352 



CARNEGIE INSTITUTION OF WASHINGTON. 



It is witli great regret that the writer announces the retirement of 

 Dr. W. W. Holland, after nine years of devoted and effective service. 

 Much of the success of the investigation has been due to his resource- 

 fulness, skill in difficult manipulation, tireless energy, and unconquer- 

 able optimism. 



Noyes, Arthur A., Massachusetts Institute of Technology, Cambridge, 

 Massachusetts. Researches upon the properties of solutions in relation 

 to the ionic theory. (For previous reports see Year Books Nos. 2-14.) 



During the past year the researches referred to in previous reports, 

 on the electromotive forces of concentration-cells and on the equi- 

 librium-relations of oxidizing and reducing agents, have been continued. 



Dr. J. H. p]llis and Mr. F. W, Hall continued the investigation 

 of the electromotive force of cells of the type H2, HCl, Hg2Cl2 + Hg, 

 with the purpose of determining the magnitude of the deviations 

 from the laws of perfect solutions which largely ionized solutes 

 exhibit; and a description of this work has been published. Difficul- 

 ties were encountered in the case of solutions more dilute than 0.1 

 normal, but these have now been overcome by using a silver-chloride 

 silver electrode in place of the calomel electrode, and accurate results 

 have been obtained down to 0.003 normal. 



These researches have shown a remarkable divergence between the 

 so-called ionization-coefficient of the hydrochloric acid (as derived 

 kinetically in the usual way from electrical conductivity measure- 

 ments) and its ion activity-coefficient as derived thermodynamically 

 from these electromotive-force measurements. This is shown by the 

 following table of values of the two quantities : 



Molal concentration . . 

 Ionization-coefficient. . 

 lonactivity-coefficient . 



0.001 



0.99 



0.99 



0.01 

 0.97 

 0.93 



0.1 



0.92 



0.82 



0.3 



0.90 



0.78 



. .■) 



0.89 



0.77 



1.0 



0.84 



0.84 



2.0 

 1.06 



4.5 

 2.25 



Dr. E. W. Wescott has completed the research on the equilibrium 

 conditions in aqueous solution of the reaction PbCl2 (solid) + CL 

 (gas) -h H+Cl~ = H+PbCl5~. The results, which furnish a measure 

 of the oxidation tendency of plumbous to plumbic lead, will soon be 

 published. 



A new Ime of investigation on the water-vapor-pressure of salt 

 hydrates (such as CUSO45H2O, Na2HP04l2H20) has been undertaken 

 and has been actively prosecuted during the past year with the aid 

 of several assistants. The work has thus far been directed mainly 

 towards the development of satisfactory experimental methods, to 

 replace the inexact time-consuming method commonly employed of 

 allowing the vapor-pressure of the hydrate to establish itself in an 

 evacuated tensimeter. Two such methods have been worked out. 

 One of these consists in placing the salt hydrate in one pan of a small 



