Thus, as chemistry advances towards perfection, by dividing and subdividing, it is impossible to say where it is to end; and these things we at present suppose simple may soon be found quite otherwise. All we dare venture to affirm of any substance is, that it must be considered as simple in the present state of our knowledge, and so far as chemical analysis has hitherto been able to show. We may even presume that the earths must soon cease to be considered as simple bodies; they are the only bodies of the salifiable class which have no tendency to unite with oxygen; and I am much inclined to believe that this proceeds from their being already saturated with that element. If so, they will fall to be considered as compounds consisting of simple substances, perhaps metallic, oxydated to a certain degree. This is only hazarded as a conjecture; and I trust the reader will take care not to confound what I have related as truths, fixed on the firm basis of observation and experiment, with mere hypothetical conjectures.

The fixed alkalies, potash, and soda, are omitted in the foregoing Table, because they are evidently compound substances, though we are ignorant as yet what are the elements they are composed of.

TABLE of compound oxydable and acidifiable bases.

Names of the radicals.

Oxydable or acidifiable { Nitro-muriatic radical or base, from the mineral { base of the acid formerly kingdom. { called aqua regia.

{ Tartarous radical or base. { Malic. } { Citric. } { Pyro-lignous. } Oxydable or acidifiable { Pyro-mucous. } hydro-carbonous or { Pyro-tartarous. } carbono-hydrous radicals { Oxalic. } from the vegetable { Acetous. } kingdom. { Succinic. } Radicals { Benzoic. } { Camphoric. } { Gallic. } } Oxydable or acidifiable { Lactic. } radicals from the animal { Saccholactic. } kingdom, which { Formic. } mostly contain azote, { Bombic. } and frequently phosphorus. { Sebacic. } { Lithic. } { Prussic. }

Note.—The radicals from the vegetable kingdom are converted by a first degree of oxygenation into vegetable oxyds, such as sugar, starch, and gum or mucus: Those of the animal kingdom by the same means form animal oxyds, as lymph, &c.—A.

SECT. II.—Observations upon the Table of Compound Radicals.

The older chemists being unacquainted with the composition of acids, and not suspecting them to be formed by a peculiar radical or base for each, united to an acidifying principle or element common to all, could not consequently give any name to substances of which they had not the most distant idea. We had therefore to invent a new nomenclature for this subject, though we were at the same time sensible that this nomenclature must be susceptible of great modification when the nature of the compound radicals shall be better understood[37].

The compound oxydable and acidifiable radicals from the vegetable and animal kingdoms, enumerated in the foregoing table, are not hitherto reducible to systematic nomenclature, because their exact analysis is as yet unknown. We only know in general, by some experiments of my own, and some made by Mr Hassenfratz, that most of the vegetable acids, such as the tartarous, oxalic, citric, malic, acetous, pyro-tartarous, and pyromucous, have radicals composed of hydrogen and charcoal, combined in such a way as to form single bases, and that these acids only differ from each other by the proportions in which these two substances enter into the composition of their bases, and by the degree of oxygenation which these bases have received. We know farther, chiefly from the experiments of Mr Berthollet, that the radicals from the animal kingdom, and even some of those from vegetables, are of a more compound nature, and, besides hydrogen and charcoal, that they often contain azote, and sometimes phosphorus; but we are not hitherto possessed of sufficiently accurate experiments for calculating the proportions of these several substances. We are therefore forced, in the manner of the older chemists, still to name these acids after the substances from which they are procured. There can be little doubt that these names will be laid aside when our knowledge of these substances becomes more accurate and extensive; the terms hydro-carbonous, hydro-carbonic, carbono-hydrous, and carbono hydric[38], will then become substituted for those we now employ, which will then only remain as testimonies of the imperfect state in which this part of chemistry was transmitted to us by our predecessors.

It is evident that the oils, being composed of hydrogen and charcoal combined, are true carbono-hydrous or hydro-carbonous radicals; and, indeed, by adding oxygen, they are convertible into vegetable oxyds and acids, according to their degrees of oxygenation. We cannot, however, affirm that oils enter in their entire state into the composition of vegetable oxyds and acids; it is possible that they previously lose a part either of their hydrogen or charcoal, and that the remaining ingredients no longer exist in the proportions necessary to constitute oils. We still require farther experiments to elucidate these points.

Properly speaking, we are only acquainted with one compound radical from the mineral kingdom, the nitro-muriatic, which is formed by the combination of azote with the muriatic radical. The other compound mineral acids have been much less attended to, from their producing less striking phenomena.

SECT. III.—Observations upon the Combinations of Light and Caloric with different Substances.

I have not constructed any table of the combinations of light and caloric with the various simple and compound substances, because our conceptions of the nature of these combinations are not hitherto sufficiently accurate. We know, in general, that all bodies in nature are imbued, surrounded, and penetrated in every way with caloric, which fills up every interval left between their particles; that, in certain cases, caloric becomes fixed in bodies, so as to constitute a part even of their solid substance, though it more frequently acts upon them with a repulsive force, from which, or from its accumulation in bodies to a greater or lesser degree, the transformation of solids into fluids, and of fluids to aeriform elasticity, is entirely owing. We have employed the generic name gas to indicate this aeriform state of bodies produced by a sufficient accumulation of caloric; so that, when we wish to express the aeriform state of muriatic acid, carbonic acid, hydrogen, water, alkohol, &c. we do it by adding the word gas to their names; thus muriatic acid gas, carbonic acid gas, hydrogen gas, aqueous gas, alkoholic gas, &c.

The combinations of light, and its mode of acting upon different bodies, is still less known. By the experiments of Mr Berthollet, it appears to have great affinity with oxygen, is susceptible of combining with it, and contributes alongst with caloric to change it into the state of gas. Experiments upon vegetation give reason to believe that light combines with certain parts of vegetables, and that the green of their leaves, and the various colours of their flowers, is chiefly owing to this combination. This much is certain, that plants which grow in darkness are perfectly white, languid, and unhealthy, and that to make them recover vigour, and to acquire their natural colours, the direct influence of light is absolutely necessary. Somewhat similar takes place even upon animals: Mankind degenerate to a certain degree when employed in sedentary manufactures, or from living in crowded houses, or in the narrow lanes of large cities; whereas they improve in their nature and constitution in most of the country labours which are carried on in the open air. Organization, sensation, spontaneous motion, and all the operations of life, only exist at the surface of the earth, and in places exposed to the influence of light. Without it nature itself would be lifeless and inanimate. By means of light, the benevolence of the Deity hath filled the surface of the earth with organization, sensation, and intelligence. The fable of Promotheus might perhaps be considered as giving a hint of this philosophical truth, which had even presented itself to the knowledge of the ancients. I have intentionally avoided any disquisitions relative to organized bodies in this work, for which reason the phenomena of respiration, sanguification, and animal heat, are not considered; but I hope, at some future time, to be able to elucidate these curious subjects.

[Trancriber's note: The following table is presented in four sections to comply with 75 character line limitation.]

TABLE of the binary Combinations of Oxygen with simple Substances

-+ Names of First degree of oxygenation. the simple + substances. New Names. Ancient Names. {Caloric Oxygen gas {Vital or { {dephlogisticated { {air { { {Hydrogen. Water(A). { {Azote {Nitrous oxyd, or }Nitrous gas or air { {base of nitrous gas } { {Charcoal {Oxyd of charcoal, or}Unknown Combinations{ {carbonic oxyd } of oxygen { with {Sulphur Oxyd of sulphur Soft sulphur simple { non-metallic{Phosphorus Oxyd of phosphorus {Residuum from the } substances. { {combustion of } { {phosphorus } { {Muriatic radical}Muriatic oxyd Unknown { {Fluoric radical }Fluoric oxyd Unknown { {Boracic radical }Boracic oxyd Unknown {Antimony Grey oxyd of Grey calx of { antimony antimony { {Silver Oxyd of silver Calx of silver { {Arsenic Grey oxyd of arsenic Grey calx of arsenic { {Bismuth Grey oxyd of bismuth Grey calx of bismuth { { {Cobalt Grey oxyd of cobalt Grey calx of cobalt { {Copper Brown oxyd of copper Brown calx of copper{ { { {Tin Grey oxyd of tin Grey calx of tin { {Iron Black oxyd of iron Martial ethiops { Combinations{ of oxygen {Manganese Black oxyd of Black calx of with the { manganese manganese simple { metallic {Mercury Black oxyd of Ethiops mineral(B) { substances. { mercury { { {Molybdena Oxyd of molybdena Calx of molybdena { {Nickel Oxyd of nickel Calx of nickel { {Gold Yellow oxyd of gold Yellow calx of gold { {Platina Yellow oxyd of Yellow calx of { platina platina { {Lead Grey oxyd of lead Grey calx of lead { { { {Tungstein Oxyd of Tungstein Calx of Tungstein { { {Zinc Grey oxyd of zinc Grey calx of zinc

-+ Names of Second degree of oxygenation. the simple + substances. New Names. Ancient Names. {Caloric { {Hydrogen. { {Azote {Nitrous acid Smoaking nitrous { { acid { {Charcoal {Carbonous acid Unknown Combinations{ { of oxygen {Sulphur Sulphurous acid Sulphureous acid with simple { non-metallic{Phosphorus Phosphorous acid {Volatile acid of } substances. { {phosphorus } { {Muriatic radical}Muriatous acid Unknown { {Fluoric radical }Fluorous acid Unknown { {Boracic radical }Boracous acid Unknown {Antimony White oxyd of {White calx of } { antimony {antimony } { {diaphoretic antimony} { {Silver { {Arsenic White oxyd of White calx of { arsenic arsenic { {Bismuth White oxyd of White calx of { bismuth bismuth { {Cobalt { {Copper Blue and green oxyds}Blue and green { of copper }calces of copper { {Tin White oxyd of tin {White calx of tin, } { {or putty of tin } { {Iron Yellow and red oxyds}Ochre and rust of { of iron }iron Combinations{ of oxygen {Manganese White oxyd of White calx of with the { manganese manganese simple { metallic {Mercury Yellow and red oxyds{Turbith mineral, } substances. { of mercury {red precipitate, } { {calcinated mercury, } { {precipitate per se } { {Molybdena { {Nickel { {Gold Red oxyd of gold {Red calx of gold, } { {purple precipitate } { of cassius { {Platina { {Lead Yellow and red oxyds}Massicot and minium { of lead } { {Tungstein { {Zinc White oxyd of zinc {White calx of zinc, } { {pompholix }

