THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



SEPTEMBER 1879. 



XXII. Chemical Affinity. By M. M. Pattison Mtjir, Prelec- 

 tor in Chemistry j Gonville and Cains College, Cambridge* . 



IN the year 1780 Bergmann formulated a general theory of 

 chemical affinity. The leading points in Bergmann's 

 theory were these. The affinity between two bodies is inde- 

 pendent of the masses of these bodies which may be brought 

 into mutual contact; under like condition the value of this 

 affinity is constant. The relative affinity-values of various 

 substances may be empirically represented by the amounts of 

 these bodies which mutually combine together : thus, if an 

 acid combine with a series of bases to form neutral salts, the 

 affinity of the acid is greatest for that base the greatest amount 

 of which is taken up by the acid. Conversely, a base has the 

 greatest affinity for that acid which combines with it in largest 

 quantity. 



In 1803 Berthollet published his great work Statique Chi- 

 miqne, in which he sought to show that the chemical action 

 of one substance upon a second substance is proportional to 

 the mass of the first and its affinity for the second. The pro- 

 duct of these two quantities is called by Berthollet the " che- 

 mical mass " of the substance. Complete decomposition of 

 one compound by another is never brought about, according 

 to Berthollet, by chemical affinity alone ; this force must 

 always be aided by what the French chemist called cohesion 

 and elasticity. 



Bergmann considered only the affinity of one body for 

 * Communicated by the Author. 



Phil Mag. S. 5. Vol. 8. No. 48. Sept. 1879. 



