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are considered as possessing the pro- gam of potassium, in contact with any perties of earths in the greatest per- of the earths proper under naphtha, fection, and which some chemical is exposed to the galvanic energy for writers have, on that account, called some time, if it be thrown into water, earths proper. These are silica, alu- not only potash but an earthy matter mina, glucina, yttria, and zirconia. likewise is formed. From these and After the decomposition of the alka- several similar experiments made on lies and alkaline earths, it was natural the earths proper by Mr Davy, it is for Mr Davy to turn his attention rendered probable that they likewise towards these bodies, in order to as. are metallic oxides. He proposes to certain whether they are not metal. distinguish their metallic bases by the lic oxides like the fixed alkalies and names of silicium,alumium, zirconium, alkaline earths. Silica and alumi- glucium, and yttrium. na are the most important of these 8. Ammonia is an alkali, the conbodies. Their properties have some stituents of which were first pointed resemblance to several of the saline out by Scheele, and more accurately bodies. It was, therefore, necessary determined by the experiments of to ascertain, in the first place, whe- Berthollet. These philosophers had ther they might not be compounds shewn it to be a compound of hydroof an acid with some unknown base. gen and azote, and M. Berthollet's When silica was exposed to the ac. experiments were considered as rigid. tion of the galvanic battery, in a ly accurate. They had been congolden vessel filled with pure water, firmed by those of Dr Austine. Both potash was evolved; but it was found of these gentlemen had established to be only mixed with the silica, and that ammonia is composed of nearly to have been derived from the potash four parts by weight of azote, and employed in the original preparation one part of hydrogen ; a determinaof the silica. The silica itself was tion which was acceded to by all che. not found to be acted on by the gal. mists without exception. But after vanic battery thus applied. Hence Mr Davy had demonstrated the ex. there was no reason to consider it as a istence of oxygen in the fixed alka. salt.

lies, analogy led him to look for it None of the earths proper are al. also in ammonia, which is a volatile tered when exposed in a state of pu- alkali. He made a set of experiments rity to a powerful galvanic battery. accordingly, and convinced himself When melted with potash, and expo- that ammonia is a triple compound of sed to the action of the battery, while azote, hydrogen, and oxygen. But still in a state of fusion, metallic glo- his experiments were not of that conbules separate, swim on the surface, clusive nature as to produce convicand burn with great brilliancy, and tion. But it induced Dr Henry and small metallic scales remain attached M. Berthollet, junior, to repeat the to the platinum wire employed to analysis of ammoniacal gas with every complete the circuit. These scales possible precaution, in order to de burn spontaneously when exposed to termine whether oxygen be present in the air, and potash and an earthy it or not. The method employed matter are formed. The same sub- originally by Dr Priestley and Berstances are formed if the scales be thollet was followed by both these thrown into water. When an amal- philosophers. Ammoniacal gas, made

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as dry as possible, is let up into a about five times its usual bulk, loses glass tube, and exposed to the action a good deal of its fluidity, and assumes of repeated electrical shocks. Its the consistence of butter. In short, bulk is nearly donbled, and it is con- it is converted into an amalgam ; of verted into a mixture of azote and course the mercury has combined hydrogen gases. This mixture is with a metallic body. If this amalfired with oxygen gas, and by that gam be plunged into water, a portion mcans the proportion of hydrogen of hydrogen gas is disengaged, the present determined, from which it is mercury immediately resumes its orieasy to deduce the proportion of ginal state, and some ammonia is found azote. This experiment requires many dissolved in the water. From these precautions to secure accuracy. The facts it is scarce possible to avoid mercury over which the gas is recei- concluding, that, by the galvanic enved ought to be newly boiled, in or- ergy, assisted by the presence of the der to remove all moisture, and the mercury, the ammonia has been degas itself ought to be well dried by composed, that its basis is a metal means of pieces of dry potash placed which amalgamates with the mercury, for some time in contact with it. that when the amalgam is plunged

The result of the experiments of into water, the metallic basis decomHenry, Berthollet, and the new ana- poses the water, combines with its lysis of Davy, very nearly coincide. oxygen, and is converted into ammoBy electricity, 100 measures of am- nia, while the hydrogen of the water moniacal gas are expanded to 180 is set at liberty. But, if these conmeasures, and these consist of 74 mea. clusions be well founded, it follows sures of hydrogen and 26 measures of that ammonia is a compound of a meazote per cent. These experiments tallic basis and oxygen ; a conclusion do not indicate the presence of any very different from that drawn from oxygen : azote and hydrogen are the the decomposition of ammonia by only constituents evolved.

