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be the same substance as is procured by the direct action of iodine on ammonia, which is a compound of that body with azote. Chlorionic acid occasions a copious precipitation when added to solutions of the metallic salts; and as the action is unaccompanied by any effervescence, Sir H. presumes, from analogy, that the precipitate consists of a triple combination of the metal with iodine and oxygene. Sulphate of iron, nitro-muriate of lead and tin, and nitrate of copper, are the only metallic salts with which the experiment appears to have been made.

Of the compound gases, Sir H. has submitted iodine to the action of sulphuretted hydrogene, olefiant gas, nitrous gas, and carbonic oxide. It combines with sulphuretted hydrogene, forming a reddish brown-coloured liquid, which when thrown into water is decomposed, hydroionic acid being formed, and sulphur precipitated. By subliming iodine repeatedly in dry olefiant gas, a small quantity of a reddish-brown liquid was formed, which is volatile at a low temperature, and gives a yellow tint to water, but does not make it acid. The quantity of gas absorbed is very small. Iodine has no effect on nitrous gas; nor was any combination effected by subliming it in carbonic oxides in ordinary day light: but when the vessel containing carbonic oxide and iodine in a gaseous state was exposed to the dirert rays of the sun, a small quantity of a limpid fluid, having an acrid taste, was formed; so that it is probable, like chlorine, it may be combined with carbonic oxide by the action of solar light

The best test of the presence of iodine in any compound, is afforded by its action upon silver. Water which contains less than Tooo part of its weight of the double or triple alkaline compound, tarnishes polisted silver, and the effect produced by the compounds of iodine may be distinguished by this circumstance from that produced by the alkaline sulphurets or sulphuretted hydrogene, that the solutions containing sulphurets lose their power of tarnishing silver, by being boiled slightly with a little muriatic acid, but those which contain iodine do not. .

Sir H. examined specimens of alkali produced from vegetables growing on the sea shore, from Sicily, from Spain, and from the Roman states, without obtaining any indications of the presence of iodine; nor did he gain any unequivocal evidence of its existence by the evaporation of sea-water taken up on the coast of Liguria, in a part of the bay remote from any source of fresh water. But the first crystals of salt which were formed, appeared to him to tarnish silver on which they were fused more than the last. It is scarcely possible to doubt that iodine does exist in sea-water in minute quantity, and Sir H. thinks it is probably in a state of triple union with oxygene and sodium, and that it is separated with the first crystals

of muriate of soda which are formed. Sir H. thinks it not improbable that the superiority of bay-salt over rock-salt, in preserving meat and fish, may be owing to the presence of a minute quantity of this singular body. Some of the binary and triple compoun is of iodine with sodium, were rubbed on pieces. of beef which had been several days killed, and they did not putrify Observations respecting the natural Production of Saltpetre

on the Walls of subterraneous and other Buildings. By John Kidd, M. D. Professor of Chemistry at Oxford.

This is an ingenious paper, but it is not susceptible of abridgement, nor does it throw any new light upon the most curious and obscure part of the subject to which it relates, viz. the source of the potash which is contained in the nitre, and the existence of which in the situations where nitre spontaneously forms, is unsupported by any evidence which is not entirely gratuitous. Observations conducted with the minuteness and accuracy which characterize this paper, and connected with more refined analytical researches, can alone afford any 'satisfactory elucidation of the subject.. On the Nature of the Salts termed triple Prussiates, and on Acids formed by the Union of certain Bodies with the Elements of the Prussic Acid. By Robert Porrett, jun.

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This is an elaborate communication which opens some new and interesting views of the nature of Prussic acid, and its combinations. The object of the paper is very clearly stated by its Author, to be “to reconcile with the general properties of other saline bodies the anomalies which the triple prussiates

present; to simplify the received opinion respecting their na«ture, and to make known some new acids which I have dis6 covered.' Mr. Porrett considers the class of salts which have been termed triple Prussiates, as binary compounds, of which the acid is not the Prussic, but a new acid into which the black oxide of iron enters as a component part, that substance being superadded to the other elements of Prussic acid in order to its formation. The evidences adduced in support of this view of the subject, in addition to the anomalies which encumber the received theory, are, the results of the decomposition of the triple Prussiates by the Voltaic battery, and also by the agency of ordinary chemical affinities. Triple Prussiate of soda was exposed to a battery of small plates for twenty hours, and the soda was attracted to the negative pole, the iron passing over with the other elements of the Prussic acid to the positive

one, which Mr. P. fairly concludes would hardly have been the case if the iron had entered into the composition of the salt as a base, and not as a component part of the acid.

Triple prussiate of barytes was decomposed by sulphuric acid, the utmost care being taken not to add more acid than was necessary to saturate the barytic earth contained in the solution; the pure acid of the triple Prussiate consequently remained in the solution after the sulphat of barytes had subsided. It exbibited the following characters. Its colour was a pale lemon yellow, it had no smell, and was decomposed by a gentle heat, or a strong light; Prussic acid being then formed, and white triple Prussiate of iron, which rapidly absorbing oxygen from the atmosphere, become the blue triple Prussiate. It forms the triple Prussiate by direct combination with the alkalies, earths, or metallic oxides. It displaces acetic acid from all its combinations in the cold; and it expels all other acids from those combinations with the base of which it forms an insoluble salt. Its ready decomposition by heat sufficiently accounts for its not being obtained from the triple Prussiate by distillation, and for the formation in these cases of Prussic acid, and triple Prussiate of iron..

