with the Zaire, by means of the lakes of Wangara. We have not space to follow his arguments on this head, which we think are urged with great ingenuity: but perhaps the whole style of the book, as far as regards the labour of the Editor, is a little too polemical, and more resembling that we have been used to observe in a popular Journal, than what would have been expected from the Secretary of the Admiralty, in his official capacity. We shall close our very imperfect account, by observing that Mr. Barrow is supported in his theory, by a note in Capt. Tucky's Journal, nearly the last he made, in which he says, "extraordinary quiet rise of the river shows it to issue from some lake, which had received almost the whole of its waters to the north of the line." And after this, in the same Journal, the words "hypothesis confirmed," occurs; and in a private letter written at Yellala, he dwells more particularly on this proposition. ART. XVIII. Remarks on Dr Ure's "Experiments to determine the Constitution of Liquid Nitric Acid,"* &c. By Richard Phillips, Esq. F. L. S. & M. Geol. Soc. DR. Ure has asserted, in his observations upon the composition of nitric acid, that "the exact proportion of its two constituents, azote and oxygen, is a problem which seems hitherto to have baffled the best directed efforts of modern science. M. Gay Lussac states, as its composition in 100 parts, 30.4 azote+ 69.6 oxygen; and Mr. Dalton 26.7 azote + 73.3 oxygen. Thus discordant are the latest determinations." To which Dr. Ure adds, "I hope soon to be able to present to the public some researches, which may possibly tend to clear up this mystery." I propose to examine the accuracy of Dr. Ure's opinion on this subject, by collecting and comparing the statements which have been recently made with respect to the acid in question, by philosophers of the highest reputation. The first to whom I shall refer, is Sir H. Davy, who observes in p. 265 of his * Journal of Science and the Arts, vol. iv. p. 291. Elements of Chymical Philosophy, "101 will be the number for the acid contained in the pale acid, and in the salts called nitrates, and it will consist of one [proportion] of azote, and five [proportions] of oxygen." Now as Sir H. Davy represents a proportion of azote by 26, and one of oxygen by 15, nitric acid must be composed of 25.742 azote 74.258 oxygen 100.000 The evidence which I shall next adduce as to the composition of nitric acid, is that stated by Dr. Wollaston, in his memoir on Chymical Equivalents. Alluding to some experiments which he had just described, Dr. Wollaston says, "I have no hesitation in prefering the estimate to be obtained from Richter's analysis of nitrate of potash, which gives 67,45, from which if we subtract one portion of azote 17,54, there remain 49,91, so nearly 5 portions of oxygen; that I consider the truth to be 17.54 [azote] +50 [oxygen,] or 67.54." If then 67.54 of nitric acid contain 17.54 of azote, 100 parts must consist of 25.97 azote 100.00 To these determinations I shall add that of M. Gay Lussac, who is indeed quoted by Dr. Ure, to prove that discordance, rather than agreement exists on this subject; if, however, Dr. Ure had extended his researches for evidence sufficiently, he would have seen that this profound chymist, with candour worthy of imitation, has acknowledged the inaccuracy of that analysis, which Dr. Ure erroneously supposes to be, and quotes as the result of his latest experiments. In the Annales de Chimie et de Physique, (tome i. p. 404.) M. Gay Lussac states nitric acid to be composed of 100 volumes of azote+ 250 of oxygen; we have then merely to ascertain the comparative densities of these gases to determine their relative weights. According to Biot and Arago, equal volumes of azote and oxygen are to each other in weight as 0.96913 to 1.10359; therefore a compound of 100 volumes of azote and 250 of oxygen consists of 25.995 azote. 74.005 100.000 These numbers, it will be observed, are nearly identical with those which I have copied from Dr. Wollaston's memoir; they differ immaterially from those given by Sir H. Davy, and do not vary much from Mr. Dalton's analysis, as quoted by Dr. Ure. Considering all who have preceded him in this inquiry, as having failed in the accomplishment of their intention, Dr. Ure appears to be very naturally anxious to supply the deficiency he has discovered. It would seem indeed, as if he had completed the investigation with no ordinary degree of celerity, considering the acknowledged difficulty of the subject; for when alluding in a subsequent part of his paper, to the composition of liquid nitric acid, he says, "when we inquire more