-+ Names of Third degree of oxygenation. the simple + substances. New Names. Ancient Names. {Caloric { {Hydrogen. { {Azote {Nitric acid {Pale, or not } { { {smoaking nitrous } { {acid { Combinations{Charcoal {Carbonic acid Fixed air of oxygen { with {Sulphur Sulphuric acid Vitriolic acid simple { non-metallic{Phosphorus Phosphoric acid Phosphoric acid substances. { {Muriatic radical}Muriatic acid Marine acid { {Fluoric radical }Fluoric acid Unknown till lately { {Boracic radical }Boracic acid {Homberg's sedative { } {salt {Antimony Antimonic acid { {Silver Argentic acid { {Arsenic Arseniac acid Acid of arsenic { {Bismuth Bismuthic acid { {Cobalt Cobaltic acid { {Copper Cupric acid { {Tin Stannic acid { {Iron Ferric acid Combinations{ of oxygen {Manganese Manganesic acid with the { simple { metallic {Mercury Mercuric acid substances. { {Molybdena Molybdic acid Acid of molybdena { { {Nickel Nickelic acid { {Gold Auric acid { {Platina Platinic acid { {Lead Plumbic acid { {Tungstein Tungstic acid Acid of Tungstein { { {Zinc Zincic acid

+ Names of Fourth degree of oxygenation. the simple + - substances. New Names. Ancient Names. - {Caloric { {Hydrogen. { {Azote {Oxygenated nitric Unknown { {acid { {Charcoal {Oxygenated carbonic Unknown Combinations{ {acid of oxygen { with {Sulphur Oxygenated sulphuric Unknown simple { acid non-metallic{Phosphorus Oxygenated phosphoric Unknown substances. { acid { {Muriatic radical}Oxygenated muriatic {Dephlogisticated { acid marine acid { {Fluoric radical } { {Boracic radical } { } {Antimony { {Silver { {Arsenic Oxygenated arseniac Unknown { acid { {Bismuth { {Cobalt { {Copper { {Tin { {Iron { Combinations{ of oxygen {Manganese with the { simple { metallic {Mercury substances. { {Molybdena Oxygenated molybdic Unknown { acid {Nickel { {Gold { {Platina { {Lead { {Tungstein Oxygenated Tungstic }Unknown { acid { {Zinc -

[Note A: Only one degree of oxygenation of hydrogen is hitherto known.—A.]

[Note B: Ethiops mineral is the sulphuret of mercury; this should have been called black precipitate of mercury.—E.]

SECT. IV.—Observations upon the Combinations of Oxygen with the simple Substances.

Oxygen forms almost a third of the mass of our atmosphere, and is consequently one of the most plentiful substances in nature. All the animals and vegetables live and grow in this immense magazine of oxygen gas, and from it we procure the greatest part of what we employ in experiments. So great is the reciprocal affinity between this element and other substances, that we cannot procure it disengaged from all combination. In the atmosphere it is united with caloric, in the state of oxygen gas, and this again is mixed with about two thirds of its weight of azotic gas.

Several conditions are requisite to enable a body to become oxygenated, or to permit oxygen to enter into combination with it. In the first place, it is necessary that the particles of the body to be oxygenated shall have less reciprocal attraction with each other than they have for the oxygen, which otherwise cannot possibly combine with them. Nature, in this case, may be assisted by art, as we have it in our power to diminish the attraction of the particles of bodies almost at will by heating them, or, in other words, by introducing caloric into the interstices between their particles; and, as the attraction of these particles for each other is diminished in the inverse ratio of their distance, it is evident that there must be a certain point of distance of particles when the affinity they possess with each other becomes less than that they have for oxygen, and at which oxygenation must necessarily take place if oxygen be present.

We can readily conceive that the degree of heat at which this phenomenon begins must be different in different bodies. Hence, on purpose to oxygenate most bodies, especially the greater part of the simple substances, it is only necessary to expose them to the influence of the air of the atmosphere in a convenient degree of temperature. With respect to lead, mercury, and tin, this needs be but little higher than the medium temperature of the earth; but it requires a more considerable degree of heat to oxygenate iron, copper, &c. by the dry way, or when this operation is not assisted by moisture. Sometimes oxygenation takes place with great rapidity, and is accompanied by great sensible heat, light, and flame; such is the combustion of phosphorus in atmospheric air, and of iron in oxygen gas. That of sulphur is less rapid; and the oxygenation of lead, tin, and most of the metals, takes place vastly slower, and consequently the disengagement of caloric, and more especially of light, is hardly sensible.

Some substances have so strong an affinity with oxygen, and combine with it in such low degrees of temperature, that we cannot procure them in their unoxygenated state; such is the muriatic acid, which has not hitherto been decomposed by art, perhaps even not by nature, and which consequently has only been found in the state of acid. It is probable that many other substances of the mineral kingdom are necessarily oxygenated in the common temperature of the atmosphere, and that being already saturated with oxygen, prevents their farther action upon that element.

There are other means of oxygenating simple substances besides exposure to air in a certain degree of temperature, such as by placing them in contact with metals combined with oxygen, and which have little affinity with that element. The red oxyd of mercury is one of the best substances for this purpose, especially with bodies which do not combine with that metal. In this oxyd the oxygen is united with very little force to the metal, and can be driven out by a degree of heat only sufficient to make glass red hot; wherefore such bodies as are capable of uniting with oxygen are readily oxygenated, by means of being mixed with red oxyd of mercury, and moderately heated. The same effect may be, to a certain degree, produced by means of the black oxyd of manganese, the red oxyd of lead, the oxyds of silver, and by most of the metallic oxyds, if we only take care to choose such as have less affinity with oxygen than the bodies they are meant to oxygenate. All the metallic reductions and revivifications belong to this class of operations, being nothing more than oxygenations of charcoal, by means of the several metallic oxyds. The charcoal combines with the oxygen and with caloric, and escapes in form of carbonic acid gas, while the metal remains pure and revivified, or deprived of the oxygen which before combined with it in the form of oxyd.

All combustible substances may likewise be oxygenated by means of mixing them with nitrat of potash or of soda, or with oxygenated muriat of potash, and subjecting the mixture to a certain degree of heat; the oxygen, in this case, quits the nitrat or the muriat, and combines with the combustible body. This species of oxygenation requires to be performed with extreme caution, and only with very small quantities; because, as the oxygen enters into the composition of nitrats, and more especially of oxygenated muriats, combined with almost as much caloric as is necessary for converting it into oxygen gas, this immense quantity of caloric becomes suddenly free the instant of the combination of the oxygen with the combustible body, and produces such violent explosions as are perfectly irresistible.

By the humid way we can oxygenate most combustible bodies, and convert most of the oxyds of the three kingdoms of nature into acids. For this purpose we chiefly employ the nitric acid, which has a very slight hold of oxygen, and quits it readily to a great number of bodies by the assistance of a gentle heat. The oxygenated muriatic acid may be used for several operations of this kind, but not in them all.

I give the name of binary to the combinations of oxygen with the simple substances, because in these only two elements are combined. When three substances are united in one combination I call it ternary, and quaternary when the combination consists of four substances united.

TABLE of the combinations of Oxygen with the compound radicals.

Names of the radicals. Names of the resulting acids. New nomenclature. Old nomenclature.

Nitro muriatic} Nitro muriatic acid Aqua regia. radical }

(A) Tartaric Tartarous acid Unknown till lately. Malic Malic acid Ditto. Citric Citric acid Acid of lemons. Pyro-lignous Pyro-lignous acid Empyreumatic acid of wood. Pyro-mucous Pyro-mucous acid Empyr. acid of sugar. Pyro-tartarous Pyro-tartarous acid Empyr. acid of tartar. Oxalic Oxalic acid Acid of sorel. Acetic {Acetous acid Vinegar, or acid of vinegar. {Acetic acid Radical vinegar. Succinic Succinic acid Volatile salt of amber. Benzoic Benzotic acid Flowers of benzoin. Camphoric Camphoric acid Unknown till lately. Gallic Gallic acid {The astringent principle {of vegetables.

(B) Lactic Lactic acid Acid of sour whey. Saccholactic Saccholactic acid Unknown till lately. Formic Formic acid Acid of ants. Bombic Bombic acid Unknown till lately. Sebacic Sebacic acid Ditto. Lithic Lithic acid Urinary calculus. Prussic Prussic acid Colouring matter of Prussian blue.

[Note A: These radicals by a first degree of oxygenation form vegetable oxyds, as sugar, starch, mucus, &c.—A.]

[Note B: These radicals by a first degree of oxygenation form the animal oxyds, as lymph, red part of the blood, animal secretions, &c.—A.]

SECT. V.—Observations upon the Combinations of Oxygen with the Compound Radicals.

I published a new theory of the nature and formation of acids in the Memoirs of the Academy for 1776, p. 671. and 1778, p. 535. in which I concluded, that the number of acids must be greatly larger than was till then supposed. Since that time, a new field of inquiry has been opened to chemists; and, instead of five or six acids which were then known, near thirty new acids have been discovered, by which means the number of known neutral salts have been increased in the same proportion. The nature of the acidifiable bases, or radicals of the acids, and the degrees of oxygenation they are susceptible of, still remain to be inquired into. I have already shown, that almost all the oxydable and acidifiable radicals from the mineral kingdom are simple, and that, on the contrary, there hardly exists any radical in the vegetable, and more especially in the animal kingdom, but is composed of at least two substances, hydrogen and charcoal, and that azote and phosphorus are frequently united to these, by which we have compound radicals of two, three, and four bases or simple elements united.

From these observations, it appears that the vegetable and animal oxyds and acids may differ from each other in three several ways: 1st, According to the number of simple acidifiable elements of which their radicals are composed: 2dly, According to the proportions in which these are combined together: And, 3dly, According to their different degrees of oxygenation: Which circumstances are more than sufficient to explain the great variety which nature produces in these substances. It is not at all surprising, after this, that most of the vegetable acids are convertible into each other, nothing more being requisite than to change the proportions of the hydrogen and charcoal in their composition, and to oxygenate them in a greater or lesser degree. This has been done by Mr Crell in some very ingenious experiments, which have been verified and extended by Mr Hassenfratz. From these it appears, that charcoal and hydrogen, by a first oxygenation, produce tartarous acid, oxalic acid by a second degree, and acetous or acetic acid by a third, or higher oxygenation; only, that charcoal seems to exist in a rather smaller proportion in the acetous and acetic acids. The citric and malic acids differ little from the preceding acids.

