156 REPORTS ON INVESTIGATIONS AND PROJECTS. 



ing the atomic weight of silver ; but this is not as yet far enough advanced 

 for discussion here. This also will be continued in the near future. 



Turning now to the second subject covered by the grant, namely, experi- 

 mental chemical energetics, there are four other researches to report, as 

 follows : First among these may be mentioned — 



(5) A comparison of the compressibilities, surface tensions, specific grav- 

 ities, vapor tensions, and heats of vaporization of certain organic compounds, 

 carried out with the assistance of J. H. Mathews. Nearly all the data 

 involved in this comparison were determined anew, with carefully prepared 

 material and new and improved apparatus. Thirty-five typical substances 

 were investigated. The investigation was undertaken with the hope of 

 obtaining new light upon the nature of cohesion and its relation to the 

 so-called chemical afiinity, and this hope was not wholly unwarranted. The 

 results, in so far as they are capable of interpretation, support the hypothesis 

 of compressible atoms. Both data and conclusions are too voluminous to 

 find a place here. The work upon heat of vaporization was not wholly 

 finished ; it will be continued next year. The remainder of the work is 

 almost ready for publication. 



The investigation next described dealt with an allied subject : 



(6) The compressibilities of various inorganic solids and liquids. It was 

 carried out with the assistance of F. N. Brink. This work was a continu- 

 ation and amplification of the work of W. N. Stull mentioned in the last 

 report. Other elements and simple compounds were studied, and much time 

 was spent in obtaining a new absolute measurement of the compressibility 

 of mercury, which serves as the standard for other substances. 



Three years ago, in an attempt to discover the reason for the difference 

 between the free energy change and the total energy change of a given 

 reaction, the author suggested that this difference might be partly due to the 

 difference in total heat contents between the factors and products of the 

 reaction. With the assistance of F. G. Jackson this hypothesis was sub- 

 mitted to preliminary experimental trial in the research next to be reported, 

 to which may be given the title — 



(7) Bound energy and change of heat capacity. In order to obtain sig- 

 nificant results it was necessary to evaluate the heat capacities of both the 

 factors and the products of a reversible reaction between the absolute zero 

 and ordinary temperatures. With the help of the admirable liquid-air 

 plant of the Chemical Laboratory of Harvard College results at very low 

 temperatures were obtained, which showed such a well-marked linear tend- 

 ency that extrapolation to the absolute zero was reasonably safe. The 

 factors and products of three reversible galvanic cells were studied, and in 

 each case it was found that the heat expelled by diminution of the heat 

 contents of the sj^stem was of the same order and the same sign as the 



