Chapter XII: Introduction (2)

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.

[Note A: All these combinations were unknown to the ancient chemists.--A.]

SECT. XXXI.--_Observations upon Pyro-mucous Acid, and its Combinations._

This acid is obtained by distillation in a naked fire from sugar, and all the saccharine bodies; and, as these substances swell greatly in the fire, it is necessary to leave seven-eighths of the retort empty. It is of a yellow colour, verging to red, and leaves a mark upon the skin, which will not remove but alongst with the epidermis. It may be procured less coloured, by means of a second distillation, and is concentrated by freezing, as is directed for the citric acid. It is chiefly composed of water and oil slightly oxygenated, and is convertible into oxalic and malic acids by farther oxygenation with the nitric acid.

It has been pretended that a large quantity of gas is disengaged during the distillation of this acid, which is not the case if it be conducted slowly, by means of moderate heat.

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

_Bases._ _Neutral Salts._

Lime Oxalat 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.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
mercury mercury.
silver silver.
gold gold.
platina platina.

[Note A: All unknown to the ancient chemists.--A.]

SECT. XXXII.--_Observations upon Oxalic Acid, and its Combinations._

The oxalic acid is mostly prepared in Switzerland and Germany from the expressed juice of sorrel, from which it cristallizes by being left long at rest; in this state it is partly saturated with potash, forming a true acidulous oxalat of potash, or salt with excess of acid. To obtain it pure, it must be formed artificially by oxygenating sugar, which seems to be the true oxalic radical. Upon one part of sugar pour six or eight parts of nitric acid, and apply a gentle heat; a considerable effervescence takes place, and a great quantity of nitrous gas is disengaged; the nitric acid is decomposed, and its oxygen unites to the sugar: By allowing the liquor to stand at rest, cristals of pure oxalic acid are formed, which must be dried upon blotting paper, to separate any remaining portions of nitric acid; and, to ensure the purity of the acid, dissolve the cristals in distilled water, and cristallize them afresh.

+---------------+------------------+--------------------------------------- | _Bases._ | _Neutral salts._ |_Names of the resulting neutral salts_ | | | |_according to the old nomenclature._ | |---------------+------------------+---------------------------------------+ |Barytes |Acetite of barytes{Unknown to the ancients. Discovered by | | | {Mr de Morveau, who calls it _barotic | | | {acete_. | | | | | |Potash | ---- potash {Secret terra foliata tartari of Muller.| | | {Arcanum tartari of Basil Valentin and | | | {Paracelsus. Purgative magistery of | | | {tartar of Schroeder. Essential salt of | | | {wine of Zwelfer. Regenerated tartar of | | | {Tachenius. Diuretic salt of Sylvius | | | {and Wilson. | | | | | |Soda | ---- soda {Foliated earth with base of mineral | | | {alkali. Mineral or crystallisable | | | {foliated earth. Mineral acetous salt. | | | | | |Lime | ---- lime {Salt of chalk, coral, or crabs eyes; | | | {mentioned by Hartman. | | | | | |Magnesia | ---- magnesia |First mentioned by Mr Wenzel. | | | | | |Ammoniac | ---- ammoniac {Spiritus Mindereri. | | | {Ammoniacal acetous salt. | | | | | |Oxyd of zinc | ---- zinc {Known to Glauber, Schwedemberg, | | | {Respour, Pott, de Lassone, and Wenzel, | | | {but not named. | | | | | | ---- manganese| ---- manganese |Unknown to the ancients. | | | | | | ---- iron | ---- iron {Martial vinegar. Described by Monnet, | | | {Wenzel, and the Duke d'Ayen. | | | | | | ---- lead | ---- lead {Sugar, vinegar, and salt of lead or | | | {Saturn. | | | | | | ---- tin | ---- tin {Known to Lemery, Margraff, Monnet, | | | {Weslendorf, and Wenzel, but not named. | | | | | | ---- cobalt | ---- cobalt |Sympathetic ink of Mr Cadet. | | | | | | ---- copper | ---- copper {Verdigris, crystals of verditer, | | | {verditer, distilled verdigris, crystals| | | {of Venus or of copper. | | | | | | ---- nickel | ---- nickel |Unknown to the ancients. | | | | | | ---- arsenic | ---- arsenic {Arsenico-acetous fuming liquor, | | | {liquid phosphorus of Mr Cadet. | | | | | | ---- bismuth | ---- bismuth {Sugar of bismuth of Mr Geoffroi. Known | | | {to Gellert, Pott, Weslendorf, Bergman, | | | {and de Morveau. | | | | | | ---- mercury | ---- mercury {Mercurial foliated earth, Keyser's | | | {famous antivenereal remedy. Mentioned | | | {by Gebaver in 1748; known to Helot, | | | {Margraff, Baume, Bergman, and | | | {de Morveau. | | | | | | ---- antimony | ---- antimony |Unknown. | | | | | | ---- silver | ---- silver {Described by Margraff, Monnet, and | | | {Wenzel; unknown to the ancients. | | | | | | ---- gold | ---- gold {Little known, mentioned by Schroeder | | | {and Juncker. | | | | | | ---- platina | ---- platina |Unknown. | | | | | |Argill | ---- argill |According to Mr Wenzel, vinegar | | | |dissolves only a very small proportion | | | |of argill. | +---------------+------------------+---------------------------------------+

From the liquor remaining after the first cristallization of the oxalic acid we may obtain malic acid by refrigeration: This acid is more oxygenated than the oxalic; and, by a further oxygenation, the sugar is convertible into acetous acid, or vinegar.

The oxalic acid, combined with a small quantity of soda or potash, has the property, like the tartarous acid, of entering into a number of combinations without suffering decomposition: These combinations form triple salts, or neutral salts with double bases, which ought to have proper names. The salt of sorrel, which is potash having oxalic acid combined in excess, is named acidulous oxalat of potash in our new nomenclature.

The acid procured from sorrel has been known to chemists for more than a century, being mentioned by Mr Duclos in the Memoirs of the Academy for 1688, and was pretty accurately described by Boerhaave; but Mr Scheele first showed that it contained potash, and demonstrated its identity with the acid formed by the oxygenation of sugar.

SECT. XXXIII.--_Observations upon Acetous Acid, and its Combinations._