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Those too lerge to be entirely included in one exposure ere filmed beginning in the upper left hend comer, left to right and top to bottom, ae many framae ae required. The following diagrams illustrate the method: l.ee cartae, plancliee, tebleeux, etc., peuvent Atre fllmAe A dee taux da rAductlon diff Arents. Lorsque le document eet trop grend pour Atre reprodult en un seul clichA, ii est filmA A pertir de i'engle eupArieur gauche, de geuche A droite. et de heut en bee. en prenent le nombre d'imegee nAcesseire. Les diegremmes suivents lllustrent la mAthode. 1 2 3 1 2 3 4 5 6 h-r.^-jh,"-^ ^-"^ • O-v^ ON THE THEORY OF TYPES IN CHEMISTRY. BT T. 8TBBBT HUITT, M.A., F.B.S. (From the Cwuidian Journal for Marehf 1861.^ In the Annalen der Chetnie Und Pharmaeie for March, 1860, (cxiii., 293) Mr. Kolbe has given a paper on the natural relations between mineral and organic compounds, considered as a scientific basis for a new classification of the latter. He objects to the four types admitted by Gherhardt, namely, hydrogen, hydrochloric acid, water, and ammonia, that they sustain to organic compounds only ar- tificial and external relations, while he conceives that between these and certain other bodies there are natural relations having reference to the origin of the organic species. Starting from the fact that all the bodies of the carbon series found in the vegetable kingdom are derived from carbonic acid with the concurrence of water, he pro- ceeds to show how all the compounds of carbon, hydrogen and oxygen may be derived from the type of an oxide of carbon, which 8 either C3O4, GgOa, or the hypothetical CjO. When in the former we replace one atom of oxygen by one^of 3.C! ^ / y .V" ON THE THEORY OF TYPES IN CHEMISTRY. hydrogen we have G3O3H, or anhydrous formic acid; the replace- ment of a second equivalent would yield CgO^Ha, or the unknown formic aldelyde; a third, CaOHg, the oxide of methyle ; and a fourth, C3H4, or formene. By substituting methyle for one or more atoms of hydrogen in the previous formula, we obtain those of the corresponding bodies of the vinio series, and it will be readily seen that by introducing the higher alcohoHo radicals we may derive from O3O4 the formulas of all the alcoholic series. A g^nnre ob- jection to this view iti however found ih the ftict thatt while this compound may be made the type of the aldehydes, acetones, and hydrocarbons, it becomes necessary to assume the hypothetical C2O3, HO, as the type of the acids and alcohols. Oxide of carbon, OgOg, is according to Kolbe, to be received as the type of hydro- carbons like oleflant gas, (GaHATe,) while C^O, in which ethyle re- places oxygen, is GgHg or lipyle, the supposed triatomic base of glycerine. The monobasic organic acids are thus derived from one atom of C3O4, while the bibasic acidii, like the succinic, are by Kolbe, deduced from a double molecule G40g, and tribasic acids, like the citric, from a triple molecule GgOi^. He moreover compares sul- phuric acid to carbonic acid, and derives from it by substitution the various sulphurib organic compounds. Ammonia, arseniuretted and phosphuretted hydrogen, are regarded as so many types ; and by an extension of his view of the replacement of oxygen by electro-posi- tive groups, . the ethylids ZnEt, FbEt-^-, and BiEts^ ^^* ^7 Kolbe, assimilated to the oxides of ZnO, FbO^, and BiOg. Ad. Wurtz, in the Repertoire de Chimie Pure for October, 1860| has given an analysis of Eolbe's memoir, (to which, not having the origiaal before me, I am indebted for the preceding sketch) and follows it by a judicious criticism, While Kolbe adopts as typeu a number of mineral species, including the oxides of carbon, of sulphur and the metals, Wurtz would maintain but three, hydrogen, (H3) water, (H3O3) and ammonia, (NHq)) and these three types, as he endeavoured to show in 1855, represent different degrees of conden- sation of matter. The molecule of hydrogen, Hj (M3), corres* ponding to four volumesi combines with two volumes of oxygen (O,) to form four volumes of water, and may thus be regarded as condensed to one-half in its union with oxygen, and derived from a double mole- Qpleb M.M«. In like manner, four volumes of ammonia contain two ON THE THEORY Of TYHSS IN OHBMISTRT. volinnes of nitrogen and six of hydrogen, which, being reduced to one*tbird, correspond to a triple moleoule, M3M3, so that these three types and their multiples are reducible to that of hydrogen mff^ or less condensed. — (Wtt^tz, Anmhg de Ohimie et dePhynque, (a) JcHv. 804). As ^regards