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From these experiments it appears that the specific heat of diamond increases uninterruptedly as the temperature increases Ay from -50° to +250°,-the velocity of this increase, slowly
accelerating from -50° to +60°, and from +60° to +250° constantly diminishing. In the neighbourhood of +60° there is a turning-point in the curve representing the specific heat of diamond. The constant diminution, from 60° upwards, of the value makes it probable that this diminution will continue to increase at higher temperatures, and that there exists a tem
perature at which becomes exceedingly small, or even disappears entirely-and, further, that there is a definite limit of value towards which, as the temperature rises, the specific heat tends. To test the truth of this expectation, the specific heat of the diamond was determined for three temperatures between 500° and 1000° by the aid of the double calorimeter already described. The crystals used in the foregoing experiments could not now be made use of, as at the high temperatures employed
considerable injury might be done to the costly cut diamonds. Professor Tschermack, Director of the Imperial Mineral Cabinet in Vienna, had the extreme goodness to allow me to make use of seven colourless transparent diamonds (slightly sparkling crystals, rounded pieces, and angular fragments).
In the following Tables the meanings of the letters are as follows:-
weight of substance employed.
Q water-value of the calorimeter (inclusive of stirrer and thermometer).
increase of temperature (corrected) which the calorimeter showed after the addition of the glowing substance. the product of Q into At.
the difference between the initial temperature T of the substance brought into the calorimeter and the final temperature To of the same substance (calculated from W and the known specific heat of platinum). CT.-T the average specific heat for the temperature-interval T-To
b. Experiments at High Temperatures carried out by means of the double Calorimeter.
182 Specific Heats of the Elements Carbon, Boron, and Silicon.
Platinum... 32.390 201-61 5.178 1043.8
Platinum... 32-390 200-03 5.269 1054.0
Platinum... 32-390 241-21 5.112 1233.0
From the first experiments
From the second experiments W9228-329-4.
At. W. AT. CT.-T. To.
With the aid of the value already obtained, y22-5=0.1228, we can reduce these eight results to a common lower limit of temperature, to the average temperature 22-5. By this reduction the first decimals in the numerical value of WT, remain unchanged; we obtain :
22.5 22.5 =0·4438,
From the first experiments
225 224-4, W922-8=329.4,