Ought we then to conclude that the oils are the radicals of the vegetable and animal acids? I have already expressed my doubts upon this subject: 1st, Although the oils appear to be formed of nothing but hydrogen and charcoal, we do not know if these are in the precise proportion necessary for constituting the radicals of the acids: 2dly, Since oxygen enters into the composition of these acids equally with hydrogen and charcoal, there is no more reason for supposing them to be composed of oil rather than of water or of carbonic acid. It is true that they contain the materials necessary for all these combinations, but then these do not take place in the common temperature of the atmosphere; all the three elements remain combined in a state of equilibrium, which is readily destroyed by a temperature only a little above that of boiling water[39].

TABLE of the Binary Combinations of Azote with the Simple Substances.

Simple Substances. Results of the Combinations. New Nomenclature. Old Nomenclature.

Caloric Azotic gas Phlogisticated air, or Mephitis. Hydrogen Ammoniac Volatile alkali.

{Nitrous oxyd Base of Nitrous gas. {Nitrous acid Smoaking nitrous acid. Oxygen {Nitric acid Pale nitrous acid. {Oxygenated nitric acid Unknown.

{This combination is hitherto unknown; should it {ever be discovered, it will be called, according to Charcoal {the principles of our nomenclature, Azuret of {Charcoal. Charcoal dissolves in azotic gas, and {forms carbonated azotic gas.

Phosphorus. Azuret of phosphorus. Still unknown.

{Azuret of sulphur. Still unknown. We know Sulphur {that sulphur dissolves in azotic gas, forming {sulphurated azotic gas.

{Azote combines with charcoal and hydrogen, and Compound {sometimes with phosphorus, in the compound radicals {oxydable and acidifiable bases, and is generally {contained in the radicals of the animal acids.

{Such combinations are hitherto unknown; if ever Metallic {discovered, they will form metallic azurets, as substances {azuret of gold, of silver, &c.

Lime { Magnesia { Barytes {Entirely unknown. If ever discovered, they will Argill {form azuret of lime, azuret of magnesia, &c. Potash { Soda {

SECT. VI.—Observations upon the Combinations of Azote with the Simple Substances.

Azote is one of the most abundant elements; combined with caloric it forms azotic gas, or mephitis, which composes nearly two thirds of the atmosphere. This element is always in the state of gas in the ordinary pressure and temperature, and no degree of compression or of cold has been hitherto capable of reducing it either to a solid or liquid form. This is likewise one of the essential constituent elements of animal bodies, in which it is combined with charcoal and hydrogen, and sometimes with phosphorus; these are united together by a certain portion of oxygen, by which they are formed into oxyds or acids according to the degree of oxygenation. Hence the animal substances may be varied, in the same way with vegetables, in three different manners: 1st, According to the number of elements which enter into the composition of the base or radical: 2dly, According to the proportions of these elements: 3dly, According to the degree of oxygenation.

When combined with oxygen, azote forms the nitrous and nitric oxyds and acids; when with hydrogen, ammoniac is produced. Its combinations with the other simple elements are very little known; to these we give the name of Azurets, preserving the termination in uret for all nonoxygenated compounds. It is extremely probable that all the alkaline substances may hereafter be found to belong to this genus of azurets.

The azotic gas may be procured from atmospheric air, by absorbing the oxygen gas which is mixed with it by means of a solution of sulphuret of potash, or sulphuret of lime. It requires twelve or fifteen days to complete this process, during which time the surface in contact must be frequently renewed by agitation, and by breaking the pellicle which forms on the top of the solution. It may likewise be procured by dissolving animal substances in dilute nitric acid very little heated. In this operation, the azote is disengaged in form of gas, which we receive under bell glasses filled with water in the pneumato-chemical apparatus. We may procure this gas by deflagrating nitre with charcoal, or any other combustible substance; when with charcoal, the azotic gas is mixed with carbonic acid gas, which may be absorbed by a solution of caustic alkali, or by lime water, after which the azotic gas remains pure. We can procure it in a fourth manner from combinations of ammoniac with metallic oxyds, as pointed out by Mr de Fourcroy: The hydrogen of the ammoniac combines with the oxygen of the oxyd, and forms water, whilst the azote being left free escapes in form of gas.

The combinations of azote were but lately discovered: Mr Cavendish first observed it in nitrous gas and acid, and Mr Berthollet in ammoniac and the prussic acid. As no evidence of its decomposition has hitherto appeared, we are fully entitled to consider azote as a simple elementary substance.

TABLE of the Binary Combinations of Hydrogen with Simple Substances.

Simple Resulting Compounds. Substances. New Nomenclature. Old Names.

Caloric Hydrogen gas Inflammable air. Azote Ammoniac Volatile Alkali. Oxygen Water Water.

Sulphur {Hydruret of sulphur, or } {sulphuret of hydrogen } Hitherto unknown (A). Phosphorus {Hydruret of phosphorus, or } {phosphuret of hydrogen }

Charcoal {Hydro-carbonous, or } Not known till lately. {carbono-hydrous radicals(B)}

Metallic {Metallic hydrurets(C), as } Hitherto unknown. substances, {hydruret of iron, &c. } as iron, &c. { }

[Note A: These combinations take place in the state of gas, and form, respectively, sulphurated and phosphorated oxygen gas—A.]

[Note B: This combination of hydrogen with charcoal includes the fixed and volatile oils, and forms the radicals of a considerable part of the vegetable and animal oxyds and acids. When it takes place in the state of gas it forms carbonated hydrogen gas.—A.]

[Note C: None of these combinations are known, and it is probable that they cannot exist, at least in the usual temperature of the atmosphere, owing to the great affinity of hydrogen for caloric.—A.]

SECT. VII.—Observations upon Hydrogen, and its Combinations with Simple Substances.

Hydrogen, as its name expresses, is one of the constituent elements of water, of which it forms fifteen hundredth parts by weight, combined with eighty-five hundredth parts of oxygen. This substance, the properties and even existence of which was unknown till lately, is very plentifully distributed in nature, and acts a very considerable part in the processes of the animal and vegetable kingdoms. As it possesses so great affinity with caloric as only to exist in the state of gas, it is consequently impossible to procure it in the concrete or liquid state, independent of combination.

To procure hydrogen, or rather hydrogen gas, we have only to subject water to the action of a substance with which oxygen has greater affinity than it has to hydrogen; by this means the hydrogen is set free, and, by uniting with caloric, assumes the form of hydrogen gas. Red hot iron is usually employed for this purpose: The iron, during the process, becomes oxydated, and is changed into a substance resembling the iron ore from the island of Elba. In this state of oxyd it is much less attractible by the magnet, and dissolves in acids without effervescence.

Charcoal, in a red heat, has the same power of decomposing water, by attracting the oxygen from its combination with hydrogen. In this process carbonic acid gas is formed, and mixes with the hydrogen gas, but is easily separated by means of water or alkalies, which absorb the carbonic acid, and leave the hydrogen gas pure. We may likewise obtain hydrogen gas by dissolving iron or zinc in dilute sulphuric acid. These two metals decompose water very slowly, and with great difficulty, when alone, but do it with great ease and rapidity when assisted by sulphuric acid; the hydrogen unites with caloric during the process, and is disengaged in form of hydrogen gas, while the oxygen of the water unites with the metal in the form of oxyd, which is immediately dissolved in the acid, forming a sulphat of iron or of zinc.

Some very distinguished chemists consider hydrogen as the phlogiston of Stahl; and as that celebrated chemist admitted the existence of phlogiston in sulphur, charcoal, metals, &c. they are of course obliged to suppose that hydrogen exists in all these substances, though they cannot prove their supposition; even if they could, it would not avail much, since this disengagement of hydrogen is quite insufficient to explain the phenomena of calcination and combustion. We must always recur to the examination of this question, "Are the heat and light, which are disengaged during the different species of combustion, furnished by the burning body, or by the oxygen which combines in all these operations?" And certainly the supposition of hydrogen being disengaged throws no light whatever upon this question. Besides, it belongs to those who make suppositions to prove them; and, doubtless, a doctrine which without any supposition explains the phenomena as well, and as naturally, as theirs does by supposition, has at least the advantage of greater simplicity[40].

TABLE of the Binary Combinations of Sulphur with Simple Substances.

Simple Resulting Compounds. Substances. New Nomenclature. Old Nomenclature.

Caloric Sulphuric gas

{ Oxyd of sulphur Soft sulphur. Oxygen { Sulphurous acid Sulphureous acid. { Sulphuric acid Vitriolic acid.

Hydrogen Sulphuret of hydrogen } Azote azote } Unknown Combinations. Phosphorus phosphorus } Charcoal charcoal }

Antimony antimony Crude antimony. Silver silver Arsenic arsenic Orpiment, realgar. Bismuth bismuth Cobalt cobalt Copper copper Copper pyrites. Tin tin Iron iron Iron pyrites. Manganese manganese Mercury mercury Ethiops mineral, cinnabar. Molybdena molybdena Nickel nickel Gold gold Platina platina Lead lead Galena. Tungstein tungstein Zinc zinc Blende.

{ Alkaline liver of sulphur Potash potash { with fixed vegetable alkali.

{ Alkaline liver of sulphur Soda soda { with fixed mineral { alkali.

{ Volatile liver of sulphur, Ammoniac ammoniac { smoaking liquor { of Boyle.

Lime lime Calcareous liver of sulphur. Magnesia magnesia Magnesian liver of sulphur. Barytes barytes Barytic liver of sulphur. Argill argill Yet unknown.

SECT. VIII.—Observations on Sulphur, and its Combinations.

Sulphur is a combustible substance, having a very great tendency to combination; it is naturally in a solid state in the ordinary temperature, and requires a heat somewhat higher than boiling water to make it liquify. Sulphur is formed by nature in a considerable degree of purity in the neighbourhood of volcanos; we find it likewise, chiefly in the state of sulphuric acid, combined with argill in aluminous schistus, with lime in gypsum, &c. From these combinations it may be procured in the state of sulphur, by carrying off its oxygen by means of charcoal in a red heat; carbonic acid is formed, and escapes in the state of gas; the sulphur remains combined with the clay, lime, &c. in the state of sulphuret, which is decomposed by acids; the acid unites with the earth into a neutral salt, and the sulphur is precipitated.

