ceding paper as existing in the Saxon grey ore of manganese was examined, soon after the publication of the paper, by Berzelius; and the appearances were shown by him not to depend upon the presence of any new metal, but to be owing to manganese. ARTICLE VI. Experiments on the Nature of Azote, of Hydrogen, and of Ammonia, and upon the Degrees of Oxidation of which Azote is susceptible. By Jacob Berzelius, M. D. F. R. S. Professor of Chemistry and Pharmacy in Stockholm.* THE following experiments are to be considered as a continuation of those which I have already published on the same subject in the Annales de Chimie of Paris, and in the Annalen der Physique of Gilbert, during the years 1811 and 1812. I have endeavoured to prove that azote contains oxygen, and that nitric acid neutralized by a saline base contains six times as much oxygen as that base. By the most accurate of my experiments I have found that the nitrate of lead is composed of Oxide of lead .... .67.3 .32.7 100.0 Hence 100 parts of nitric acid are neutralized by 205.31 of oxide of lead, a quantity which contains 14-715 of oxygen. In the nitrate of barytes 100 parts of acid are combined with 140 73 parts of barytes, which contain 14.73 of oxygen (Ann. de Chim. Nov. 1811, p. 174). Thus these two analyses mutually confirm each other. I have endeavoured to prove that it is a general law that when two oxidized substances combine, the oxygen contained in the one is always either equal in quantity to that contained in the other, or it is a multiple of it by a whole number. If we admit this law to be correct, it follows from it that 100 parts of nitric acid ought to contain a certain number of times 14-715 of oxygen. This number of times must be greater than 4, because decisive experiments have demonstrated that the acid contains more oxygen than 14-715 × 4: but it cannot be greater than 7, because that constitutes more than the weight of the acid. Hence It may be proper to mention, for the information of Dr. Berzelius, that this paper, though dated the 22d April, did not reach the Editor till the end of August. the acid must contain either 5 or 6 times 14.715 of oxygen. But nitric acid has the property of forming with oxide of lead several salts with excess of base; as I have shown in my memoir on the composition of salts with excess of base (Ann. de Chimie, June 1812). And among these subnitrates there is one in which the acid is combined with twice as much base as in the neutral nitrate: but if the above-mentioned law be just, it is clear that the oxygen in nitric acid cannot be 5 times 14.715; because, were that the case, the oxygen of the acid in the subnitrate just mentioned would not be a multiple of that in the base by a whole number, but by 24; consequently the true quantity of oxygen in 100 parts of nitric acid must be 6 times 14.715, or 88.29. But as the most exact experimenters have not indicated so great a quantity of oxygen in nitric acid, it is necessary that the oxygen wanting should be contained in the azote, which of course must be a compound of oxygen and a combustible radicle. Such are the conclusions which I have drawn from my experiments hitherto published. I do not know how far chemical philosophers will allow them to be well founded; but, in hopes that the laws of chemical proportions which I have endeavoured to establish will be one day examined and admitted, I will continue in this paper my researches respecting the nature of the bodies announced in the title; and I shall commence with the composition of nitric acid, supposing it to have azote for its radicle. It is well known that M. Gay-Lussac accompanied his important discovery of the proportions in which gaseous bodies combine by an analysis of the oxides of azote, and of nitrous and nitric acids. He found that nitric acid contains one volume of azotic gas and two volumes of oxygen gas, which amounts in weight to 30 5 azote, and 69.5 oxygen. Messrs. Cavendish and Davy had obtained nearly the same result from their analytical experiments on this acid. These excellent authorities induced me to confide in this determination; and in my analysis of the subnitrates and subnitrites I obtained a satisfactory confirmation of it; that is to say, I thought I obtained a subnítrate such that the acid and oxide contained each an equal quantity of oxygen, supposing the acid composed as above stated. I was struck with this anomaly; and I have stated (Ann. de Chim. June 1812) the experiments which it induced me to make, though they led me to no satisfactory explanation. In consequence of the new determination of the composition of nitric acid by Dalton and Davy, I have been engaged to resume my researches, and have been happy enough to see the anomaly disappear, and to obtain results which throw much light on the nature of azote. Mr. Dalton, who has given, in his New System of Chemical Philosophy, a corpuscular theory from which the doctrine of definite proportions follows as a necessary consequence, has stated (vol. ii. p. 329), that the smallest quantity of nitrous gas, which in his experiments was condensed by 100 parts in volume of oxygen gas, was always 130. If we convert these volumes into weights we obtain nearly 73.5 oxygen and 26.5 azote, When I compared this determination with the results of my analyses of the nitrates, I found, to my great surprise, that they accorded much better with it than with the determination of Gay-Lussac, though the difference in the weights that ought to be obtained in the analysis of the nitrates, nitrate of ammonia for example, according to the one or the other of these determinations, was so little, that it was impossible to decide by experiment which of the two was the most just. During my residence in London last summer, Sir Humphry Davy informed me that he had found, by experiments made with the greatest care, that nitric acid is composed in volume of 100 parts of azote and 250 of oxygen; that is to say, of 26.5 parts, by weight, of azote, and 73 5 of oxygen: for when nitrate of ammonia is distilled in a moderate heat, it is completely changed into nitrous oxide gas and water, without any trace of azotic gas. In the Elements of Chemistry published soon after by this illustrious chemist he has represented nitric acid as a compound of one proportion of azote and five of oxygen. It follows that in the neutral nitrates the acid saturates a