202 REPORTS OP INVESTIGATIONS AND PROJECTS. 



chloride carried on by the author and Drs, Kothner and Tiede in the Uni- 

 versity of BerHn. Many preparations of ammonium bromide have been pre- 

 pared and analyzed with the greatest care, and conclusive evidence has been 

 gained that the atomic weights of both nitrogen and silver are lower than 

 Stas supposed them to be. The exact figures are not yet ready for publica- 

 tion. This work will be continued during the coming winter. 



(3) An investigation concerning the compressibilities of the chlorides, 

 bromides, and iodides of sodium, potassium, thallium, and silver, carried 

 on with the assistance of Dr. Grinnell Jones. By means of the method of 

 Richards and Stull, described in Publication No. 7 of the Carnegie Institu- 

 tion of Washington, the compressibilities of these substances were studied 

 with great care. Regularities of a striking and interesting nature were found 

 upon comparison of results, and the investigation led to the first rational ex- 

 planation of the negative coefficient of expansion of silver iodide. The re- 

 sults of this research may be said to furnish the best support as yet ofifered 

 for the theory of atomic compressibility, because they explain certain facts 

 which might otherwise appear to be exceptions. Moreover, even supposing 

 the theories should be disproved, the facts discovered in this investigation are 

 certain to be of value. The paper has been prepared for publication and is 

 now in press. 



(4) An investigation of the relations exhibited by many physico-chemical 

 properties of simple organic substances, carried on with the assistance of Dr. 

 J. H. Mathews. For this purpose it was necessary in the first place to pre- 

 pare large quantities of the substances in a state of great purity. When this 

 had been accomplished, the substances (about 40 in number) were studied 

 with regard to their surface tensions, compressibilities, heats of vaporization, 

 boiling-points, vapor-pressures at 20°, and specific gravities. Relations be- 

 tween these properties of great interest and important significance were 

 found, especially between surface-tension and compressibility. The relation- 

 ship in this case was that predicted by the theory of compressible atoms ; and 

 the other relationships also, in so far as they are traceable, appear to be in ac- 

 cord with this theory. This investigation is finished, and is being prepared 

 for publication. 



(5) An investigation of the heats of reaction of metals upon acids, carried 

 on with the assistance of L. L. Burgess. These data form the basis of com- 

 puting the heats of formation of the salts of all metals. The determinations 

 made previously by others made no pretense to be anything more than ap- 

 proximate, and advantage was taken of the exactness of the recently devised 

 Harvard method of adiabatic calorimetry to redetermine these fundamental 

 constants. Thus far the metals of magnesium, zinc, cadmium, aluminium, 

 and iron have been studied, and in the following winter the work will be ex- 

 tended to other metals. 



