partment of writing in which he does not very eminently excel. We are at a lofs to perceive the neceflity of rejecting the terms oxygenate and oxidate, for oxygenize and oxidize, with their ehmly derivatives, oxygenizement and oxidizement. Concentrate (for concentrated) we are inclined to rank among errors in grammar, rather than neologifms. Solidification is a word which we apprehend owes its being to Mr Chenevix; and it is rather unaccountable how to fcrupulous a nomenclator should retain the old barbarous term cinnabar. We are happy to obferve, however, that he has over come his antipathy to the term oxide, founded, if we rightly re member, on the notion that this word is apt to be confounded with ex-bide. And, whatever objections our author's fcientific phrafeology may be liable to, we would infinitely rather have him coin as many new words, or revive as many obfolete ones as he pleases, than continue his former practice of ftopping perpetually to introduce a differtation upon the propriety of his language.

With refpect to his general observations, the following extract may perhaps juftify our inability to applaud his talent for this fpecies of writing.

If a theory is fometimes ufeful as a standard to which we may re fer our knowledge, it is at other times prejudicial, by creating an attachment in our minds to preconceived ideas, which have been admitted, without inquiring whether from truth or from convenience, We eafily correct our judgement as to facts; and the evidence of experiment is equally convincing to all perfons. But theories not admitting of mathematical demonftration, and being but the interpretation of a feries of facts, are the creatures of opinion, and are governed by the various impreffions made upon every individual. Nature laughs at our fpeculations; and though from time to time we receive fuch warnings as fhould awaken us to a due fenfe of our limited knowledge, we are prefented with an ample compenfation in the extenfion of our views, and a nearer approach to immutable truth.' p. 317.

The two moft remarkable circumftances in the conftitution of palladium, for the knowledge of which the fcientific world is indebted to Mr Chenevix, are the peculiarity of the properties that diftinguish it from every other metal, and the impoffibility of decompounding it by any known procefs. He has infifted a good deal upon the fingularity of its qualities differing fo widely from thofe of mercury and platina; but we acknowledge ourfelves unable to perceive any thing peculiar in this difference. It is one of the most general laws of elective attraction, that the compound body poffeffes properties entirely different from the ingredients by the union of which it is formed. Nothing furely can lefs resemble fulphuric acid, than fulphate of foda; or can any bodies exhibit lefs fimilarity than water or fteam,

trix, was either defcribed or exhibited. No perfon of fcientific authority came forward to vouch for the account given of the fingular properties which this fubftance was faid to poffefs; and thofe properties were only unfolded as an advertisement of an article of commerce. All these circumftances contributed to involve the authenticity of the fpecimens in a great degree of sufpicion, and to render it extremely probable that the fubftance expofed to fale as a new metal, was only a compound or other modification of known minerals, effected by artificial means. With a view to the determination of this point, Mr Chenevix undertook the course of experiments which forms the fubject of the paper now before us. And, as he very foon discovered, in the famples which he examined, properties extremely different from thofe of the known metals, he was led to extend his inquiries, and to procure, for this purpose, the whole of the fpecimens offered to the public by the proprietor. In prefenting our readers with an abftract of this investigation, we fhall confider, first, the experi ments made upon the properties and habitudes of this doubtful fubftance: thefe did not fuffice to determine its precife nature, which was only difcovered, by attempting to form a fimilar body from a union of fimple fubftances. We fhall, in the fecond place, confider the fynthetical experiments. After having by this procefs afcertained the component parts of palladium, our author endeavoured to separate the compound body into its ingredients: These attempts to analyse the alloy will form the last object of

attention.

I. The fpecific gravity of the fpecimens varied from 10.972 to 11.482: a heat much greater than that of melting gold was required to fufe them; and the specific gravity of the button was increafed to 11.871. Sulphur makes it melt at a low temperature, and forms with it a very brittle fulphurate. Charcoal appears to have no fort of affinity with palladium. This fubftance, when polished, resembles platina very nearly; when melted, it affumes the appearance of cryftallization, and is extremely malleable.

The alloy of palladium with equal parts of filver, had a lower fpecific gravity than palladium itself: the alloy with platina had a much greater specific gravity: the alloys with lead and bifmuth bore a ftriking refemblance to each other; a new circumftance, our readers will remark, in the analogy formerly pointed out between those two metals by Mr Hatchett. (No. VI. p. 454-)

The alkalies act weakly on palladium, with the affistance of atmospherical air. The mineral acids act much more violently, particularly the nitric and muriatic, and most of all the nitromuriatic acid. With all these folvents it forms a red liquor,

from

from which it is precipitated in the form of an orange-coloured powder, by alkalies, earths, and all the metals except gold, filver, and platina.

Notwithstanding the analogy of many of the properties of palladium to those of platina, yet, in feveral refpects, the above experiments were entirely irreconcileable with the known habitudes either of that fubftance, or of gold or filver. Some other tefts which our author applied, rendered it equally improbable that either lead, copper, or mercury, fhould have contributed to the formation of this fingular body. Above all, the specific gravity of palladium and its habitudes, both with the acids and with refpect to the other metals, were fuch as could never have been expected from the known properties either of platina or mercury; and yet our author found, rather by a cafual experiment than by the refult of the trials above analysed, that those two metals might be fo united as to form a compound in which the most obvious properties of each were entirely concealed, and new properties exhibited, exactly correfponding with those of palladium.

II. When a folution of platina is made by nitro-muriatic acid, and red oxide of mercury made by nitric acid is added to the former folution until it is faturated; and when the whole mixture is heated with green fulphate of iron; a copious precipitate of metallic powder is formed, which is with difficulty fufible into a button, which readily melts when fulphur is added, is foluble in nitric acid, has a fpecific gravity of 11.2, and is entirely fimilar to palladium. This alloy contains about one part of mercury and two of platina.

