8 REACTIONS OF THE IODIDE, BROMIDE, AND CHLORIDE OF POTAS SIUM, IN THE PRESENCE OF CERTAIN SALTS. Nitrate of ammonia.... Prompt decompo-Of a yellow color; Abundant violet vapors Sulphate of magnesia.. mine much less easy than that of iodine Nothing very perceptible Disengagement of hydrobromic acid. Nothing Nothing Nothing Disengagement of hy Idem Idem Nitrate of lime........ Idem Idem Chloride of calcium.... Idem Idem Nitrate of potassa ... Idem Idem drobromic acid A little vapor of bro mine Nothing 4 CHLORIDE OF POTASSIUM. Nitrate of ammonia... Nothing apparent Nothing percepti-Disengagement of chlo ble Phosphate of ammonia Hydrochlorate of ammonia. rine at a powerful heat Disengagement of hydrochloric acid No reaction: disengagement of acid towards the Sulphate of magnesia.. Disengagement of sulphuric and hydrochlo ric acids ........ Sulphate of soda...... Nitrate of potassa..... Nitrate of lime From these reactions it results :1. Chloride of potassium is much more stable than the bromide and especially than the iodide of the same base. 2. All the ammoniacal salts seem to be able to decompose iodide of potassium at the ordinary temperature, and to liberate the iodine. 3. The salts of lime and magnesia act in the same manner. 4. The salts of soda liberate iodine only after aqueous fusion, consequently over 212 degrees. 5. It is probable that all the salts containing water of crystallisation would have an analogous action, as well as the weaker acids. 6. It is not astonishing that the atmosphere contains iodine; it must be free and not conbined in it, since it is here demonstrated that the most stable iodide loses its iodine under the influence of simple contact with calcareous magnesian and ammoniacal salts which are constantly found in all waters and soils and that at the ordinary temperature. 7. On the contrary, salts of potassa retain or fix the iodine. This perfectly accounts for the advantage, for the necessity, perhaps, of adding a little caustic or carbonate of potassa, before incinerating products to be tested for iodine, such as cod and skate liver oils, and plants containing a small quantity of iodides. 8. The decomposition of the bromides is much more difficult than that of the iodides, and much easier than that of the chlorides. If bromine had presented as clear and decisive reactions as iodine, it would have been discovered first, whilst iodine, being disengaged with so much facility, and existing, moreover, in such minute quantity in waters and soils, it is easy to explain why it so long escaped the observation of chemists. 9. Notwithstanding the much greater stability of the chlorides, the saline residues of the calcination, either of waters or of or Nothing Nothing Nothing ganic products, do not always represent the whole of the clorides which they contain, and the quantity of free alkalis will vary according to the nature of the elements present, and the temperature at which the incineration has been effected. 10. Finally, there exists a very special mode of action on the part of sulphate of magnesia, a mode of action which would tend to bring this oxide nearer to alumina in the class of which it has generally been suppressed.--Comptes Rendus, No. 5. NOTE ON THE ACTION WHICH CARBONIC ACID EXERTS ON IRON IN THE PRESENCE OF WATER. BY M. GOLFIER BESSYERE. BERZELIUS, in the present (French) edition of his Traité de Chimie, vol. II., p. 660, states, "that iron is oxidised very rapidly in humid air, especially in the presence of a large quantity of carbonic acid. "That iron, in being covered with rust, is not oxidised solely at the expense of the water, the hydrogen of which combines in the nascent state with the nitrogen of the air, producing ammonia." In the Cours de Chimie Générale of MM. Pelouze and Frémy, Vol. II., p. 298, the authors state that :-" Iron, exposed to humid air, is covered with a layer of hydrated oxide of iron, which is called rust; the metal is oxidised with rapidity, because an element of a battery is formed, of which the rust is the negative, and the metal, the positive pole: the water is then decomposed, and the iron oxidises rapidly. The oxidation of the iron is accelerated by the presence of carbonic acid." So far as I am aware, nothing more explicit has been published concerning the chemical mode of action which takes place between carbonic acid and iron in the presence of water; the testimony of such respectable authorities has rendered further bibliographical researches unnecessary. From these quotations one would be naturally led to conclude that the elements of the air and water are dissociated only by means of electricity, or because ammonia