yellow oxide. Hence the portion of acid amounts to 1:352. Hence this subsalt is composed of Now 82.98 of oxide contain 5.933 of oxygen, 13.52 of acid 11.93 contain 11.93, and 3.5 of water contain 3.08: but 2 ≈ 5·965, and 3·08 × 2 = 6·16. Hence in this salt the acid contains twice as much oxygen as the oxide, and the oxide twice as much as the water. Farther, we find that 135·2 of acid are united with 829'8 of oxide, therefore 100 of acid combine with 615 of oxide; but 205.81 x 3 = 617-43; that is to say, that in this salt the acid is combined with three times as much oxide as in the neutral nitrate. I ought to observe that I repeated a second time the preparation and analysis of this subsalt, and obtained as the result 82.975 oxide, 3.25 of water, and 13.775 of acid. The slight difference between these two experiments is to be ascribed to the great care and patience necessary to procure the subsalt entirely free from all admixture of the two other subsalts; for when there is a slight excess of ammonia a small quantity of the subnitrate at a maximum is formed: and when too little ammonia has been employed, or the mixture not digested sufficiently long, the precipitate is contaminated with the subsalt at a minimum: and in this last case the quantity of water diminishes in proportion as that of the acid augments. These experiments prove that the subnitrate at a maximum, of which I have given a description and analysis in my essay already quoted, was in reality merely a mixture of the two subnitrates just examined: and consequently that a subnitrate in which the acid saturates 12 as much of base as in the neutral nitrate does not exist. Nitric acid, then, has the property of combining with four different proportions of oxide of lead; that is to say, a, with 205:81 of oxide, forming the neutral nitrate; b, with twice that quantity=411-62, forming the subnitrate at a minimum ; c, with 205-81 × 3 = 617-43, forming the intermediate subnitrate; and, finally, d, with 205.81 × 6 = 1234·86, forming the subnitrate at a maximum. As these subnitrates, or at least It is proper to observe, that a subnitrate in which the acid is combined with four times 205-81 of oxide cannot exist, because in that case the oxygen of the oxide would be a fractional part of that of the acid. the difference between them, have been hitherto unknown to chemists, I shall here give a sketch of their properties and composition. 1. The First Subnitrate, or Subnitrate at a Minimum, is produced when nitrate of lead is precipitated by a smaller quantity of ammonia than is sufficient to neutralize one-half of the nitric acid. It is composed of such proportions that the acid contains three times as much oxygen as the oxide. It contains no water of combination. When decomposed by heat it leaves its oxide in an agglutinated and reddish coloured mass, just as happens when the neutral nitrate is treated in the same way. It is very soluble in water, and boiling water dissolves a much greater quantity of it than cold water. On cooling it deposites the salt in small transparent crystals, which decrepitate strongly. when heated. 2. The Second, or Intermediate Subnitrate, is formed when the neutral nitrate of lead is mixed with a quantity of ammonia exactly sufficient to neutralize 3 of the nitric acid. When more or less of the alkali is employed there is formed a mixture of the intermediate subnitrate with one or other of the two other subnitrates. The intermediate subnitrate is composed in such a manner that the acid contains twice as much oxygen as the base, while the water of combination contains half as much oxygen as the base. When heated it loses its water and becomes yellowish, but recovers its white colour again on cooling; so that it contains. enough of acid to conceal the colour of the oxide. It is feebly soluble in pure water; but the addition of any other salt, even nitrate of lead, precipitates it again. When heated to redness it is decomposed, leaving the oxide of lead in the state of a very minute powder, and of a very fine yellow colour. 3. The Third Subnitrate, or Subnitrate at a Maximum, is obtained when nitrate of lead is mixed with a considerable excess of concentrated ammonia. It is so constituted that the acid and oxide contain equal quantities of oxygen. It contains water of combination, the oxygen of which is of that of the oxide. It loses its water at a moderate heat, and becomes of a deep yellow colour, which it retains when cold. It is scarcely soluble in water. When decomposed by heat it leaves its oxide in a fine powder and yellow colour, like the preceding subnitrate. The anomaly in my first experiments having disappeared, and the only circumstance in which these experiments did not coincide with those of Davy and Dalton being removed, it remains only to verify by direct experiment their determination of the quantity of azote contained in nitric acid. My method of proceeding was as follows: I dissolved in water in a convenient apparatus 12:05 parts of nitrate of barytes, previously reduced to powder and strongly dried. With this solution I mixed concentrated muriatic acid, and then added 9 parts of copper. The solution of the copper was promoted by the application of heat, and at the end of six hours it was all dissolved. The liquor had assumed a brownish blue colour, holding in solution a little of the muriate of copper (murias cuprosus). The evolution of nitrous gas continued still four hours longer, and the liquid gradually assumed a green colour. After sixteen hours the apparatus was allowed to cool. When the greenish liquid was mixed with distilled water it became milky, in consequence of the precipitation of the murias cuprosus; but the precipitate subsided very slowly, and was for the most part (as usually happens) converted into murias cupricus before it could be collected, dried, and weighed. To judge from appearances, its weight could not have amounted to one part. Its presence, however, shows that the nitric acid was entirely decomposed. The nitrous gas, examined by means of muriate of iron, left so small a quantity of unabsorbed residue, that we can only ascribe it to the azotic gas disengaged from the water in the pneumatic apparatus. Let us examine the result of this