foreign matter: and if we may suppose the second to have contained the same quantity, and each of the buttons to have retained 0.01 of carbon, it would follow, that these oxidules were composed of 33 oxigen to 100 of iron. Priestley and Chaussier both disoxidated iron by raising it and with hi to a high temperature, and thus exposing it to the action drogen gas, by Priestley, of hidrogen gas. Amédée Berthollet has since announced Chaussier, A. the same result in a paper read to the Institute for 1807. Berthollet As neither of these gentlemen has pointed out the diminution of weight of the oxidule in these experiments, Mr. Charbaut, a pupil at the Practical School at Moustier, and myself repeated them in the summer of 1807. We found, Haffenfratz. that 11:58 grains of oxidule of iron from the island of Elba lost in reduction 3.34 grains; whence it would follow, that 140.53 of oxidule contained 40-53 of oxigen to 100 of iron; supposing it to be perfectly pure, which is very probable; though of this we are not certain, as we did not analyse it. Charbaut, and ments. From these experiments we may conclude, that it is very Remarks on difficult, if not impossible, to carry back the oxide, either these experi. by means of heat alone, or of heat and carbon, to the state of oxidule. From the reduction of the oxidule of the valley of Aost by charcoal it would appear to consist, taking the nearest round numbers, of 77 iron and 23 oxigen. At the conclusion of these observations we will examine, to what the difference between the oxidules of Aost and Elba is ascribable. 3d Method. Oxidation of iron by metallic oxides. of other me Iron has not yet been oxided by the help of any other Oxidation of metallic oxides, that have less affinity than itself for oxigen, iron by oxides but those of arsenic and mercury; because these two me- tals, tals, when disoxidated, evaporate at a high temperature. Guyton fused in a closed crucible equal parts of iron and by Guyton, oxide of arsenic. The latter metal evaporated, and the iron was oxided. The increase of weight was 27·1 on 100 of iron. Lavoisier fused iron both with oxide of arsenic and oxide and-Lavoisier. Dig Acad. Diss. sur le Phlogistique, p. 199. of No accurate be drawn from these of mercury. He found, that in these two fusions the iron increased from 35 to 40 per cent. In the table which follows his paper he gives the increase of iron by arsenic as 30 of oxigen to 100 of metal; and in his Elementary Treatise of Chemistry he quotes au experiment, in which iron treated with oxide of mercury gained 32 per cent. It is not easy to deduce from these experiments any posiinferences to tive conclusion respecting the proportion of oxigen in the two degrees of oxidation, because, 1st, the quantities of oxigen combined vary too much: 2dly, the state of the oxide after oxidation was not accurately ascertained: 3dly, it is not certain, that the arsenic, which has a great affinity for iron, did not carry away some of it when volatilized. It appears too, that Guyton, in his experiment, did not mix a sufficient quantity of oxide of arsenic with the iron; for, according to the experiments of Proust*, the white oxide of this metal contain but 33 of oxigen to 100 of arsenic; whence the 100 parts of oxidecould only have yielded about 25 of oxigen to the iron. Oxidation of Martial ethi ops. 4th Method. Oxidation of iron by water. The black oxide has long been prepared in the shops, iron by water. under the name of martial ethiops, by putting iron filings into a bottle full of water, shaking the mixture from time to time, and opening the bottle after every shaking, to let out the hidrogen gas evolved. To accelerate the process, Rouelle proposed to acidulate the water with vinegar, Croharé with a little nitric acid†. Lavoisier. Cavazzely. Bucholz. Lavoisier found, that iron filings gained an increase of 30 or 35 per cent by agitation in pure water; and the same if the water were acidulated‡. Cavazzely, on oxiding iron by means of water, obtained an oxide increased 35 per cent on the iron employed §. Bucholz, repeating the, experiment of oxidation by water alone at the common temperature of the atmosphere, * Journ. de Phys. 1799, tom. II, p. 150. ↑ Ann. de Chim, vol. XXXI, p. 333 and fol. Ac. des Sciences, 1782, p. 543 and fol. § Ann. de Chim. vol. XLIII, p. 94, remarked, remarked, that the oxide was covered with a crust of yellow oxide, while another part was in the state of black oxide. account, The great variation in the weight of the oxide obtained These experi by this method, and the observation of yellow oxide formed ments of no on its surface, show, that nothing can be deduced from experiments of the kind. Lefebvre, Stoutz, and myself, when in Carinthia, satis- Water assisted fied ourselves, that red hot iron immersed in water decom- by heat. posed it; the iron being oxided, and hidrogen evolved*. The illustrious Lavoisier, taking the hiut from this experi- Lavoisier. ment, heated little bits of iron twisted spirally in a copper tube, and passed the vapour of water through them while red hot. The water was decomposed, and the iron oxided. The iron had increased in weight 31.38 per cent. The hi drogen gas, which he collected and weighed, was found to be in the proper proportion for forming water with the oxi gen combinedt. Bucholz, repeating the experiment of Lavoisier by pass- Bucholz. ing the vapour of water through iron filings heated red hot in a close vessel, obtained a black oxide containing 767 of iron and 23.3 of oxigen. The result obtained by Lavoisier appears accurate, and that of Bucholz rather too low. It is to be regretted that this process was not oftener repeated, but I shall notice this result again, when recapitulating those that may be considered as accurate. (To be concluded in our next.) .V. Some Remarks on the Observations and Experiments of Mr. Murray on the Nature of Oximuriatic Acid, and its Rela tions to Muriatic Acid. By Mr. JOHN DAVY. SIR, To Mr. NICHOLSON. IT is generally adinitted as a fundamental principle of Substances not modern chemistry, that all bodies not yet decompounded decomposed to Mém. de l'Acad. des Sciences, 1781, p. 475. + Traité élém. de Chim. tom. I, p. 92 and fol. VOL. XXVIII.