extended so as to embrace a large class of the ammoniacal compounds newly discovered, but can it embrace all? When calomel is treated by water of ammonia there is formed the body, Hg, Cl + Hg2 NH2. If the ammonium theory be applied to this body, are we to make a new compound radical, and say it is Cl + N H2 Hg4, and to say that the corresponding body SO3 Hg2O + Hg2 Ad is SO3. ONH, Hg1? Here, then, is no parallel whatever; these bodies lie altogether out of the possibility of replacement connecting them with ordinary ammonium; and it would be far too violent a supposition to assume the existence of a body, N H6, in order to support the disputed existence of a more likely body, NH4. I consider this example as being fatal to Graham's view. Sublimate Cl Hg gives white precipitate Cl Hg. Hg Ad, calomel Cl Hg2 gives black precipitate Cl Hg2. Hg2 Ad; relations so simple, so natural, that it should require very strong reasons indeed to prove that they are not those consonant to truth. If the theory of metallic ammoniums were adopted, it would be only just to give to it its proper form. A sulphate of ammonia perfectly isomorphous with sulphate of potash contains SO. NH3+2 HO. The replacing element of the potassium is therefore (NH2O); there is no doubt of this; it is one of Mitscherlich's best-established determinations; (NH4) and (N HO) are equally isomorphous with potassium. Hence as sublimate treated in the cold with ammonia gives Cl N H1 and Cl. NH2 Hg, so in boiling water we get CI+ (N H2 Hg4 O2) equally equivalent, and a sort of complex ammonium. The ammonia turbeth is thus: SO3 + O (NH2 Hg4 O2); there is NO3+ O (NH2 Hg4 O2) and I (NH, Hg4O2), and so on. Now the correspondence of the common oxychloride of mercury to these bodies has been proved by Ullgren, and it should therefore be looked upon as a chloride of a compound radical Cl + (Hg4 O3). This is truly the principle involved in Graham's idea of compound ammoniums; for no matter where we begin, we find the chain by which the common salts of ammonia and the common basic salts are connected so perfect, that whatever principle we apply to one includes the others. Already, two years ago (May, 1838, Annalen der Pharmacie), I started the question, Were basic salts salts of compound radicals? and Liebig, in adapting a theory to the salts of platina discovered by Gros, approached nearly to the embodying of the same idea; but further examination showed me that it is one which is at present quite unfit for science, the even partial adoption of which would throw into confusion the most positive and simplest systematic arrangements that chemistry possesses, and hence do much harm and no good. Having so far considered the degree of weight which should be attached to the extension of the ammonium theory proposed by Graham, I shall now pass to the objections which have appeared to Rose to lie against some portions of my theory. Admitting the consistency and completeness of the arrangement which the compounds of ammonia with the dry oxygen acids and with the hydrogen acids assume according to my views, the illustrious analyst of Berlin yet considers that the assimilation of the hydrated ammonia salts of oxygen acids to those salts of the same acids which contain two equivalents of base is forced and unnatural; and he says that in place of attending to the great fact of the isomorphism of ammonium and potassium, I have neglected and suppressed that fact. This I by no means did; but this isomorphism was not the only thing to be taken into account. In fact, when all things were considered, the argument about the isomorphism of the two alkalies is of most force on the other side, and my opinion is that on the side of ammonia we have outflanked, as it were, the line of metallic bases, and that the constitution of ammonium, subamidide of hydrogen, is that which we shall hereafter find the alkaline metals to possess. The masterly researches of Rose himself on the sulphates and carbonates of ammonia are, as I believe, remarkably in favour of my view. In the carbonates of ammonia CO2. NH3+CO2. NH. HỌ and CO2 HO+CO2. HO.NH3 what complete evidence do we obtain of the identity of type of N H = Ad H and HO? In like manner if we look upon the series SO3. Ad H + SO3 HO. Ad H, we are driven, in order to avoid considering the recognised ammonium salt as a salt with two equivalents of base, to the adoption of the views of metallic ammoniums already sufficiently refuted. On my theory the only hypothetic assumption is the existence of amidogen. The subsequent principles adopted that 1. Ammonia NH3 is N H2. H = Ad + H, 2. Sal-ammoniac Cl H. NH3 is Cl H + H Ad, 3. White precipitate Cl Hg, N H2 is Cl Hg + Hg Ad, 4. Sulphate of } ammonia SO. HONH3 is SO.OH + H Ad, 5. The black substance Cl Hg4 N H2 is Cl Hg2 + Hg, Ad, 6. Ammonium if ever isolated N H1 is H2 Ad, are all experimental and necessary results; there is nothing hypothetical about them; everything follows from experi ment. Now the existence of amidogene is one of the best-established and most universally received hypotheses in chemistry; moreover, it is adopted also by Graham and by Rose. But how many more hypotheses must they adopt for the theory of ammonium! I shall only count up a very few, or better, state that the number of hypothetical bodies necessary for the complete ammonium theory would be equal to the number of possible metallic amidides, therefore equal to the number of metallic chlorides and oxides at present known; and this without at all touching on the theory of basic salts, which, as I have shown, is a necessary consequence of the theory of complex