the rejection of water as a type of organic compounds, sod the substitution of carbonic acid, founded upon the considera- tion that these in nature are derived from G3O4, Wurtz has well reimarked that water, as the source of hydrogen, is equally essential to their formation, and indeed that the carbonic anhydrid G3O4, like ail other anhydrous acids, may be regarded as a simple derivative of the water type. Having then adopted the notion of referring a great variety of bodies to a mineral species of simple constitution, water is to be preferred, to carbonic anhydrid, first, because we can com- pare with it many mineral compounds which can with difficulty be compared with carbonic acid ; and secondly, because the two atoms of water being replaceable singly, the mode of derivation of a great number of compounds (acids, alcohols, ethers, etc.,) is much more simple and natural than from carbonic acid. As Wurtz happily remarks, Kolbe has so fully adopted the theory of types that he wishes to multiply them, and even admits condensed types, which are, however, molecules of carbonic acid and not of water ; " he combats the types of G^rhardt and at the same time counterfeits them." Thus far we are in accordance with Mr. Wurtz, who has shown himself one of the ablest and most intelligent expounders of this doctrine of molecular types, a» above defined, now almost univer- sally adopted by chemists. He writes, — " to ray mind this idea of re^jrring to water, taken as a type, a very great number of com- pounds, is one of the most beautiful conceptions of modern chemis- try." — (Repertoire de Chimie Pure, 1860, p. 359) ; and again, h© declares; the idea of regarding both water and ammonia as represen- tatives of the hydrogen type, mQre or less condensed, to be so simple and so general in its application that it is worthy " to form the basis of a system of chemistry.— (liiJ. p. 356.) We have in this theory two important conceptions : the first is that of hydrogen and water regarded as types to which both mineral and organic compounds may be referred ; and the second is the notion of condensed and derived types, according to which we not only ON THE THEORY OF TYPES IN CHEMISTRY. asiume two or three molecules of hydrogen or water as typical forms, but even look on water as the deriyative of hydrogen, which is itself the primal type. As to the history of these ideas, Wurtz remarks that the propo- sition enunciated by Kolbe that all organic bodies are derived by substitution from mineral compounds is not new, but known in the science for about ten years. "Williamson was the first who said that alcohol, ether, and acetic acid were comparable to water — organic waters. Hoffman and myself had already compared the compound ammonias to ammonia itself." * * * ** To Gerhardt belongs the merit of generalizing these ideas, of developing them, and sup- porting them with his beautiful discovery of anhydrous monobasic acids. Although he did not introduce into the science the idea of types, which belongs to M. Dumas, he gave it a new form which is expressed and essentially reproduced by the proposition of Eolbe. G«rhardt reduced all organic bodies to four types — hydrogen, hydro- chloric acid, water and &mmom&!^{Ibidf p. 355.) The historical inaccuracies of the above quotation are the more surprising since in March, 1854, 1 published in the American Journal of Science^ (xvii. 194) a concise account of the progress of these views. This paper was re-published in the Chemical Gazette, (1854, p. 181,) and copies of it were by myself placed in the hands of most of the distinguished chemists of England, Prance and G-ermany. In this paper I have shown that the germ of the idea of mineral types is to be found in an essay of Auguste Laurent, (Sur les Oom- binaisons Azoteea, Ann. de Chimie et Physique, Nov., 18000 where he showed that alcohol may be looked upon as water (H^O.,) in which ethyle replaces one atom of hydrogen, and hydric ether as the result of a complete substitution of the hydrogen by a second atom of ethyle. Hence he observed that while ether is neutral, alcohol is monobasic and the type of the monobasic vinic acids, as water is the type of bibasic acids. In extending and developing this idea of Laurent's, I insisted in March, 1846, and again in January^ 1850, upon the relation between the alcohols and water as one of homology, water being the first term in the series, and Hg being in like manner the homologue of acetene and formene, while the bases of Wurtz were said to ''sustain to their corresponding alcohols the same relation that ammonia does to water." {Am, Jour. 8ci, v. 265; iz.65; xiii.206.) ON THB THXORY OV TYPKt IN CHEMTITRT. 