the metallic state ; for it is evident that this mercury must have 89.225 .100.000 10.775...... 12.077 100.000 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 Oxygen 10.863 12.187 100.000 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 upaltered 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 salts. This, however, does not hinder the calcu have con+355 gold. gold, 24.24 o the de of ce he 1 manner. 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 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 Platinum 7.65...... 8•287 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 Platinum 85.93. Oxygen 14.07. 16.38 100 the otain ..92:35., ......100 .100 ona Fong has 100.00 e of ed a to it is 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 Oxygen. 14.227 ...... 16:587 e of is a the the 100.000 fate this Siile old 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 platinum. He ascertained how much mercury is necessary to decompose a given quantity of muriate of palladium, and reduce that B 2 substance to the metallic state. He found that 100 mercury are 87:56. 12:44. 14.209 .100 100.00 This will require a small correction, if we consider peroxide of mercury as composed of 100 metal 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 Metal. 100 + 6.71 Deutoxide 100 + 13:42 Peroxide 100 + 20:13 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 temperatuse 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 1706 given by the Ei 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 pasec 1001 12 a chemical purposes. Its specific gravity is in general not so high as our London platinum, though I once had a crucible made in Paris above 21 in specific gravity. M. Leithner, who has the charge of the porcelain manufactory at Vienna, has lately proposed a new method of rendering platinum malleable. It is exceedingly simple, and appears to answer well enough in a small scale, though it is not adapted for the construction of large vessels. It consists in making up the fine powder of pure platinum into a paste with oil of turpentine, and laying it in coats upon paper, allowing one coat to dry before another is applied, and continuing to add coats till the layer of platinum is of sufficient thickness. When this is done upon porcelain, and the vessel afterwards exposed to the temperature of from 14° to 18° Wedgwood, the platinum adheres, and may be burnished. When laid upon paper, and then exposed to a strong heat gradually raised, a sheet of platinum remains, which may be hammered, and converted into any shape that is wanted. 7. Palladium and Rhodium.-Vauquelin's method of separating these metals from crude platina, and obtaining them in a state of purity, has been given so lately in the Annals of Philosophy, that I do not think it necessary to repeat it here. It is sufficiently complicated ; and, as far at least as palladium is concerned, does not seem nearly so easy as the method previously given by Dr. Wollaston by means of prussiate of mercury, though it is possible that Vauquelin's process may yield a greater quantity. 8. Gilding on Steel.-Gehlen has tried the following method of gilding on steel, and found it to answer. The steel is to be in the first place polished; the part to be gilt is to be rendered rough by means of nitric acid; the steel is then to be dipped into the solution containing the gold ; the gold adheres to the rough part of the steel, and may be burnished. 9. Phosphuret of Copper. If we believe Dobereiner, phosphuret of copper, prepared by Sage's method, contains not only copper and phosphorus, but likewise calcium. To this last metal, in his opinion, the analogy of the phosphuret to steel is owing. 10. Separation of Gold and Silver ---Professor Schnaubert, of Moscow, has lately made several attempts to separate silver from gold by boiling the alloy in sulphuric acid ; this acid dissolves the silver, and leaves the gold. The process, though by no means . brought to a state of perfection, promises at present to be attended with success. The great difference between the price of sulphuric acid and nitric acid, which is usually employed for the purpose, Tenders it desirable that this process, which I conceive originated with Mr. Keir, should be subjected to farther trials. 11. Zinc.-- From my analysis of blende, published in the Annals of Philosophy, iv. 89, we may conclude that oxide of zinc is composed of 100 metal + 24:42 oxygen ; and sulphuret of zinc of 100 metal + 48.84 sulphur; and an atom of zinc weighs 4.095. 12. Antimony. From my analysis of sulphuret of antimony, (Ibid. p. 95,) it follows that it is composed of 100 metal + 35.556 O , both de in a which to the olfram experi Allan h che E pub ethods ate of gravity gravity S, and ily to Innals arther sulphur. If we suppose it a compound of one atom metal + two atoms sulphur, then an atom of antimony will weigh 11.249. V. Re-agents. I shall state under this head the result of some experiments undertaken by different persons to determine the best re-agents for detecting the presence of different bodies in solution. 1. Mercury.- Professor Pfaff, of Kiel, has made a set of experiments on the best means of detecting mercury in solution, especially when in the state of corrosive sublimate. The following are , the general conclusions which he considers himself as warranted to draw from these experiments : The experiments hitherto made on the action of sulphureted hydrogen on solutions of mercury, are in contradiction with each other, and of course insufficient to answer the purpose for which they were intended. Water impregnated with sulphureted hydrogen is the most delicate test of the presence of corrosive sublimate and pernitrate of mercury; for it discovers these salts, though diluted with 40,000 times their bulk of water, and though they do not exceed the quantity of or the part of a grain. The action of this liquid upon solutions of mercury is distinguished from its action on all other metals by this circumstance—if there be present in the solution any peroxide of mercury, the precipitate, which is at first in brownish or blackish flocks, becomes very speedily white. The addition of the smallest quantity of peroxide of mercury will render the black precipitate white, provided it be agitated. Protoxide of mercury in all cases produces a black precipitate with sulphureted hydrogen. If a small piece of copper coin be put into the solution suspected to contain mercury, it will be covered with a white coating, or at least with white streaks; which, when rubbed, acquire the metallic lustre. By this method Mr. Pfaff was able to detect the presence of of a grain of corrosive sublimate when dissolved in 20,000 times its weight of water. 2. Muriatic Acid.Mr. Meyer, of Stettin, has made some curious observations on the delicacy of nitrate of silver, pronitrate of mercury, pernitrate of mercury, and the solution of subpernitrate of mercury in water, as tests for the discovery of muriatic acid, He found nitrate of silver the most delicate of these four salts. It detected one part of muriatic acid dissolved (in the state of common salt) in 113,664,000 parts of water; but upon very dilute solution the other three salts had no effect. A solution of one part acid in 56,832,000 parts of water was not affected by the mercurial salts. A solution of one part muriatic acid in 28,416,000 parts of water was rendered slightly opalescent by the pronitrate of mercury, but not altered by the two other mercurial salts. 'A boluțion of one part of muriatic acid in 14,208,000 parts of wątes, a - ធី វ៉ា chu qua free |