364 J. W. Langley—Chemical Affinity. 
much of one acid must be taken to displace another. Although 
Wenzel’s work attracted but little attention at the time, we can 
now see on looking back that it marked a very important dis- 
covery, for he must be regarded as the first man who appre- 
hended with any distinctness that fundamental law of chemistry, 
definiteness of action, which was subsequently enunciated an 
‘law of definite 
sistent and earnest opponent of the new doctrines. In his well 
known work, Essai de Statique Chimigue, published in 1808, he 
maintains the proposition that all unions are caused by the 
by a combination, we must 
look to the reciprocal action (cohesion) of the parts which 
