I04 CARNEGIE INSTITUTION OF WASHINGTON. 



Wilder D. Bancroft, Cornell University, Ithaca, N, Y. Grant 

 No. 140. For a systematic chemical shidy of alloys. (First report 

 is in Year Book No. 2, p. xxix.) $500- 



Abstract of Report. — During the year the equilibrium relations for 

 the copper-zinc alloys have been determined. The two metals form 

 no compounds. The freezing-point curve has six branches, each one 

 corresponding to a series of solid solutions. Following the example 

 of Heycock & Neville, these have been called the «, /?, y, <\ £, and 

 rj crystals, beginning at the copper end. Below about 450° the 

 phase <^ is instable, and only five series of solid solutions occur. The 

 a crystals change with increasing content of zinc from the red of 

 copper to a full yellow. The /? crystals are distinctly redder than 

 the a crystals with which the}- can coexist. The other solid solu- 

 tions are silvery in color. Since the ;? crystals are ductile and the y 

 crystals are very brittle, a brass containing 41 per cent of copper has 

 a silvery fracture, while the polished surface is a pale yellowish red. 

 The ingot breaks along the y crystals, while polishing emphasizes 

 the /5 crystals. 



The conclusions from the temperature measurements have been 

 confirmed by a careful microscopic study of the alloys. Forty-six 

 photomicrographs are reproduced in the account of this work pub- 

 lished in the June number of the Journal of Physical Chemistry. 



Now that the equilibrium diagram has been finished, it will be 

 possible to take up the study of the mechanical properties of brass 

 and their variation with composition and heat treatment. The corre- 

 sponding studies on the bronzes, reported under grant 176, have led 

 to very interesting results. The work on the brasses will probably 

 not yield such striking results, but it will be equally important as 

 giving a rational explanation for the heat treatment. 



In the report of last year there was submitted a provisional con- 

 centration-temperature diagram for the copper-tin-lead alloys. The 

 work has been repeated so as to obtain more accurate freezing-point 

 determinations. This has involved several changes in the recording 

 pyrometer, and we now have an instrument which is inexpensive 

 and yet capable of considerable accuracy. Automatic stirring and 

 the addition of nuclei have been resorted to in all determinations. 

 The more accurate results thus obtained have necessitated a revision 

 of some portions of the diagram. 



Another point has delayed the publication of this work. In the 

 first report it was thought sufficient to accept Heycock & Neville's 