electricity. This metallic substance But there is a very extraordinary evolved from ammonia by the galvaexperiment, first made by Berzelius, nic energy has received the name of and afterwards confirmed and varied ammonium. All attempts to procure by Mr Davy, which it is necessary it, except in the state of an amalgam, to consider before we draw any final have entirely failed. Indeed the quanconclusions respecting the constitu- tity of it present in the mercury is so ents of ammonia. If you take a lump small as to bid defiance to our meof sal ammoniac, moisten its surface so thods of investigation. A globule far as to make it a conductor of elec. of mercury weighing 50 grains comtricity, and placing a globule of mer- bines only with about oth part of cury in a hollow previously made in a grain of ammonium. That so miits surface, bring it in contact with nute a portion of matter added to the a disc of platinum connected with the mercury should make so great an alpositive extremity of a galvanic bat- teration in its properties, is one of tery, while a wire proceeding from the most extraordinary facts hitherto the negative end of the battery is observed in chemistry. brought in contact with the globule In order to reconcile this experiof mercury, the mercury thus cir- ment with the analysis of ammonia cumstanced gradually swells up to by ordinary electricity into hydrogen

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and azote, we are under the necessity which he concluded that he had de. of concluding, that either hydrogen composed it, and that its basis was a or azote, or both, are compounds, con- substance similar to charcoal. Oxytaining oxygen as one of the consti. gen from analogy was considered as tuents. The simplest theory would one of its constituents. Hence it ocbe to consider hydrogen as a metallic curred to Mr Davy, that potassium body in a gaseous state, azote as an might be employed with effect to se. oxide of hydrogen, and ammonia as parate its basis from the oxygen with a peroxide of the same body. which it was united. He made some

A very curious set of experiments experiments soon after the discovery made by Mr Davy on the action of of that metal, but did not prosecute potassium on ammoniacal gas, seem- the subject far. Meanwhile Thenard ed at first to lead directly to these and Guy Lussac, by mixing boracic conclusions. The ammonia was ab- acid and potassium, and heating the sorbed, and the potassium converted mixture in a copper tube, succeeded into an olive.coloured substance. in decomposing it, and examined the When this substance was heated, properties of its basis in detail. Be(supposing water excluded,) it gave fore the result of their experiments out hydrogen and azote, the consti- reached Britain, Mr Davy again turntuents of the ammonia absorbed ; but ed his attention to the subject, sucthe proportion of hydrogen was great ceeded in decomposing the acid by a er and that of azote smaller than they similar process, and published a very ought to have been. Hence it was elaborate and complete account of its concluded that the azote had been properties. He gave to the basis of partly decomposed, and that hydro- boracic acid the name of boracium. gen had been evolved as one of its To obtain boracium, two parts of constituents. But when these expe- potassium and one part of vitreous riments were repeated by Mr Davy boracic acid are mixed together, exwith a more perfect apparatus, the posed in a copper or iron tube to a proportion of hydrogen and azote heat gradually raised nearly to redobtained corresponded nearly with the ness, and kept two or three minutes usual proportions obtained by the de- in that heat. The whole is allowed composition of ammonia by electrici. to cool, and the contents of the tube ty. We have no other proof there are washed out with water. The fore of the compound nature of azote potash formed during the experiment than the singular amalgam above de- is saturated with muriatic acid, and scribed ; but that proof is almost the whole is thrown upon a filter. equivalent to a demonstration. Hence The boracium remains upon the filit appears to follow, that ammonia ter. It is to be well washed and contains oxygen as a constituent, but dried. that the oxygen exists only as one of Boracium, thus obtained, is a subthe component parts of azote. Hy- stance of a dark olive green colour, drogen, it would seem, is the other without either taste or smell. It is constituent part of that substance. very friable, and its powder does not

9. Boracic acid has long eluded the scratch glass. In close vessels it may attempts of chemists to ascertain its be exposed to any degree of heat composition. Crell made a set of ex. whatever, without undergoing any periments several years ago, from change. When heated in the open air, or in contact with oxygen gas, it facts Mr Davy suspects that the batakes fire at a temperature below the sis of boracium is of a metallic nature. boiling point of olive oil, and burns 10. The fluoric acid discovered by with a red light, sparkling like char. Scheele as one of the constituents of coal, and is converted into boracic the stone called fuor spar, or fluate of acid. It is difficult to burn it com- lime, is one of the most singular subpletely, because the boracic acid first stances in nature. It has not been formed forms a vitreous crust, which so much examined as it deserves, protects the residue of the boracium chiefly on account of the difficulty of from the action of the oxygen. When obtaining it in a state of purity. this crust is washed off, the boracium When obtained in the usual way by is found in the state of a black mat. heating a mixture of Auor spar and ter, which does not take fire till it be sulphuric acid in a glass vessel, it is a heated nearly to redness, and which gaseous body, holding in solution a absorbs less oxygen during its com- considerable quantity of silicious earth bustion than the olive-coloured mat- which it has taken from the glass ter. Hence it is probable that it is vessel. This foreign body disguises an oxide of boracium. From the ex. its properties so much, that we canperiments of Mr Davy, it appears not determine its exact nature when that boracic acid is composed of thus obtained. 100 boracium,

