478 



NA TV RE 



[September 14, 1893 



by Koenig, Mallard, Daubree, and by Friedel in the supposed 

 meteorite of Caiion de Diablo in Arizona. Members of the 

 Section will probably have the opportunity of examining some 

 of these artificial diamonds through the courtesy of M. Moissan, 

 who has also, at my request, been so good as to arrange for us 

 a demonstration of the properties of the element fluorine, which 

 he succeeded in isolating in 18S7. 



Not less interesting or valuable are the studies of Dr. Perkins, 

 on electro-magnetic rotation ; of Lord Rayleigh, on the relative 

 densities of gases ; of Dewar, on chemical relations at ex- 

 tremely low temperatures ; of Clowes, on exact measure- 

 ments of flame-cap indications afforded by miners' testing 

 lamp?; of Horace Brown and Morris, on the chemistry and 

 physiology of foliage leaves, by which they have been led 

 to the startling conclusion that cane-sugar is the first sugar 

 produced during the assimilation of carbon, and that starch 

 is formed at its expense as a more stable reserve material 

 for subsequent use of the plant ; or of Cross, Bevan, 

 and Beadle, on the interaction of alkali-cellulose and 

 carbon bisulphide, in the course of which they have proved 

 that a cellulose residue can act like an alcohol radical in the 

 formation of thiocarbonates, and thus have added another to 

 the authors' valuable contributions to our knowledge of members 

 of the complex group of celluloses. 



But it is now an idle task for a President of this Section to 

 attempt a slight sketch of the works of chemical philosophers 

 even during the short space of twelve months ; they are too 

 numerous and generally too important to be lightly treated, 

 hence we can but apply to them a paraphrase of the ancient 

 formula — Are they not written in the books of the chronicles we 

 term " Jahresberichte," "Annales," or "Transactions and 

 Abstracts," according to our nationality? 



I would, however, in this connection ask your consideration 

 for a question relating to the utilisation of the vast stores of 

 facts laid up^some might even say buried — in the records to 

 which reference has just been made. The need exists, and 

 almost daily becomes greater, for facile reference to this ac- 

 cunjulated wealth, and of such a kind that an investigator, 

 commencing a line of inquiry » ith whose previous history he i? 

 not familiar, can be certain to learn all the facts known on the 

 subject up to a particular date, instead of having only the 

 partial record to be found in even the best edited of the 

 diciionaries now available. The best and mo-t obvious method 

 of attaining this end is the publication of a subject-matter index 

 of an ideally complete character. I am glad to know that the 

 Chemical Society of London will probably provide us in the 

 years to come with a compilation which will doubtless aim at a 

 high standard of value as a work of reference to memoirs, and 

 in some degree to their contents, so far as the existing indexes 

 of the volumes of the Society's Journal supply the information. 

 Whether this subject-matter index is published or not, the time 

 has certainly arrived for adopting the immediately useful course 

 of publishing monographs, analogous to those now usual in 

 Natural Science, which shall contain all the information gained 

 up to a particular date in the branch of chemistry with which 

 the author is specially familiar by reason of his own work in the 

 subject. Such monographs should include much more than any 

 mere compilation, and would form the best material from which 

 a complete subject-matter index might ultimately be evolved. 



My attention was forcibly drawn to the need of such special 

 records by noting the comparatively numerous cases of re-dis- 

 covery and imperfect identification of derivatives of thiourea. 

 In my laboratory, where this substance was isolated, we 

 naturally follow wi h interest all work connected with it, and 

 therefore readily detect lapses of the kind just mentioned. 

 But when it is remembered that the distinct derivatives of 

 thiourea now known number considerably over six hundred 

 substances, and that their desciiptions are scattered through 

 numerous British and foreign journals, considerable excuse c.in 

 lie found for workers overlooking former results. The difficulty 

 which exists in this one small department of the science I hope 

 shortly to remove, and trust that others may be induced to pro- 

 vide similar works of reference to the particular branches of 

 chemistry with which they are personally most familiar. 



