NATURE 



561 



THURSDAY, OCTOBER 15, 1891. 



PHYSICAL CHEMISTRY. 

 Outlines of General Chemistry. By Wiihelm Ostwald. 

 Translated with the Author's sanction by James Walker, 

 D.Sc, Ph.D. Pp. 396. (London : Macmillan and Co, 

 1890.) 



THAT much may be gained by a judicious use of the 

 methods of the physicist in elucidating chemical 

 phenomena most chemists will admit ; and, considering 

 the rapid strides made of late years in physical chemistry, 

 it seems surprising that so little has been done to give a 

 connected account, suited to the wants of the student, of 

 the main researches in this important field of investigation. 

 Original communications on physical chcmisiry are on 

 the increase. The chemist has now, in the Zeitsckrift 

 fiir physikalische Chemie, a periodical devoted exclusively 

 to this branch of his science, and during the four years or 

 so of the existence of this journal, its success has testified 

 amply to the want which it supplies. 



Ready access to original memoirs is not, however, the 

 boon of the ordinary student ; and, even if it were other- 

 wise, the want of some scheme whereby to systematize 

 his reading and classify his information, much of which 

 is still open to wide difference of opinion, would almost 

 invariably lead to confusion. 



The majority of the text-books make little or no 

 attempt at supplying this want. Occasionally a few of 

 the larger chemical treatises spare a few pages to 

 " physical methods," and such text-books as Meyer's 

 " Modernen Theorien" or Muir's "Principles of Che- 

 mistry " contain much of the matter classed under 

 physical chemistry. 



Yet a comprehensive idea of what has been done in 

 tracing relationships between physical properties and 

 chemical composition and in utilizing physical mea- 

 surements in investigating chemical change, cannot be 

 obtained from most text-books. Indeed, so far as we 

 know, only one is designed to serve this purpose, and 

 that is the " Lehrbuch der Allgemeinen Chemie " of Prof. 

 Ostwald. " Allgemeinen " rather than " Physikalische " 

 " Chemie " has been used as a title for the work ; but in 

 the main it deals with physical chemistry. The book 

 under notice seems to be an English translation of an 

 abstract of the " Lehrbuch " ; and, were it for no other 

 reason than that it furnishes a well-conceived syllabus of 

 the subject-matter of general and physical chemistry, it 

 would be worthy of careful consideration. 



The book is divided into two parts — Part L' chemical 

 laws of mass ; Part IL chemical laws of energy. 



The first part opens with stoichiometry. The laws of 

 chemical combination, the determination of atomic 

 weights, and a useful summary of the atomic weight 

 estimations of the different elements are here given. 

 Then follow sections treating of such of the physical 

 properties of gases, of liquids, of solutions, and of solids 

 as the chemist must be familiar with, and of the more 

 important relations which have been established between 

 such physical properties and chemical composition. 



The section dealing with solutions is noteworthy as 

 containing the first fairly complete statement, in an Eng- 

 NO. 1146, VOL. 44] 



lish text-book, of the facts grouped around the physical 

 theory of solution which has arisen out of a knowledge 

 of osmotic pressure. Part L closes with chapters on 

 chemical systematics— the choice of atomic weights, the 

 periodic law, the development of the present conception 

 of molecular structure. 



In the earlier portions of the second part, thermo- 

 chemistry, photo-chemistry, and electro-chemistry are 

 discussed. The last takes up the constitution of 

 electrolytes, electric conductivity, and the Arrhenius 

 dissociation hypothesis. 



Chemical dynamics and chemical affinity are treated 

 in the last two sections, and afford many illustrations of 

 the use of physical methods in the study of chemical 

 change. In the case of acids competing for the same 

 base are found instances where physical methods alone 

 are available to estimate the nature and extent of the 

 chemical action. In these sections, the exposition of the 

 law of mass action, and of the velocity of chemical 

 change, is especially clear. Owing to recent work on the 

 subject, the discussion of affinity is here more complete 

 than in the " Lehrbuch," and however unsatisfactory the 

 notion of fixing specific affinity constants be considered, 

 the account set out is the most systematic and plausible 

 yet published. 



There is no doubt that the general conception of the 

 book is admirable ; it contains much that is new ; to the 

 advanced reader it will be refreshing after the time- 

 honoured methods of the ordinary text-books. Yet the 

 general impression which we think will be formed on 

 looking through it, is that the attempt made to compress 

 information into too small a compass has detracted much 

 from its value. 



A certain amount of detail is always necessary to in- 

 telligent comprehension, and in many parts of the book 

 there is too much bald statement to satisfy the reader 

 who approaches the subject for the first time. Mainly 

 for this reason it is a question whether the work will 

 answer the expectation of the author that it will " meet 

 the requirements of the student who, while not intending 

 to devote himself to the detailed study of general che- 

 mistry, still wishes to follow intelligently the progress 

 recently made in this important branch of science." 



The time which has been spent in preparing the 

 chapters on several important topics seems to have been 

 inadequate. For instance, the molecular volumes of 

 liquids are disposed of in little more than three pages. 

 Kopp's laws are quoted, although not one of them can 

 now be taken as valid ; Schiff's inaccurate rule as to the 

 volumes of isomers also finds a place. Instead of appa- 

 rently settling the question by stating " molecular volumes 

 to be additive magnitudes subject to constitutive influ- 

 ence," little more space would have been occupied in 

 showing how, in different groups of isomers, the volume 

 varies with the constitution. If recent progress on the 

 subject was to be made use of, the facts that the effects of 

 molecular weight and constitution cannot be disen- 

 tangled, that even from the comparison of compounds of 

 similar constitution, definite atomic volumes, determined 

 for the boiling-point, cannot be obtained— that, in short, 

 atomic volumes cannot be regarded as physical constants 

 — ought surely to have been emphasized. 



The desire to economize space is probably the cause 



B B 