TABLE of the Binary Combinations of Phosphorus with the Simple Substances.

Simple Substances. Resulting Compounds.

Caloric Phosphoric gas.

{ Oxyd of phosphorus. Oxygen { Phosphorous acid. { Phosphoric acid.

Hydrogen Phosphuret of hydrogen. Azote Phosphuret of azote. Sulphur Phosphuret of Sulphur. Charcoal Phosphuret of charcoal. Metallic substances Phosphuret of metals(A).

Potash } Soda } Ammoniac } Phosphuret of Potash, Lime } Soda, &c.(B) Barytes } Magnesia } Argill }

[Note A: Of all these combinations of phosphorus with metals, that with iron only is hitherto known, forming the substance formerly called Siderite; neither is it yet ascertained whether, in this combination, the phosphorus be oxygenated or not.—A.]

[Note B: These combinations of phosphorus with the alkalies and earths are not yet known; and, from the experiments of Mr Gengembre, they appear to be impossible—A.]

SECT. IX.—Observations upon Phosphorus, and its Combinations.

Phosphorus is a simple combustible substance, which was unknown to chemists till 1667, when it was discovered by Brandt, who kept the process secret; soon after Kunkel found out Brandt's method of preparation, and made it public. It has been ever since known by the name of Kunkel's phosphorus. It was for a long time procured only from urine; and, though Homberg gave an account of the process in the Memoirs of the Academy for 1692, all the philosophers of Europe were supplied with it from England. It was first made in France in 1737, before a committee of the Academy at the Royal Garden. At present it is procured in a more commodious and more oeconomical manner from animal bones, which are real calcareous phosphats, according to the process of Messrs Gahn, Scheele, Rouelle, &c. The bones of adult animals being calcined to whiteness, are pounded, and passed through a fine silk sieve; pour upon the fine powder a quantity of dilute sulphuric acid, less than is sufficient for dissolving the whole. This acid unites with the calcareous earth of the bones into a sulphat of lime, and the phosphoric acid remains free in the liquor. The liquid is decanted off, and the residuum washed with boiling water; this water which has been used to wash out the adhering acid is joined with what was before decanted off, and the whole is gradually evaporated; the dissolved sulphat of lime cristallizes in form of silky threads, which are removed, and by continuing the evaporation we procure the phosphoric acid under the appearance of a white pellucid glass. When this is powdered, and mixed with one third its weight of charcoal, we procure very pure phosphorus by sublimation. The phosphoric acid, as procured by the above process, is never so pure as that obtained by oxygenating pure phosphorus either by combustion or by means of nitric acid; wherefore this latter should always be employed in experiments of research.

Phosphorus is found in almost all animal substances, and in some plants which give a kind of animal analysis. In all these it is usually combined with charcoal, hydrogen, and azote, forming very compound radicals, which are, for the most part, in the state of oxyds by a first degree of union with oxygen. The discovery of Mr Hassenfratz, of phosphorus being contained in charcoal, gives reason to suspect that it is more common in the vegetable kingdom than has generally been supposed: It is certain, that, by proper processes, it may be procured from every individual of some of the families of plants.

As no experiment has hitherto given reason to suspect that phosphorus is a compound body, I have arranged it with the simple or elementary substances. It takes fire at the temperature of 32 deg. (104 deg.) of the thermometer.

TABLE of the Binary Combinations of Charcoal.

Simple Substances. Resulting Compounds.

{ Oxyd of charcoal Unknown. Oxygen { Carbonic acid Fixed air, chalky acid.

Sulphur Carburet of sulphur } Phosphorus Carburet of phosphorus } Unknown. Azote Carburet of azote }

{ Carbono-hydrous radical Hydrogen { Fixed and volatile oils

{ Of these only the carburets of Metallic substances Carburets of metals { iron and zinc are known, and { were formerly called Plumbago.

Alkalies and earths Carburet of potash, &c. Unknown.

SECT. X.—Observations upon Charcoal, and its Combinations with Simple Substances.

As charcoal has not been hitherto decomposed, it must, in the present state of our knowledge, be considered as a simple substance. By modern experiments it appears to exist ready formed in vegetables; and I have already remarked, that, in these, it is combined with hydrogen, sometimes with azote and phosphorus, forming compound radicals, which may be changed into oxyds or acids according to their degree of oxygenation.

To obtain the charcoal contained in vegetable or animal substances, we subject them to the action of fire, at first moderate, and afterwards very strong, on purpose to drive off the last portions of water, which adhere very obstinately to the charcoal. For chemical purposes, this is usually done in retorts of stone-ware or porcellain, into which the wood, or other matter, is introduced, and then placed in a reverberatory furnace, raised gradually to its greatest heat: The heat volatilizes, or changes into gas, all the parts of the body susceptible of combining with caloric into that form, and the charcoal, being more fixed in its nature, remains in the retort combined with a little earth and some fixed salts.

In the business of charring wood, this is done by a less expensive process. The wood is disposed in heaps, and covered with earth, so as to prevent the access of any more air than is absolutely necessary for supporting the fire, which is kept up till all the water and oil is driven off, after which the fire is extinguished by shutting up all the air-holes.

We may analyse charcoal either by combustion in air, or rather in oxygen gas, or by means of nitric acid. In either case we convert it into carbonic acid, and sometimes a little potash and some neutral salts remain. This analysis has hitherto been but little attended to by chemists; and we are not even certain if potash exists in charcoal before combustion, or whether it be formed by means of some unknown combination during that process.

SECT. XI.—Observations upon the Muriatic, Fluoric, and Boracic Radicals, and their Combinations.

As the combinations of these substances, either with each other, or with the other combustible bodies, are hitherto entirely unknown, we have not attempted to form any table for their nomenclature. We only know that these radicals are susceptible of oxygenation, and of forming the muriatic, fluoric, and boracic acids, and that in the acid state they enter into a number of combinations, to be afterwards detailed. Chemistry has hitherto been unable to disoxygenate any of them, so as to produce them in a simple state. For this purpose, some substance must be employed to which oxygen has a stronger affinity than to their radicals, either by means of single affinity, or by double elective attraction. All that is known relative to the origin of the radicals of these acids will be mentioned in the sections set apart for considering their combinations with the salifiable bases.

SECT. XII.—Observations upon the Combinations of Metals with each other.

Before closing our account of the simple or elementary substances, it might be supposed necessary to give a table of alloys or combinations of metals with each other; but, as such a table would be both exceedingly voluminous and very unsatisfactory, without going into a series of experiments not yet attempted, I have thought it adviseable to omit it altogether. All that is necessary to be mentioned is, that these alloys should be named according to the metal in largest proportion in the mixture or combination; thus the term alloy of gold and silver, or gold alloyed with silver, indicates that gold is the predominating metal.

Metallic alloys, like all other combinations, have a point of saturation. It would even appear, from the experiments of Mr de la Briche, that they have two perfectly distinct degrees of saturation.

TABLE of the Combinations of Azote in the state of Nitrous Acid with the Salifiable Bases, arranged according to the affinities of these Bases with the Acid.

Names of the bases. Names of the neutral salts. New nomenclature. Notes.

Barytes Nitrite of barytes. { Potash potash. { These salts are only Soda soda. { known of late, and Lime lime. { have received no particular Magnesia magnesia. { name in the old Ammoniac ammoniac. { nomenclature. Argill argill. {

{ As metals dissolve both in nitrous and Oxyd of zinc zinc. { nitric acids, metallic salts must of iron iron. { consequence be formed having manganese manganese. { different degrees of oxygenation. cobalt cobalt. { Those wherein the metal is nickel nickel. { least oxygenated must be lead lead. { called Nitrites, when more so, tin tin. { Nitrats; but the limits of this copper copper. { distinction are difficultly bismuth bismuth. { ascertainable. The older antimony antimony. { chemists were not acquainted arsenic arsenic. { with any of these salts. mercury mercury. {

silver { It is extremely probable that gold, silver gold { and platina only form nitrats, and cannot subsist platina { in the state of nitrites.

TABLE of the Combinations of Azote, completely saturated with Oxygen, in the state of Nitric Acid, with the Salifiable Bases, in the order of the affinity with the Acid.

Bases. Names of the resulting neutral salts.

New nomenclature. Old nomenclature.

Barytes Nitrat of barytes Nitre, with a base of heavy earth. Potash potash Nitre, saltpetre. Nitre with base of potash.

Soda soda { Quadrangular nitre. Nitre with base of { mineral alkali.

{ Calcareous nitre. Nitre with Lime lime { calcareous base. Mother water { of nitre, or saltpetre.

Magnesia magnesia Magnesian nitre. Nitre with base of magnesia. Ammoniac ammoniac Ammoniacal nitre.

{ Nitrous alum. Argillaceous nitre. Nitre Argill argill { with base of earth of alum.

Oxyd of zinc zinc Nitre of zinc. iron iron Nitre of iron. Martial nitre. Nitrated iron. manganese manganese Nitre of manganese. cobalt cobalt Nitre of cobalt. nickel nickel Nitre of nickel. lead lead Saturnine nitre. Nitre of lead. tin tin Nitre of tin. copper copper Nitre of copper or of Venus. bismuth bismuth Nitre of bismuth. antimony antimony Nitre of antimony. arsenic arsenic Arsenical nitre. mercury mercury Mercurial nitre. silver silver Nitre of silver or luna. Lunar caustic. gold gold Nitre of gold. platina platina Nitre of platina.

SECT. XIII.—Observations upon the Nitrous and Nitric Acids, and their Combinations.

The nitrous and nitric acids are procured from a neutral salt long known in the arts under the name of saltpetre. This salt is extracted by lixiviation from the rubbish of old buildings, from the earth of cellars, stables, or barns, and in general of all inhabited places. In these earths the nitric acid is usually combined with lime and magnesia, sometimes with potash, and rarely with argill. As all these salts, excepting the nitrat of potash, attract the moisture of the air, and consequently would be difficultly preserved, advantage is taken, in the manufactures of saltpetre and the royal refining house, of the greater affinity of the nitric acid to potash than these other bases, by which means the lime, magnesia, and argill, are precipitated, and all these nitrats are reduced to the nitrat of potash or saltpetre[41].

