the thin a n in the ther; but perceived half those and the ci a gave at the number d connection is nearly Timents d is of solar 1815.] is, I OWL 13 in the Physical Sciences. d so well d greater. It has a peculiar smell, is very volatile, and very poisonous him which in its nature when taken internally. Its specific gravity is rather less than four, that of water being one. cable of the Iodine, as far as experiment has hitherto gone, must be consith referrine dered as a simple substance; and it belongs to the class of supals of Phi porters, though it is by far the worst supporter known. Its vapour supports the combustion of potassium, and it combines rapidly with ble of the phosphorus, evolving much heat, though no light. When iodine Dr. Wollas is heated, it is volatilized at rather a low temperature, and converted into a beautiful violet-coloured vapour, froin which it has received its name. This vapour, as far as I can find, possesses very little elasticity at the temperature of 212o. Iodine combines with chlorine, and forms a peculiar acid. It does not appear to combine with oxygen. With hydrogen it unites, and forms an acid very much resembling muriatic acid in its smell, , though I consider it as rather more pungent than that of muriatic acid. It unites with sulphur, phosphorus, and the metals; and forms a class of bodies, analogous to the oxides, called iodes. Some of these possess the properties of acids. It combines with alkalies and earths, and forms with them two classes of salts. The first, consisting of iodine and the base, may be considered as analogous to the iodes; the second, consisting of iodine, oxygen, and the base, have been called oxiodes, and may be considered as analogous to the hyper-oxymuriates. It scarcely possesses the property of separating carbonic acid from the bases, and cannot therefore be united with the carbonates so as to form salts; though these bodies readily dissolve a portion of iodine. An atom of iodine weighs about 12.5. 2. Chlorine.--Chlorine has the property of combining with two different proportions of oxygen, and of forming two new acids, which have received the names of chloric and chlorous acids, The first was discovered by Gay-Lussac ; the second, by Sir H. Davy. The Germans have given to chlorine the name of halogen. It is scarcely worth while to notice the experiments of the Dutch chemists L. A. Von Meerten and S. Stratingh on this gas, as I do not perceive any thing new in them. Meerten says that chlorine has the property of converting sulphurous acid into sulphuric acid, and nitrous gas into nitric acid. These were the first two experiments that I tried; when Davy published his paper to show that chlorine is still an undecomposed substance; and I soon procured the fullest evidence that neither of these gases is altered by pure but when chlorine contains a mixture of common air, which it usually does, it renders nitrous gas yellow in an instant. Meerten found likewise that ether burns in chlorine gas. This discoast a covery was made many years ago by Cruickshank, and published by him in the last volume of Nicholson's quarto Journal, and by my- sity of the Vollaston , solar says ray; and spectrum ago tha ray, they peated i pounds me yeah was first avy, and ery easy zlosophy chlorine; sh kelp -re more ton re, derably and! a Christian Frederick Bucholz made a set of experiments, in 1812, to determine the quantity of oxygen which can be obtained from hyper-oxymuriate of potash. His experiments were not attended with much success; but he ascertained that a red heat is necessary to drive off this gas. I have myself repeated this experiment more . than once, and obtained a result which approached very near to that previously established by the experiments of Chenevix. 3 Fluorine.—Sir H. Davy has published several papers upon this hypothetical basis of fluoric acid ; but all attempts to obtain it in a separate state have hitherto failed. Indeed, supposing it to exist, its action upon all other bodies seems necessarily to be so violent that there can be little hopes entertained of ever procuring it except in a state of combination. 4. Azote.-The two laws of Berzelius relative to chemical proportions do not hold when applied to the combination of azote with oxygen. The reason of this he conceives to be, that azote is not an element, but a compound of oxygen and an unknown base, to which he has given the name of nitricum. He has calculated from his theory the quantity of oxygen which azole must contain; and he shows that when this correction is made, the nitrates, as well as other bodies, come under the dominion of his two laws. Mr. Mliers, of London, had been of opinion for several years that azote is a compound of oxygen and hydrogen, and that the experiments of Girtanner were not so inaccurate as has been supposed. In a paper published in the Annals of Philosophy, vol. iii. p. 364, he shows that the supposition, that it is a compound of one atom osygen and six atoits hydrogen, will tally exactly with the atomic theory, and give the weight of the different atons into which azote entered the very same as they are at present, supposing azote to be a simple substance. This ingenious paper was sufficient to show us that the opinion of Mr. Miers was neither impossible nor improbable. It was not, however, suflicient to determine the opinions of chemists in favour of an hypothesis of so much importance, that the consequence of