180 



SCIENCE. 



[Vol. V., No. 108. 



THE PRINCIPLES OF CHEMISTRY. 



To most persons, and indeed to most chem- 

 ists, chemistry is the science which has to deal 

 only with the composition of bodies. No one 

 can doubt the prime importance of the science 

 regarded from this stand-point ; but it may 

 fairly be asked whether the determination of 

 the composition of bodies is the final object of 

 chemistry, even if by composition we mean 

 not only the kinds of matter of which the 

 bodies are made up, but the arrangement of 

 their smallest particles. 



The determination of composition in this 

 broad sense forms the principal work of the 

 chemists of the present generation, and of many 

 generations past. In a rough wa}', to be sure, 

 attempts have been made to discover the laws 

 which govern the changes in composition which 

 bodies undergo, but our knowledge of these 

 laws is as yet extremely limited. It is the dis- 

 covery of these laws which forms the highest 

 object of chemistry. It is one thing to know, 

 that, when hydrogen and oxygen are brought 

 together under certain circumstances, water is 

 formed, and that under certain other circum- 

 stances water can be decomposed into hydro- 

 gen and ox3 T gen. It is another thing to know 

 something about what takes place in the inter- 

 val between the disappearance of the 113'drogen 

 and oxygen and the formation of the water, or 

 vice versa. We have here to deal with a natu- 

 ral phenomenon, which should be studied as 

 other natural phenomena are studied ; as, for 

 example, the falling of bodies, etc. Suppose 

 that in studying the falling of a body we 

 should confine our attention to the body at 

 rest before it falls, and after it has fallen, how 

 extremely imperfect our knowledge of the phe- 

 nomenon would be ! It is plain that we could 

 never discover the laws of falling bodies hy 

 such observations ; and yet our observations 

 in the case of chemical phenomena are almost 

 exclusively of this kind. The reason is, that 

 chemical action usually takes place so rapidly 

 that it is practically impossible to make accu- 

 rate observations during its progress. Of late, 

 however, there has been a marked tendency to 

 the study of the course of chemical reactions ; 

 and the indications are clear that chemists are 

 beginning to give the subject of chemical ac- 

 tion as such more serious attention than has 

 heretofore been the case. 



The book before us has largely to deal with 

 the recent developments in the scientific study 



A treatise on the principles of chemistry. By M. M. Patti- 

 son Muir, M.A., F.R.S.E., fellow and praelector in chemistry 

 of Gonville and Caius college, Cambridge. Cambridge, Univer- 

 sity press, 1884. 24+488 p. 8°. 



of Chemical phenomena, and with well-known 

 facts and hypotheses which have a bearing 

 upon the deeper problems of chemistry. In 

 his zeal for the new work, the author is per- 

 haps now and then unfair towards the old ; but 

 in general he gives evidence of a spirit of fair- 

 ness, and a desire to weigh conscientiously the 

 facts and the inferences which they seem to 

 permit. As regards the subjects treated in 

 the book, we quote from the preface : — 



" The book is divided into two parts. The first 

 part is occupied with the statement and discussion 

 of the atomic and molecular theory, and the applica- 

 tions thereof to such subjects as allotropy, isomerism, 

 and the classification of elements and compounds. 

 Somewhat full accounts are also given, in this part, 

 of thermal, optical, and other departments of physi- 

 cal chemistry, in so far as the results and methods of 

 these branches of the science are applicable to the 

 questions regarding the composition of chemical sys- 

 tems which are connoted by the term ' chemical 

 statics.' 



" The second part of the book is devoted to the 

 subjects of dissociation, chemical change and equi- 

 librium, chemical affinity, and the relations between 

 chemical action and the distribution of the energy of 

 the changing system. These and cognate questions 

 I have ventured to summarize in the expression 

 ' chemical kinetics.' " 



The first part gives us a clear treatment of 

 the subjects of atoms and molecules, and the 

 structure of molecules. The chief character- 

 istic of the author's method of treatment is 

 an absence of dogmatism, and a clear deter- 

 mination to be governed by facts, and not b} r 

 lrypotheses. We commend this part of the 

 book to advanced students of chemistry who 

 have become contaminated with the dogmatic 

 methods which are so much in vogue. We 

 earnestly beg our teachers to study it, and, if 

 possible, to profit bj^ it. 



In the second part of the book are found 

 chapters on subjects which are not commonly 

 treated in text-books of chemistry. The re- 

 searches of Gulclberg and Waage, and of Ost- 

 wald, of Pfaundler, Horstman, and Willard 

 Gibbs, are fully and clearly treated for the first 

 time in a chemical text-book in the English 

 language, and treated in such a way as to con- 

 vej T a correct idea in regard to the relations of 

 the various investigations to the general prob- 

 lems of chemistr} T . The chapter on affinity is 

 worthy of special mention and of special study. 



It may be questioned whether, in his views 

 regarding valence and structure, the author 

 does not allow himself to be carried too far. 

 Thus, p. 463, we read, — 



"When ... we do not know the molecular- 

 weights of compounds in the state of gas, conclu- 

 sions regarding the structure of the molecules of 

 these compounds are very apt to degenerate into 



