CHEMISTRY. 255 



physical chemistry throws much light on these questions ; therefore, with the 

 help of C. R. Hoover, the author has begun a careful revision of the whole 

 subject. Promising preliminary results have already been obtained, and be- 

 fore the issue of the Year Book of 191 3 definitive figures are to be expected. 



(5) The heats of neutralisation of acids and alkalies: 



With the help of Dr. A. W. Rowe, this subject was continued, adding new 

 acids and alkalies to the list and obtaining further data as to change of the 

 heats of reaction with the temperature and with the dilution of the reagents. 



(6) The heats of dilution of aqueous solutions of acids, bases, and salts: 

 In connection with the investigation mentioned under the preceding head, 



the heats of dilution of the substances concerned were determined with 

 unusual exactness by means of the adiabatic calorimeter. The voluminous 

 data thus obtained, together with those concerning heats of neutralization, 

 form a highly interesting basis for the study of the nature of aqueous solu- 

 tions of electrolytes and will be subjected to critical study and submitted for 

 publication during the coming winter. This research has extended far 

 beyond the original intention, and bids fair to yield results even more 

 interesting than had at first been expected. 



(7) The heats of combustion of hydrocarbons: 



With the assistance of Dr. Frederick Barry, a number of hydrocarbons 

 of unusual purity have been studied, especially endeavoring to compare sub- 

 stances in homologous series. This work is a continuation of that already 

 published by the author in conjunction with Dr. R. H. Jesse, jr., and affords 

 further basis for the conclusions emphasized in the earlier research. 



(8) The compressibilities of allied organic substances: 



This investigation, which has been in progress for nearly ten years, has as 

 its object the discovery of the relations of the compressibilities of analogous 

 substances to one another and to other properties. Last winter much time 

 was spent in the construction of an absolute pressure gauge, because the 

 other details of the process had been previously carried to a degree of pre- 

 cision exceeding that of the gauges heretofore employed. Mr. J. W. Ship- 

 ley, who assisted in this work, then proceeded to the determination of the 

 compressibilities of a number of hydrocarbons, alcohols, and other allied 

 compounds, concerning which no satisfactory data are to be found in physico- 

 chemical literature; and the work will be continued next autumn. At the 

 same time, much of the previous unpublished Harvard work on this subject 

 was carefully recalculated, using the appropriate corrections as found with 

 the new gauge, and prepared for publication. The data thus collated were 

 found to confirm indubitably the following rule : The more compressible the 

 substance, the greater is the decrease of its compressibility with increasing 

 pressure. This rule was shown to be consistent with the theory of com- 