When we consider the drift of investigation in recent years, 

 it is easy to recognise a distinct reaction from extreme specialisa- 

 tion in the prominence now given to general physico-chemical 

 problems, and to those broad questions concerning the relations 

 of the elements which I would venture to group under the head 

 of " Comparative Chemistry." Together these lines of inquiry 



NO. I 246, VOL. 48I 



afford promise of definite information about the real nature 

 the seventy or more entities we term "element.s," and ab 

 the mechanism of that mysterious yet definite change in mai 

 which we call " chemical action." Now and again one or ot 

 class of investigation enables us to get some glimpse beyond 

 known which stimulates the imaginative faculty. 



For example, a curious side-light seems to be thrown on 

 nature of the elements by the chemico-physical discussior 

 the connection existing between the constitution of certain 

 ganic compounds and the colours they exhibit. Without 

 tempting to intervene in the interesting controversy in wh 

 Armstrong and Hartly are engaged as to the nature of 

 connection, we may take it as an established fact that a relat 

 exists between the power which a dissolved chemical compoi 

 possesses of producing the colour impression within our C( 

 paratively small visual range, and the particular mode of gro 

 ing of its constituent radicals in its molecule. Further, 

 reality of this connection will be most freely admitted in 

 class of aromatic compounds; that is, in derivatives of benze 

 whose constituents are so closely linked together as to exh: 

 quasi-elemental persistence. If then, the possession of what 

 call colour by a compound be connected with its constituti 

 may we not infer that "elements" which e.ihibit disti 

 colour, such as gold and copper, in thin layers and in tf 

 soluble compounds, are at least complexes analogous tc definit 

 decomposable substances ? This inference, while legitimate 

 it stands, would obviously acquire strength if we could sh 

 that anything like isomerism exists among the elements ; 

 identity of atomic weight of any two chemically distinct £ 

 ments must, by all analogy with compounds, imply dissimilai 

 in constitution, and, therefore, definite structure, independec 

 of any argument derived from colour. Now, nickel and cot 

 are perfectly distinct elements, as we all know, but, so far 

 existing evidence goes, the observed differences in their atot 

 weights (nickel 58 0, cobalt 587) are so small as to be will 

 the range of the experimental errors to which the determinatii 

 were liable. Here, then, we seem to have the required exam 

 of something like isomerism among elements, and consequen 

 some evidence that these substances are complexes of diffen 

 orders ; but in the cases of cobalt and nickel we also know tl 

 in transparent solutions of their salts, if not in thin layers of I 

 metals themselves, they exhibit strong and distinct colour 

 compare the beautiful rosy tint of cobalt sulphate with the bi 

 liant green of the corresponding salt of nickel. Therefore, 

 exhibiting characteristically different colours, these substani 

 afford us some further evidence of structural differences betwe 

 the matter of which they consist, and support the conclusion 

 which their apparent identity in atomic weight would lead 1 

 By means of such side-lights we may gradually acquire sot 

 idea of the nature of the elements, even if we are unable to % 

 any clue to their origin other than such as may be found 

 Crookes' interesting speculations. 



Again, while our knowledge of the genesis of the chemii 

 elements is as small as astronomers possess of the origin oft 

 heavenly bodies, much suggestive work has recently be 

 accomplished in the attempt to apply the principle of gravitatic 

 which simply explains the relative motions of the planets, 

 account for the interactions of the molecules of the eleraen 

 The first step in this direction was suggested by Mendelecf in 

 Royal Institution lecture (May 31, 1889) wherein he propo? 

 to apply Newton's third law of motion to chemical molecal 

 regarded as .systems of atoms analagous to double stars. T 

 Rev. Dr. Haughton has followed up this idea with his w( 

 known mathematical skill, and, in a series of papers just pi 

 lished, has shown that the three Newtonian laws are applica 

 to explain the interactions of chemical molecules, " with t 

 diflerence, that whereas the specific coefficient of gravity is' 

 same for all bodies, independent of the particular kind 

 matter of which they are composed, the atoms have speci 

 coefficients of attraction which vary with the nature 

 the atoms concerned." The laws of gravitation, with t 

 proviso, were found to apply to all the definite cases examim 

 and it was shown that a chemical change of combination 

 equivalent to a planetary catastrophe. So far the fundamen 

 hypothesis of " Newtonian Chemistry " has led to conclusK 

 which are not at variance with the facts of the science, wWw 

 gives promise of help in obtaining a solution of the great probf 

 of the nature of chemical action. 



Passing from considerations of the kind to which I haKJ: 

 ] referred, permit me to occupy the rest of the time at ray <j 



