XVIII. On the Theoretical Constitution of the Compounds of Ammonia. By ROBERT KANE, M.D., M.R.I.A. I N the course of the investigations to which I have subjected the various classes of compounds that ammonia is capable of forming, it has been my lot to submit to the consideration of chemists a great number of theoretical views to which I had been led by my experimental results, and by which I conceived that the mutual connexion of the different classes of ammoniacal compounds could be explained, and their origin and properties accounted for more satisfactorily than it was possible to do by means of the ideas that had been previously received in science. In advancing this new theory of the nature of ammonia and its compounds, I was not so sanguine as to expect that our ideas of a department of chemistry so complex and so important could be immediately or easily modified, or that the adoption of my views could take place without much conflicting reasoning and discussion. In this respect I have had cause to be very much gratified. All principles that can be considered as really vital to my theory have been adopted by the most eminent chemical philosophers, and in place of being dissatisfied that in the collateral parts of the theory some portions have been thought not positively proved, and which have hence been criticized and left for the time aside by Graham and by Rose, I was at once surprised and pleased to see how little had appeared in the eyes of these acute-minded chemists unfit for being at once adopted into science. I believe, however, that even in those portions of the theory to which Graham and Rose have not acceded, some of the difficulties arise from a want of clearness and detail in the description of my views, into which error I fell from being too anxious to avoid prolixity. As also since that period some additional evidence has been obtained which corroborates my opinions, I shall now advert to those points which are yet debated, and perhaps place them in a clearer point of view than had been done in my former paper. So far as regards the action of ammonia without water, all my ideas have been adopted; but in the relation of the ammonia and water in the common ammoniacal salts, where the ammonium theory of Berzelius comes into question, the evidence for my theory has not appeared so perfect. In fact, in order to see the true relation of the Berzelian theory to mine, it is necessary to contemplate the common salts of ammonia under two different points of view,-1st, their position as alkaline salts, and 2nd, their po sition as compound bodies, without reference to any other circumstance. In the first the proper theory of the salts of ammonia is that of Berzelius, but for the second purpose it is necessary to adopt the ideas on which mine is founded. For in fact the question is, What is sal-ammoniac? Its most striking philosophical character is its equivalence to chloride of potassium. It has the same crystalline form. It enters into combination subject to the same laws. They are two bodies formed decidedly upon the same plan. But chloride of potassium contains only two elements, while sal-ammoniac contains three. There is one common to both. The residual elements are equivalent, and Cl K and Cl NH4, as well as K and NH4, are bodies which correspond to each other. Ammonium when isolated, as it has, in the amalgam, all but been, appears to possess the properties of an alkaline metal; it markedly resembles potassium. That is the Berzelian theory, in which to the full I believe as well as Berzelius. The equivalency of sal-ammoniac and chloride of potassium is a fact, and the equivalency of the K in the one and of the NH1 in the other, is the natural inference from it. When therefore the equivalency of the ammoniacal and potash salts is under question, the ammonium theory is correctly used: it is not ammonia, it is not amidide of hydrogen which replaces potash, but it is to be called oxide of ammonium in compari son. But if we for a moment cease to consider the relation of the ammoniacal and the potash compounds, and taking sal-ammoniac by itself, proceed to examine what light can be derived from other sources towards illustrating its internal constitution, the question presents itself, can we believe the ammonium to be ready-formed in sal-ammoniac? Can we consider the ammonium, which in the amalgam gives up its hydrogen spontaneously, to retain it so strongly when in contact with iodine or chlorine, and to enter into combination only as a single and perfect group? The answer to this question, in the framing of which all the classes of ammonia compounds require to be taken into account, led me to the development of my theory. The combinations of ammonia with the anhydrous chlorides of copper, zinc, and mercury, resemble in all essential characters sal-ammoniac, and moreover, like it, those which are volatile or soluble without decomposition are found to belong to the regular system of crystallization. They further combine with the metallic chlorides of the magnesian class to form double chlorides. Thus there are 1. CIHN and Cl Cu + Cl H14 N. 2. Cl Cu NH3 and Cl Cu + Cl Cu H3 N. The completeness of the analogy thus indicated is acknowledged by Graham, who proposes to extend the Berzelian theory so as to include these cases. He assumes, that in the compound radical ammonium the hydrogen may be replaced by a metal, and thus a cuprammonium NH, Cu, a zincammonium NH3 Zn, a hydrargammonium NH3 Hg, may be capable of individual existence. If Hg and Hare replaceable, then Hg, H, N is equivalent to H1 N, and thus he agrees with me that the type of sal-ammoniac and white precipitate (Cl H . H Ad and Cl Hg + Hg Ad on my theory) is the same. But why have we not Cl Hg, HN, or Cl Cu, HN, or Cl Hg4 N and Cl Zn, N, taking their place among these bodies generated by ammonia? For Cu1 N or Zn4 N would also be equivalent to ammonium. The replacement stops when there remain yet two equivalents of hydrogen to the nitrogen; and it is only by a temperature such as destroys completely the constitution of these bodies that a metallic azoturet can be produced. The compounds containing oxygen acids are precisely similar to those chlorides just described. The bodies 3 SO3. O CuN H3 and SO3. O Cu + SO3. O Cu NH3 SO3. OZn NH3 and SO3. O Zn + SO3. O Zn NH SO.OHNH3 and SO3. OH + SO3. OΗΝΗ and SO3.NH3+SO.OHΝΗ are so obviously similar in constitution, that the one explanation of their internal structure must be admitted. There exist thus two sorts of compounds, which are ordinary ammoniacal salts with metallic oxide in place of water, or in the words of the theory of Graham, that contain ammonium in which hydrogen is replaced by a metal; those as Cl. Hg NH3, in which one equivalent, and those as Cl. Hg NH, Hg, in which two equivalents have been thus replaced. The substitution stopping there shows that N H2 is fixed, and thus that even if these various sorts of ammonium be admitted, the amidogene must be considered as pre-existing in them; and as Graham admits my formula for ammonium NH1 = Ad so his metallic ammoniums become H Hg and so on. Under this form the ammonium theory is capable of being 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. Hg2 O + Hg, Ad is SO3. ON H2 Hg4? 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 Hg, 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 (NH, O); 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 Hgg, so in boiling water we get CI+ (NH2 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 (NH2 Hg4 O2), 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 O2). 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 C O2. 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 SO. Ad H + SOHO. Ad H, 3. 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 ClH. NH3 is Cl H + H Ad, 3. White precipitate Cl Hg2 N H2 is Cl Hg + Hg Ad, 2 4. Sulphate ammonia S so. HONH, is SO3. OH + H Ad, 3 5. The black substance Cl Hg4 N H2 is Cl Hg2 + Hg, Ad, 6. Ammonium if ever isolated N H1 is H, Ad, are all experimental and necessary results; there is nothing |