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hcat. When the iron turnings are water, with which alcohol, ether, and raised to a white heat, the potash is other similar Auids are always conta. melted by means of a chauffer, and minated. The liquid, in which it suffered to pass slowly through the can be preserved for the greatest turvings. It is decomposed ; hy. length of time unaltered, is newly. drogen gas rushes out of the glass distired naphtha : Oil of turpentine tube in abundance, and after the pro- likewise answers pretty well. Hydrocess is at an end, the potassium is gen gas dissolves it in considerable found towards the extremity of the quantity when assisted by heat, and gun-barrel to which the glass tube forms a compound gas, to which Davy is luted. This process has not hi- has given the name of pot-assureted therto succeeded in furnishing sodi- hydrogen.
It combines with various doses of 3. Potassium possesses the follow- oxygen, and of course forms different ing properties, as ascertained by Mr oxides. The peroxide is readily Davy. Its colour is white like that formed by fusing together potassium of mercury. At the temperature of and potash. It has a brown colour 100° Fahrenheit, it is as Auid as when hot, but on cooling becomes mercury; at 500 it is a soft and grey. When exposed to the air, it malleable solid ; while at 32° it is absorbs more oxygen, and becomes hard, brittle, and crystallized in fa- potash. There is reason to conclude cets. It is much lighter than any from some of Mr Davy's recent ex. other metallic body known, swim- periments, that potassiumis capable of ming in all liquids, even the lightest uniting with a greater proportion of oils. Mr Davy estimated its specific oxygen than exists in potash, and of gravity at 0.770. Its affinity for forming a peroxide, which readily oxygen is so great, that it cannot be gives out oxygen when heated. left exposed to the atmosphere with- Potassium combines readily with out instantly changing its state. sulphur and phosphorus, and with The surface is immediately covered all the metals hitherto tried. These with a coat of potash, which absorbs alloys are destroyed by water or air, water ; this water is decomposed, the potassium being converted into new potash formed, and in a very potash, and the other metal set at li. short time the whole mass is convert. berty. One part of potassium rened into liquid potash. When thrown ders 70 parts of mercury solid, and upon water, it decomposes that li- forms with it a soft amalgam, which quid with great rapidity, hydrogen is speedily decomposed by water, gas is evolved, which holds a little of hydrogen gas being evolved, potash the potassium in solution, and, in con- formed, and the mercury set free. sequence takes fire as soon as it comes Potassium is capable of decomposing in contact with the air. This combus- all the metallic oxides, and likewise tion kindles the potassium, which in. all salts hitherto tried. A very costantly burns with a kind of explo- pious set of experiments on the subsion. One grain of potassium, when ject was made by Thenard and Guy thrown into water, evolves 1.0625 Lussac. Most of the decompositions cubic inches of hydrogen gas. Potas- were accompanied by combustion. sium, in like manner, decomposes the It follows, from Mr Davy's experiments, that potash is composed alkalies likewise. This is a rude and of 86 potassium,
rather unforeseen shock to the theory 14 oxygen,
of that ingenious philosopher, and
points out the impropriety of con100
structing a language upon the prioor the oxygen in potash amounts to ciples of theory alone, as was the about one-seventh of its weight. case with the chemical nomenclature
4. The properties of sodium are contrived by the French chemists,very analogous to those of potas- a nomenclature extravagantly praisium.
sed, but defective and erroneous in It is a white metal like silver, and some of its most material parts. at the common temperature of the 5. The striking analogy between atmosphere is solid, but very mallea- the four alkaline earths, barytes, ble, and so soft that two pieces of it strontian, lime, and magnesia, and the may be welded together by simple fixed alkalies, rendered it probable pressure. It begins to melt at 120°, that they were similar also in their and is completely fluid at 180°. It composition. Indeed it had been does not volatilize at a heat sufficiently long the opinion of certain chemists, strong to melt plate-glass. Its spe- that the earths are metallic oxides, cific gravity is 0.9348.
