July 31, 1914] 



SCIENCE 



173 



gram. The expression " during its whole life 

 history " has no meaning 'whatever in this 

 connection. Concerning the last of the above 

 statements it may be said that undoubtedly 

 the equilibrium quantity of radium is meant, 

 but it is not so stated. 



On page 287 it is said that "the radium 

 emanation induces radioactivity on all objects 

 on which it is deposited." It is the disintegra- 

 tion products of the emanation which are 

 deposited, and not the emanation itself. The 

 next sentence, which reads, " This induced 

 radioactivity decays or disappears, as the 

 emanation which causes it decays," while per- 

 haps not entirely wrong, certainly does not 

 state the facts clearly. 



In discussing the disintegration of radio- 

 active substances the author uses the expres- 

 sion " life history " sometimes to mean the 

 " half period " of Eutherf ord, as, for instance, 

 on page 283, when he speaks of thorium ema- 

 nation as having a much shorter " life history " 

 than radium emanation; at other times, as on 

 page 288, it is apparently synonymous with 

 " mean life," for he here speaks of 2,000 to 

 S,000 years instead of 1,760 years; while in 

 another place, pages 294-295, he uses the ex- 

 pression with obviously still another meaning, 

 for he here says that " the life history of 

 radium is between two and three thousand 

 years. This means that none of the radium 

 now present existed more than twenty-five 

 hundred years ago." There may be a legiti- 

 mate sense in which one may speak of the 

 " life history " of a radioactive substance, but 

 certainly the expression should not be used in 

 place of " mean life " or " haK period." It 

 may be remarked that, quite contrary to the 

 above statement of the author, a very consid- 

 erable proportion of the radium now present 

 in the earth's crust was in existence twenty- 

 five hundred years ago. 



In the judgment of the reviewer the author 

 also indulges far too freely in sweeping, un- 

 qualified statements. As an example of such 

 a statement the following is quoted from the 

 chapter on the " Origin of Stereochemistry," 

 page 58. " Kekule had converted empiricism 

 in the study of carbon into system. Van't 



Hoil had made possible the beginning of a 

 science of organic chemistry." Most organic 

 chemists will probably say of this, that while 

 there is possibly a difference in degree, there 

 is hardly a difference in kind between the 

 achievement of Van't Hoff and that of 

 Kekule. 



Another example is taken from page 137. 

 " It (water) owes its existence to the fact that 

 hydrogen and hydroxyl ions can not remain 

 in the presence of one another uncombined." 

 This, of course, in a sense, is true. But then 

 the following equally impressive statement is 

 also true. Hydrogen chloride owes its exist- 

 ence to the fact that, depending upon condi- 

 tions, chlorine and hydrogen ions can or can 

 not remain in the presence of each other un- 

 combined, which is equivalent to saying that 

 hydrogen chloride owes its existence to the 

 fact that it is hydrogen chloride. Moreover, 

 hydrogen and hydroxyl ions can and do exist 

 together uncombined, and it is to this fact that 

 the many important phenomena of hydrolysis 

 are due. 



It is always of doubtful expediency to criti- 

 cize an author's English; nevertheless, the re- 

 viewer ventures to quote the following from 

 pages 117 and 268: 



" Take, for example, water. We would find 

 most of the hydrogens united with oxygen to 

 form molecules of water; but, in addition, we 

 would have some free hydrogens and some free 

 oxygens." 



" Take a salt like potassium chloride. When 

 it is thrown into water an electron passes from 

 the potassium over to the chlorine. The 

 chlorine having received an additional elec- 

 tron thus becomes charged negatively, while 

 the potassium having lost an electron becomes 

 charged positively. . . . Take, again, a salt 

 like potassium sulphate. Each potassium loses 

 one electron to the SO,, which thus acquires 

 two negative charges, the potassium having 

 each one positive charge." If this sort of 

 description is justified by its directness and 

 dramatic effect, then perhaps the only criticism 

 to be offered is that " potassium " (four lines 

 above) should read "potassiums." 



One is disappointed after reading of the 



