1876.] 
Recent Chemical Researches . 
33 
In a preliminary series of experiments Prof* Weber 
showed that the specific heat of diamond increases, with 
increase of temperature, more quickly than that of any 
other substance— -the values at o°, ioo°, and 200°, being 
almost in the ratios 1:2:3. Hence it follows that there is 
a close relation between the specific heat of diamond and the 
temperature, and that these quantities increase simultane- 
ously. The value of this increase, however, diminishes at 
a red-heat and upwards to a white-heat, until it becomes 
but a seventeenth part of what it was for the temperature- 
interval o° to 100°. 
From a red-heat upwards the value of this increase is not 
greater than that of the increase noticed in the case of the 
elements which obey the law of Dulong and Petit. 
The actual numbers representing the specific heat of 
diamond at high temperatures are as follows : — ■ 
Temp. Spec. Heat. 
6o6° C. ........ . 0*4408 
8o6° ......... 0*4489 
985° ......... 0-4589 
By multiplying these numbers by the generally received 
atomic weight of carbon we obtain a produbt varying from 
5*2 to 5*5. Other elements which have small atomic weights 
give very similar numbers : thus the product obtained by 
multiplying the atomic weight of aluminium into its specific 
heat is 5*7 ; of phosphorus, 5*5 ; of sulphur, 5*5 ; &c. 
Crystallised boron shows a like increase in specific heat with 
increasing temperature: at — 39*6°the number expressing the 
specific heat is 0*1915, while at 233*2° it is 0*3663. By rea- 
soning from these numbers the conclusion is drawn that at 
a red-heat the specific heat of boron attains a constant 
value equal to about 0*5. If this number be multiplied by 
11, the generally-received atomic weight of boron, we 
obtain the product 5*5, which expresses the atomic heat of 
this element. 
Similar researches, carried out with crystallised silicon, 
have led to similar results, viz., that the specific heat of 
silicon is a function of the temperature, and that at about 
200° it attains a constant value : 0*2029 is the experimental 
number representing the specific heat of this element at the 
temperature 232*4° ; 28, which is the received atomic weight 
of silicon, multiplied into 0*2029 gives us the product 5*68. 
The three elements, carbon, boron, and silicon, are there- 
fore no longer to be considered exceptions to the generalisa- 
tion of Dulong and Petit ; and we may, with more certainty 
VOL. vi. (n.s.) f 