may be produced in these circumstances, or else that the presence of air is essential to the exertion of this action of carbonic acid. These explanations did not appear to me sufficiently clear or sufficiently demonstrated; however, I still remained in doubt, when an accidental circumstance induced me to undertake the investigation of the most authentic facts. M. Welter, a friend of mine, was ordered by his physician, to use the water of Bussang as a ferruginous water; and as by analysis he was unable to detect any trace of iron in this water, he asked me at the commencement of the year 1850: 1st. if this water really contained ; 2ndly, into what is the true mode of action of carbonic acid on iron in the presence of water? The following was the result of the experiments which I made on this subject. Water powerfully charged with carbonic acid, put in contact with iron turnings, immediately gives rise to a solution of protocarbonate of iron, which is perfectly colorless and extremely limpid. This solution, exposed in an open vessel with free access of air, in a short time abandons all its iron in the state of hydrated peroxide. This well-proved fact is sufficient for explaining how it is that some chemists have detected the presence of carbonate of iron in certain mineral waters, whilst others, in analysing the same waters have found none. Indeed, it is probable that these waters are really ferruginous on leaving the spring; but, as they are collected to be put into bottles only at a certain distance and after a certain lapse of time, these circumstances may, according to the above observations, be the cause of the complete disappearance of the iron. They may likewise explain why I found no trace of iron in the analysis to which I had subjected several bottles of the water of Bussang, whilst M. Barruel, who has given the analysis of it, found some in it, very little it is true, but he detected 16 thousands. I observed an analogous fact with regard to the springs of Saint-Alyre and SaintNectaire, (Puy de Dôme), where a little speculation is carried on in moulding the calcareous deposit of these waters, it has long been found necessary to make them describe a certain course in the trenches where they deposit the hydrated oxide of iron which, without this precaution, would color the products. One serious consequence of the fact thus proved is, that carbonate of iron can be administered as a therapeutical agent only in presence of a great excess of carbonic acid. As to the question of what is the true mode of action of carbonic acid on iron in presence of water, the result of my experiments is still more clear. I will now describe the apparatus which I used. I made a constant source of carbonic acid by means of a large bottle to which was adjusted, under a hermetic closure, a long dropping tube, whose small orifice passed under a diaphragm of copper, which was supported by three copper wires, and charged with large pieces of white marble; the closure was furnished with a tube for the gas to pass through, fitted with a stop-cock, by means of which the disengagement of gas could be regulated. The carbonic acid was washed in an intermediate vessel, containing an alkaline carbonate, and thence passed into a flask filled with iron turnings, communicating with the intermediate vessel by means of a tube which reached nearly to the bottom of the flask containing the iron turnings; this vessel may be filled with water deprived of air by means of an S tube; it is, besides, furnished with a tube for collecting gases, and with a syphon furnished at its lower end with a stop-cock, by means of which the ferruginous water may be drawn off conveniently, and without dismounting the apparatus. I operate by pouring dilute sulphuric acid into the dropping tube until the marble is evidently acted on; then I close the stopcock, and when no more carbonic acid is produced, and that produced has raised the liquid in the dropping tube as much as possible, I again add acid to the height of about 50 centimetres; and then I open the stop-cock moderately in order to drive all the air out of the apparatus by means of the carbonic acid; then, without interrupting the disengagement, I close the stop-cock of the syphon, and I pour into the S tube water deprived of air, until the flask containing iron turnings is quite full. Then I relax the current of carbonic acid and moderate it in such a manner as to have one bubble in the second, and the apparatus thus arranged acts for a long time alone and with perfect regularity. Now the following is what is produced :the water becomes much more limpid, and after a certain time, it