Apfil 1 6, 1874] 



NATURE 



459 



ing. The reward of grappling with the intricacies 

 of organic bodies to which each worker is entitled who 

 adduces new facts — no matter to how limited an extent — 

 consists just in the intellectual treat of supplying perhaps 

 some of these many missing links. There can be no 

 question which system of classification will assist him to 

 do this most speedily. 



A student's perplexity will not be diminished on following 

 our author into the vexed question of formula. We take 

 it for granted that chemical formuL-e have been devised 

 to express the phenomena produced by the action of 

 chemical force. That theyexpressatpresent the final result s 

 rather than the agencies and forces which have been at 

 work to produce them may likewise be taken as correct. 

 They are, at the very best, poor representations only of the 

 chemical changes which we witness daily. Whether it 

 will ever be possible to prove that the atoms or groups 

 of atoms of which chemical compounds are supposed to 

 consist really stand to each other in certain definite rela- 

 tions, because they exhibit certain analogies under the 

 influence of the chemical force which holds them together 

 or loosens them, may well remain matter for specula- 

 tion. As long as no differences of opinion respecting 

 chemical facts are involved, views may differ on the mode 

 of expressing them by formuLx, provided always that the 

 choice between two different modes of expression falls 

 upon the one which recalls the greatest number of 

 analogies in the most simple and rational manner, and 

 can therefore become more fruitful in new discoveries. 

 Several rational formute are possible for one and 

 the same compound according as different relations are 

 to be expressed. A knowledge of the order or position of 

 the atoms is out of the reach of experimental demonstra- 

 tion. If the so-called position-theory of the carbon atoms 

 in certain organic compounds can assist us, however, in 

 ehicidating certain relations and analogies, and if this 

 theory is leading rapidly to numerous new discoveries, 

 then, by all means, let us avail ourselves of it. It seems 

 that constitutional, or, as they are sometimes called, 

 structural formula; excite the ire of some of our critics 

 of chemical literature inversely to the understanding 

 they display of them, and the very name constitutional 

 formula, or the sight of a graphic representation thereof, 

 inflames their fury as violently as a red cloak excites an 

 infuriated bull. However much ridicule may attach in 

 the eyes of some people to constitutional or structural 

 representation, it is pleasant to observe that the chemists 

 who now dispense with it altogether form the exception 

 rather than the rule. 



Mr. Schorlemmer makes an especially liberal use of struc- 

 tural formute, showing the relative position and units of 

 combining capacity of carbon atoms, with the view mainly 

 of explaining isomeric bodies. Every student of organic 

 chemistry will thank him for this, for, on perusing the 

 journal of the Berlin Chemical Society, for instance, one 

 cannot help being struck with the remarkable impulse 

 which the conception of structural representation of the 

 chemical composition of bodies has given to the study of 

 organic chemistry in Germany. Chemists find it, no 

 doubt, difficult to disengage themselves entirely from 

 some of the various theories that have held sway during 

 the last twenty years, and hence we look with leniency 

 upon the want of uniformity of formulas and chemical 



nomenclature displayed in this book. On pp. 3, 4, 



and 5, for instance, the brace is used in a double sense' 

 showing the formation of molecular bodies by the direct 



combination of element with element as in ^ ^ '^ \ ^^\ ■ 



and again by uniting two or more elements with a poly- 



H] 

 valent element, as m H ^ N, without any connection 



existmg between the monad elements themselves other 

 than through the polyad element. Such names as Tin 

 chloride, SnCl4, Platinum chloride, PtClj, and others, 

 must create the impression that these are the only com- 

 pounds which tin, &c. forms with chlorine. The different 

 atomic groups in structural formula; are sometimes sepa- 

 rated by points, sometimes by lines (forks, prongs, or 

 whiskers, as some fastidious critics have called them). In the 

 absence of these various graphic representations free use 

 is made of molecular formula; ; indeed it strikes us that 

 the author has been often over-cautious, and has not 

 attempted constitutional formulae where such representa- 

 tion would appear of particular interest to the student, as, 

 for instance, in the case of the isomers of aldehyde, of 

 aldines, &c. 



Certain groups of atoms contained in a great number 

 of organic bodies, such as nitroxyl, NO^, sulphuryl, SO.,, 

 phosphoryl, PO, way be viewed otherwise than as monad, 

 dyad, or triad compound radicals. Why, for instance, 

 should PO in phosphorous acid be a triad radical when one 

 of the hydrogen atoms is not replaceable, but " remains 

 together" with the PO group? or in hypophosphorous 

 acid, where two atoms of hydrogen remain linked to PO ? 

 Considering the liberality displayed by the author regard- 

 ing formula;, we shall be pleased to see him shake off the 

 trammels which still encumber his inorganic compounds. 

 We cannot see why NO., should combine with OH to 

 form nitric acid, and with H to form nitrous acid, or why 



SOo should form the compound radical in SO., ] p, and 



( OH 

 in sulphuric acid SO, ] qj^' and also in sulphurous acid 



( H 

 SO2 Qjj. Our author writes ethyl nitrite CjH-O.NO, 



and not CoHjNO,, "because in the former the N is 

 linked to the ethyl by means of an atom of oxygen, whilst 



in the isomeric nitro ethane CoHjN ! q > the nitrogen is 



linked directly, and the oxygen atoms satisfy each other." 

 We need scarcely say that this latter compound may 

 also be viewed differently. We might greatly extend the 

 list of similar incongruities, taking our examples espe- 

 cially from the organic silicon and boron compounds, 

 which, more than anything else, show that the same idea 

 of grouping elements that is now so freely admitted to 

 prevail for carbon compounds must logically hold good 

 also for ino'-j-anic bodies. 



The nomenclature first proposed by Hofmann and 

 adopted by our author of designating the different parallel 

 hydro-caibon seri s by the terminations, ane, ene, ine, 

 one, une has some inconveniences which perhaps are less 

 apparent to the teacher than to the student of organic 

 chemistry, who must be sorely puzzled to distinguish, for 

 instance, between ethine and phosphine, stibine, oxytc- 

 traldine, &c. ; and it is with regret we see some authors 