experiment: 12:05 parts of Bitrate of barytes contain 5.00 parts of pure nitric acid, which (supposing the determination of Davy and Dalton accurate) is composed of 2-207 oxygen and 2.793 of nitrous gas: but if the determination of Gay-Lussac be the most correct, the five parts of acid are composed of 1.738 of oxygen and 3.262 of nitrous gas. According to the first supposition the 5.00 of acid will be capable of peroxidizing 9-12 parts of copper, while according to the second they will only peroxidize 7.00 parts of that metal: but in the experiment above described 9.5 parts of copper had been dissolved, while at the same time a small quantity of muriate of copper had formed, owing to the surplus of copper dissolved. We cannot attribute the difference between 7 and 94 to the formation of muriate of copper, because in that case the quantity of muriate deposited would have amounted to 7 parts, which is much greater than the truth. Experiments prove, then : 1. That azote cannot be considered as the radicle of nitric acid; but that the acid must contain another radicle, the weight of which must be 11-72 per cent. of the acid. 2. That nitric acid does not contain more than 26.43 of azote to 73.57 of oxygen, nearly the numbers established by Davy in his Elements of Chemical Philosophy. 3. That the acid containing only 11.72 per cent. of radicle, but 26.43 per cent. of azote, it follows that 11.72 of radicle united to 14.71 of oxygen constitutes azote. Hence azote is composed as follows: 1 Radicle .....44 32.... 79'64....100.00 Now this composition approaches very nearly to what I had obtained in my preceding memoirs on this subject. 4. That nitric acid is composed as follows: That is to say, that if we consider it as having azote for its radicle it neutralizes a quantity of base containing 4th of the oxygen in the acid; but if we consider it as having a particular radicle it neutralizes a quantity of base, the oxygen of which amounts to th of that in the acid. I shall now show that the radicle of azote is not, as I supposed for some time, the metallic body conceived to constitute the radicle of ammonia (or at least in the present state of our knowledge we cannot consider it as such); but another body, for which we must have a name in order to avoid circumlocutions. I propose, according to the principles explained in my essay on chemical nomenclature (Jour. de Physique, 1811), to give it the name of nitricum; as we say caloricum, carbonicum, &c. The word nitrogenium, though sanctioned by two words of the same kind, cannot well be employed, because it has always had the same meaning with azote. Azote, or nitrogen, according to my nomenclature, is the suboxide of nitric, suboxidum nitricum, just as carbonic oxide gas is the suboxide of carbon; that is to say, that both belong to a class of oxides incapable of combining with other oxides till they have united with a greater proportion of oxygen. ARTICLE VII. An Account of the Explosion of Inflammable Air which lately occurred in the Collingwood Main Colliery. Drawn up for the "Annals of Philosophy." On Saturday the 17th of July, at two o'clock, p. m. in the Collingwood Main Colliery, situated upon the river Tyne, near North Shields, a very considerable quantity of inflammable air, or carbureted hydrogen gas, came into contact with the pitmen's candles, which caused a most tremendous explosion, by which eight persons were killed upon the spot, and two severely wounded and scorched. The following particulars of this melancholy disaster were communicated verbatim at the abovementioned colliery, a few days after the accident, to the writer of this, by Henry Hall, who fortunately escaped, though in the midst of imminent danger. At the time when the explosion took place the above-named Henry Hall, and five other pitmen, were proceeding with burthens of timber through the old workings or excavations (the proper road being obstructed by a creep, *) in the full confidence of safety, having been assured by Mr. Hope, the under viewer, that there was no fear of the "mine firing." In an instant this young man, Henry Hall, and the five pitmen who were with him, were by the explosion thrown upon their faces; and the shock was so great as to deprive him of sensation, as well as volition, till the after-blast, or after-damp,† as it is called, gave him such excitement that he faintly recollects being urged like a ball along the floor of the mine with incredible velocity. Soon after this he was again deprived of sensation, in which state he continued for about twenty minutes, till he breathed the pure atmospheric air upon the bank, at the top of the shaft, to which place his brother had carried him, who descended into the mine as soon as he possibly could, upon hearing the explosion, at the risk of his own life, for the purpose of saving that of his brother, or of any other person whoan he could find. I may remark, by the by, that according to the rules of the Royal Humane Society, if my memory serves me, H. Hall's brother, and several others, are entitled to rewards from that very excellent institution. H. Hall reports, that after he recovered sensation he felt his whole body racked with pain, the burnt places giving him no uneasiness, comparatively speaking; and that his suffering continued without intermission for two days. Bad as H. Hall's case was, the other five pitmen who were with him had not even such an escape, for four of them were instantly killed, and Ralph Stokell so dangerously bruised and burnt in several places that his life was for some time despaired of. At a distant part of the mine, where some other pitmen were employed in taking up metal plates, timber, &c. Mr. Hope, the under viewer, Mr. Wild, the overman, and two pitmen, were suffocated by the choak-damp, or carbonic acid gas. Mr. Wild had wandered at least a hundred yards before he met his death by suffocation. * In working the coal, the pitmen leave pillars, in the form of parallelograms, for the support of the roof. If these pillars are narrow, and the floor of the mine soft or tender, they are apt to sink into the floor, and cause such an approximation as to prevent ventilation, &c. This is technically called a creep. + Vide Annals of Philosophy, vol. i. p. 359, |