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 exhibited 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 component 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 acids 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 name 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 charcoal, 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 diminu tion of volume in the experiment with charcoal from alcohol, was equal to 194.5 grains of mercury, the quantity burnt 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 improbable 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 one 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

drawing it. The width is in general determined by that of the common gun barrel, but may be increased to a certain degree. I have had the thick part of a gun barrel so much enlarged by hammering it thinner, as to contain twice as much iron turnings and potash, and have employed it with success. But, on the other hand, there are limits to this extension of width, arising from the increased difficulty of making the heat penetrate throughout. The opening of the barrels at the top must be covered with a cap or wide tube, which being at a distance from the fire need only be fastened with sealing wax; but for the greater security of keeping this part cool, the whole of the tube which is out of the fire should be wrapped round with linen or blotting paper kept wet. The opening of the wide tube must be closed with a cork, having a crooked tube of glass through it, containing a drop of mercury, which being moved by the passage of the air, shews that the vessels are perfectly tight.'

In this mode, as in the common one, a very strong heat is necessary to be kept up for near an hour, and to enable the barrel to support it, a coating of lute, carefully applied, is necessary. Mr. T. recommends the lute to be made of a mixture of Stourbridge clay, with a larger proportion of the same clay burnt and pulverized.

On the Influence of the Nerves upon the Action of the Arteries. By Sir Everard Home, Bart. F. R. S.

The facts which form the basis of this communication are not numerous, but the evidence they afford of the action of the arteries being under the influence of the nerves, is tolerably conclusive. The carotid artery of several animals was laid bare, and the nervous bundle formed by the intercostal nerve and parvagum was separated by a probe being introduced under it; it was then touched by a solution of caustic potash at the part which passed over the probe, and the effect, as remarked by several competent observers, was a considerable increase in the force of action of the artery, which continued several minutes. A few experiments were also made to ascertain the relative power of heat and cold, as stimulants to the nervous system, one arm being surrounded by bladders filled with ice, and the other immersed in water heated to 120° or 130°, beyond which the heat could not be borne. The stroke of the pulse in the arm which was surrounded with ice, was distinctly the most vigorous, that of the heated arm being comparatively soft and weak. This experiment was made on several individuals with uniform results.

On the Means of producing a double Distillation by the same Heat. By Smithson Tennant, Esq. F. R. S.

The economical application of the heat employed in distilla

tion proposed in this paper, depends upon the well known fact, that the removal of the pressure of the atmosphere occasions all liquids to boil at a much lower temperature than under the common atmospheric pressure. To effect a second or double distillation by the same heat, it is only necessary, therefore, that the water employed to condense the steam of the first distillation, should be inclosed in a vessel made perfectly air tight, and supplied with stop cocks. These are to be closed as soon as the atmospheric pressure has been removed by the formation of steam, to effect which the assistance of additional heat is necessary, in the first instance, but it is no longer wanted after the stop cocks have been closed. When this has been effected, the heat supplied by the condensation of the steam of the first distillation will carry on the second process; and if proper precautions are used to prevent the escape of heat from the surface of the apparatus, about three-fourths of the quantity obtained by the first distillation may be procured by the second. In situations, therefore, where fuel is expensive, it is obvious that the improvement suggested by Mr. T. might be adopted with advantage.

An Account of some Experiments on Animal Heat. By John Davy, M. D. F. R. S.

The experiments detailed in this communication, refer to the relative capacities of venous and arterial blood for heat, to their comparative temperature in the living animal, and the temperature of different parts of the animal body. These are inquiries obviously of primary importance in reference to the true theory of animal temperature, though the want of correspondence in some of the results obtained by different experimentalists, still leaves the subject open to further investigation. Dr. Davy, for example, states, that in all his experiments he found the temperature of arterial higher than that of venous blood, (generally by two or three degrees,) and the temperature of the left ventricle of the heart higher than that of the right; while the observations of Mr. Astley Cooper and of Mr. Coleman stand directly opposed to them, though their competency as observers is most unquestionable. The general conclusions of Dr. Davy from his experiments, are

That there is no material difference between venous and arterial blood in respect to specific caloric, excepting what arises from difference of specific gravity; that the temperature of arterial is higher than that of venous blood, and the temperature of the left side of the heart than that of the right; and lastly, that the temperature of parts diminishes, as the distance of the parts from the heart increases. These conclusions (he observes,) are evidently in direct opposition to Dr. Crawford's hypothesis; the essence of which is, that the capa