minutely into the peculiarity attending the above compound of greatest density, we shall find it to consist of 7 atoms of water =79.24, united to 1 atom of dry acid: = 67.5." It is scarcely necessary to observe, that the number representing a compound body, cannot be ascertained without a previous knowledge of the proportions of its constituents; and it must be allowed, that Dr. Ure would not represent nitric acid by a number which he knew to be inaccurate; but having denied the correctness of every previous analysis, we are at liberty to conjecture that 67.5, as above quoted, result from the performance of those experiments, before the close of his paper, which he appears only to have contemplated at its commencement. But supposing this to be the case, it is very remarkable that Dr. Ure should not have allowed, that 67.5 is almost precisely the number by which nitric acid is represented on Dr. Wollaston's scale, for he is acquainted with this instrument, and even quotes it on another occasion to prove its inaccuracy: in the present instance, therefore, it would have been but candid to have excepted Dr. Wollaston from those whose efforts have been "baffled." The principal intention of Dr. Ure in the paper now under consideration, is to determine the constitution of liquid nitric acid, a subject which he describes as "involved in perhaps still greater obscurity and contradiction," than that of the dry acid. To prove the justness of this observation, Dr. Ure quotes and compares the statements of Sir H. Davy, Kirwan, Dalton, and Dr. Wollaston, and he concludes them all to be erroneous. According to Dr. Ure, 41.7 of carbonate of potash, consisting of 13.094 of carbonic acid + 28.606 potash, require 32.394 of dry nitric acid for their decomposition, and the nitrate of potash resulting weighs 61 grains: this determination agrees very nearly with Dr. Wollaston's scale, by which it appears that 41.7 of carbonate of potash, consisting of 13.26 carbonic acid + 28.44 potash are decomposed and converted into 60.94 nitrate of potash, by 03.5 of dry nitric acid; and as Dr. Ure considers that 32.394 of dry nitric acid are equivalent to 40.64 of liquid acid of sp. gr. 1.5, this acid must consist in 100 parts of 79.71 dry acid, 20.29 water. 100.00 By Dr. Wollaston's scale, liquid nitric acid of sp. gr. 1.5 is constituted of 67.54 one atom of dry acid, + 22.64, or two atoms of water, 100 parts must therefore consist of 74.895 dry acid, 25.105 water. 100.000 It appears then that whilst the composition of nitrate of potash is nearly similar according to these statements, in Dr. Wollaston's estimate the dry acid in liquid acid of sp. gr. 1.5 is to that of Dr. Ure, as 74.895 to 79.71. Before I mention the experiments which I have made on this subject, I shall notice and compare Dr. Ure's statements with each other. I have already quoted a passage, in which he represents acid of a certain density, as consisting of 7 atoms, water 79.24 united to one atom of dry acid 67.5; these numbers appear to be from Dr. Wollaston's scale, and of course they are considered as correctly representing the quantity of water and acid in question. If, however, we compare these numbers with those which are to be derived from Dr. Ure's analysis of liquid nitric acid of 1.5, it will appear that this acid is composed of 67.5, one atom acid united to 16.79 water, and consequently of one atom acid, and one atom and 54% of an atom of water, a conclusion, of which it may be truly stated in the language of Dr. Ure, that it "exhibits internal proofs of inconsistency and error." To examine the subject experimentally as well as theoretically, I prepared some pure nitric acid, which had a sp. gr. of 1.496, so nearly 1.5, that they may be considered as identical in experiment. Of this acid, I saturated 150 grains with potash, and evaporated the solution of nitrate of potash to dryness; the salt obtained weighed 215 grs.; and according to Dr. Ure, 61 of nitre contain 32.394 of dry acid, agreeing very nearly with 32.5, which is Dr. Wollaston's proportion, as then 61 give 32.5, 215 must contain 114.55 of dry acid derived from 150 of liquid. One hundred parts of the liquid acid appear to be composed of 76.367 acid 23.633 water 700.000. The dry acid it will be seen exceeds Dr. Wollaston's estimate by 1,472, and is less than Dr. Ure's by 3.343. It is easier, for obvious reasons, to obtain more accurate results with carbonate of lime than with carbonate of potash ; I shall therefore now state the experiments which I have made with this substance. I ascertained some years since, that 476 grains of carbonate of lime require 681.75 of liquid nitric acid, |