and Lavoisier had stated the probabiIts affinity for oxygen is similar to lity of this opinion in his Elements. that of potassium. Like potassium, It was natural for Mr Davy, after it is converted into soda by simple having succeeded in decomposing the exposure to the air, and when thrown
fixed alkalies, to apply the same meupon water, decomposes that liquid thod of analysis to the alkaline earths; rapidly, hydrogen gas being evolved. but his first attempts were not crown. It is not soluble in hydrogen gas. ed with success. Hence the reason why it does not He tried to decompose them by burn when thrown upon water like the action of the galvanic battery potassium. Like potassium, it com. under naphtha, having previously bines with various doses of oxygen. moistened them slightly to make It combines likewise with phospho- them conductors. In these cases in. rus, sulphur, and the metals, and flammable gas was evolved, and the forms alloys as easily decomposable earths, where in contact with the neas the alloys of potassium.
gative wires, soon became dark-coSoda, according to the experi- loured, and small metallic points apments of Mr Davy, is composed peared, which became white when ex. of 78 sodium,
posed to the air. In these experi22 oxygen,
ments there was reason for believing
that the earths had been decompo. 100
sed; but the quantity of metallic matThus it has been ascertained, that both ter evolved was so minute as to elude the fixed alkalies are metallic oxi- examination. des : a discovery quite unexpected An attempt was made to decom. by chemists, which destroys the pro- pose the alkaline earths, by heating priety of the term oxygen, invented them with potassium in glass tubes ; by Lavoisier ; since that principle is but it did not succeed. The earths, not only the former of acids but of indeed, became dark-coloured, but the glass was always acted on, and no ficult to drive off the whole of it, and metallic globules were obtained. Mix- obtain the metallic basis of the earth tures of potash and the earths were in a state of purity. fired together, and then exposed to 6. The metallic basis of barytes, the action of the galvanic battery. obtained in this way, is a white meBy this means metallic globules were tal like silver, solid at the usual temobtained less fusible than potassium, perature of the atmosphere, but be. and which, when exposed to the air, coming Auid before ignition. When were converted into potash and a heated it acts violently on the glass white powder. Hence they must vessel in which the experiment is have been alloys of potassium and made. It flattened by pressure, but the basis of the earth employed. required a considerable force for this
When the earths were mixed with effect. When exposed to the air, it a portion of red oxide of mercury, rapidly tarnished, and fell into a white and exposed to the action of the gal. powder, which was barytes. When vanic battery, globules were obtain thrown into water it sunk to the bot. ed, which were alloys of mercury and tom ; hydrogen gas was evolved, and the earthy basis of the earth employ- it was converted into barytes. It is ed. But these globules did not in- 4 or 5 times heavier than water. crease after the first application of When confined with oxygen gas, it the galvanic battery, and they were absorbs a portion of it, and is contoo minute for accurate examination, verted into barytes. Hence it folMr Davy at last succeeded in ob- lows, that barytes is a compound of taining satisfactory results, by em. this metal and oxygen. The metal ploying a method suggested by Pro- of barytes has been distinguished by fessor Berzelius of Stockholm. A the name of barium. portion of the earth to be decompo
The metal of strontian possesses sed was placed upon a disc of plati- nearly the same characters with that num connected with the positive ex- of barytes, excepting that, when ex. tremity of the galvanic battery, a posed to the air, or thrown into wa. globule of mercury was placed upon ter, it absorbs oxygen, and is convert. the earth, and a wire from the nega- ed into strontian. It has received tive extremity of the battery was the name of strontium. brought in contact with the mercu- The metal from lime is of a similar ry. The earth was decomposed, and nature. When heated it burns with its metallic basis formed an amalgam a white light and great brilliancy. It with the mercury. To facilitate the has received the name of calcium. process, Mr Davy usually mixed the The metal of magnesia is similar alkaline earth with a portion of red in appearance to the others. When oxide of mercury. The amalgam exposed to the air, or thrown into thus obtained was put into a glass water, it is converted into magnesia. tube filled with naphtha; the naph. It is much more easily obtained from tha was boiled off, and while the sulphate of magnesia than from pure tube was filled with the vapour of magnesia ; probably in consequence that fluid, it was hermetically sealed. of the insolubility of this last in waHeat was then applied to drive off ter. This metal has received thethe
mercury. It was easy to drive name of magnium. off a portion of the mercury, but dif- 7. There are five substances which 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 basc. 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 deburn 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
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 fuidity, and assumes of repeated electrical shocks. Its the consistence of butter. In short, bulk is nearly doubled, 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 means 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 en. ved 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