CHEMISTRY. 



Noyes, Arthur A., California Institute of Technology, Pasadena, California. 

 Researches upon {1) the properties of solutions in relation to the ionic theory; 

 {2) free energies and reduction-potentials; (3) a system of qualitative analysis 

 including the rare elements; (4) the structure of crystalline substances 

 determined by X-rays; (5) the rates of chemical reactions; (6) theoretical 

 thermodynamics. (For previous reports see Year Books Nos. 2-21.) 



1. Properties of Solutions in Relation to the Ionic Theory. 



The anomalies in the properties of largely ionized substances have for many 

 years been the subject of extended investigations, in which, through the 

 grants to which this report relates, the Carnegie Institution has actively 

 participated. These investigations are now rapidly coming to fuller fruition 

 as the result of the mathematical development by Milner and by Debye and 

 Hiickel of a theory which shows that the deviation of the behavior of these 

 substances from that of perfect solutes can be accounted for quantitatively 

 (at least approximately) by evaluating the potential energy due to the elec- 

 trical attraction between the positive and negative ions. Consequently, the 

 researches during the past year have been directed to a simplification of 

 the form of presentation of the theory, and to testing it with the aid of the 

 already accumulated data. During the coming year the theory will be 

 developed in forms specifically applicable to the different properties of fairly 

 concentrated solutions, and it will be further tested in these directions. 



To verify the theory adequately, new data relating to mixtures of salts 

 of multivalent types have already been found necessary; and, as these data 

 can be best derived from the solubilities of salts in the presence of one another, 

 further experiments in this direction have been carried out with the aid of 

 R. M. Bozorth and R. H. Dalton and R. Pomeroy. 



2. Free Energies and Reduction-Potentials. 



A report has been completed and published by D. F. Smith and Hubert 

 K, Woods on a research concerning the free energy and heat of formation 

 of lead monoxide from its elements. The work consisted in measurements 

 at 25° and 45° of the electromotive force of the cell Pb(s)+PbO(s), Ba(0H)2 

 (0.0766-0.2242 m.), H2 (1 atm.). Its free energy was found to be -45,050 

 calories and its heat of formation — 52,360 calories. This free-energy value 

 is in fair agreement with the value ( — 45,460 calories) derived from the new 

 heat of formation and low-temperature heat-capacity measurements with the 

 aid of the constant entropy principle (the so-called third law of thermo- 

 dynamics), thus affording a further confirmation of that principle. 



The free energy of another oxide, the type of compounds for which data are 

 now most needed, has been determined, with the assistance of Mr. Reinhardt 

 Schuhmann, who has studied antimony trioxide by measuring at 25° the 

 electromotive force of cells of the type Sb(s)-|-Sb203(s), HCIO4 (0.1 — 1.0 n.), 

 H2 (1 atm.). Its free energy at 25° was found to be —148,600 calories. 

 Arsenic trioxide is now being investigated by the same method. 



By determining the solubilities of antimony trioxide in perchloric-acid solu- 

 tions of concentrations between 0.1 and 1.1 normal, and applj'^ing to the 

 results the mass-action law, it was found that the antimony exists in these 

 solutions mainly in the form of the univalent antimonyl ion (SbO"^) ; and from 

 the solubilities and the electromotive forces the molal reduction-potential for 



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