cold water, but more soluble in hot water; when it is thrown into concentrated nitric, or sulphuric, or phosphoric acids, it has no violent action on them. By heat it may be dissolved in them, and the solutions, when saturated, congeal and form crystalline substances intensely acid. When the substance formed by the triple compound and the nitric acid is strongly heated, the nitric acid flies off, and at the temperature at which it is entirely expelled, the substance itself begins to decompose, and affords a little iodine and much oxygene.

If the solution of the triple compounds in sulphuric or phosphoric acids be heated strongly at the temperature at which the acids sublime, the triple compound itself is decomposed, and it affords oxygene and iodine, and leaves acid sulphate and phosphate of potassa. If when the mixture is rendered fluid by heat, a little sugar or other combustible matter is added, there is a violent action, and iodine is disengaged with great rapidity.

The triple compound dissolves without decomposition in solution of phosphorous acid; but on heating the solution, oxygene is attracted by it, iodine appears, and phosphate of potassa is formed.

When the triple compound is thrown into concentrated muriatic acid, there is an effervescence, the smell of chlorine is perceived, the fluid becomes yellow, and when evaporated yields the chlorionic acid.

When the solution of the hydroionic acid in water is poured upon the triple salt, iodine is instantly produced in great quantities.

Acetic aud oxalic acids dissolve the triple compound without decomposing it. On heating the solution in oxalic acid, the acid becomes brown from the deposition of charcoal, and iodine immediately appears.

• When the triple compound is thrown into solution of sulphurous acid, iodine is instantly produced, and sulphuric acid formed, and if the sulphurous acid is not in too large a proportion, the solution becomes yellow by dissolving iodine; if more sulphurous acid is added, water is decomposed, and sulphuric acid and hydroionic acid formed.'

Sir H. then gives an account of the double compound of potassium and iodine; and he informs us that the triple compound is composed of one proportion of iodine about 165, one of potassium 75, and six of oxygen 90; which is a composition exactly analogous to that of the hyper-oxymuriate of potassa.' He proposes to name the triple compounds oxy-iodes, an appellation which appears to be unobjectionable: but we are not yet reconciled to the author's method of terminating the words according to the state of the base; as oxy-potassame, instead of oxy-iode of potassium.

Section ii. contains some observations on hydroionic acid, and on the compounds procured by means of it.' This acid was described in the former paper as produced by the action of iodine on phosphorus, which was at first mistaken for muriatic acid; but it was proved by the author to be possessed

of

of peculiar properties, which are described with his accus tomed accuracy. In the third section, we have an account of the other acid compounds of iodine;' first, that of iodine and chlorine, which the author calls the chlorionic acid, and conceives to be composed of one proportion of iodine and one of chlorine. The properties of this acid are detailed at considerable length; after which we find a few observations on the compounds of iodine and tin, and of iodine and iron, which exhibit acid-properties. Section iv. is on the action of some compound gases on iodine. The gases employed were sulphurated hydrogen, olefiant gas, nitrous gas, and carbonic oxyd. Section v. treats on the mode of detecting iodine in combinations, and on certain properties of its compound with sodium.' The principal object of the experiments here detailed was to ascertain from what marine productions iodine might be obtained.

Observations respecting the natural Production of Saltpetre on the Walls of subterraneous and other Buildings. By J. Kidd, M.D. Professor of Chemistry at Oxford.--The circumstance which occasioned Dr. Kidd's observations was the appearance of an efflorescence of nitre, on some part of the walls of the laboratory of the Ashmolean Museum in Oxford. He gives a minute account of the construction of the building, its situation, its materials, which are calcareous free-stone, the parts on which the efflorescence usually appears, and other facts connected with it which might seem to lead to a knowlege of the cause. Of these the most important is the state of the atmosphere; and the chief object of this paper is to point out the connec tion between these circumstances. It is stated that this formation of nitre never occurs except where lime is present, chiefly on buildings constructed of lime-stone, but occasionally on bricks that are formed of a calcareous clay. From observations made on the same part of the wall, and continued regu- larly for several months, Dr. Kidd found that a clear, frosty, and dry state of the atmosphere tended principally to the formation of the salt but that, in the most favourable circumstances, it can never increase beyond a certain limit. In a moist atmosphere, the formation is very slow, or is entirely suspended; and even the salt which had been formed gradually disappears, This disappearance has even taken place during frost, and it does not seem to be owing to the salt being absorbed into the stone. The nitre obtained from the walls in question was found, on examination, to be nearly pure nitrate of potash, In considering the theory of this process, the author observes that the only substances which appear to be essentially neces sary are atmospherical air and lime-stone; which may be re

solved into the following elements, oxygen, nitrogen, hydrogen, and carbon, together with iron, and the metallic bases of some of the earths.'

The component parts of nitrate of potash, of which the saltpetre under consideration almost entirely consists, are nitric acid, water, and potash; which may be resolved into the following elements-oxygen, nitrogen, hydrogen, and potassium: and all these elements are experimentally known to be present in the situations where saltpetre is formed, with the exception of potassium.

In the supposition then that the saltpetre is a product and not an educt of the above process, since no potash can be detected either in the air or limestone, the potassium must either be contained in a free state in the atmosphere or in the limestone, which from its remarkable attraction for oxygen is inadmissible: or it must be a component principle of some one of the elements present; or lastly, it must be itself a compound of two or more of the principles of those elements, or of two or more of the elements themselves."