If in this experiment there be fubftituted for fulphate of iron, either iron, zinc, or phofphate of ammonia, no palladium is produced; nor can platina and mercury be united fo as to form palladium, either by direct trituration and digeftion, or by mixture of their folutions in acids, or by expofing the two bodies together to violent degrees of heat, or by palling the vapours of the one over the other in a ftate of intenfe fution, or by exhibiting the metals to each other under the action of the most powerful galvanic pile. By two methods befides the one firft afcertained, palladium may be formed: fulphurated hydrogen gas may be paffed through the mixed folution of platina and mercury; or the precipitate of platina by ammonia, from its folution in nitromuriatic acid, may be triturated with mercury, and then expofed to a violent heat. The fuccefs of both these methods, however, is extremely uncertain; and the union of the metals in every way, except the procefs of reduction by fulphate of iron, feems to depend upon fo great a number of unknown circumstances, that the operation may fairly be confidered as. one of the most capricious

in chemistry. We are, however, warranted in concluding, that various alloys of mercury and platina may be formed, which do not poffefs the diftinguishing properties of palladium. To unite the two metals fo as to increafe the fufibility and diminish the fpecific gravity of the platina, is by no means difficult: But the compound does not acquire the characteristic qualities of palladium until a much greater proportion of the mercury has been combined; and its folubility in nitric acid only takes place when the specific gravity has been reduced to 12 or 12.5.

III. It is fingular with what force the component parts of palladium are united, notwithstanding their repugnance to enter into combination. All the experiments which our author made with a view to analyse this fubftance, completely failed. He tried the converfe of all his fynthetical operations without effect. He expofed palladium to a violent heat; fubjected it to cupellation; burnt it both in oxygen gas and by means of the galvanic pile, without the flightest tendency to feparation being evinced by the component parts. When it was burnt, a thick white smoke arose, which, on being collected, was found to confift of palladium, entirely unaffected by the operation. Thefe experiments were tried not only upon the fpecimens expofed to fale, but upon the fubftance produced by our author's experiments; and, what is not a little remarkable, it was found as impoffible to decompofe the imperfect kind of palladium, formed by a flight union of platina and mercury, as to feparate thefe two metals, from the union of which they are fufceptible in the largest proportions.

Mr Chenevix concludes his paper with fome experiments upon the mutual affinities of metals, and the affinities of platina with acids. The former clafs of experiments is not very interefting in the latter, it is afcertained that fulphuric acid has a stronger affinity for platina than muriatic acid; from whence our author infers, that the opinion is fallacious which accounts for the folution of platina in nitro-muriatic acid, upon the fup. pofition that the muriatic acid affifts the process in the fame manner as fulphuric acid aids the decompofition. of water by iron. One argument, which he omits to adduce on this point, may be drawn from the opinion now univerfally entertained by the best chemifts, that, in the nitro-muriatic acid, neither of the component acids exifts entire, as the fulphuric acid exifts in its mixture with water; but that, in fact, a new acid, with a feparate radical, is formed by the combination of the other two.

Mr Chenevix has in this, as in all his other papers, needlessly expofed himself to criticifm, both by the affectation of his no menclature, and by the introduction of general reflections; a de

partment

partment of writing in which he does not very eminently excel. We are at a lofs to perceive the neceffity of rejecting the terms oxygenate and oxidate, for oxygenize and oxidize, with their clumfy de: ivatives, oxygenizement and oxidizement. Concentrate (for concentrated) we are inclined to rank among errors in grammar, rather than neologifms. Solidification is a word which we apprehend owes its being to Mr Chenevix; and it is rather unaccountable how to fcrupulous a nomenclator fhould retain the old barbarous tera cinnabar. We are happy to obferve, however, that he has overcome his antipathy to the term oxide, founded, if we rightly re member, on the notion that this word is apt to be confounded with ox-hide. And, whatever objections our author's fcientific phrafeology may be liable to, we would infinitely rather have him coin as many new words, or revive as many obfolete ones as he pleases, than continue his former practice of ftopping perpetually to introduce a differtation upon the propriety of his language.

With respect to his general obfervations, the following extract may perhaps juftify our inability to applaud his talent for this fpecies of writing.

If a theory is fometimes ufeful as a ftandard to which we may re fer our knowledge, it is at other times prejudicial, by creating an attachment in our minds to preconceived ideas, which have been admitted, without inquiring whether from truth or from convenience, We eafily correct our judgement as to facts; and the evidence of experiment is equally convincing to all perfons. But theories not admitting of mathematical demonftration, and being but the interpretation of a feries of facts, are the creatures of opinion, and are governed by the various impreffions made upon every individual. Nature laughs at our fpeculations; and though from time to time we receive fuch warnings as fhould awaken us to a due fenfe of our limited knowledge, we are prefented with an ample compenfation in the extenfion of our views, and a nearer approach to immutable truth.' p. 317.

The two moft remarkable circumftances in the conftitution of palladium, for the knowledge of which the scientific world. is indebted to Mr Chenevix, are the peculiarity of the properties that diftinguish it from every other metal, and the impoffibility of decompounding it by any known procefs. He has infifted a good deal upon the fingularity of its qualities differing so widely from thofe of mercury and platina; but we acknowledge ourfelves unable to perceive any thing peculiar in this difference. It is one of the most general laws of elective attraction, that the compound body poffeffes properties entirely different from the ingredients by the union of which it is formed. Nothing furely can lefs refemble fulphuric acid, than fulphate of foda; nor can any bodies exhibit lefs fimilarity than water or fteam,