CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL 

 LABORATORY, HARVARD UNIVERSITY. 



AN INVESTIGATION OF THE ERRORS IN COOLING CURVES 



AND METHODS FOR AVOIDING THESE ERRORS; 



ALSO A NEW FORM OF CRUCIBLE. 



By Harvey C. Hayes. 



Presented by John Trowbridge, Februarj- 8, 1611. Received December 29, 1910. 



Two main difficulties are encountered by one who attempts to make 

 an accurate study of the physical properties of alloys. The first diffi- 

 culty is the preparation of an alloy which shall contain only the desired 

 elements in its make-up. Foreign elements may enter the alloy through 

 lack of purity in the component metals (and the difficulty of getting 

 chemically pure metals is never appreciated until one has attempted 

 it), also impurities are almost sure to get into the alloy from the 

 crucible. The chemist can, with sufficient pains, prepare pure samples 

 of nearly all the metals ; but thus far science has not produced a 

 crucible that will keep them pure while melting them into an alloy. 

 Impurities from this source have been a hindrance to the study of 

 alloys, especially a study of their magnetic properties, and have been 

 a cause for more or less error in the work that has thus far been done. 



Roberts- Austen, in his classic experiment, showed that solids diffuse, 

 even at comparatively low temperatures. This makes doubtful the 

 possibility of finding a crucible that will not diffuse somewhat into 

 the alloy at such a temperature as the melting point of most metals. 

 One solid that does not seem to diffuse into metals, and apparently 

 the only one that does not, is quicklime. A block of lime with a hol- 

 low scooped out ofttimes serves the chemist for a crucible, for all that 

 he requires of a crucible is that it shall hold together long enough to 

 melt a small portion of metal and then slowly cool. But for the study 

 of alloys such a crucible will not suffice, as it is often necessary to chill 

 the melt. A block of lime will not stand such treatment ; and even if 

 it would, the lime is so poor a conductor of heat that it would be im- 

 possible to chill an alloy through the comparatively thick walls of such 

 a crucible. 