4^/ In a notice of his essay, published in September, 1848, ,(Ihidt vi., 178) I endeavored to show that Laurent's view might be farther extended, so as to include in the type of water " all those taline cotnbinationt (acids) which contain oxygen ;" and in a paper read before the American Association for the Advancement of Science at Philadelphia, in Sept., 1848, 1 farther suggested that as many neutral oxygenized compounds which do not possess a saline character are derivatives of acids which are referable to the type HgOj,, "we may regard all oxygenized bodies as belonging to this type" which I farther showed in the same essay, is but a derivative of the primal type H,, to which I referred all hydro-carbons and their chlorinized derivatives, as also the volatile alkaloids, which were regarded " as amidized species " of the hydro-carbons, in which the residue amidogen, NHg, replaced an atom of H or Gl., or what ia equivalent, the residue NK was substituted for O3 in the corres- ponding alcohols. (Ibid viii., 92.) In the paper published in Sept., 1*848, 1 showed that while water is bibasic, the acids which like hypochlorous and nitric acids were derived from it by a simple substitution of Gl and NO4 for H, were necessarily monobasic, and I then pointed out the possible existence of tho nitric anhydrid (N'0^)j,Oa, which was soon after discovered by Deville. G-erhardt at this time denied the existence of anhydrids of the monobasic acids, while he regarded anhy- drids as characteristic of polybasic acids, and indeed was only led to adopt my views by the discovery of the very anhydrids whose forma- tion I had foreseen.^ In explaining the origin of bibasic acids I described them as produced by the replacement, in a second equivalent of water, of an atom of hydrogen by a monobasic saline group ; thus sulphuric acid would be (S2H0aH)03. Tribasic acids in like manner are to be regarded as derived from a third equivalent of water in which a bibasic residue replaces an atom of hydrogen. The idea of poly- meric types was further illustrated in the same paper, where three hydrogen types were proposed, (HH) (H3H2) and (H3H3) corres- ponding to the chlorids MGI, MGI3 and MGlg. It was also * The anhydrids of the monobasio acids correspond to two equivalents of the acid, minus one of water, as, 2 (.CLB.4 O4)— H, Og^Cs H, Os, while one equivalent of a bibasic acid (Itself derived from 2 (Ha O2) loses one of water, and becomes an anhydrid as Oa H, Og— Ha O3 = Oa O4. So that both classes of anhydrids are to be referred to the type of one molecule of water Ha Oa> 9 oir nil VRZORY or tytks in chkkutry. illiiilsmtflid b J sulphur in its ordinary state, which I showed is to be r^fanded as a triple molecule Ss* (or Sg =4 volumes) and referred siiilpliunHis acid SO, ^ this t^pe, to which also probably belongs Bolswiic oxide. {Ai the same time I suggested that the odorant form ct.ojsygea or, osone was possibly O 3 .) Wurtz in his memoir, publish- ed in,185|5, adopts my view, and makes sulphur vapour at 400° the type of the triple molecule. I farther suggested {American Journal of ScUnfe, y. 408, vi. 172,) that gaseous nitrogen is NN, an a^Jnydrid amid or nitryl« corresponding to nitrite of ammonia, (NOg, li^^^O) — H4O4 = JJN. This view a late writer attributes to Qerhardty who adopted it from me, (Ann. de Chimie et Phya^ Ix. 381.) M«y not. nitrogen gas, as I have elsewhere suggested, regenerate ujodier pertain ooinditions, ammonia and a nitrite, and thus explain not only tilie frequent formation of ammonia in presence of air and reduc- ing fl^^ts* but certain cases of nitrification P* I endeavoured still further to show that hydrogen is to be looked 141011 as the< fundam^tal type from which the water type is derived by tlie replacement of an atom of H by the residue HO 2, (American Jfliltmal, viii. 93.) In the same way I reguded ammonia as water in whiflh the residue NH replaced O2. I have always protested against the view which regards the so- called rational formulas as expressing in any way the real structure of the bodies ifhidi are thus represented. These formulas are ii^lFmt^d ! to .explain a certain class of reactions, and we may con- sti^it^t from o^her points of view, other rational formulas which are equally admissabl'^. As I have elsewhere said " the various hypotheses of cq>ulajtea ^nd radicals are based upon the notion of dualism, which haa no other foundation than the observed order of generation, and e^ have no place in a theory of science." All