508 THE POPULAR SCIENCE MONTHLY 



Of course, every one knows that the conception of the discontinuity 

 of " matter " appears in ancient history. And, when we descend to 

 modern times, Boyle (1627-91) speaks of corpuscles, Boerhaave (1668- 

 1738), Alhrecht von Haller's master, of massulce. Moreover, Dal ton 

 was a youth of only seventeen when the most important developments 

 occurred. First, and with special reference to the framework of possible 

 method, we have Lavoisier's (1743-94) celebrated memoir, " Eeflections 

 concerning Phlogiston/' where he dismisses the dominant theory in 

 sarcastic terms, 17 and establishes the quantitative method on a firm 

 basis. In the same year (1783) Bergman (1735-84), the last of the 

 great phlogistic chemists, published his notable work on what he called 

 "elective attraction" (i. e., affinity), a phenomenon attributed by him 

 to the attraction between the most minute particles. Naturally, Berg- 

 man's table of " single elective attractions in the moist way, and in the 

 dry way," with its curious alchemical signs, was a description of quali- 

 tative relations. It marked the beginning of investigation of mass 

 action, and provoked the striking researches of Berthollet (1748-1822), 

 who, in 1799, presented his paper, " Eecherches sur les lois de l'affinite," 

 out of which grew his major work, " Essai de statique chimique " 

 (1803). The main result of his assault upon Bergman was to show 

 that chemical change depends, not merely upon the affinities of the 

 substances involved, but upon their quantities. In other words, a new 

 method asserted itself. For, as Berthollet says-: 



To find the affinity of two substances towards a third, in accordance with 

 the conception we have now gained of affinity, can mean nothing other than to 

 determine the ratio in which this third substance divides itself between the 

 two first. 



Therefore, chemical change hinges upon the nature of the relative 

 masses of the substances involved, but, " to determine the ratio of the 

 affinities of two substances towards a third ... is attended by unsur- 

 mountable obstacles." Here was the blank wall, so to speak, that 

 shadowed Berthollet's services till the time of Guldberg and Waage 

 (1864). As Berthollet stood to Bergman, so did Proust (1755-1826) 

 to Berthollet. Baffled in every attempt to determine the distribution 

 of salts in solution, Berthollet had good reason to doubt the doctrine of 

 constant composition. Here was Proust's opportunity. Having dis- 

 tinguished between " combinations of elements " and " associations of 

 combinations," the latter variable under analysis, Proust was able to 

 enunciate the law of fixed proportions — in his own words, " Election 

 and proportion [i. e., affinity and fixity of composition] are the two 

 poles about which revolves immutably the whole system of true com- 

 pounds, whether produced by Nature or by Man " ; or, as Lothar Meyer 

 phrases it, " Definite chemical compounds always contain their con- 



" Cf. " GEuvres," Vol. II., pp. 623 f. 