The nitric acid is procured from this salt by distillation, from three parts of pure saltpetre decomposed by one part of concentrated sulphuric acid, in a retort with Woulfe's apparatus, (Pl. IV. fig. 1.) having its bottles half filled with water, and all its joints carefully luted. The nitrous acid passes over in form of red vapours surcharged with nitrous gas, or, in other words, not saturated with oxygen. Part of the acid condenses in the recipient in form of a dark orange red liquid, while the rest combines with the water in the bottles. During the distillation, a large quantity of oxygen gas escapes, owing to the greater affinity of oxygen to caloric, in a high temperature, than to nitrous acid, though in the usual temperature of the atmosphere this affinity is reversed. It is from the disengagement of oxygen that the nitric acid of the neutral salt is in this operation converted into nitrous acid. It is brought back to the state of nitric acid by heating over a gentle fire, which drives off the superabundant nitrous gas, and leaves the nitric acid much diluted with water.

Nitric acid is procurable in a more concentrated state, and with much less loss, by mixing very dry clay with saltpetre. This mixture is put into an earthern retort, and distilled with a strong fire. The clay combines with the potash, for which it has great affinity, and the nitric acid passes over, slightly impregnated with nitrous gas. This is easily disengaged by heating the acid gently in a retort, a small quantity of nitrous gas passes over into the recipient, and very pure concentrated nitric acid remains in the retort.

We have already seen that azote is the nitric radical. If to 20-1/2 parts, by weight, of azote 43-1/2 parts of oxygen be added, 64 parts of nitrous gas are formed; and, if to this we join 36 additional parts of oxygen, 100 parts of nitric acid result from the combination. Intermediate quantities of oxygen between these two extremes of oxygenation produce different species of nitrous acid, or, in other words, nitric acid less or more impregnated with nitrous gas. I ascertained the above proportions by means of decomposition; and, though I cannot answer for their absolute accuracy, they cannot be far removed from truth. Mr Cavendish, who first showed by synthetic experiments that azote is the base of nitric acid, gives the proportions of azote a little larger than I have done; but, as it is not improbable that he produced the nitrous acid and not the nitric, that circumstance explains in some degree the difference in the results of our experiments.

As, in all experiments of a philosophical nature, the utmost possible degree of accuracy is required, we must procure the nitric acid for experimental purposes, from nitre which has been previously purified from all foreign matter. If, after distillation, any sulphuric acid is suspected in the nitric acid, it is easily separated by dropping in a little nitrat of barytes, so long as any precipitation takes place; the sulphuric acid, from its greater affinity, attracts the barytes, and forms with it an insoluble neutral salt, which falls to the bottom. It may be purified in the same manner from muriatic acid, by dropping in a little nitrat of silver so long as any precipitation of muriat of silver is produced. When these two precipitations are finished, distill off about seven-eighths of the acid by a gentle heat, and what comes over is in the most perfect degree of purity.

The nitric acid is one of the most prone to combination, and is at the same time very easily decomposed. Almost all the simple substances, with the exception of gold, silver, and platina, rob it less or more of its oxygen; some of them even decompose it altogether. It was very anciently known, and its combinations have been more studied by chemists than those of any other acid. These combinations were named nitres by Messrs Macquer and Beaume; but we have changed their names to nitrats and nitrites, according as they are formed by nitric or by nitrous acid, and have added the specific name of each particular base, to distinguish the several combinations from each other.

TABLE of the Combinations of Sulphuric Acid with the Salifiable Bases, in the order of affinity.

Names of the bases. Resulting compounds. New nomenclature. Old nomenclature.

Barytes Sulphat of barytes Heavy spar. Vitriol of heavy earth.

Potash potash {Vitriolated tartar. Sal { de duobus. Arcanum { duplicatam.

Soda soda Glauber's salt. Lime lime Selenite, gypsum, calcareous vitriol. Magnesia magnesia Epsom salt, sedlitz salt, magnesian vitriol. Ammoniac ammoniac Glauber's secret sal ammoniac. Argill argill Alum.

Oxyd of zinc zinc {White vitriol, goslar { vitriol, white coperas, { vitriol of zinc.

iron iron {Green coperas, green { vitriol, martial vitriol, { vitriol of iron.

manganese manganese Vitriol of manganese. cobalt cobalt Vitriol of cobalt. nickel nickel Vitriol of nickel. lead lead Vitriol of lead. tin tin Vitriol of tin.

copper copper {Blue coperas, blue vitriol, { Roman vitriol, { vitriol of copper.

bismuth bismuth Vitriol of bismuth. antimony antimony Vitriol of antimony. arsenic arsenic Vitriol of arsenic. mercury mercury Vitriol of mercury. silver silver Vitriol of silver. gold gold Vitriol of gold. platina platina Vitriol of platina.

SECT. XIV.—Observations upon Sulphuric Acid and its Combinations.

For a long time this acid was procured by distillation from sulphat of iron, in which sulphuric acid and oxyd of iron are combined, according to the process described by Basil Valentine in the fifteenth century; but, in modern times, it is procured more oeconomically by the combustion of sulphur in proper vessels. Both to facilitate the combustion, and to assist the oxygenation of the sulphur, a little powdered saltpetre, nitrat of potash, is mixed with it; the nitre is decomposed, and gives out its oxygen to the sulphur, which contributes to its conversion into acid. Notwithstanding this addition, the sulphur will only continue to burn in close vessels for a limited time; the combination ceases, because the oxygen is exhausted, and the air of the vessels reduced almost to pure azotic gas, and because the acid itself remains long in the state of vapour, and hinders the progress of combustion.

In the manufactories for making sulphuric acid in the large way, the mixture of nitre and sulphur is burnt in large close built chambers lined with lead, having a little water at the bottom for facilitating the condensation of the vapours. Afterwards, by distillation in large retorts with a gentle heat, the water passes over, slightly impregnated with acid, and the sulphuric acid remains behind in a concentrated state. It is then pellucid, without any flavour, and nearly double the weight of an equal bulk of water. This process would be greatly facilitated, and the combustion much prolonged, by introducing fresh air into the chambers, by means of several pairs of bellows directed towards the flame of the sulphur, and by allowing the nitrous gas to escape through long serpentine canals, in contact with water, to absorb any sulphuric or sulphurous acid gas it might contain.

By one experiment, Mr Berthollet found that 69 parts of sulphur in combustion, united with 31 parts of oxygen, to form 100 parts of sulphuric acid; and, by another experiment, made in a different manner, he calculates that 100 parts of sulphuric acid consists of 72 parts sulphur, combined with 28 parts of oxygen, all by weight.

This acid, in common with every other, can only dissolve metals when they have been previously oxydated; but most of the metals are capable of decomposing a part of the acid, so as to carry off a sufficient quantity of oxygen, to render themselves soluble in the part of the acid which remains undecomposed. This happens with silver, mercury, iron, and zinc, in boiling concentrated sulphuric acid; they become first oxydated by decomposing part of the acid, and then dissolve in the other part; but they do not sufficiently disoxygenate the decomposed part of the acid to reconvert it into sulphur; it is only reduced to the state of sulphurous acid, which, being volatilised by the heat, flies off in form of sulphurous acid gas.

Silver, mercury, and all the other metals except iron and zinc, are insoluble in diluted sulphuric acid, because they have not sufficient affinity with oxygen to draw it off from its combination either with the sulphur, the sulphurous acid, or the hydrogen; but iron and zinc, being assisted by the action of the acid, decompose the water, and become oxydated at its expence, without the help of heat.

TABLE of the Combinations of the Sulphurous Acid with the Salifiable Bases, in the order of affinity.

Names of the Bases. Names of the Neutral Salts.

Barytes Sulphite of barytes. Potash potash. Soda soda. Lime lime. Magnesia magnesia. Ammoniac ammoniac. Argill argill. Oxyd of zinc zinc. iron iron. manganese manganese. cobalt cobalt. nickel nickel. lead lead. tin tin. copper copper. bismuth bismuth. antimony antimony. arsenic arsenic. mercury mercury. silver silver. gold gold. platina platina.

Note.—The only one of these salts known to the old chemists was the sulphite of potash, under the name of Stahl's sulphureous salt. So that, before our new nomenclature, these compounds must have been named Stahl's sulphureous salt, having base of fixed vegetable alkali, and so of the rest.

In this Table we have followed Bergman's order of affinity of the sulphuric acid, which is the same in regard to the earths and alkalies, but it is not certain if the order be the same for the metallic oxyds.—A.

SECT. XV.—Observations upon Sulphurous Acid, and its Combinations.

The sulphurous acid is formed by the union of oxygen with sulphur by a lesser degree of oxygenation than the sulphuric acid. It is procurable either by burning sulphur slowly, or by distilling sulphuric acid from silver, antimony, lead, mercury, or charcoal; by which operation a part of the oxygen quits the acid, and unites to these oxydable bases, and the acid passes over in the sulphurous state of oxygenation. This acid, in the common pressure and temperature of the air, can only exist in form of gas; but it appears, from the experiments of Mr Clouet, that, in a very low temperature, it condenses, and becomes fluid. Water absorbs a great deal more of this gas than of carbonic acid gas, but much less than it does of muriatic acid gas.

That the metals cannot be dissolved in acids without being previously oxydated, or by procuring oxygen, for that purpose, from the acids during solution, is a general and well established fact, which I have perhaps repeated too often. Hence, as sulphurous acid is already deprived of great part of the oxygen necessary for forming the sulphuric acid, it is more disposed to recover oxygen, than to furnish it to the greatest part of the metals; and, for this reason, it cannot dissolve them, unless previously oxydated by other means. From the same principle it is that the metallic oxyds dissolve without effervescence, and with great facility, in sulphurous acid. This acid, like the muriatic, has even the property of dissolving metallic oxyds surcharged with oxygen, and consequently insoluble in sulphuric acid, and in this way forms true sulphats. Hence we might be led to conclude that there are no metallic sulphites, were it not that the phenomena which accompany the solution of iron, mercury, and some other metals, convince us that these metallic substances are susceptible of two degrees of oxydation, during their solution in acids. Hence the neutral salt in which the metal is least oxydated must be named sulphite, and that in which it is fully oxydated must be called sulphat. It is yet unknown whether this distinction is applicable to any of the metallic sulphats, except those of iron and mercury.

TABLE of the Combinations of Phosphorous and Phosphoric Acids, with the Salifiable Bases, in the Order of Affinity.

Names of the Names of the Neutral Salts formed by Bases. Phosphorous Acid, Phosphoric Acid.

