SCIENCE 



Friday, July 2, 1909 



CONTENTS 



The Use and Abuse of the lonio Theory: 

 Pbofessob Gilbert N. Lewis 1 



The Colleges of the United States and the 

 Campaign against Tuberculosis: Pkofessoe 

 W. H. NOETON 6 



Proposed Publication of Euler's Works: Peo- 



EESSOR G. A. MiLLEB 10 



Report of the Committee to Visit the Museum 

 of Comparative Zoology 12 



Scientific Notes and Neios 13 



University and Educational News 15 



Discussion and Correspondence: — 



Joint Meetings of Zoological Societies: 

 Pbofessob M. A. Bigelow. The Birthplace 

 of Leading Americans and the Question of 

 Heredity: Pbofessob Feedebick Adams 

 Woods. Fair Play and Toleration in Criti- 

 cism: Pbofessob Joseph Babeell. Deter- 

 mination of the Coefficient of Correlation: 

 Professor Kael PJearson. The Darwin 

 Celebration at Cambridge: Pbofessob A. 

 C. Sewabd 16 



Quotations : — 

 Vivisection .- 25 



Scientific Books: — 



Guttmann's Manufacture of Explosives : 

 Professor Charles E. Munboe'. Enowl- 

 ton's Birds of the World : Professor Fran- 

 cis H. Hebbick 26 



Special Articles: — 

 A Simple Fabry and Perot Interferometer : 

 Professor James Barnes. Some Com- 

 m-ents on the Reactions of Perichceta: Pbo- 

 fessob E. H. Harper 29 



Entomological Conference on the Pacific 

 Coast : W. B. Herms 30 



Societies and Academies: — - 



The Philosophical Society of Washington: 



R. L. Fabis 31 



MSS. intended for publicatiou and tooks, etc., intended for 

 reyiew should be sent to the Editor of Sciehce, Garrison-on- 

 Hudson, N. Y. 



THE USE AND ABUSE OF THE IONIC 

 THEORY 1 



Twenty-five years have elapsed since 

 Arrhenius advanced the theory that acids, 

 bases and salts in aqueous solution are dis- 

 sociated into their constituent ions. Now 

 that the storm of contention aroused by 

 this doctine is clearing, it may not be inap- 

 propriate to consider in cooler blood this 

 proposition of Arrhenius, to reinspect the 

 foundations, and to weigh without preju- 

 dice the pros and eons, the successes and 

 failures of the ionic theory. 



To show that an electrolyte in solution 

 suffers a change analogous to dissociation, 

 Arrhenius brought forward evidence of 

 three different kinds. First, he pointed 

 out that the various methods of deter- 

 mining molal concentration in solution 

 (freezing-point, boiling-point, vapor pres- 

 sure, osmotic pressure), all of which are 

 identical in principle and yield nearly 

 identical results, indicate that in a salt 

 solution the number of molecules dissolved, 

 or less hypothetically the number of mols, 

 is greater than the niunber calculated from 

 the simple chemical formula of the salt. 



The second argument rests upon the ob- 

 servation that in an aqueous solution of a 

 strong electrolyte the properties are purely 

 additive. Thus a dilute solution of hydro- 

 chloric acid has no properties which are 

 peculiarly its own. It tastes sour, turns 

 litmus red, dissolves metals, inverts sugar 

 and possesses a number of other well-known 

 properties, all of which are possessed in 

 some degree by every acid. Moreover, it 

 precipitates silver and mercurous salts, and 



' Address of chairman of the Section of Physical 

 Chemistry, Baltimore, December 29, 1908. 



