THE RELATIONS OF PHYSICAL CHEMISTRY TO PHYSICS 



AND CHEMISTRY 



BY JACOBUS HENRICUS VAN 7 T HOFF 



[Jacobus Henricus van 't Hofif, Member of the Academy of Sciences, Berlin; Ordi- 

 nary Honorary Professor, University of Berlin, Germany, b. August 30, 1852, 

 Rotterdam. Ph.D. Polytechnic School, Delft; M.D. University of Utrecht; 

 LL.D. University of Chicago; ibid. Harvard University. Honorary course, 

 Griefswald and Utrecht. Tutor in Clinics, Veterinary School, Utrecht, 1876- 

 78; Professor in Chemistry, Mineralogy and Geology, University of Amsterdam, 

 1878-96. Member of various societies in Amsterdam, Bologna, Christiania, Delft, 

 Erlangen, Frankfurt. Gottingen, Batavia, Copenhagen, Lund, Mexico, New 

 York, Philadelphia, Rotterdam, St. Petersburg, Turin, Utrecht, Vienna, Venice, 

 Washington.] 



ACCORDING to the Programme, I have to consider the "General 

 Principles and Fundamental Conceptions which connect Physical 

 Chemistry with the Related Sciences, reviewing in this way the 

 development of the science in question itself." 



Let me begin by defining physical chemistry as the science devoted 

 to the introduction of physical knowledge into chemistry, with the 

 aim of being useful to the latter. On this basis I can limit my task to 

 the relations of physical chemistry to the two sciences it unites, 

 chemistry and physics. 



But even if I limit myself to these relations, which are not the only 

 two, 1 1 wish to restrict myself yet more, in order, in the spirit of this 

 Congress, to call your attention to broad views. So I shall follow up 

 only two lines, in answering two questions regarding two funda- 

 mental problems in chemistry: (1) What has physical chemistry 

 done for our ideas concerning matter? (2) What has it done for our 

 ideas concerning affinity? 



The small table which I have the honor to put before you will 

 enable us to answer these questions by appeal to the scientific develop- 

 ment of our science, which also I have to review: 



I. Ideas concerning Matter 



(1) Lavoisier, Dalton (1808). 



(2) Gay-Lussac, Avogadro (1811). 



(3) Dulong, Petit, Mitscherlich (1820). 



(4) Faraday (1832). 



(5) Bunsen, Kirchhoff (1861). 



(6) Periodic System (1869). 



1 In Chicago I devoted to this subject eight lectures, which have since appeared 

 in the Decennial Publications under the title ' Physical Chemistry in the Service 

 of the_Sciences, ' Chicago, 1903. 