ammoniums. If general and simple laws can be obtained by the introduction of an hypothesis, and according as experimental research proceeds, the new facts gained are found to regulate themselves according to it, a real and important service is conferred upon science by him to whom we are indebted for it. But when a theory must change its shape and make a new assumption for each new fact discovered, as soon as the direct tendency of the theory is at an angle with that of research, and it must tack from side to side to keep the course of discovery in its line, its day has passed; and notwithstanding the services rendered to chemical theory by the hypothesis of ammonium, it is now, as I conceive, incapable of retaining its old position. Its great utility was in fixing attention on the relations of the ammoniacal and potash salts; but for explaining the immensely extended classes of compounds which ammonia is now known to form, it is insufficient. In a paper lately published by Mitscherlich, he describes a compound of chloride and azoturet of mercury 2 HgCl + NHg3, and he makes an observation which, as connected with the present subject, I shall here notice. He says that the equivalent of white precipitate is not Cl Hg + Hg Ad, but three times that, because it requires 3 (ClHg+ Hg Ad) to give Cl Hg+2NH3 and 2 Cl Hg + NHg3: he says that also amide of potassium KNH2 should be taken 3 K Ad, because it gives 2 N H and K3 N. Now this appears to me to be a very irrational method, for then the body Cl Hg NH3, the simple formula of which Mitcherlitch admits, should be 8 (ClHg NH3), because it gives 2 Cl Hg + 3 Cl Hg + N + 4 NH3+3Cl NH4. The hydrate of phosphorous acid should be 4 PO3+3 H O, because it gives PH3 and 3PO3; and a crowd of other examples might be brought forward. The equivalent formula of a body cannot be fixed thus from a single action or property. The formula of sulphate of ammonia is not 4 (SO3. NH4O), because by heat it gives 2 (SO2. NH4O) + 2 S O2 + 2 N, but every property must be taken into account, and our idea of the body derived from a careful induction, based on a study of all the facts known of it and of its congeners. The red substance described by Mitscherlich resembles, in fact, those obtained by Rose with sublimate and phosphuretted hydrogen, and the bodies I have myself described, containing arsenic. In fact, as Laurent and Bineau have noticed for azote, and I myself for arsenic and phosphorus, these substances replace oxygen or amidogene in the proportion of onethird of their ordinary equivalent. Phosphuretted hydrogen P PH3 does not resemble ammonia NH3 = Ad H, but H 3 resembles Ad Hor HO. The compound of iodide and phosphuret of hydrogen resembles not the hydriodate of ammonia, which is I H + H Ad, but the oxy-chloride of mercury, and the compound of chloride and phosphuret of mercury is similar. There are thus Now the ammonia compounds when decomposed by heat pass into this class, in one or two cases the action being sufficiently violent spontaneously to effect it, and the substance of Mitscherlich is N 2 Hg Cl + 3 Hg resembling the above. I discovered this body myself when analysing white precipitate; but as I did not wish to stray from the direct discussion of the amidides, I did not publish anything about it at the time. I formed also some others of the same class, which, as soon as I can obtain leisure I will complete the examination of, and give the details of their history. XIX. On the Composition of Inulin. By Mr. E. A. PARNELL*. THIS substance, which was first discovered by V. Rose in the root of Inula Helenium, in 1804, has since been found by Payen and other chemists in several other roots, as * Communicated by Professor Graham, Angelica Archangelica, Colchicum autumnale, Helianthus tuberosus, &c., and in a few lichens, as L. fraxineus and L. fastigiatus. Although known to be closely related to starch, and interesting as a probable member of the starch family (especially in being converted into gum and starch sugar by the action of dilute acids), no examination of its composition has, as far as I am aware, been made. To supply this deficiency, I have performed a few analytical experiments on inulin and its compounds, the results of which form the subject of the present communication. The inulin analysed was prepared from the root of the dahlia, as follows: the moist root, with the skin previously removed, was sliced, macerated, and washed with cold water. This was boiled in five parts of water for about an hour and a half, and filtered. The solution was nearly colourless, and quite neutral to test paper*. It was then evaporated until a pellicle appeared on the surface, and on setting aside to cool a large quantity of inulin was deposited in the form of a white pulverulent precipitate. This was collected on a calico filter, and washed with cold water until all the salts present were removed. It was then perfectly tasteless. Dried at a gentle heat, it became gummy, transparent, and easily pulverised; very soluble in hot, but sparingly in cold water. The liquid filtered from the first deposit of inulin gave an additional quantity on evaporation, which was obtained pure by washing, resolution, and evaporation. That used in the two first analyses was prepared by adding alcohol to a strong aqueous solution; on standing the inulin was deposited perfectly pure. That used in the third analysis was made without alcohol. 1st. -6.70 grains gave 10-65 carbonic acid, and 3.824 water. 100.00 100.00 100.00 100.00 This nearly approaches the formula C24 H21 021; thus * Payen directs chalk to be added, a free acid being present. |
