atom of the acid would weigh only 7.263, which is considerably less than an atom of each of the constituents, which together weigh 10-829. If, on the other hand, we take the proportion of black oxide of iron and prussic acid as a criterion, the atom of acid ought to weigh 22.485, and it might be a compound of one iron + one oxygen + six carbon + five azote + six hydrogen; besides which many other numbers might be chosen. These anomalies render Mr. Porrett's analysis of the ferrureted chyazate of potash somewhat doubtful. Ferrureted chyazate of barytes he found composed of 3. Sulphureted Chyazic Acid.-Mr. Porrett discovered this acid in 1808, by boiling three or four parts of Prussian blue in powder with one part of sulphuret of potash, and a sufficient quantity of water. The new acid is gradually formed, and neutralizes the potash in the solution. Various other processes were attended with success. To obtain the acid from this solution in a state of purity, Mr. Porrett employed the following method:-Add sulphuric acid till the liquid acquires a decidedly sour taste: then keep it for some time nearly at the boiling point. When cold, add to it a little black oxide of manganese, which will turn it to a beautiful crimson colour. Filter the liquid, and add to it a solution containing two parts of sulphate of copper and three parts of prosulphate of iron, till the crimson colour disappears. A copious white precipitate falls, composed of protoxide of copper combined with sulphureted chyazic acid. Boil the precipitate in a solution of potash, which separates the acid, and leaves the oxide of copper. Mix the potash solution with sulphuric acid, and distil. The sulphureted chyazic acid comes over into the reservoir. It is still mixed with some sulphuric acid, from which it may be freed by carbonate of barytes. The acid thus obtained is colourless, has a strong smell, analogous to that of acetic acid, and its specific gravity is 1·022. At a boiling temperature it dissolves a little sulphur. This acid consists of twothirds of its weight of sulphur and one-third of the constituents of prussic acid. The salts which it forms have the following properties: Sulphureted chyazate of potash: a deliquescent salt, soluble in alcohol.. of soda ditto, crystallizes in rhombs. of lime: ditto, soluble in alcohol, from which it may be obtained in needle-form crystals. of ammonia: ditto, not crystallizable. of magnesia: ditto, when dried has a micaceous appearance. of alumina crystallizes in octahedra, which do not deliquesce. of barytes: a deliquescent salt, crystallizing in long slender prisms of a brilliant white. It is composed of of strontian a deliquescent salt, crystallizing in long slender prisms in groups radiating like zeolite. of silver: a white insoluble powder. of mercury: a white insoluble powder. of potash and prussiate of mercury: a brilliant silvery lustre; very soluble in hot, and little soluble in cold, water. of protoxide of copper: a white powder, insoluble in water. Its constituents are, of protoxide of lead: a soluble salt in obtuse rhombs. of protoxide of iron: a colourless and very soluble salt. of peroxide of iron: a beautiful crimson salt, very deliquescent. The sulphureted chyazates of tin, bismuth, manganese, zinc, cobalt, nickel, palladium, uranium, molybdenum, and chromium, are very soluble. 4. Fuming Sulphuric Acid.-The singular qualities of the fuming sulphuric acid manufactured at Nordhausen, in Germany, from green vitriol, have long attracted the attention of chemists, and various solutions of the anomalies which it presents have been given. Fourcroy's explanation of it, by affirming that it is a mixture of sulphuric and sulphurous acids, has been pretty generally acceded to; yet it appears that it is not the true one. Mr. Vogel, apothecary at Bayreuth, has lately published a very elaborate set of experiments on this acid, which, as far as they go, appear decisive. The following are the facts which he has established by his experiments: Fuming sulphuric acid contains no sulphurous acid; nor can it be formed by uniting these two acids together, nor by distilling a mixture of sulphur and sulphuric acid. Fuming sulphuric acid attracts no oxygen, nor does it produce any alteration on atmospherical air. When mixed with water, it is converted into common sulphuric acid. When combined with bases, it forms common sulphates. It dissolves some sulphur, and acquires a brown, green, or blue colour, according to the proportion of sulphur which it holds in solution. It combines, likewise, with phosphorus. Vogel considers it as common sulphuric acid united with some imponderable substance, and brought by its means to a more, powerful acid state. The direct consequence from his experiments seems to be, that it is sulphuric acid free from water. There is, however, a