930 



SCIENCE. 



[N. S. Vol. VIII. No. 209. 



simplified analytically. The ground is also 

 unusually fruitful for applying and develop- 

 ing the fuudamental generalizations which 

 have been reached in chemistry iu the last 

 few years. 



When, in 1843, Kopp declared that a new 

 stage of development in chemistry would 

 follow the period of quantitative investiga- 

 tion, first by union with another branch o^ 

 science, he saw in advance what is now 

 being effected in the union of chemistry and 

 physics, which is being accomplished by the 

 new physical chemistry. Let us call atten- 

 tion to the importance of applying the two 

 fundamental principles of thermodj'namics 

 to chemistrj^ and how far consequences de- 

 rived from these principles can be subjected 

 to experiment, and what the result is. 



The problems solved in this way, belong 

 to the most important of oar science, but 

 receive a solution which has so little in 

 common with our atomic and structural 

 conceptions that they often do not appeal 

 to chemists trained in the latter school. By 

 this means problems will be solved, also bio- 

 logical problems, which lie out of the scope 

 of the configuration method. By applying 

 thermodynamics to chemistry it is chiefly 

 inorganic chemistry which is advanced. 



We must mention first the problem of 

 affinity. Thermodynamics does not refer 

 affinity to the reciprocal action of atoms, 

 but measures affinity bj^ the maximum 

 work which the reaction can perform. Let 

 us consider reactions which take place with 

 increase in volume, saj^ the union of copper 

 and calcium acetates to form the double 

 salt. If this reaction takes place in a closed 

 vessel, the walls are broken. On the other 

 hand, the reaction can be hindered bj^ bring- 

 ing a counter pressure to bear on the salts, 

 say by a piston and cylinder ; and Spring 

 has actually shown that the double salt 

 can be broken down bj' subjecting it to sev- 

 eral thousand atmospheres of pressure. This 

 counter pressure, which just prevents the re- 



action, is very closely connected with affinity 

 regarded as force, and affinity is determined 

 as work by the mechanical work which is 

 doue by the reaction against the maximum 

 pressure. 



The reaction may complete its maximum 

 work iu other ways, as in an electric bat- 

 tery, and it can then be measured from the 

 electromotive force of the battery. 



We arrive, iu this way, at a generaliza- 

 tion of very great importance : 



A transformation will, then, only take place 

 of itself in ease it is in a position to do a positive 

 amount of work. If the amount of %mrk done is 

 negative the transforniatiori can only take 2^la,ce 

 of itself in the opposite sense. If the work done 

 is zero it can take ]}lace in neither sense. 



This work and the possibilitj^ of reaction 

 depending upon it, can be calculated in any 

 given case, provided the work is ascertained, 

 once for all, which is done when each of 

 the substances in question is formed from 

 the elements. This work can be expressed, 

 e. g., in calories. This ' work of formation,' 

 bj' simple addition andsubtractiou, leads to 

 the ' work of transformation,' the sign of 

 which conditions the possibility of the 

 transformation. This program has been 

 carried out, to a certain extent for the mer- 

 cury compounds, by Nernst and Bugasky. 

 It should be mentioned that from this prin- 

 ciple it was foreseen that mercurous chloride 

 must be decomposed by potassium hydrox- 

 ide, although the transformation takes place 

 with heat absorption. 



We have obtained, also, a generalization 

 for reactions which only partly complete 

 themselves, on account of the introduction 

 of the opposite reaction, which leads to a 

 condition of so-called chemical equilibrium, 

 as in the combination of iodine and hydro- 

 gen, and in etherification. It is essential 

 that, in such cases, changes in concentra- 

 tion should be produced during the reaction, 

 and on account of the reaction. These de- 

 crease the work of transformation, finally 