-MAR. 1811. are be deemed simple. tween the doctrine, are to be considered as simple substances. In this respect the phlogistic principally differs from the antiphlogistic Difference be doctrine: the former is hypothetical, the latter theoretical. phlogistic and The phlogistic hypothesis in its most perfect form, as ad antiphlogistic vanced by Mr. Cavendish, could not be confuted: it was simple, luminous, and perfectly well adapted to explain all the phenomena of chemistry; but it was still an hypothesis. TheDifference be- ory is a history of generalisation and facts, hypothesis is a se tween theory ries of suppositions. Mr. Murray 'does not observe this dise and hypothe tinction, he makes promiscuous use of the two words. Sometimes he speaks of the theory, and at other times of the hypothesis of Mr. Davy. I think it necessary to point out what to me appeared a loose mode of expression. It is of main importance, that expressions of facts be not misrepresented. It is of great consequence, that things be not termed notions-that theory be not considered as spe culation. sis. Mr Davy's conclusions Before I examine the objections of Mr. Murray to Mr. Lot hypotheti- Davy's conclusions, I shall endeavour to show, that these conclusions are not tainted by the slightest admixture of hypothesis. With this object in view I beg leave to recapitulate a few leading circumstances. cal. Formation of muriatic acid gas from oximuriatic and hidrogen. Metals form Muriatic acid gas is formed by detonating together equal volumes of oximuriatic gas and hidrogen gas; and, if the experiment is correctly made, there is no condensation attending their union*. The metals combine immediately with oximuriatic gas, peculiar com- and form with it a peculiar class of compounds, many of pounds with which are decomposed by water; and when this occurs, a oximuriatic gas: metallic oxide and muriatic acid gas are always produced. and the same compounds with muriatic acid gas, hidrogen being set free. When the metals of the fixed alkalis, or the common metals, mercury, iron, tin, and zinc, are heated in muriatic acid gas, hidrogen gas equal to one half of the volume of the acid gas consumed appears free, and substances are produced exactly similar to those formed by the direct union of The quantity the same metals with oximuriatic acid. In these experiments there is no difference in the proportion of hidrogen gas li of hidrogen Dot at all af. I have seen this experiment made a number of times, in vessels that had been exhausted, and over mercury, and with similar results. berated berated: it is not less, when the acid gas has been previ- fected by the ously exposed to the action of salts having a strong attrac- presence of tion for water: nor is it greater in relation to the quantity of muriate formed, when liquid muriatic acid is used. water. metal of an When metallic oxides are acted on by oximuriatic gas, Oximuriatic oxigen gas is evolved; and when acted on by muriatic acid gas seizes the gas, water is produced. In the one instance the oxigen oxide, and exdisengaged is the exact quantity contained in the oxide; pels its oxigen; which, if and in the other case, the water produced has as much muriatic acid hidrogen, as existed in the muriatic acid gas, and as much gas be employ. oxigen as the metallic oxide. contained. ed, combines with its hidro water. Such I conceive are the principal facts, which constitute gen, and forms the foundation of my brother's theory, that oximuriatic gas Mr. Davy's is a simple body. He combines this gas with hidrogen gas theory. and forms muriatic acid gas. In his theory muriatic acid gas is a compound of oximuriatic gas and hidrogen. He combines oximuriatic gas with sulphur, phosphorus, and the metals and in his theory, the resulting substances are compounds of the inflammable and metallic bodies respectively, and oximuriatic gas. Here we perceive no supposition, but a simple expression of facts, and this I humbly conceive is pure and genuine theory. ury. Having stated my opinion respecting Mr. Davy's views, Mr Murray's, I shall proceed to examine Mr. Murray's. This gentle- or the old the man is of the old opinion, that oximuriatic gas is a compound body, consisting of muriatic acid and oxigen; that the muriates, substances formed by the combustion of the metals in oximuriatic gas, are composed of muriatic acid and metallic oxides: and likewise, that the constituents of the compounds resulting from the combustion of sulphur and phosphorus in oximuriatic gas are the respective acids of these two bodies and muriatic acid. Let it be kept in remembrance, that Mr. Murray does not Mr. Murray's mean, when he speaks of muriatic acid, the ponderable muriatic acid not the whole, part of muriatic gas, which combined with ammonia, con- ponderable stitutes muriate of ammonia. The idea he attaches to the part of muria. uc acid gas, word is very different, for he says, that water is absolutely necessary to the existence of muriatic acid in the gaseous state; that muriatic acid has not yet been decomposed; and that it has an important and an anomalous relation to wa |