is remarked that the spires of iron are covered with bubbles of gas, which are at first very small, but which gradually grow larger and are ultimately detached; these bubbles are not carbonic acid, and if the excess of the latter be care- | it yields by distillation neither acetic acid fully collected in a flask filled with liquid nor any other organic acid: as regards ammonia, the excess of carbonic acid ab-phosphoric acid, as phosphate of lime exsorbed leaves as a residue pure hydrogen. ists in the gastric juice, it follows that if I think, therefore, that I may affirm that | phosphoric acid also exists in it, it must be carbonic acid in presence of iron and water determines the decomposition of the latter and gives rise to the formation of a protosalt of iron which it retained in solution in the water, so long as there is an excess of carbonic acid and absence of contact with the air, but that it separates under the form of a white precipitate, if this excess of carbonic acid be driven off without contact with the air, or else that it very soon passes to the state of a mixture of carbonate and oxide of iron if we operate in an open vessel. I think that we have here the explanation of a geological fact connected with the formation of certain deposits of spathic iron. I have even tried some experiments with the object of effecting the crystallisation of the above-mentioned deposit; the in the state of acid phosphate. A simple and characteristic fact confirms me in this view. Gastric juice put in contact with an exeess of carbonate of lime, causes no effervescence, and is not perceptibly neutralised; now, as, of all acids and of all acid salts known, the earthy biphosphates alone act thus, it is strong reason for thinking that the acidity in question should he attributed to biphosphate of lime. It has been objected, it is true, that if the gastric juice is not neutralised by the carbonate of lime, it is because the carbonic acid disengaged remains in solution; but this will, I think, be sufficiently refuted when I state that the same negative effects were observed at the boiling temperature. It has also been pretended that if the fluid in question apparatus which I have just described is does not effervesce with chalk, it is owing perfectly adapted to every experiment of to the extreme dilution of its free acid, and which this little work is susceptible, which as a proof, it is stated that it attacks it very moreover may be summed up by the follow-well when it is concentrated; but may it ing equation :-Fe + CO2 + HO=FeOCO2 +H.-Annales de Chimie et de Physique, August, 1851. NEW CHEMICAL RESEARCHES ON BY M. N. BLONDLOT. THE gastric juice is always acid; this is a fact beyond dispute: but there is by no means so much certainty with respect to the principle to which this acidity is due. It has been asserted by turns that it is acetic acid, phosphoric acid, hydrochloric acid, and, lately, lactic acid. I alone have stated that this acidity is due exclusively to biphosphate of lime, and, notwithstanding | the objections which have been made to this assertion, I am more than ever convinced of its correctness. Moreover, the new work which I submit to the Academy may be divided into two parts, the first having for its object to demonstrate the nature, and the second the origin, of the acid principle which predominates in the gastric juice. FIRST PART. I at once proved that the principle in question could not be one of the four acids above-mentioned, because it does not coagulate albumen, in which it differs from lactic and hydrochloric acids, and because not rather be feared that that is owing to a portion of hydrochloric acid disengaged from the chlorides by the biphosphate, under the influence of heat, being retained in the residue by the organic matter, and that it is then this acid which acts on the carbonate of lime. Moreover, I can bring in support of my assertion a direct experiment. After having neutralised some gastric juice with a slight excess of carbonate of soda, I filtered and concentrated the liquor and incinerated the residue. The ash was dissolved in water acidulated with a little sulphuric acid, at the boiling temperature: now the filtered liquid gave, with lime water, a perfectly characterised phosphate of lime, which, in the absence of any other phosphate, demonstrates that the acid which held the phosphate of lime in solution was really phosphoric acid in the state of biphosphate. SECOND PART. To determine the origin of the biphosphate of lime contained in the gastric juice, I proceeded first to the investigation of the other inorganic elements of this fluid, as follows: