Page:Science vol. 5.djvu/196

 [Vol,, v., Ko. loa

��THE PRINCIPLES OF CHEMISTRY.

To most persoQs, nnd indeed to most chem- isU. cheiuiatry is the science which has to deal only with the compositioo of bodies. No one can doubt the prime importance of the science regarded from this Bland-point : but it may fairly be asked wliethei' 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 ttic arrangement of their smallest particles.

The determination of composition in this broad sense forms the principal work of the chemiatsofthepresentgeneration.audofmany generations past. In a rough way, lo be sure, fttpempts 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 circnni- stances watur can be decom|H)3ed into hydro- gen and oxygen. It is another thing to know something about what takes place in the inter- val between the disappearance of the hydrogen and oxygen and the formation of the water, or vice vena. We have here to deal with a natu- ral phenomenon, which should be studie<l as other natural phenomena are studied ; as, for example, the falling of bodies, etc. Suppose that in stud3'ing the falling of a body we should confine our attention to the body at rest tx?fore it falls, and alter 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 by 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 arc 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 l)ook before us has largely to deal with the recent developments in the scientific study

A Irmliir an thr prbtripli* of chnnltiry. Bj M. M. P*tti- B»H UuiH. U.A.. F.U.S.E., Allow and ptuWlur tn cl.nnlalry uf Ounvllk nnd CiKii collri.. Cuobrlilttu. Catubrldtfo, rxlcn-.

��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, .tbe 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 wcigli conscientiously the facts and the inferences which they seem to permit. As regards the subjects treated in the book, we quote from the preface : —

"Tbe book is divided into Iwo paita. The fint part is occupied with the statement and dlscnarion of the atomic and molecular ttieoriTi "<"1 the applies^ Cious thereof lo such subjects as nllolropy. Isomerism, and the classiHcation of elements and compounda. Somewhat full accounts are also given, In Ihii put, of thermal, optical, and other departments of ptajsl- cal chemistry, in so far ai the results and methods ot these branches of the science are applicable to the ijuestioiis regarding the composUioii uf chemical syv tem4 which are connoted b; the term ' cbemicul BUtic.«.'

"The second part at the book is devoted lo Iba subjects of dissociation, chemical change and eqlll- Ubrluni, chemical affinitr. and the relations betWHH chemical action and the diatrihutlon of the eaerg; of the changing system. These and CDgiiate quaslions 1 have ventured to aummarizi! In the expresdon ' 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 tiogmatism, and a clear detei^ mination lo be governed by facts, and not hypotheses. We commend this part of lK>ok to advanced students of chemistry have become contaminated with the dogmi metho<Is which are so much in vogue. earnestly beg our teachera to study it, and, possitile, to profit by it.

In the second part of the book are found chapters on subjects which are not commonly treated in test-books of chemistry. The re- searches of GnMberg and Waage. and of Ost- wald, of Pfanndler, 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- vey a correct idea in regard to the relations of the various investigations to the general prob- lems of chemistry. The chapter on aJEnity is worthy of special mention and of special stud}-.

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 (be stale of gas. conclu- Bious regarding the mructuru of Ibe molecules ot these eomjKiund] are very apt lo degenerate liiis

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