CHEMISTRY. 365 



5. Further Stxjdy of Compressibility of Elements and Compounds. 



With the help of Mr. James Hallett Hodges, the study of compres- 

 sibility both of elements and compounds was continued. Dr. Wein- 

 traub, of the General Electric Company, courteously loaned to us a 

 fine and unusually compact specimen of pure boron for the purpose of 

 determining its compressibility, which was measured for the first time. 

 This element shows, as would have been expected from the previous 

 Harvard researches upon this subject, a very small compressibility 

 (0.0000003), consistent with its small atomic volume and high melting- 

 point. The compressibilities of various other substances, especially 

 hydrocarbons and alcohols, were also determined with great care, 

 using the new steel piezometer mentioned in the last Year Book, the 

 determinations being made both at 20° and at 0°. Several improve- 

 ments in technique were introduced. The outcome of the recent work 

 upon compressibility of the elements conducted with these grants has 

 provided data for 38 elements, which agree essentially (in those few 

 cases where others have worked upon similar material) with the best 

 preceding work. This being the case, it seemed worth while to consider 

 the relations of these accurately determined data with other properties 

 of the elements in question, and a preliminary paper upon this sub- 

 ject, recording certain empirical relationships between compressibihty, 

 atomic volume, melting-point, and coefficient of expansion, was pub- 

 lished and is recorded on page 37 of this volume. 



6. The Effect of Pressure upon Solubility. 



Thermodynamically, the nature of the effect of pressure upon solu- 

 bifity of salts is clear, but, nevertheless, it seemed worth while to make 

 a careful study of the facts, in order to verify the thermodynamic 

 relationship, as well as to correlate this phenomenon with modem 

 theories concerning the nature of the solution of electrolytes. Accord- 

 ingly, with the help of Dr. Herbert Fowler Sill, a comparatively simple 

 and very efficient apparatus for determining solubihties under pressure 

 was devised, and careful experiments were made with solutions of 

 sodium chloride, potassium chloride and bromide, and barium hydrox- 

 ide. Care was taken to obtain saturation, through the approach of 

 equiUbrium from opposite directions. In order to apply thermo- 

 dynamic reasoning to these results, the heats of solution of the sub- 

 stances at the saturation point was necessary, in addition to other data 

 furnished by the researches of others. Accordingly, these were deter- 

 mined with the help of the adiabatic calorimeter. The results thus 

 obtained give calculated values for solubihty under different pressures, 

 confirming within a reasonable hmit of error all the experimental work, 

 and supporting Baxter's interpretation of the conditions holding in solu- 

 tions of these electrolytes, in accordance with the dissociation theory 

 and the hypothesis of compressible atoms. 