After having evaporated some gastric juice to dryness, I carbonised the residue. During this operation, some hydrochlorate of ammonia was sublimed. The charcoal being washed with distilled water, the washing waters, which were perfectly neutral, were not rendered turbid by lime water, which shows the absence of soluble phosphates. When evaporated, they deposited cubic crystals of chloride of sodium, whilst the mother-liquor contained a deliquescent salt, soluble in alcohol, which was no other than chloride of calcium. Finally, the incinerated charcoal furnished a certain quantity of phosphate of lime, which existed in the normal juice in the state of biphosphate of lime, as we have seen. After this qualitative analysis, I determined, by quantitative analysis the proportions by weight of the different elements of the fluid under investigation. The result is expressed in the following table : The attention is here attracted by the large proportion of solid matters compared with the water. Calcareous salts are present in very remarkable quantity. What is their origin? The blood, being alkaline, cannot contain them ready formed, but it contains the elements of them, namely, neutral phosphate of lime and chloride of sodium. Indeed, the latter may be decomposed, in the sides of the stomach, into soda which remains in the blood and into hydrochloric acid which reacts on the neutral phosphate of lime in excess, and the two salts in question will be simultaneously produced as indicated in the following equation : (CaO), (CaO)2, Pho PhO5 + HCl Neutral phos } phate of lime. CaCl Chloride of calcium. Hydrochloric acid. + = CaO, PHO5+ Biphosphate of lime. HO Water. The neutral phosphate yielding half of its base to the hydrochloric acid, there must be as much calcium in one as in the other of the salts produced; now this is precisely the case, for 0.60 of biphosphate of lime produce, within an insignificant quantity, as much lime as 0-32 of chloride of calcium. In the eyes of a chemist, this fact is peremptory. This explanation is further supported by the smallness of the quantity of chloride of sodium contained in the gastric juice, the greater part of this salt having been decomposed to furnish the hydrochloric acid. Finally, a peculiarity which, in some measure, puts the seal on this theory, is that, when the dilute hydrochloric acid reacts on the excess of neutral phosphate of lime, there always remains an almost imperceptible trace of this acid in the state of absolute freedom, which is explained by the well known laws of affinity: now the gastric juice itself also contains a trace of free acid, which enables it to tarnish the surface of calcareous spar, but the quantity of which is, however, so small that it cannot be entered into the account of the acidity of that fluid. As to the cause which determines the decomposition of the chloride of sodium, I think, agreeing on this point with many distinguished chemists and physiologists, that it may be attributed to an electrical action set up in the sides of the stomach. It is certain that the reactions above-mentioned may be artificially reproduced, by submitting to the action of a feeble battery a very simple apparatus, in which neutral phosphate of lime is held in suspension in a solution of common salt: now, whilst the soda goes to the negative pole, at the positive pole is formed a mixture of biphosphate of lime and chloride of calcium, with an infinitesimal trace of free acid. Comptes Rendes, No. 5. ON THE BEHAVIOR OF SULPHUROUS ACID TOWARDS SOME PERSALTS OF COPPER. BY O. DEPPING. MR. DEPPING points out the behavior of sulphurous acid towards the nitrate, acetate and sulphate of copper. In a very dilute solution of nitrate of copper the acid produced no change. What is stated with respect to the other two salts contains nothing more than is known from the researches of Messrs. Chevreul, Berthier, Vögel, Rammelsberg and Muspratt. The red crystals which sulphurous acid precipitates from the solution of pernitrate of copper, and those which are subsequently obtained by saturating with carbonate of soda, are regarded by the author as a new sulphite of the protoxide of copper, 3Cu2O+4SO2+4HO. The red crystals may be washed with water, in which they are insoluble, have no odor either in the moist or in the dry state and do not alter in appearance when dried. They dissolve in hydrochloric acid with a yellow color, with evolution of sulphurous acid; and on the addition of water, protochloride of copper separates unless too much hydrochloric acid has been added. Chloride of barium produces no precipitate in this hydrochloric solution; a solution of |