298 



Dr. H. F. Weber on the Specific Heat of 



of silicon increases from 200° to 300° in the same proportion as 

 it does from 184° to 232°, it will attain the value 02055 at 

 300°. Multiplying this number by 28 (the atomic weight of 

 silicon deduced in accordance with Avogadro's law), we obtain 

 the number 5*75. This number is in keeping with those ex- 

 pressing the atomic heats of the metals. Then, taking Regnault's 

 determination, we have the following atomic heats : — 



5-8. 



60. 



6-1 to 6-3. 



6-4 to 6-6. 



For aluminium. 



Magnesium. 



Copper. 



Silver. 



Nickel. 

 Cobalt. 

 Ir on 



Osmium. 



Ruthenium. 



Palladium. 



Platinum. 



Gold. 



Iridium. 



Indium. 

 Tin. 

 &c. 



Silicon does not form an extraordinary exception to the law of 

 Dulong and Petit; so soon as the temperature passes 200° it 

 comes within the sphere of this law. From these experiments 

 it also follows, that the smallest relative weight of silicon (28) 

 hitherto found in the molecule of any of the gaseous compounds of 

 this element is in reality the atomic weight of silicon. 



V. General Results. 



(1) The values of the specific heats of the elements carbon, 

 boron, and silicon change with the temperature; these values 

 gradually increase with an increase of temperature until a point 

 is reached at which they are constant. This point is situated at 

 about 600° for carbon and boron, at about 200° for silicon. 

 The specific heat of carbon at 600° is about seven times, that of 

 boron about two and a half times as great as at —50°. The 

 nature of the function expressing the relation between the spe- 

 cific heat y T and the temperature appears to be the same for the 

 three elements, and to have the form 



a n l + hT 



qT 



A>B 



q>h, 



where A, B, q, and h represent positive quantities, and T the 

 temperature calculated for absolute zero. 



The specific heats of the elements are not, generally speaking, 

 expressed by constant numbers, the physical condition of the 

 elements influencing their specific heats as much as their che- 

 mical nature. The idea that the temperature exercises but an 

 insignificant influence upon the magnitude of the specific heats 

 of the elements, and that this influence may be overlooked with- 