fact stated by Dobereiner, in a very long dissertation which he has published on the action of the different kinds of sulphuric acid on nitric acid, which, if accurate, would require an explanation. He says that when a mixture of fuming sulphuric acid and nitric acid is heated, the nitric acid is decomposed into nitrous gas and oxygen gas, but no such change is produced by heating a mixture of common sulphuric acid and nitric acid. I do not perceive very clearly how this fact was ascertained. Supposing nitrous gas and oxygen gas to be evolved together out of the liquid, they could not be collected, for they would instantly combine, and form nitrous acid; but supposing the fact correct, I can conceive it to be owing to this circumstance. The fuming sulphuric acid deprives the nitric acid of the whole of its water. Now in this state it is probably much more easily decomposed than when it contains water. Common sulphuric acid will not produce this effect so completely, because it is already combined with an atom of water. 5. Prussic Acid.-Mr. Bergeman, apothecary in Berlin, discovered, in 1811, that the bark of the prunus padus contained a notable quantity of prussic acid. Water distilled from this bark proved fatal to animals when taken internally. 6. Acetic Acid.-The following very extraordinary experiment was made by Nasse, one of the members of the Imperial Academy of St. Petersburg, and is related by him in a letter to Professor John. Take a glass vessel and fill it with a mixture of equal bulks of carbonic acid gas and common air, and put into it a little water so as hardly to cover the bottom of the vessel. Stop it up, and lay it aside for some months, shaking it occasionally. Then open it, and leave it for some weeks with the mouth slightly covered. Acetic acid will be perceived formed in it, both by the taste and smell. Nasse obtained his carbonic acid by the action of dilute sulphuric acid on Carrara marble. Here is the formation of acetic acid without the presence of any animal or vegetable substance: nothing else than carbonic acid, common air, and water. The experiment would deserve a careful repetition. If correct, how much light would it not throw on the nature of acetic acid? 7. Arsenious Acid.-Various and discordant statements have been published respecting the solubility of white arsenic in water. The result of Klaproth's trials was lately published in the Annals of Philosophy. Since that time a still more elaborate set of experi ments on the same subject has been published by Bucholz. His results agree more nearly with those of Klaproth than with any other; though there are several anomalies in his experiments which are sufficiently puzzling. 1 have long been of opinion that the white oxide of arsenic exists in two states; namely, in the state of pure oxide, and in the state of hydrate of arsenic. When first prepared, it is transparent and colourless, like glass; but it gradually becomes white and opake, and puts on the appearance of enamel. The glass 1 conceive to be the pure oxide of arsenic; the enamel, to be a hydrate. Now if this opinion be well founded, we may expect to find a difference in the solubility of white arsenic in these two states. I think it probable that several of the anomalies are owing to chemists not having hitherto attended to this difference of state. VII. Salts. This is always one of the most prolific departments of chemistry, on account of the great number of salts, and the importance of being acquainted with their properties; but this historical sketch has already swelled so much, that I shall omit all the salts treated of in the Annals of Philosophy during the last year. 1. Calomel. Mr. Jewel's improvement in the manufacture of calomel, by making it pass in the state of vapour into water, is known, I presume, to most of my readers; having been made known to the public by Mr. Luke Howard, in whose manufactory it took place, about four years ago. 2. Oxalates.-Vogel, of Bayreuth, has published two very elaborate, and I conceive very accurate, sets of experiments on the analysis of several of the oxalates. I cannot attempt in this place to do more than give a bare table of his results. What makes these experiments more valuable, is their agreement with the views of Berzelius respecting the composition of salts; though when Vogel made his experiments (at least the set of them first published.) it. does not appear that he was acquainted with Berzelius' opinions on the subject. A hundred parts of oxalic acid require for saturation a quantity of base which contains 21.2 parts of oxygen; or in other words, in the neutral oxalates the acid contains three times as much oxygen as the base. When binoxalate of potash is poured upon carbonate of copper, a solution takes place, and two salts are formed, distinguished from |