IOWA ACADEMY OF SCIENCES. 
19 
assumption is made that all ordinary chemical reactions occur- 
ring with inconceivable rapidity in solutions are in reality reac- 
tions between ions and not between molecules, the latter requir- 
ing an appreciable time for reaction. Thus, a solution of sodium 
chloride gives an immediate precipitate of silver chloride when 
treated with silver nitrate, whereas, under the same conditions, 
chloroform, in spite of its much larger percentage of chlorine, 
gives no reaction ; the reason being that the sodium chloride is 
dissociated and contains chlorine ions, while the chloroform is 
not dissociated, and therefore contains none. We have, there- 
fore, for the first time, an adequate explanation of the familiar 
fact that the usual reactions of an element are not manifested 
by all the compounds containing that element. 
It would be aside from the purpose of the present paper to 
discuss in detail the electrolytic dissociation theory. My object 
has been simply to sketch in the briefest way one of the most 
recent developments of chemical thought and probably the most 
important, historically, of the last half of the nineteenth cen- 
tury. 
Is there any question as to what reception should be accorded 
to the new view ? 
To say of any doctrine or theory, old or new, “It is true,” is 
to assume for human intellect a finality of judgment which it 
can never possess. To ask, “ Is it fruitful?” is the only legiti- 
mate question, upon the answer to which every scientific 
hypothesis must stand or fall. A doctrine that makes possible 
a more comprehensive grasp of phenomena already known, and 
serves as a trusty guide to the investigator in the discovery of 
new facts, does all that any theory can do. It becomes the gen- 
uinely scientific man, then, to accept the services of the latest 
theory so long as it is serviceable, much as he would accept the 
aid of a beast of burden to carry him across a ford, not carpingly 
or with irrelevant questions as to pedigree or absolute truth, 
nor with a demand for everlasting life, but gratefully, demand- 
ing only that it should have strength to reach the other shore. 
