oxygen, is equally decisive. These two sets of experiments seem at first sight incompatible with each other, and show us that there is something connected with the nature of azote still unknown. The fact that no substance constitutes a saline base, or is capable of uniting with acids, and forming salts, unless it contains oxygen (ammonia alone excepted), is a strong analogical argument in favour of the existence of oxygen in ammonia. It has accordingly induced Berzelius to embrace that opinion; and I must acknowledge that it is difficult to resist so very general an analogy. The anomaly respecting the composition of ammonia will be removed completely whenever it is proved in a satisfactory manner that azote is a compound of oxygen and hydrogen. This circumstance renders that question of still greater importance than it otherwise would be. 7. Sulphuret of Carbon. The properties and constituents of this singular substance, as determined by Drs. Berzelius and Marcet, were stated in our sketch of chemistry given at the beginning of last year. Since that time Berzelius has published additional observations on the combination of sulphuret of carbon with the bases. (Annals of Philosophy, iii. 186.) To these compounds he has given the name of carbo-sulphurets. The following table exhibits the colour of the precipitates obtained by mixing different metallic salts with a solution of sulphuret of carbon in potash: Muriate of cerium.. White, or yellowish white. Sulphate of zinc.. ..White. Dr. Brewster has found that sulphuret of carbon exceeds all fluid bodies in refractive power, and that in this respect it even surpasses flint glass, topaz, and tourmaline. In dispersive power it exceeds every fluid substance except oil of cassia, holding an intermediate place between phosphorus and balsam of Tolu. 8. Potassureted Hydrogen Gas.-Sementini, of Naples, published, about two years ago, a dissertation on potassium, in which he relates his experiments on potassureted hydrogen gas, which was discovered by Davy during his experiments on the metal of potash. The following are all the facts that I can find in these experiments: 1. Potassureted hydrogen gas is heavier than pure hydrogen, and lighter than phosphoreted hydrogen gas. 2. It takes fire, with a kind of explosion, when it comes in contact with the air emitting in alkaline odour. The explosion is louder when the gas comes in contact with oxygen or chlorine gases. 3. Electricity causes it to expand, and throws down the greatest part of the potassium. 4. Though kept in contact with water, it does not lose the whole, but only a part, of its potassium. Hence Sementini concludes that hydrogen has the property of combining with two proportions of potassium. the 9. Nitrous Oxide.-From the experiments of Professor Pfaff, of Kiel, it appears that when the nitrate of ammonia employed to prepare this gas contains sal ammoniac, as is commonly the case, gas which comes over is the same as that noticed by Proust and Vauquelin, which has a peculiar taste and odour, and acts with violence upon the lungs. Hence the method of preventing the occurrence of this foreign gas is obvious. 9. Sulphureted Azotic Gas.-A controversy has been carried on in Germany for some years respecting the existence of this gas. It was first announced by Gimbernat as existing in the mineral waters of Aix-la-Chapelle. Then appeared the analysis of these waters by Dr. Reaumont, and by Messrs. Monheim and Lausberg; the experiments of Westrumb on the same subject; and the attempts of Berzelius and Hedenberg to form sulphureted azotic gas artificially, which were not attended with success. I do not consider it as necessary to enter into the particulars of this controversy. I shall merely state what I conceive to be the result of it. No person has ever succeeded in forming sulphureted azotic gas artificially. The waters of Aix-la-Chapelle seem to contain both azotic gas and sulphureted hydrogen gas. The sulphureted azotic gas of Gimbernat seems to have been nothing else than a mixture of these two gases. IV. Metals. The most indefatigable experimenter of late years on the metallic oxides is Professor Berzelius. For the greater part of his results I must refer to his dissertation On the Cause of Chemical Proportions, published in the third volume of the Annals of Philosophy, where almost the whole of his results will be found; but as the details of the experiments are frequently omitted in that dissertation, and as I am aware, from conversations which I have had on the subject with different young chemists, that some of these details would be very acceptable, I shall take the present opportunity of stating some of those which seem most important in this place. 1. Oxides of Gold.-The facility with which gold parts with its oxygen is well known, and every chemist is aware of the impossibility of obtaining the oxides of this metal in a state of purity. Berzelius' method of estimating the quantity of oxygen in the peroxide of gold, which alone can be subjected to direct examination, was very simple and ingenious, but required considerable dexterity. He dissolved a given quantity of gold in aqua regia, evaporated the solution gently to dryness, to get rid of the excess of acid, and then redissolved the salt in water. He now ascertained, with rigid accuracy, how much mercury was necessary to precipitate the gold in VOL. V. N° I. B the metallic state; for it is evident that this mercury must have [JAN. united with exactly the quantity of oxygen which the gold contained. In one experiment, 14.29 of mercury precipitated 9.355 of gold; in another, 9.95 of mercury precipitated 6-557 of gold. According to these experiments, it appears that 15-912 of gold, when in the state of peroxide, contain just as much oxygen as 24-24 of mercury, when in the state of peroxide. But according to the experiments of Sefstrom, whom Berzelius follows, peroxide of mercury is composed of 100 mercury+79 oxygen. Hence he reckons the peroxide of gold a compound of Gold 100.000 If we consider the red oxide of mercury as composed of 100 metal + 8 oxygen, as I have done in my table inserted in the second volume of the Annals of Philosophy, in that case we obtain the composition of peroxide of gold as follows: .... Gold 89 137..... 