Phosphites of(B) Phosphats of(C) Lime lime lime. Barytes barytes barytes. Magnesia magnesia magnesia. Potash potash potash. Soda soda soda. Ammoniac ammoniac ammoniac. Argill argill argill. Oxyds of(A) zinc zinc zinc. iron iron iron. manganese manganese manganese. cobalt cobalt cobalt. nickel nickel nickel. lead lead lead. tin tin tin. copper copper copper. bismuth bismuth bismuth. antimony antimony antimony. arsenic arsenic arsenic. mercury mercury mercury. silver silver silver. gold gold gold. platina platina platina.

[Note A: The existence of metallic phosphites supposes that metals are susceptible of solution in phosphoric acid at different degrees of oxygenation, which is not yet ascertained.—A.]

[Note B: All the phosphites were unknown till lately, and consequently have not hitherto received names.—A.]

[Note C: The greater part of the phosphats were only discovered of late, and have not yet been named.—A.]

SECT. XVI.—Observations upon Phosphorous and Phosphoric Acids, and their Combinations.

Under the article Phosphorus, Part II. Sect. X. we have already given a history of the discovery of that singular substance, with some observations upon the mode of its existence in vegetable and animal bodies. The best method of obtaining this acid in a state of purity is by burning well purified phosphorus under bell-glasses, moistened on the inside with distilled water; during combustion it absorbs twice and a half its weight of oxygen; so that 100 parts of phosphoric acid is composed of 28-1/2 parts of phosphorus united to 71-1/2 parts of oxygen. This acid may be obtained concrete, in form of white flakes, which greedily attract the moisture of the air, by burning phosphorus in a dry glass over mercury.

To obtain phosphorous acid, which is phosphorus less oxygenated than in the state of phosphoric acid, the phosphorus must be burnt by a very slow spontaneous combustion over a glass-funnel leading into a crystal phial; after a few days, the phosphorus is found oxygenated, and the phosphorous acid, in proportion as it forms, has attracted moisture from the air, and dropped into the phial. The phosphorous acid is readily changed into phosphoric acid by exposure for a long time to the free air; it absorbs oxygen from the air, and becomes fully oxygenated.

As phosphorus has a sufficient affinity for oxygen to attract it from the nitric and muriatic acids, we may form phosphoric acid, by means of these acids, in a very simple and cheap manner. Fill a tubulated receiver, half full of concentrated nitric acid, and heat it gently, then throw in small pieces of phosphorus through the tube, these are dissolved with effervescence and red fumes of nitrous gas fly off; add phosphorus so long as it will dissolve, and then increase the fire under the retort to drive off the last particles of nitric acid; phosphoric acid, partly fluid and partly concrete, remains in the retort.

TABLE of the Combinations of Carbonic Acid, with the Salifiable Bases, in the Order of Affinity.

Names of Resulting Neutral Salts. Bases New Nomenclature. Old Nomenclature.

Barytes Carbonates of barytes(A) Aerated or effervescent heavy earth.

Lime lime {Chalk, calcareous spar, { Aerated calcareous earth.

Potash potash {Effervescing or aerated fixe { vegetable alkali, mephitis of { potash.

Soda soda {Aerated or effervescing fixed mineral { alkali, mephitic soda.

Magnesia magnesia {Aerated, effervescing, mild, or { mephitic magnesia.

Ammoniac ammoniac {Aerated, effervescing, mild, or { mephitic volatile alkali.

Argill argill {Aerated or effervescing argillaceous { earth, or earth of alum.

Oxyds of zinc zinc Zinc spar, mephitic or aerated zinc. iron iron Sparry iron-ore, mephitic or aerated iron. manganese manganese Aerated manganese. cobalt cobalt Aerated cobalt. nickel nickel Aerated nickel. lead lead Sparry lead-ore, or aerated lead. tin tin Aerated tin. copper copper Aerated copper. bismuth bismuth Aerated bismuth. antimony antimony Aerated antimony. arsenic arsenic Aerated arsenic. mercury mercury Aerated mercury. silver silver Aerated silver. gold gold Aerated gold. platina platina Aerated platina.

[Note A: As these salts have only been understood of late, they have not, properly speaking, any old names. Mr Morveau, in the First Volume of the Encyclopedia, calls them Mephites; Mr Bergman gives them the name of aerated; and Mr de Fourcroy, who calls the carbonic acid chalky acid, gives them the name of chalks.—A]

SECT. XVII.—Observations upon Carbonic Acid, and its Combinations.

Of all the known acids, the carbonic is the most abundant in nature; it exists ready formed in chalk, marble, and all the calcareous stones, in which it is neutralized by a particular earth called lime. To disengage it from this combination, nothing more is requisite than to add some sulphuric acid, or any other which has a stronger affinity for lime; a brisk effervescence ensues, which is produced by the disengagement of the carbonic acid which assumes the state of gas immediately upon being set free. This gas, incapable of being condensed into the solid or liquid form by any degree of cold or of pressure hitherto known, unites to about its own bulk of water, and thereby forms a very weak acid. It may likewise be obtained in great abundance from saccharine matter in fermentation, but is then contaminated by a small portion of alkohol which it holds in solution.

As charcoal is the radical of this acid, we may form it artificially, by burning charcoal in oxygen gas, or by combining charcoal and metallic oxyds in proper proportions; the oxygen of the oxyd combines with the charcoal, forming carbonic acid gas, and the metal being left free, recovers its metallic or reguline form.

We are indebted for our first knowledge of this acid to Dr Black, before whose time its property of remaining always in the state of gas had made it to elude the researches of chemistry.

It would be a most valuable discovery to society, if we could decompose this gas by any cheap process, as by that means we might obtain, for economical purposes, the immense store of charcoal contained in calcareous earths, marbles, limestones, &c. This cannot be effected by single affinity, because, to decompose the carbonic acid, it requires a substance as combustible as charcoal itself, so that we should only make an exchange of one combustible body for another not more valuable; but it may possibly be accomplished by double affinity, since this process is so readily performed by Nature, during vegetation, from the most common materials.

TABLE of the Combinations of Muriatic Acid, with the Salifiable Bases, in the Order of Affinity.

Names of the Resulting Neutral Salts. bases. New nomenclature. Old nomenclature.

Barytes. Muriat of {Sea-salt, having base of barytes { heavy earth.

Potash potash {Febrifuge salt of Sylvius: { Muriated vegetable fixed { alkali.

Soda soda Sea-salt. Lime lime Muriated lime. Oil of lime. Magnesia magnesia {Marine Epsom salt. Muriated magnesia. Ammoniac ammoniac Sal ammoniac.

Argill argill {Muriated alum, sea-salt { with base of earth of alum. Oxyd of zinc zinc Sea-salt of, or muriatic zinc. iron iron Salt of iron, Martial sea-salt. manganese manganese Sea-salt of manganese. cobalt cobalt Sea-salt of cobalt. nickel nickel Sea-salt of nickel. lead lead Horny-lead. Plumbum corneum. tin smoaking of tin Smoaking liquor of Libavius. solid of tin Solid butter of tin. copper copper Sea-salt of copper. bismuth bismuth Sea-salt of bismuth. antimony antimony Sea-salt of antimony. arsenic arsenic Sea-salt of arsenic.

{sweet of mercury {Sweet sublimate of mercury, { { calomel, aquila alba. mercury { { {corrosive of {Corrosive sublimate of { mercury { mercury.

silver silver Horny silver, argentum corneum, luna cornea. gold gold Sea-salt of gold. platina platina Sea-salt of platina.

TABLE Of the Combinations of Oxygenated Muriatic Acid, with the Salifiable Bases, in the Order of Affinity.

Names of the Neutral Salts by Names of the Bases. the new Nomenclature.

Oxygenated muriat of Barytes barytes. Potash potash. Soda soda. Lime lime. Magnesia magnesia. Argill argill. Oxyd of zinc zinc. iron iron. manganese manganese. cobalt cobalt. nickel nickel. lead lead. tin tin. copper copper. bismuth bismuth. antimony antimony. arsenic arsenic. mercury mercury. silver silver. gold gold. platina platina.

This order of salts, entirely unknown to the ancient chemists, was discovered in 1786 by Mr Berthollet.—A.

SECT. XIX.—Observations upon Muriatic and Oxygenated Muriatic Acids, and their Combinations.

Muriatic acid is very abundant in the mineral kingdom naturally combined with different salifiable bases, especially with soda, lime, and magnesia. In sea-water, and the water of several lakes, it is combined with these three bases, and in mines of rock-salt it is chiefly united to soda. This acid does not appear to have been hitherto decomposed in any chemical experiment; so that we have no idea whatever of the nature of its radical, and only conclude, from analogy with the other acids, that it contains oxygen as its acidifying principle. Mr Berthollet suspects the radical to be of a metallic nature; but, as Nature appears to form this acid daily, in inhabited places, by combining miasmata with aeriform fluids, this must necessarily suppose a metallic gas to exist in the atmosphere, which is certainly not impossible, but cannot be admitted without proof.

The muriatic acid has only a moderate adherence to the salifiable bases, and can readily be driven from its combination with these by sulphuric acid. Other acids, as the nitric, for instance, may answer the same purpose; but nitric acid being volatile, would mix, during distillation, with the muriatic. About one part of sulphuric acid is sufficient to decompose two parts of decrepitated sea-salt. This operation is performed in a tubulated retort, having Woulfe's apparatus, (Pl. IV. Fig. 1.), adapted to it. When all the junctures are properly lured, the sea-salt is put into the retort through the tube, the sulphuric acid is poured on, and the opening immediately closed with its ground crystal stopper. As the muriatic acid can only subsist in the gaseous form in the ordinary temperature, we could not condense it without the presence of water. Hence the use of the water with which the bottles in Woulfe's apparatus are half filled; the muriatic acid gas, driven off from the sea-salt in the retort, combines with the water, and forms what the old chemists called smoaking spirit of salt, or Glauber's spirit of sea-salt, which we now name muriatic acid.

The acid obtained by the above process is still capable of combining with a farther dose of oxygen, by being distilled from the oxyds of manganese, lead, or mercury, and the resulting acid, which we name oxygenated muriatic acid, can only, like the former, exist in the gasseous form, and is absorbed, in a much smaller quantity by water. When the impregnation of water with this gas is pushed beyond a certain point, the superabundant acid precipitates to the bottom of the vessels in a concrete form. Mr Berthollet has shown that this acid is capable of combining with a great number of the salifiable bases; the neutral salts which result from this union are susceptible of deflagrating with charcoal, and many of the metallic substances; these deflagrations are very violent and dangerous, owing to the great quantity of caloric which the oxygen carries alongst with it into the composition of oxygenated muriatic acid.

