6oS 



NATURE 



\C)d. 28, 1880 



lectures on astronomy, he so excited the public interest 

 that the necessary funds were supplied for erecting an 

 observatory at Harvard. A remarkable series of lectures 

 on "Ideality in Science," delivered by him in 1879 

 before the Lowell Institute in Boston, attracted the 

 general attention of American thinkers, on account of 

 the thoughtful consideration of the vexed question of 

 science and religion. 



Much of Prof. Pcirce's activity was absorbed by his 

 duties as the head of the American Coast Survey, a 

 position in which he succeeded Prof. Bache. He brought 

 to this work the same degree of zeal and ability which 

 were so brilliantly evidenced by his predecessor, and 

 constantly maintained the well-earned reputation of the 

 Coast Survey among the hydrographic efforts of our day. 

 Prof. Peirce was one of the founders of the American 

 National Academy of Sciences. In 1853 he presided 

 over the American Association for the Advancement of 

 Science. The degree of LL.U. was conferred upon him 

 twice, by the University of North Carolina (1847), and by 

 Han-ard University (1867). He was elected an Associate 

 of the Royal Astronomical Society (1849), and a Fellow 

 of the Royal Society of London (1852), and of the Royal 

 Societies of Edinburgh and Gottingen. 



Prof. Peirce leaves behind him his w-ife, a daughter, and 

 three sons. Of the latter one is Professor of Mathematics 

 at Harvard, and another is Professor at Johns Hopkins 

 University. 



RECENT CHEMICAL RESEARCH 

 'T'HE masses of facts accumulated in the text-books on 

 ■*■ chemistry are already portentous : each month, 

 almost each week, adds to the store. 



The difficulty of getting a stable standing-ground from 

 which to survey, in order, if possible, to find the meaning 

 of these facts, increases hkewise. 



Fortunately from time to time there are found investi- 

 gators who, turning from the easy toil of adding new 

 compounds to those which are as yet but imperfectly 

 known, concern themselves with the fundamental ques- 

 tions of chemical science. 



Why are the pi-operties of bodies so largely modified 

 under certain conditions .' This is the all-important 

 question for the chemist. Before this question can be 

 answered for a series of substances the properties of those 

 substances must be accurately known, and the variations 

 in their properties under varying conditions — themselves 

 definitely ascertained — must be determined. Among the 

 properties of substances those which we usually call 

 physical are, as a rule, more susceptible of accurate 

 measurement than those which we call chemical. 



But these physical properties must be connected in 

 someway with the chemical structure of the little parts, or 

 molecules, of which we conceive the substances to be 

 built up. 



To determine what this connection is in the case of a 

 definite physical property, and for a series of chemical 

 substances, is at present one of the most promising 

 problems which presents itself to the chemical inquirer. 



But these physico-chemical problems require for their 

 solution, a practical knowledge both of chemical and 

 physical methods ; methods of laboratory work and 

 methods of reasoning on the results obtained. Students 

 of nature trained in both methods are not extremely 

 abundant. 



The suggestion made in the preface to Armstrong and 

 Grove's new volume on Organic Chemistry, that each 

 chemical school should regularly prepare special series of 

 pure compounds, and should let it be known that physical 

 observers can procure these compounds in order to deter- 

 mine their physical properties, is well worthy of being 

 acted on by all in whose hands may rest the arrangement 

 of the work of any chemical school. 



The older method of regarding chemical physics as 

 consisting of a little chemistry loosely tacked on to a great 

 deal ofordinary physics, is disappearing; and chemists and 

 physicists now recognise that the problems which each 

 attacks are, in veiy many instances, but difterent aspects 

 of the same question. 



The more thoroughly the chemical worker is trained in 

 the correct use of dynamical principles and dynamical 

 reasoning, the more likely is he to succeed in his search 

 for chemical truth. 



^^ery recently two papers have appeared, the contents 

 of which illustrate the importance of the results obtainable 

 by physico-chemical methods. 



Briihl has published in Liebig's Annalen — and in a 

 condensed form in the Berlin Berichtc — the results of 

 his investigations on the connection between physical 

 properties and chemical constitution of carbon com- 

 [jounds ; and Thomson, in the Journal fiir prac/ische 

 Chcinie (and also in the Btrichte) has given the first two 

 instalments of his thermal work bearing on the isomerism 

 of carbon compounds. 



I propose to give a short account of the work of these 

 two chemists : let us begin with Thomsen's. 



The "heat of formation" of a compound substance is 

 the difference between the sum of the heats of combustion 

 of the constituent elements of the compound, and the 

 heat of combustion of the compound itself. But this 

 heat is not the true ''heat of formation" of the molecule 

 of the compound; it is only the algebraic sum of various 

 heat disturbances. The thermal change which accom- 

 panies the formation of a compound molecule from 

 various elementary molecules consists of various parts : 

 (i) heat absorbed in dissociating the molecules of the 

 different elements ; (2) in some cases, heat absorbed in 

 liquefying or gasefying the constituent elements ; (3) 

 heat evolved in the formation, from the dissociated ele- 

 mentary atoms, of the new compound molecules ; and 

 (4) in some cases heat evolved in the liquefaction or 

 solidification of the gaseous compound molecules. If the 

 physical state of the various substances concerned be 

 constant throughout the experiment, (2) and (4) may be 

 neglected ; ancl the heat of formation will be equal to 

 the difference between the heat absorbed in splitting the 

 elementary molecules, and that evolved in the falling 

 together of the atoms so produced, in the new configura- 

 tion. The value of the first part of this operation will 

 always be constant for the same element or elements ; 

 but the value of the second part will depend upon the 

 configuration assumed by the elementary atoms in the 

 new compound molecules. 



Now the generally accepted chemical theory of isomerism 

 is that it (isomerism) is dependent on varying configuration 

 of the same atoms. Some chemists have urged that iso- 

 merism is more probably due to the possession, by the 

 different compounds, of different amounts of energy. 

 But these two theories are really parts of the same theory. 

 Thomsen's method, indeed, may be said to be based on 

 this fundamental identity. 



Given the dissociated elementary atoms, they may 

 arrange themselves in various ways, each arrangement 

 will bo attended with a definite but different evolution of 

 heat, hence, inasmuch as the heat absorbed in the pre- 

 liminary elemental dissociation is fixed, the heats of 

 formation of the various isomeric molecules will be 

 different. 



But when it is said that isomerism depends on atomic 

 configuration, two things are included in this statement. 

 Let us consider isomerism in a hydrocarbon : the carbon 

 atom combines with four, and not more than four, 

 hydrogen atoms.to form a compound molecule. The carbon 

 atom is said to be tetravalent ; this is usually graphically 

 expressed by the symbol =C=. The maximum number 

 of hydrogen atoms which two carbon atoms can com- 

 bine with to form a definite molecule will be six, 