chemical changes are reducible to union (identification,) and division (differentiation). When in these changes only one species is concerned, we designate the process as metamorphosis, which is either by condensation or by * Tho fomwtion of a nitrite in the experiments of Gloez appears to be independent of the pr^mape of a^nmoni*, apd to require only the elements of air and water (C'omptes Rendus.) Some experiments now in progress lead me to conclude that the appearance of a nitrite in tlie various processes for ozone, is due to the power of nascent oxygen to destroy by oxyda< tion the ammonia generated by the action of water on nitrogen, the nitrous nitryl ; so that the odor and many of the reactions assigned to ozone or nascent oxygen are really due to the nitrous acid which is set firee when the former encounters nitrogen and moisture. On the otfa»r hand, nascent hydrogen, which readily reduces nitrates and nitrites to ammonia, hf dsrtn^Dg the regenerated nitrite of the nitiyl, produces ammonia in many cases tifftu •tmoipherio nitrogen. ON TUB TBEORY Or TYPK8 RV CSHMmCrrKV. f expaosion, (homogefneous differentiation.) Iti id«ttgeneisli, cm IdM contrary, unlike species may unite, and by a subsequeitt hibtumgkiaiBh 0U8 differentiation give rise to new speoies, coAttitutlitagI' whit is called double decomposition, the results of which, dilBbiently inter- preted, have given origin to the hypothesis of radicals and th« notioB of aubstitution by residues, to express the relations betWMH 1^ parent bodies and their progeny. The chemical history of bodioi ia then a record of their changes ; it is in fact their genealogy; and in making use of typical formulas to indicate the deriviition of chemical species, we should endeavour to show the ordinary riiodte of their generation. (See On the Theory of Chemical Ghangw, Am. Jour, Set. xv. 226, L. E. & D. Fhil. Mag. {^) v. 526* and 6Hm» Oentralhlatt, 1853, p. 849. Alao Thoughts on SolUtioWf Jmk JbilK Set. xix. 100, and Chemical Gazette, 1855, p. 92. Keeping this principle in mind let us now examine the theory of the formation of acids. As we have just seen I tanght^in 1B48 that the monobasic, bibasicand tribasic acids are derived respeotivvljr from one, two and three molecules of water, H3O3. Mr. Wurti; seven years later, (in 1855) put fbrth » similar view. Hie supposiM a monatomic radical FO'4 a diatomic radical !^^Q^, aind a tif atbii^ie radical PO'^a, replacing respectively one, two and tUree atom» of byfc drogen in HjO^.H^O^, and HgOo, thus (PO'^HE) Oa(P0'3fl?a)O4 and (P0"'3H3)0g. These radicals evidently correspond tb PO^^ which has lost one, two and three atoms of oxygen in rieactihg' updti the hydrogen of the water type, and these acids may be accoidib^lji^ represented as formed by the substitution of the retndu^ PO's— -O for H, etc. To this manner of representiiig 'the generatioii of poiybasic aeida we object that it encumbers the science with numerous hy^iothetical radicals, and that it moreover fails to show the actual stlccdssive generation of the series of acids in question. Wheii ph(js|)hbric anhydrid, P30io = (P04)202» is placed in contact with water it combines with one equivalent, H3O2. The union is follbw^d by homogeneous differentiation, and two equivalents of metaphbsphdrid result, (P04)202+H202 = 2(P04H)02. Two equivalents df this acid with one of water at ordinary temperatures are Aovdj transformed into two of pyrophosphoric acidi by a reaction pre- cisely similar to the last. 2 (PHOe) = (PH05)203 -h K^0\,:±: 2 (PH05H)0a, and two equivalents of pyrophospHoric acid ^fttt 8 ON TBS THIORY OV TYPKS IN OBBMIITRY. heated with a third equivalent of water yield, in like manner, two of tribaaic phosphoric acid; 2 (PHaO,) s {TB.,0^)^0^ •{- HgO, = 2(PH,OeH)0, = 2PH30,. Gerhardt long since maintained that we cannot distinguish between polybasic salts and what are called sub-salts, which are as truly neu- tral salts of a particular type. Thus the bibasic and tribasic phos- phates are to be looked upon as subsalts, which sustain the same relation to the monobasic phosphates that the basic nitrates bear to the neutral nitrates. He succeeded in preparing two crystalline sub- nitrates of lead and copper, having the formulas NO„M,0,,HO (tribasic), and NOg.M^O^jHgO, (quadri or heptabasic), both of which retain their water of composition at 392^ F. The compounds of sulphuric acid are: Ist. The true monobasic sulphate 8,0, MO, corresponding to the Nordhausen acid and ihe anhydrous bisulphates ; 2nd. The ordinary neutral sulphates, 8,0^, MgO, ; 3rd. The so- called disulphatcs, SgOg, M^O^, corresponding to the glacial acid density 1*780 ; 4th. The type, S^Og, M,0,, represented by turpeth mineral; and, 5th. The so-called quadribasic sulphates, S,0,M,0,. The copper salt of this type, according to Gerhardt, retains, moreover, 6H0 at 392® F {Gerhardt on Salts, Jour, de Pharmacie, 1848, vol. xii. ; Am. Jour. Sci. vi. 337.) Without counting the still more basic sulphates of zinc and copper, described by Kane and Schindler, we have the following salts, which in accordance with Wurtz^s notation, correspond to the annexed radicals : 1. Monobasic SgHO, =8,05 monatomic. 