TABLE of the Combinations of Nitro-muriatic Acid with the Salifiable Bases, in the Order of Affinity, so far as is known.

Names of the Bases. Names of the Neutral Salts.

Argill Nitro-muriat of argill. Ammoniac ammoniac. Oxyd of antimony antimony. silver silver. arsenic arsenic. Barytes barytes. Oxyd of bismuth bismuth. Lime lime. Oxyd of cobalt cobalt. copper copper. tin tin. iron iron. Magnesia magnesia. Oxyd of manganese manganese. mercury mercury. molybdena molybdena. nickel nickel. gold gold. platina platina. lead lead. Potash potash. Soda soda. Oxyd of tungstein tungstein. zinc zinc.

Note.—Most of these combinations, especially those with the earths and alkalies, have been little examined, and we are yet to learn whether they form a mixed salt in which the compound radical remains combined, or if the two acids separate, to form two distinct neutral salts.—A.

SECT. XX.—Observations upon the Nitro-Muriatic Acid, and its Combinations.

The nitro-muriatic acid, formerly called aqua regia, is formed by a mixture of nitric and muriatic acids; the radicals of these two acids combine together, and form a compound base, from which an acid is produced, having properties peculiar to itself, and distinct from those of all other acids, especially the property of dissolving gold and platina.

In dissolutions of metals in this acid, as in all other acids, the metals are first oxydated by attracting a part of the oxygen from the compound radical. This occasions a disengagement of a particular species of gas not hitherto described, which may be called nitro-muriatic gas; it has a very disagreeable smell, and is fatal to animal life when respired; it attacks iron, and causes it to rust; it is absorbed in considerable quantity by water, which thereby acquires some slight characters of acidity. I had occasion to make these remarks during a course of experiments upon platina, in which I dissolved a considerable quantity of that metal in nitro-muriatic acid.

I at first suspected that, in the mixture of nitric and muriatic acids, the latter attracted a part of the oxygen from the former, and became converted into oxygenated muriatic acid, which gave it the property of dissolving gold; but several facts remain inexplicable upon this supposition. Were it so, we must be able to disengage nitrous gas by heating this acid, which however does not sensibly happen. From these considerations, I am led to adopt the opinion of Mr Berthollet, and to consider nitro-muriatic acid as a single acid, with a compound base or radical.

TABLE of the Combinations of Fluoric Acid, with the Salifiable Bases, in the Order of Affinity.

Names of the Bases. Names of the Neutral Salts.

Lime Fluat of lime. Barytes barytes. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Oxyd of zinc zinc. manganese manganese. iron iron. lead lead. tin tin. cobalt cobalt. copper copper. nickel nickel. arsenic arsenic. bismuth bismuth. mercury mercury. silver silver. gold gold. platina platina.

And by the dry way, Argill Fluat of argill.

Note.—These combinations were entirely unknown to the old chemists, and consequently have no names in the old nomenclature.—A.

SECT. XXI.—Observations upon the Fluoric Acid, and its Combinations.

Fluoric exists ready formed by Nature in the fluoric spars[42], combined with calcareous earth, so as to form an insoluble neutral salt. To obtain it disengaged from that combination, fluor spar, or fluat of lime, is put into a leaden retort, with a proper quantity of sulphuric acid, a recipient likewise of lead, half full of water, is adapted, and fire is applied to the retort. The sulphuric acid, from its greater affinity, expels the fluoric acid which passes over and is absorbed by the water in the receiver. As fluoric acid is naturally in the gasseous form in the ordinary temperature, we can receive it in a pneumato-chemical apparatus over mercury. We are obliged to employ metallic vessels in this process, because fluoric acid dissolves glass and silicious earth, and even renders these bodies volatile, carrying them over with itself in distillation in the gasseous form.

We are indebted to Mr Margraff for our first acquaintance with this acid, though, as he could never procure it free from combination with a considerable quantity of silicious earth, he was ignorant of its being an acid sui generis. The Duke de Liancourt, under the name of Mr Boulanger, considerably increased our knowledge of its properties; and Mr Scheele seems to have exhausted the subject. The only thing remaining is to endeavour to discover the nature of the fluoric radical, of which we cannot hitherto form any ideas, as the acid does not appear to have been decomposed in any experiment. It is only by means of compound affinity that experiments ought to be made with this view, with any probability of success.

TABLE of the Combinations of Boracic Acid, with the Salifiable Bases, in the Order of Affinity.

Bases. Neutral Salts.

Lime Borat of lime. Barytes barytes. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Oxyd of zinc zinc. iron iron. lead lead. tin tin. cobalt cobalt. copper copper. nickel nickel. mercury mercury. Argill argill.

Note.—Most of these combinations were neither known nor named by the old chemists. The boracic acid was formerly called sedative salt, and its compounds borax, with base of fixed vegetable alkali, &c.—A.

SECT. XXII.—Observations upon Boracic Add and its Combinations.

This is a concrete acid, extracted from a salt procured from India called borax or tincall. Although borax has been very long employed in the arts, we have as yet very imperfect knowledge of its origin, and of the methods by which it is extracted and purified; there is reason to believe it to be a native salt, found in the earth in certain parts of the east, and in the water of some lakes. The whole trade of borax is in the hands of the Dutch, who have been exclusively possessed of the art of purifying it till very lately, that Messrs L'Eguillier of Paris have rivalled them in the manufacture; but the process still remains a secret to the world.

By chemical analysis we learn that borax is a neutral salt with excess of base, consisting of soda, partly saturated with a peculiar acid long called Homberg's sedative salt, now the boracic acid. This acid is found in an uncombined state in the waters of certain lakes. That of Cherchiais in Italy contains 94-1/2 grains in each pint of water.

To obtain boracic acid, dissolve some borax in boiling water, filtrate the solution, and add sulphuric acid, or any other having greater affinity to soda than the boracic acid; this latter acid is separated, and is procured in a crystalline form by cooling. This acid was long considered as being formed during the process by which it is obtained, and was consequently supposed to differ according to the nature of the acid employed in separating it from the soda; but it is now universally acknowledged that it is identically the same acid, in whatever way procured, provided it be properly purified from mixture of other acids, by warning, and by repeated solution and cristallization. It is soluble both in water and alkohol, and has the property of communicating a green colour to the flame of that spirit. This circumstance led to a suspicion of its containing copper, which is not confirmed by any decisive experiment. On the contrary, if it contain any of that metal, it must only be considered as an accidental mixture. It combines with the salifiable bases in the humid way; and though, in this manner, it is incapable of dissolving any of the metals directly, this combination is readily affected by compound affinity.

The Table presents its combinations in the order of affinity in the humid way; but there is a considerable change in the order when we operate via sicca; for, in that case, argill, though the last in our list, must be placed immediately after soda.

The boracic radical is hitherto unknown; no experiments having as yet been able to decompose the acid; We conclude, from analogy with the other acids, that oxygen exists in its composition as the acidifying principle.

TABLE of the Combinations of Arseniac Acid, with the Salifiable Bases, in the Order of Affinity.

Bases. Neutral Salts.

Lime Arseniat of lime. Barytes barytes. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Oxyd of zinc zinc. manganese manganese. iron iron. lead lead. tin tin. cobalt cobalt. copper copper. nickel nickel. bismuth bismuth. mercury mercury. antimony antimony. silver silver. gold gold. platina platina. Argill argill.

Note.—This order of salts was entirely unknown to the antient chemists. Mr Macquer, in 1746, discovered the combinations of arseniac acid with potash and soda, to which he gave the name of arsenical neutral salts.—A.

SECT. XXIII.—Observations upon Arseniac Acid, and its Combinations.

In the Collections of the Academy for 1746, Mr Macquer shows that, when a mixture of white oxyd of arsenic and nitre are subjected to the action of a strong fire, a neutral salt is obtained, which he calls neutral salt of arsenic. At that time, the cause of this singular phenomenon, in which a metal acts the part of an acid, was quite unknown; but more modern experiments teach that, during this process, the arsenic becomes oxygenated, by carrying off the oxygen of the nitric acid; it is thus converted into a real acid, and combines with the potash. There are other methods now known for oxygenating arsenic, and obtaining its acid free from combination. The most simple and most effectual of these is as follows: Dissolve white oxyd of arsenic in three parts, by weight, of muriatic acid; to this solution, in a boiling state, add two parts of nitric acid, and evaporate to dryness. In this process the nitric acid is decomposed, its oxygen unites with the oxyd of arsenic, and converts it into an acid, and the nitrous radical flies off in the state of nitrous gas; whilst the muriatic acid is converted by the heat into muriatic acid gas, and may be collected in proper vessels. The arseniac acid is entirely freed from the other acids employed during the process by heating it in a crucible till it begins to grow red; what remains is pure concrete arseniac acid.

Mr Scheele's process, which was repeated with great success by Mr Morveau, in the laboratory at Dijon, is as follows: Distil muriatic acid from the black oxyd of manganese, this converts it into oxygenated muriatic acid, by carrying off the oxygen from the manganese, receive this in a recipient containing white oxyd of arsenic, covered by a little distilled water; the arsenic decomposes the oxygenated muriatic acid, by carrying off its supersaturation of oxygen, the arsenic is converted into arseniac acid, and the oxygenated muriatic acid is brought back to the state of common muriatic acid. The two acids are separated by distillation, with a gentle heat increased towards the end of the operation, the muriatic acid passes over, and the arseniac acid remains behind in a white concrete form.

The arseniac acid is considerably less volatile than white oxyd of arsenic; it often contains white oxyd of arsenic in solution, owing to its not being sufficiently oxygenated; this is prevented by continuing to add nitrous acid, as in the former process, till no more nitrous gas is produced. From all these observations I would give the following definition of arseniac acid. It is a white concrete metallic acid, formed by the combination of arsenic with oxygen, fixed in a red heat, soluble in water, and capable of combining with many of the salifiable bases.

SECT. XXIV.—Observations upon Molybdic Acid, and its Combinations with Acidifiable Bases[43].