quantity of base of which the oxygen is 4th of that of the acid, supposing azote to be the radicle of this acid. As Davy has not admitted the result of the calculations which I have made on the composition of azote, he considers this last substance as an element, and of course he makes no inquiry about the sixth portion of oxygen which ought to exist in the azote. The only experiments of mine which did not agree with the determination of this celebrated chemist were the analyses of the subnitrates and subnitrites of lead at a maximum. I determined, therefore, to repeat them; and I shall now state the result which I obtained. The analysis of the subnitrate of lead at a maximum (mentioned in my treatise on the composition of the subsalts) being very simple, and very easy to be made with precision, I had no reason to doubt its exactness. It was more probable that I had committed some error in the method of procuring the salt. I might have obtained a mixture of hydrate of lead and subnitrate of lead, or a mixture of two different subnitrates of lead. I resolved, therefore, to examine the precipitates produced in a solution of nitrate of lead by different quantities of ammonia. Subnitrate of Lead at a Maximum.-The precipitate obtained by pouring an excess of ammonia into a solution of nitrate of lead was digested for 24 hours in concentrated and caustic am 4 monia. It was then washed upon a filter till every trace of: ammonia disappeared. When dried at a temperature a little above 212°, it assumed the form of a white powder. When applied to the tongue, it had a weak, but very styptic taste. It dissolved readily in nitric acid without effervescence, and of: course contained no carbonic acid. Neither did it contain any ammonia, as caustic potash decomposed it without the evolu tion of any ammoniacal odour. Ten parts (amounting to 15444 grains troy) of this salt exposed in a small crucible, exactly weighed, and placed in a sand-bath to a height considerably higher than that of boiling water, gave out pure water, and assumed a yellow colour. The loss of weight was 0.18. The heat being raised still higher, a little water was disengaged, but it was accompanied by red fumes. The loss now amounted to 0.198. As the last portions of water were disengaged at the same time with the acid, I cannot determine the quantity of water with rigorous exactness: but this experiment shows us that the proportion of water exceeds a little 1.8 per cent., but does not amount to 1.98. The residue, heated in the crucible till the acid was completely expelled, left a quantity of yellow oxide of lead weighing 9.08. To ascertain whether this subnitrate could be always produced with the same properties and composition when the excess of ammonia employed was great, I prepared a new quantity of it, and obtained exactly the same results: 10 parts of it left 9.064 of yellow oxide, and furnished 0-185 of water, containing traces of acid. The subnitrate at a maximum, then, is composed as follows: But 908 parts of yellow oxide of lead contain 6.492 of oxygen. The 7.37 of nitric acid, if we consider it as composed of oxygen and azote, contain only 5.417; but such a composition is inconsistent with the laws of chemical proportions. On the other hand, if we suppose azote to be an oxide, and nitric acid to be composed as we have stated at the beginning of this dissertation, then the 7:37 of acid will contain 6.508 of oxygen, that is to say, the same quantity with the oxide of lead. The 1.83 of water contains F615 of oxygen, which multiplied by four gives 6:46. Hence it follows that the oxygen of the water. * The mean of two experiments. is 4th of that of the base; and if the water be represented by 1, the acid and oxide will be represented each by 4. On the other hand, 73.7 of acid are combined with 908 of oxide; so that 100 parts of acid combine with 1236 of oxide. We have seen that in the neutral nitrate 100 parts of acid are combined with 205.81 parts of oxide. Now 205 81 × 6 = 1234.86; that is to say, that in the subnitrate at a maximum the nitric acid is combined with six times the quantity of base with which it is combined in the neutral nitrate. Intermediate Subnitrate of Lead.-I precipitated a portion of nitrate of lead by ammonia in excess, but without digesting it in pure ammonia. The precipitate was white; and when the liquid was passed through the filter I perceived that the salt began to dissolve in proportion as the ammoniacal liquor was removed; but it precipitated again in proportion as the drops fell into the liquid that had already passed through the filter. The precipitate, when washed and dried, formed a white powder; 10 parts of which exposed in a crucible to a sand heat lost 0-292 of water, and became pale yellow. Being then heated till the whole of the acid was removed, there remained 8.584 of yellow oxide. As such a composition does not accord with the laws of chemical proportions, we must conclude that this precipitate is a mixture of subnitrate at a maximum, and of that in which the acid is combined with twice the quantity of base that exists in the neutral nitrate. To obtain the intermediate subnitrate I endeavoured to employ the smallest possible excess of ammonia. I precipitated, by ammonia in a very small excess, a solution of nitrate of lead, and I digested the solution in the excess employed. To decompose the subsalt at a maximum which might have been formed, I poured drop by drop a weak solution of nitrate of lead into the mixture, and digested it for half an hour. I then added a little more of the nitrate, and digested again; and I continued this process till the liquor contained no longer any excess of ammonia, excepting a portion so small that it could no longer be recognized by the smell, but became sensible by means of a stopper dipped in muriatic acid. I then filtered, and the precipitate exhibited the same phenomenon of partially dissolving again, already mentioned. When about the fourth part of this precipitate was carried away by edulcoration I considered the residue as sufficiently edulcorated, and therefore dried it. The subsalt thus obtained was analysed in the same manner as the preceding specimens. It yielded pure water, and assumed, while still hot, a yellowish colour, but which on cooling was changed into white. Ten parts of it produced 0.35 parts of water, and left, when the acid was driven off, 8.298 |