admitting it would be an almost entire change in the notions at present entertained respecting chemical combination. Mr. Miers, sensible of the necessity of direct experimental proof in order to give currency to an opinion of such magnitude, has had recourse to direct experiment, and has published a very curious and valuable paper on the subject in the Annals of Philosophy, vol. iv. p. 180 and 260). His object in these experiments was to deprive water of a portion, but not the whole, of its oxygen, and thus to convert it into azote. The experiments of Girtanner were directed to precisely the same view. It occurred to Mr. Miers that sulphureted hydrogen gas would probably answer the purpose. Accordingly he passed a mixture of vapour of water and sulphureted hydrogen gas through a copper tube. In one experiment the whole gas that came over possessed the properties of common air, and a mixture of 80 azote and 20 oxygen. In another a gas was forined, which Mr. Miers considered as sulphureted azotic gas. In a third was a in 1812, upon this in it in a o violent it except cote with base; to ted from tin; and 5 well as al years that the en sup vo). ii. d with the there was formed an acid gas resembling sulphureted 'lıydrogen in ned from smell, but possessing very different properties. Water absorbed attended twice its bulk of it. With potash it formed a black insoluble com pound, not decomposed by any acid. Such were the different necessary résults obtained by Mr. Miers. They are highly curious and inteent more resting; but it is obvious that they require to be followed farther, - near to before they can be considered as establishing the compound' nature of azote, and that it is composed of oxygen and hydrogen. The inconsistency of the results with each other, the new facts brought to view by every repetition of them; and, above all, the circumto exist , stance of the gas, in the most decisive of all the experiments, pos- ? sessing the properties and composition of atmospherical air, lead to suspicions which require to be ohviated. It would be requisite,'' likewise, to account for the sulphur of the sulphureted hydrogen, ical pro and to show that the copper tube can have no influence on the de composition of this gas. I hope, therefore, Mr. Miers will resume is not an his experiments, and prosecute them till he obtains results free from all such anomalies, and leading to conclusions that cannot be controverted. The investigation istindisputably an object of import , ance; and he has made such progress in it, that he ought to enjoy the reputation that would infallibly result from so interesting a discovery. 5. Phosphorus--The facts respecting phosphorus, published by Thenard' in the Annales de Chimie, had been almost all anticipated long ago by Proust. Hence I conceive it to be undecessary to detail them here. Heinrich, in his treatise on the phosphorescence of of ote bodies, has stated some facts respecting the temperature at which phosphorus burns in various circumstances, which perhaps may be worth transcribing. When phosphorus is put into the bottom of a narrow glass tube, it may be heated to 482° without taking fire. In the open air phosphorus burns at 999, and in oxygen gas at 72o. I cannot avoid observing that these determinations are far from precise. Indeed, nothing definite can be established respecting the combustion of phosphorus, because the degree at which it catches in the fire depends upon its purity. Pretty pure phosphorus I found did not begin to burn rapidly till heated to the temperature of 148°; but if you keep it long in the temperature of 99', its temperature gradually increases by its slow combustion, and it will, after a certain time, burn rapidly. According to Heinrich, a compound of equal parts phosphorus and sulphur becomes luminous at 30°. 6. Ammonia.--The important experiment of Berzelius, who converted mercury into an amalgam, by causing the galvanic battery to act upon it when in contact with ammonia, has not yet been cleared up in a satisfactory manner. It follou's from it that ammonia contains a substance of a metallic nature as its base, and that when this base is deprived of oxygen by the influence of the galpanic battery. the metal amalgamates with mercury. On the other hand, the analysis of ammonia by means of electricity, and the resolution of it into hydrogen and azote without the leasť trace of o which azote to show'18 robable. hiemist conse Flas had Dus and vol. ir. deprive thus to irected at sul ccordureted whole od was ormed, 2 third a 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 enbrace 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 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. .Greenish-grey. ..White, .Pale orange, then brown. .Dark olive-green, at last black. A fine scarlet. Dark brown. Orange. ..Reddish brown. 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. Potassureied 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 0 .Black. 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. 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, the 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 Axotic 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 aitended 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 seein 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 Chernical 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 1 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 а |