368 J. W. Langley— Chemical Affinity. 
selected, or from the expressions atom and molecule. If the 
atomic theory were abandoned to-morrow the above indicated 
experimental fora jabeegshar pn of hydrogen into two states or 
s would receive our rational indorsement though all our 
vast wealth of atomic expression had perished. 
he invention of the terms valence, or “atomicity,” is gener- 
ally credited to Adolph Wurtz, but the idea behind the 
names grew up so gradually from the theor y of types, from 
the study of or me ine from the controversy on the cause of 
etherification, also ‘the labors of Laurent, Gerhardt and 
Sterry Hunt, that i is hardly prudent to assign any specified year 
as the exact date of its origin. The “periodic law” is custom- 
_ arily associated with the name of Mendelejeff,’* and molifica- 
tions in the form of the law with that of Lothar Meyer.” 
There is also an English chemist, J. cng an who claims 
to be the originator of the discovery ; his speculations pee 
biving issue of to-day that any discussion of it here acaes 
out of place. 
Fin aly, 1 I will close this review with a condensed statement 
of the ee theories of affinity, taken from Watts’ Dic- 
tionar 
; : " ‘ Y 
1.—“ Chemical combinations are produced by universal attractions. 
The most Be adherents of this view are, Newton, who 
considered affinity as identical with the force ‘of gravitation, 
and Berthollet, who held it to be the same as cohesion. 
2.—“Chemical combinations are produced — a peculiar power 
called affinity, distinct from universal attraction.” 
Under this head we may place the adits and the 
believers in elective affinity. 