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 Robt. Porrett, jun. Esq.-The author of this paper commences by pointing out some circumstances in the nature of the salts which have been termed the triple prussiates, tending to shew their want of analogy with other bodies that are supposed to be of a similar nature. The black oxyd of iron is conceived to render the simple prussiates neutral; an effect, as Mr. Porrett observes, without a parallel in chemistry. This substance cannot be thrown down by any of the tests for iron, and it always accompanies the prussic acid when the latter is transferred from one base to another by stronger affinities. From these considerations, he was induced to examine the subject afresh, and to enter on a train of expe riment, in order to reconcile the phænomena of this particular class of salts with the general properties of other saline bodies; and he thus states his opinion: I consider the salts termed triple prussiates, as binary compounds of an acid with a single base; as salts which do not contain any prussic acid, nor any oxide of iron as a base, although both the substances may be obtained from them by a decomposition of their acid.' The Voltaic pile was employed to discover whether the iron existed as a base, or as an element of a peculiar acid; and since, when placed within the action of this instrument, it was carried over to the positive pole, it was concluded to be in the latter state. Some other experiments were then performed, to prove the same point, viz. that the oxide of iron contained in the triple prussiates is an elementary part of an acid sui generis.' That it is not affected by the usual tests for iron is owing to its existing as an element

of

of an acid, in the same way that sulphur, when in the form of sulphuric acid, does not blacken metallic solutions.

Having proved the existence of this new acid, Mr. Porrett proposes a new name for it, taken from the first letters of the component parts, carbon, hydrogen, and azot, viz. the chyazic acid. The compounds of the prussic acid are restricted to those which have hitherto been considered as the simple prussiates, and the former triple prussiates are now styled ferruretted chyazates. Mr. P. then gives an account of the analyses of the ferruretted chyazates of potash, of barytes, and of peroxyds of iron, which have every appearance of accuracy, and seem to have been the result of much labour and dexterity. We have next a description of a new acid-compound, analogous to the ferruretted chyazic acid, viz. the sulphuretted chyazic acid; which was formed by boiling Prussian blue with the sulphuret of potash. At first, the author supposed it to consist of the same elements with the prussic acid, except that it contained less oxygen, and he named it prussous acid from this circumstance: but he afterward changed his opinion; and he reports, in very full detail, the experiments which led him to this change. The observations are arranged under those of a synthetical nature, those of an analytical nature, and those that relate to the salts formed by the acid. The following properties of the acid, when perfectly pure, are enumerated :

-

In this state it is generally colourless, but sometimes acquires a pinkish hu, which I believe to be owing to a commencement of oxidation. In the most concentrated form in which I have obtained it, it had the specific gravity of 1.022, and a smell as pungent, and a little resembling that of strong acetic acid; at the boiling temperature it had a slight solvent action on sulphur, when the latter had been presented to it in a very divided state, but most of the sulphur thus dissolved separated again on cooling: the rest which it still retained after cooling, and which is foreign to its composition, may be detected by nitrate of silver, or by nitrate of protoxide of mercury, which form with the red tinging acid, in the pure state, precipitates which are white and continue so, but, with the acid holding sulphur in solution, these precipitates have rather a dark colour.'

The second section concludes with these observations respecting the nature of the acid:

• I shall now drop the term red tinging acid, used merely in re lating these experiments to avoid anticipating its nature, and having, as I think, proved that this acid is composed of sulphur and of the same elements as the Prussic acid, and that consequently it belongs to the same class of acids as does the ferruretted chyazic acid, I shall call it henceforth the sulphuretted chyazic acid, and conclude this communication with giving some description of its salts, with my analyses of two of the most important of them, and by which the compo

10

composition of all its other salts may be known with comparatively little trouble.'

The account of the sulphuretted chyazates now follows: the compounds of the new acid with potash, soda, lime, ammonia, magnesia, alumina, barytes, strontia, and the different metallic oxyds: those of which a detailed analysis is given are formed by the protoxyd of copper, and by barytes. The first consists of about 37 parts of sulphuretted chyazic acid, and 63 parts of protoxyd of copper; the latter, of about 30 parts of sulphuretted chyazic acid, and 70 parts of barytes. Mr. Porrett observes that the soluble sulphuretted chyazates are excellent tests not only for indicating the presence of oxide of copper in a solution, but also for shewing its quantity with great exact ness, as they precipitate the last atom of that oxide from its solutions in the state of an insoluble salt, whose composition is known. In order that it should have this effect, however, the oxide of copper should exist in the solution as protoxide, (in which state it is seldom obtained in analyses,) or, which answers the same purpose, a deoxidating agent, such as sulphurous acid, or its salts, or a salt of protoxide of tin, or of iron, must be added to it.'

Some Experiments on the Combustion of the Diamond and other carbonaceous Substances. By Sir H. Davy, LL.D. &c.—It has been proved, by various accurate experiments, that the diamond and other carbonaceous substances consume nearly the same quantity of oxygen in combustion, and produce a gas having the same obvious qualities; yet the remarkable difference in the sensible properties of the bodies has led to many conjectures respecting its cause. Some persons have supposed that the diamond contained hydrogen; and M. de Morveau, many years ago, conceived that charcoal was the oxyd of carbon, and diamond the carbon in its pure state. Sir H. Davy for merly conjectured that diamond might contain a little oxygen; and he has more lately suggested that it might be the carbo naceous principle combined with some new light and subtile element of the class of supporters of combustion.' In this paper, he relates an account of a set of experiments which he performed on the combustion of the diamond in oxygen, by the burning lens, during his temporary residence at Florence and Rome in the last spring. It was found that the combustion was capable of being kept up after the diamond was removed from the focus; a circumstance which materially contributed to the simplicity of the process. The substances to be examined were inclosed in small platina capsules; and these were placed in glass globes, which were first exhausted by the air-pump, and afterward filled with pure oxygen. Fragments of diamond,

pure