100.000 ^^^^0 This last statement agrees better with the experiments of Oberkampf than that of Berzelius. Oberkampf found sulphuret of gold composed of 100 gold and 24-39 sulphur. Now if an atom of sulphur weigh twice as much as an atom of oxygen, it follows that peroxide of gold ought to be composed of 100 gold + 12·195 oxygen. When muriate of gold is exposed to a moderate heat upon a sand-bath, as long as it gives out chlorine gas it assumes a strong yellow colour, and becomes insoluble in water; or if the heat has not been continued long enough, only the portion of muriate of gold which is unaltered is dissolved, while that which has acquired a strong yellow colour remains undissolved. If heat be applied to this substance, or if it be simply exposed to the light of day, it is decomposed, and converted into metallic gold and permuriate of gold. According to Berzelius, the straw-coloured substance is a promuriate of gold. Heat or light deprives one portion of the protoxide of the whole of its oxygen, this oxygen unites with the remaining protoxide, and, converting it into peroxide, permuriate of gold is again formed. Now he found by experiment that in this case two-thirds of the gold are reduced to the metallic state, while one-third is converted into peroxide; so that the protoxide of gold contains just one-third of the oxygen in the peroxide. I may just observe, that these conclusions are not quite free from objections. I myself think it not unlikely that no oxygen is present in either of these alts. This, however, does not hinder the calcu lations of Berzelius from approaching to accuracy; though it were to be wished that experiments on the oxides were made in a less exceptionable manner than by combining them with muriatic acid. 2. Oxides of Platinum.-To determine the composition of protoxide of platinum, Berzelius proceeded in the following manner. He dissolved a quantity of pure platinum powder in nitro-muriatic acid, evaporated the solution to dryness, to get rid of the excess of acid, and then exposed the salt upon a sand-bath till all evolution of chlorine was at an end. The salt thus treated had an olive-green colour, and was promuriate of platinum. To ascertain its composition, he decomposed it by a red heat. Ten parts of it thus treated left 7.33 of metallic platinum, while 2·67 parts of chlorine gas made their escape. Now he assumed that the chlorine gas is a compound of muriatic acid and oxygen, and that the 2.67 of it contain just the quantity of oxygen necessary to convert 7.33 parts of platinum into protoxide; but 100 parts of chlorine gas, according to Berzelius, are composed of 100 muriatic acid and 29.454 oxygen; therefore 2.67 contain 0-6075; and protoxide of platinum is composed of Berzelius determined the oxygen in the peroxide of platinum in the same way as he did that in the peroxide of gold. He ascertained how much mercury was necessary to precipitate a given quantity of platinum in the metallic state. The result was, that 100 mercury precipitate 48-23 of platinum. He therefore considers the peroxide of platinum as composed of But if we reckon the peroxide of mercury to contain 100 metal +8 oxygen, which I believe to be very near the truth, then peroxide of platinum is composed as follows::- Platinum.. 85.773......100 100.000 Now this gives the quantity of oxygen very nearly double that which was found in the protoxide. 3. Oxide of Palladium.-Berzelius could only find one oxide of palladium. He employed the same method to analyse it that succeeded with him in the analyses of the peroxides of gold and pla tinum. He ascertained how much mercury is necessary to decompose a given quantity of muriate of palladium, and reduce that This will require a small correction, if we consider peroxide of mercury as composed of 100 nietal and eight oxygen. 4. Oxides of Rhodium.-The experiments of Professor Berzelius on the oxides of this metal being detailed in the Annals of Philosophy, iii. 252, I shall here state merely the results which he obtained. He found three oxides of this metal: the first composed of one atom metal + one atom oxygen; the second, of one atom metal + two atoms oxygen; and the third, of one atom metal + three atoms oxygen and one atom of rhodium weighs 14.903. Hence the oxides are composed respectively of 5. Tungsten.-There is hardly any metallic substance that occasions greater difficulties to practical chemists than tungsten, both on account of the want of a good process to obtain its peroxide in a state of purity, and on account of the very high temperature which is requisite to melt the tungsten after it has been reduced to the metallic state. The experiments of the El Luyarts upon wolfram are known to every chemist; as are likewise the elaborate experiments on the same metal of Vauquelin and Hecht. Messrs. Allan and Aikin succeeded in reducing it to the metallic state, and verified its great specific gravity as determined by the Spanish chemists. An elaborate set of experiments on this metal were published some years ago by Bucholz. He ascertained that the methods hitherto employed by chemists for procuring pure tungstate of ammonia do not succeed; and he verified the great specific gravity of this metal, having obtained it in grains of the specific gravity 17.4. Now this is the mean of 17.6 given by the El Luyarts, and 17.2 given by Allan and Aikin. But as I mean very speedily to publish a translation of the experiments of Bucholz in the Annals of Philosophy, I do not consider it as necessary to enter into farther particulars respecting them in this place. 6. Platinum.-The difficulty of reducing this metal to the malleable state, and its great importance in the construction of chemical vessels, are well known. Hitherto it has only been done for sale in Paris and in London. Parisian platinum is by far the dearest ; as far as my experience goes, it serves very well for |