• By proving that the oxide of iron, contained in the triple prussiates, is an elementary part of an acid, sui generis, the several anomalies mentioned in the beginning of this paper, are easily explained; for instance, its occasioning the simple prussiates to pass from an alkaline to a neutral state, is owing to its constituting, with the other elements present, a new acid having much stronger acid properties than the prussic. Its not being affected by the usual tests for iron, is owing to its existing as an element of an acid, in which state it is no more to be expected that it should be discovered by the ordinary re-agents, than that the sulphur in sulphuric acid should blacken metallic solutions. Finally, its accompanying the elements of the prussic acid in all cases of transfer from one base to another, is owing to its forming with these elements the acid of the triple prussiates, which acid when transferred by stronger affinities, carries with it of course all its com. ponent parts.

Mr. P. thinks that he has ascertained that the elements which combine to form Prussic acid, are capable of uniting with other substances besides black oxide of iron, to as to form peculiar àcids having properties perfectly distinct and characteristic. Sulphur is one of the substances which Mr. P. has discovered to enter into such a combination, and he has given some account of the new acid obtained by this means; but the investigation is as yet confessedly imperfect. In consequence of these new discoveries, Mr. P. thinks himself authorized to propose some innovations on the received nomenclature of these compounds. By forming the initial letters of the elementary bodies which enter into the composition of Prussic acid into a new word, and adding

the termination ic, he gets the term chyazic, and then by prefixing to this term the word ferruretted, sulphuretted, &c. we have distinctive appellations for the new acids. Thus the ferruretted chyazic, acid is the new pame proposed for the combination of prussic acid with black oxide of iron. We should be glad to see some logical principle adhered to in the new coinage of terms, to which the daily extension of chemical discovery may give rise ; for without this we may expect the science to be overwhelmed with names, as barbarous and uncouth as those which were swept away by the truly philosophical reformation of Lavoisier.

Mr. P. has given some elaborate analytical details relative to the composition of the ferruretted chyazate of potash, (triple Prussiate of potash)—and of barytes, and of its combination with peroxide of iron : and also of sulphuretted chyazic acid, and some of its saline compounds. Some Experiments on the Combustion of the Diamond and

other Carbonaceous substances. By Sir Humphry Davy, L. L. D. F.R.S. V. P. R. I.

These experiments were undertaken for the purpose of affording farther elucidation of the nature of the diamond, and its relation to other species of carbonaceous matter; for the extraordinary differences in physical character between diamond and common charcoal, naturally induce a doubt as to the perfect accuracy of those experiments, which when fairly followed out in their legitimate consequences, establish the absolute identity of their chemical character. The experiments detailed in this paper afford the most unequivocal evidence in support of the inference drawn from all former experiments on the diamond, that it is perfectly pure carbonaceous matter, and that consequently the only product obtained by its combustion in pure oxygen gas, is carbonic acid gas; in no respect differing from that obtained from carbonat of lime, or from any other source.

The experiments were made with the great lens in the cabinet of natural history at Florence; and Sir H. had an opportunity of observing that when diamond is strongly ignited in a thin capsule of platinum perforated with numerous orifices, so as to admit the air freely, that it continues to burn in oxygene gas after it is removed from the focus of the lens, with a strong red light so brilliant as to be visible in bright sunshine, and with a heat so intense as to fuse a platinum wire which was attached to the capsule.

The other carbonaceous substances which were made the subject of similar experiments, were, plumbago from Borrowdale, charcoal formed by the action of sulphuric acid or oil of turpentine, and some formed during the formation of sulphuric ether, and from which nitric acid had been distilled and subsequently · Vol. V. N. S.

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ignited, and charcoal of oak which had undergone the same process. In the combustion of these different varieties of cbarcoal, some aqueous moisture was uniformly produced, and when the original temperature of the globe in which the experiment was made, was restored, it was found condensed in the inside of the vessel; the largest quantity was afforded by the charcoal of oak wood, the least by that of oil of turpentine; the diminution of volume in the former case was equivalent to 513.3 grains of mercury, in the latter to 107 5 grains; the quantity of oak charcoal burnt having been 5 grains, and of the other 3 grains; the diminution of volume in the experiment with charcoal from alcohol, was equal to 194.5 grains of mercury, the quantity barnt having been 2.5 grains.

Sir H. thinks it probable from these facts, that the common carbonaceous substances contain a small portion of hydrogen in a state of intimate combination, since it is improbable that water should remain combined with them at a red heat, and igniting plumbago by Voltaic electricity, he never observed any aqueous moisture to be disengaged. The quantity of hydrogen is, however, so extremely minute, that Sir H. thinks it exceedingly im. probable it should be the source of the different physical properties which characterize those different forms of carbonaceous matter; and the essential difference he thinks, with the late Mr. 'Tennant, depends upon the state of crystallization which is peculiar to diamond. A farther proof of the existence of hydrogen in the common varieties of carbon, and of diamond being free from it, is afforded by igniting them in chlorine, for all of them except diamond, occasion the formation of muriatic acid, but the chlorine undergoes no change, and the diamond suffers no diminution of weight, when it is ignited in that gas. Some Account of the Fossil Remains of an Animal more

nearly allied to Fishes than any other classes of Animals.

By Sir Everard Home, Bart. F. R.'S... On an easier Mode of procuring Potassium than that which ... is now adopted. By Smithson Tennant, Esq. F.R.S.,

The improvement in the process for procuring potassium, suggested in this communication, is that of obtaining it by distillation in a gun barrel, the materials, iron turnings and potash, being introduced together into the barrel before it is placed in the furnace. Into the upper part of the barrel, a narrow piece, nearly fitting it, is to be inserted, open only by a perforation at the lower end to admit the vapour of the potassium to pass into it,

« The most convenient' dimensions of the apparatus are, for the external barrel to be about a foot and a half long, and the internal ope seven or eight inches. The latter should not be wholly inserted in the former, but about an inch of it left out for the greater ease in with

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