keeping themselves in a temperature considerably higher than that of the surrounding atmosphere, other animals, as frogs and serpents, are nearly of the same temperature with it; and those animals which have the largest respiratory organs, as birds, are the warmest; also the degree of heat is in some measure proportionable to the quantity of air that is respired in a given time, as in violent exercise.
It has been observed, that animals in a medium hotter than the blood have a power of preserving themselves in the same temperature. In this case the heat is probably carried off by perspiration, while the blood ceases to receive, or give out, any heat; and Dr. Crawford finds, that when an animal is placed in a warm medium the colour of the venous blood approaches nearer to that of the arterial than when it is placed in a colder medium; and also, that it phlogisticates the air less than in the former case; so that in these circumstances respiration has not the same effect that it has in a colder temperature, in giving the body an additional quantity of heat; which is an excellent provision in nature, as the heat is not wanted, but, on the contrary, would prove inconvenient.
Another most important agent in nature, and one that has a near connexion with heat, is light, being emitted by all bodies in a state of ignition, and especially by the sun, the great source of light and of heat to this habitable world.
Whether light consists of particles of matter (which is most probable) or be the undulation of a peculiar fluid, filling all space, it is emitted from all luminous bodies in right lines.
Falling upon other bodies, part of the light is reflected at an angle equal to that of its incidence, though not by impinging on the reflecting surface, but by a power acting at a small distance from it. But another part of the light enters the body, and is refracted or bent towards, or from, the perpendicular to the surface of the new medium, if the incidence be oblique to it. In general, rays of light falling obliquely on any medium are bent as if they were attracted by it, when it has a greater density, or contains more of the inflammable principle, than the medium through which it was transmitted to it. More of the rays are reflected when they fall upon a body with a small degree of obliquity to its surface, and more of them are transmitted, or enter the body, when their incidence is nearer to a perpendicular.
The velocity with which light is emitted or reflected is the same, and so great that it passes from the sun to the earth in about eight minutes and twelve seconds.
Rays of light emitted or reflected from a body entering the pupil of the eye, are so refracted by the humours of it, as to be united at the surface of the retina, and so make images of the objects, by means of which they are visible to us; and the magnifying power of telescopes or microscopes depends upon contriving, by means of reflections or refractions, that pencils of rays issuing from every point of any object shall first diverge, and then converge, as they would have done from a much larger object, or from one placed much nearer to the eye.
When a beam of light is bent out of its course by refraction, all the rays of which it consists are not equally refracted, but some of them more and others less; and the colour which they are disposed to exhibit is connected invariably with the degree of their refrangibility; the red-coloured rays being the least, and the violet the most refrangible, and the rest being more or less so in proportion to their nearness to these, which are the extremes, in the following order, violet, indigo, blue, green, yellow, orange, red.
These colours, when separated as much possible, are still contiguous; and all the shades of each colour have likewise their separate and invariable degrees of refrangibility. When separated as distinctly as possible, they divide the whole space between them exactly as a musical chord is divided in order to found the several notes and half notes of an octave.
These differently-coloured rays of light are also separated in passing through the transparent medium of air and water, in consequence of which the sky appears blue and the sea green, these rays being returned, while the red ones proceed to a greater distance. By this means also objects at the bottom of the sea appear to divers red, and so do all objects enlightened by an evening sun.
The mixture of all the differently-coloured rays, in the proportions in which they cover the coloured image above mentioned, makes a white, and the absence of all light is blackness.
By means of the different refrangibility of light, the colours of the rainbow may be explained.
The distance to which the differently-coloured rays are separated from each other is not in proportion to the mean refractive power of the medium, but depends upon the peculiar constitution of the substance by which they are refracted. The dispersing power of glass, into the composition of which lead enters, is great in proportion to the mean refraction; and it is proportionally little in that glass in which there is much alkaline salt. The construction of achromatic telescopes depends upon this principle.
Not only have different rays of light these different properties with respect to bodies, so as to be more or less refracted, or dispersed, by them, but different sides of the same rays seem to have different properties, for they are differently affected on entering a piece of island crystal. With the same degree of incidence; part of the pencil of rays, consisting of all the colours, proceeds in one direction, and the rest in a different one; so that objects seen through a piece of this substance appear double.
At the surface of all bodies rays of light are promiscuously reflected, or transmitted.
But if the next surface be very near to it, the rays of one colour chiefly are reflected, and the rest transmitted, and these places occur alternately for rays of each of the colours in passing from the thinnest to the thickest parts of the medium; so that several series, or orders, of colours will be visible on the surface of the same thin transparent body. On this principle coloured rings appear between a plane and a convex lens, in a little oil on the surface of water, and in bubbles made with soap and water.
When rays of light pass near to any body, so as to come within the sphere of its attraction and repulsion, an inflection takes place; all the kinds of rays being bent towards, or from, the body, and these powers affecting some rays more than others, they are by this means also separated from each other, so that coloured streaks appear both within the shadow, and the outside of it, the red rays being inflected at the greatest distance from the body.
Part of the light which enters bodies is retained within them, and proceeds no farther; but so loosely in some kinds of bodies, that a small degree of heat is sufficient to expel it again, so as to make the body visible in the dark: but the more heat is applied, the sooner is all the light expelled. This is a strong argument for the materiality of light. Bolognian phosphorus is a substance which has this property; but a composition made by Mr. Canton, of calcined oyster-shells and sulphur, in a much greater degree. However, white paper, and most substances, except the metals, are possessed of this property in a small degree.
Some bodies, especially phosphorus, and animal substances tending to putrefaction, emit light without being sensibly hot.
The colours of vegetables, and likewise their taste and smell, depend upon light. It is also by means of light falling on the leaves and other green parts of plants, that they emit dephlogisticated air, which preserves the atmosphere fit for respiration.
It is light that imparts colour to the skins of men, by means of the fluid immediately under them. This is the cause of tanning, of the copper colour of the North Americans, and the black of the Negroes. Light also gives colour to several other substances, especially the solutions of mercury in acids.