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PHYSICS. — Latent heat of fusion of ice. H. C. Dickinson, D. R. 



Haeper, and N. S. Osborne. Bulletin, Bureau of Standards. In 



Press. 

 Of the two experimental methods employed, one is the well known 

 method of mixtures in which an ice sample of from 100 to 200 grams 

 weight was allowed to melt in the calorimeter, cooling the water. The 

 other was an electrical method of somewhat higher precision. An ice 

 sample 500 grams in weight was put directly into the water and the 

 approximate amount of energy required to melt the ice supplied elec- 

 trically and measured, the small excess or deficiency being determined 

 from the small rise or fall of temperature of the calorimeter. The 

 usual calorimetric cooling correction was thus rendered relatively very 

 small and the heat capacity of the calorimeter needed to be known 

 only approximately^ The ice specimens used were from commercial 

 plate, can, and natural ice, and from ice frozen in the laboratory from 

 double distilled water both free from air, and containing air. They 

 were cut in the form of hollow cylinders to secure a more uniform rate 

 of melting. The samples were kept at the uniform temperature of 

 either — 0?72 or — 3?78 for several hours previous to the experiments, 

 and were so weighed and handled as to introduce each into the calo- 

 rimeter at the selected constant temperature with no significant error. 

 The heat of fusion of each of 92 samples of pure ice was determined 

 by one of the two methods. The results of the first half of these obser- 

 vations, made before the best experimental conditions were secured, 

 indicate no differences between the heats of fusion of the different 

 kinds of ice greater than the limits of precision, that is, about one part 

 in a thousand. The latter half show no difference as great as one part 

 in five thousand between the commercial Idnds of ice. The final figure 

 for the heat of fusion of pure ice is 79.63 cabs per gram mass. 



H. C. D. 

 453 