2. Bibasic S^HaOg =8,0^ diatomic. 8. Quadribasic S2H40io=S303 tetratomic. 4. 8exbasic S3HoOi,=8, hexatomic. 5. Octobasic 8aH80i4=8,— O3 octatomic. It is easy to apply a similar reductio ad abaurdum to the radical theory in the case of the oxychlorids and other basic salts, and to show that the radicals of the dualists are often merely algebraic ex- pressions. — (8ee further my remarks in the Am. Jour. Science, vii, 402—404.)* * Those who are familiar with chemical literature, will remember an amuainK jtu cPesprii of Laurent's, in which he invited the attention of the advocates of the radical theory to a newly invented electro-ncKative radical Eurhizene.—Comptes Rendua des Travaux de Chimie for 1850, pp. 251 and 376.) We observe a late writer in the Chemical News (vol. i. p. 826) proposing, as a new e]eotro>negative radical, under the name of hydrino, the pcroxyd of hydrogen HOa, the eurbisene of Laurent 1 1 ON TH^ T^PORY OF TYPBt IN CBB1II8TRY. i. 1 The above^ irhich we coi^ceive to be a simple statemcot of the prpoepiap it tftkei place in nature, dispenses alike with hypothetical radical and residues, both of which are, however, convenient for thf purposes of notation. In the selection of a typical fqrm, to which a great number of species may be referred, hydrogen or water me^ts , the preference from its simplicity, and from the important, part which it plays in the generation of species. Wa^er and carbonic anhydrid are both so directly concerned in the generation of the bodies in the carbon series, that either may be assumed as the type, but we prefer to regard G,0^, like the other anhydrids, as only a derivative of the type of water, and eventually of the hydrogen type. These views were first put forward by myself in 1848, when I ex- pressed the opinion that they were destined to form " the basis of a true natural system of chemical classification ;" and it was only after having opposed them for four years to those of Gerhardt, that this chemist, in June 1852, renounced his views, and without any ac- knowledgment, adopted my own. — (Ann. de Chim. et Phys. (3) xxxvii. 285.) Already in 1851, Williamson, in a paper read before the British Association, had developed the ideas on the water type to which Wurtz refers above, and to him the English editor of Gme' lin*t Sandbooh ascribes the theory. The notion of condensed types, and of H 3 as the primal type, was not, so far as I am aware, brought forward by either of these, and remained unnoticed until resuscitated by Wurtz in 1855, seven years after I had first announced it, and one year 4f!^my reclamation, published in the American Journal of Seienee, in March, 1854. My claims have not, however, been overlooked by Dr. Wolcott Gibbs. In an essay on the polyacid bases, he remarks that in a previous paper, he had attributed the theory of water types to Ger- hardt and Williamson, and adds, " in this I find I have not done justice to Mr. T. Sterry Hunt, to whom is exclusively due the credit of having first applied the theory to the so-called oxygen acids and to the anhydrids, and in whose earlier papers may be found the germs of most of the ideas on classification usually attributed to Gerhardt and his disciples."— (Proc. Am, Assoc. Baltimore, May, 1858, p. 197.) It will be seen, from what precedes, that I not only applied the theory, as Dr. Gibbs remarks, but except so far as Laurent's sug- gestion goes, invented it and published it in all its details some years before it was accepted by a single chemist* 10 OSf TBI THEORY OF TTm Xlf CBIMflTET. In condrin^n, I hare ojfily to ask that future Iditoriaaa w31 do juftice to the memory of Auguste Laurent, and will ascribe to -whoik it is due the credit of having given to the science a theory which hail exercised such an important influence in modem chemical speculadoi^' and rMearch, remembering that my own publications on the subject, which cover the whole ground, were some years earlier thsn those of Williamson, Gterhardt^Wurtz, or Kolbe, MoaraiAi., /aniMfy, 1861.