464 



SCIENCE. 



[N.S. Vol. XXIII. No. 586. 



This little book will be of service to two 

 classes of people: to schoolboys of ten to 

 fifteen years, for whom it was primarily in- 

 tended, and to teachers. It is doubtful if 

 the average American schoolboy would be at- 

 tracted by the method of presentation, even 

 in an English translation, though it would be 

 an interesting experiment to try and we should 

 be glad to hear of the results. But every 

 teacher will find the book worthy of a most 

 careful reading. Professor Ostwald has se- 

 lected with very great care that material which 

 appears to him most fundamental and most 

 interesting for the beginner in chemistry and 

 he has secured a clearness and accuracy in 

 presentation which deserve very high praise. 

 In both directions teachers will find here a 

 mine of useful suggestions. 



The author follows, of course, his well- 

 known attitude toward the atomic theory. He 

 is too good a teacher not to recognize and 

 make use of the ' hypothesis ' for didactic pur- 

 poses, but he evidently does this because of 

 the hardness of chemists' hearts and wishes he 

 could escape the necessity. This dislike for 

 the theory sometimes betrays him into inac- 

 curate statements or false reasoning. Thus 

 on page 38 he explains that the formula of 

 sulphuric acid is written with two combining 

 weights of hydrogen, because otherwise we 

 should have to write HS.^O. and ' the rule has 

 been laid down that fractions of combining 

 weights shall never be written.' He neither 

 gives a reason for such an arbitrary rule nor 

 does he explain why a combining weight of 16 

 might not be given to sulphur and the formula 

 written HSO„. It is not, of course, essential 

 that these matters should have been explained 

 at this point, but so misleading a reason 

 should not have been given. 



On page 42, in answer to the question, ' Are 

 not the atoms, then, just as certain as the 

 natural laws ? ' the author replies, ' Not at all, 

 for natural laws are not based on an arbitrary 

 assumption, as is the atomic hypothesis, but 

 they express definite relations between quan- 

 tities which can be measured and proved.' In 

 this statement he appears to overlook the fact 

 that the natural laws are all based on two 

 assumptions : first, that phenomena repeat 



themselves with absolute uniformity under 

 the same conditions and, second, that simple 

 relations exist between the quantities which 

 we measure. Each of these assumptions is 

 arbitrary and neither can be proved. They 

 difl^er from the assumptions which lie at the 

 basis of the atomic theory in being more 

 simple but not in their fundamental nature. 

 To illustrate: We believe in the law that the 

 atomic heats of the elements are equal because 

 many similar simple relations have been 

 found and we assume that a simple relation 

 exists here also, though we can not prove it 

 and are well aware that the deviations from 

 the law are very far in excess of the experi- 

 mental errors in the measurement of the 

 quantities involved. The assumption here is 

 clearly an arbitrary one and is based on far 

 less satisfactory evidence than that almost 

 infinite variety of phenomena which form the 

 basis for our assumption of the existence of 

 atoms. The writer of this review does not 

 claim that the existence of atoms has been 

 proved, but he does claim that the truth of 

 natural laws is also not proved, and that while 

 natural laws and the atomic theory differ 

 greatly in the complexity of the phenomena 

 on which they are based, they do not, philo- 

 sophically speaking, differ in their funda- 

 mental nature. 



On page 48 he suggests the term ' molar 

 weight ' in place of molecular weight. This 

 would be very unfortunate in English since 

 the word molar is used by us in a quite dif- 

 ferent sense. 



On page 112 we find the erroneous state- 

 ment that ' sulphuric acid is bibasic because 

 it contains two combining weights of hy- 

 drogen.' 



On pages 82 and 139 it is stated that every 

 transformation or reaction produces the less 

 stable form of an element or compound. Pro- 

 fessor Ostwald seems to accept this law as a 

 sort of axiom without attempting to give any 

 reason for it. It appears to the writer of this 

 review as closely related to Berthelot's erro- 

 neous law that every chemical reaction takes 

 place with the evolution of the maximum 

 amount of heat. Both laws are based on a 

 desire to explain chemical reactions by a 