Molybdena is a particular metallic body, capable of being oxygenated, so far as to become a true concrete acid[44]. For this purpose, one part ore of molybdena, which is a natural sulphuret of that metal, is put into a retort, with five or six parts nitric acid, diluted with a quarter of its weight of water, and heat is applied to the retort; the oxygen of the nitric acid acts both upon the molybdena and the sulphur, converting the one into molybdic, and the other into sulphuric acid; pour on fresh quantities of nitric acid so long as any red fumes of nitrous gas escape; the molydbena is then oxygenated as far as is possible, and is found at the bottom of the retort in a pulverulent form, resembling chalk. It must be washed in warm water, to separate any adhering particles of sulphuric acid; and, as it is hardly soluble, we lose very little of it in this operation. All its combinations with salifiable bases were unknown to the ancient chemists.

TABLE of the Combinations of Tungstic Acid with the Salifiable Bases.

Bases. Neutral Salts.

Lime Tungstat of lime. Barytes barytes. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Argill argill. Oxyd of antimony(A), &c. antimony(B), &c.

[Note A: The combinations with metallic oxyds were set down by Mr Lavoisier in alphabetical order; their order of affinity being unknown, I have omitted them, as serving no purpose.—E.]

[Note B: All these salts were unknown to the ancient chemists.—A.]

SECT. XXV.—Observations upon Tungstic Acid, and its Combinations.

Tungstein is a particular metal, the ore of which has frequently been confounded with that of tin. The specific gravity of this ore is to water as 6 to 1; in its form of cristallization it resembles the garnet, and varies in colour from a pearl-white to yellow and reddish; it is found in several parts of Saxony and Bohemia. The mineral called Wolfram, which is frequent in the mines of Cornwal, is likewise an ore of this metal. In all these ores the metal is oxydated; and, in some of them, it appears even to be oxygenated to the state of acid, being combined with lime into a true tungstat of lime.

To obtain the acid free, mix one part of ore of tungstein with four parts of carbonat of potash, and melt the mixture in a crucible, then powder and pour on twelve parts of boiling water, add nitric acid, and the tungstic acid precipitates in a concrete form. Afterwards, to insure the complete oxygenation of the metal, add more nitric acid, and evaporate to dryness, repeating this operation so long as red fumes of nitrous gas are produced. To procure tungstic acid perfectly pure, the fusion of the ore with carbonat of potash must be made in a crucible of platina, otherwise the earth of the common crucibles will mix with the products, and adulterate the acid.

TABLE of the Combinations of Tartarous Acid, with the Salifiable Bases, in the Order of Affinity.

Bases. Neutral Salts.

Lime Tartarite of lime. Barytes barytes. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Argill argill. Oxyd of zinc zinc. iron iron. manganese manganese. cobalt cobalt. nickel nickel. lead lead. tin tin. copper copper. bismuth bismuth. antimony antimony. arsenic arsenic. silver silver. mercury mercury. gold gold. platina platina.

SECT. XXVI.—Observations upon Tartarous Acid, and its Combinations.

Tartar, or the concretion which fixes to the inside of vessels in which the fermentation of wine is completed, is a well known salt, composed of a peculiar acid, united in considerable excess to potash. Mr Scheele first pointed out the method of obtaining this acid pure. Having observed that it has a greater affinity to lime than to potash, he directs us to proceed in the following manner. Dissolve purified tartar in boiling water, and add a sufficient quantity of lime till the acid be completely saturated. The tartarite of lime which is formed, being almost insoluble in cold water, falls to the bottom, and is separated from the solution of potash by decantation; it is afterwards washed in cold water, and dried; then pour on some sulphuric acid, diluted with eight or nine parts of water, digest for twelve hours in a gentle heat, frequently stirring the mixture; the sulphuric acid combines with the lime, and the tartarous acid is left free. A small quantity of gas, not hitherto examined, is disengaged during this process. At the end of twelve hours, having decanted off the clear liquor, wash the sulphat of lime in cold water, which add to the decanted liquor, then evaporate the whole, and the tartarous acid is obtained in a concrete form. Two pounds of purified tartar, by means of from eight to ten ounces of sulphuric acid, yield about eleven ounces of tartarous acid.

As the combustible radical exists in excess, or as the acid from tartar is not fully saturated with oxygen, we call it tartarous acid, and the neutral salts formed by its combinations with salifiable bases tartarites. The base of the tartarous acid is a carbono-hydrous or hydro-carbonous radical, less oxygenated than in the oxalic acid; and it would appear, from the experiments of Mr Hassenfratz, that azote enters into the composition of the tartarous radical, even in considerable quantity. By oxygenating the tartarous acid, it is convertible into oxalic, malic, and acetous acids; but it is probable the proportions of hydrogen and charcoal in the radical are changed during these conversions, and that the difference between these acids does not alone consist in the different degrees of oxygenation.

The tartarous acid is susceptible of two degrees of saturation in its combinations with the fixed alkalies; by one of these a salt is formed with excess of acid, improperly called cream of tartar, which in our new nomenclature is named acidulous tartarite of potash; by a second or equal degree of saturation a perfectly neutral salt is formed, formerly called vegetable salt, which we name tartarite of potash. With soda this acid forms tartarite of soda, formerly called sal de Seignette, or sal polychrest of Rochell.

SECT. XXVII.—Observations upon Malic Acid, and its Combinations with the Salifiable Bases[45].

The malic acid exists ready formed in the sour juice of ripe and unripe apples, and many other fruits, and is obtained as follows: Saturate the juice of apples with potash or soda, and add a proper proportion of acetite of lead dissolved in water; a double decomposition takes place, the malic acid combines with the oxyd of lead and precipitates, being almost insoluble, and the acetite of potash or soda remains in the liquor. The malat of lead being separated by decantation, is washed with cold water, and some dilute sulphuric acid is added; this unites with the lead into an insoluble sulphat, and the malic acid remains free in the liquor.

This acid, which is found mixed with citric and tartarous acid in a great number of fruits, is a kind of medium between oxalic and acetous acids being more oxygenated than the former, and less so than the latter. From this circumstance, Mr Hermbstadt calls it imperfect vinegar; but it differs likewise from acetous acid, by having rather more charcoal, and less hydrogen, in the composition of its radical.

When an acid much diluted has been used in the foregoing process, the liquor contains oxalic as well as malic acid, and probably a little tartarous, these are separated by mixing lime-water with the acids, oxalat, tartarite, and malat of lime are produced; the two former, being insoluble, are precipitated, and the malat of lime remains dissolved; from this the pure malic acid is separated by the acetite of lead, and afterwards by sulphuric acid, as directed above.

TABLE of the Combinations of Citric Acid, with the Salifiable Bases, in the Order of Affinity(A).

Bases. Neutral Salts.

Barytes Citrat of barytes. Lime lime. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Oxyd of zinc zinc. manganese manganese. iron iron. lead lead. cobalt cobalt. copper copper. arsenic arsenic. mercury mercury. antimony antimony. silver silver. gold gold. platina platina. Argill argill.

[Note A: These combinations were unknown to the ancient chemists. The order of affinity of the salifiable bases with this acid was determined by Mr Bergman and by Mr de Breney of the Dijon Academy.—A.]

SECT. XXVIII.—Observations upon Citric Acid, and its Combinations.

The citric acid is procured by expression from lemons, and is found in the juices of many other fruits mixed with malic acid. To obtain it pure and concentrated, it is first allowed to depurate from the mucous part of the fruit by long rest in a cool cellar, and is afterwards concentrated by exposing it to the temperature of 4 or 5 degrees below Zero, from 21 deg. to 23 deg. of Fahrenheit, the water is frozen, and the acid remains liquid, reduced to about an eighth part of its original bulk. A lower degree of cold would occasion the acid to be engaged amongst the ice, and render it difficultly separable. This process was pointed out by Mr Georgius.

It is more easily obtained by saturating the lemon-juice with lime, so as to form a citrat of lime, which is insoluble in water; wash this salt, and pour on a proper quantity of sulphuric acid; this forms a sulphat of lime, which precipitates and leaves the citric acid free in the liquor.

TABLE of the Combinations of Pyro-lignous Acid with the Salifiable Bases, in the Order of Affinity(A).

Bases. Neutral Salts.

Lime Pyro-mucite of lime. Barytes barytes. Potash potash. Soda soda. Magnesia magnesia. Ammoniac ammoniac. Oxyd of zinc zinc. manganese manganese. iron iron. lead lead. tin tin. cobalt cobalt. copper copper. nickel nickel. arsenic arsenic. bismuth bismuth. mercury mercury. antimony antimony. silver silver. gold gold. platina platina. Argill argill.

[Note A: The above affinities were determined by Messrs de Morveau and EloI Boursier de Clervaux. These combinations were entirely unknown till lately.—A.]

SECT. XXIX.—Observations upon Pyro-lignous Acid, and its Combinations.

The ancient chemists observed that most of the woods, especially the more heavy and compact ones, gave out a particular acid spirit, by distillation, in a naked fire; but, before Mr Goetling, who gives an account of his experiments upon this subject in Crell's Chemical Journal for 1779, no one had ever made any inquiry into its nature and properties. This acid appears to be the same, whatever be the wood it is procured from. When first distilled, it is of a brown colour, and considerably impregnated with charcoal and oil; it is purified from these by a second distillation. The pyro-lignous radical is chiefly composed of hydrogen and charcoal.

SECT. XXX.—Observations upon Pyro-tartarous Acid, and its Combinations with the Salifiable Bases[46].

The name of Pyro-tartarous acid is given to a dilute empyreumatic acid obtained from purified acidulous tartarite of potash by distillation in a naked fire. To obtain it, let a retort be half filled with powdered tartar, adapt a tubulated recipient, having a bent tube communicating with a bell-glass in a pneumato-chemical apparatus; by gradually raising the fire under the retort, we obtain the pyro-tartarous acid mixed with oil, which is separated by means of a funnel. A vast quantity of carbonic acid gas is disengaged during the distillation. The acid obtained by the above process is much contaminated with oil, which ought to be separated from it. Some authors advise to do this by a second distillation; but the Dijon academicians inform us, that this is attended with great danger from explosions which take place during the process.

TABLE of the Combinations of Pyro-mucous Acid, with the Salifiable Bases, in the Order of Affinity(A).

Bases. Neutral Salts.

Potash Pyro-mucite of potash. Soda soda. Barytes barytes. Lime lime. Magnesia magnesia. Ammoniac ammoniac. Argill argill. Oxyd of zinc zinc. manganese manganese. iron iron. lead lead. tin tin. cobalt cobalt. copper copper. nickel nickel. arsenic arsenic. bismuth bismuth. antimony antimony.