Thenard and Guy Lussac endea200 oxygen.

voured to procure it free from every

mixture of foreign matter. For this 300

purpose they mixed together vitreous Boracium is a nonconductor of elec- boracic acid and Auor spar in an iron tricity. It is not altered by water. tube, and exposed it to a strong heat. It combines with sulphur, but not Gas came over in abundance. This with phosphorus, hydrogen, azote, gas did not act on glass vessels like or mercury. It unites with the fixed common fuoric acid gas. When alkalies, and forms with them pale mixed with air it smoked, indicating olive-coloured compounds, which give a strong affinity for vapour. Water dark precipitates when decomposed absorbs it in great quantities; and, by muriatic acid. It burns in oxy: when saturated with it, is limpid, muriatic acid, detonates with nitre smoking, and very caustic. Heat exand hyper oxymuriate of potash, ef- pels about one fifth part of the gas, fervesces with nitric acid, and is con- but the rest remains so obstinately verted into boracic acid, blackens fixed, that it cannot be separated from sulphuric acid, and produces no effect the water by heat. The liquid thus on muriatic and acetic acids.

prepared is a heavy limpid acid, ha. Mr Davy has endeavoured to slew ving very much the appearance of that it still retains oxygen. When sulphuric acid. It is equally caustic ; mixed with potassium and heated to its boiling point is considerably higher whiteness, it becomes similar in lus: than that of water, and it may be distre to plumbago, effervesces slightly tilled over without alteration. It with water, and when exposed to the chars vegetable substances like sulair, soon acquires the common ap- phuric acid, and when distilled with pearance of boracium. From these alcohol, forms a peculiar ether. This

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remarkable acid is a compound of bined with the potash formed, and fuoric and boracic acids. Thenard being likewise mixed with siliceous and Guy Lussac, the discoverers of matter, it has not been possible to asit, have given it the name of fluo-boric certain its nature. Mr Dalton indeed acid.

draws a different consequence from When fluor spar and sulphuric acid the experiment. He thinks that the are heated in leaden vessels, no gas hydrogen gas evolved constitutes the whatever is obtained, but only an acid basis of the Auoric acid gas, and hence liquid, consisting of fuoric acid and considers it as a compound of oxygen water. When this liquid is exposed and hydrogen : but the experiment to the air, it emits vapours. When does not seem to warrant any such mixed with water, it becomes hot, and conclusion. even enters into ebullition. When 11. Muriatic acid is one of the chebrought in contact with glass, it acts mical substances which has been the

it, becomes hot, and is convert. longest known and in the most comed into siliciferous fluoric acid gas. mon use ever since men began to make When allowed to touch the skin, a experiments on metallic bodies. Many white spot is forined with the pain of attempts have been made to decom a burn, which terminates in a blister. pose it, but it resisted all the efforts When brought in contact with po. of the most indefatigable chemists, tassium, a violent combustion takes and baffled all their skill. The disa place ; hydrogen gas is evolved, and covery of potassium induced Mr Davy Auate of potash and water disengaged. to apply the action of that powerful

When potassium is placed in con- separator of oxygen, in order if postact with siliciferous fluoric acid gas, sible to detect its base. The experia white crust gradually covers its sur- ment was unsatisfactory. Thenard face. When heat is applied, the me. and Guy Lussac made the same ex. tal bursts through the crust, gradual- periment with a similar result. The ly changes its colour, and at last failure was ascribed to the presence breaks out into a most splendid com- of water in the acid gas. A set of bustion. The fuoric acid gas disap- experiments was made by these genpears, and a chocolate-coloured mass tlemen, in order to deprive the gas of remains, partly at the bottom of the water, and to prepare it quite free retort and partly sublimes. Some from water. The conclusion which hydrogen gas is evolved, but the pro- they drew from these experiments portion of it diminishes according to was, that the compounds containing the care with which the Auoric acid the acid cannot be decomposed ungas has been dried. The chocolate- less water be present, because muria. coloured mass, when viewed under the tic acid gas cannot exist in a separate microscope, appears a heterogeneous state, unless it be united with a cer. mixture of three different substances. tain portion of water. Water then, It effervesces in water, and burns it followed, was an essential consti. when heated in the open air, and is tuent of muriatic acid gas. This was converted into a white saline mass. a very singular conclusion. We are There can be little doubt that in this acquainted with about 23 gaseous experiment the fluoric acid is decom. bodies. Now water does not appear posed ; but its basis remaining come to be essential to the gaseous state of

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