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



the value of the specific heat of the former, as we have shown to 

 be the case with the latter, is a constant number. 



The results of the determination detailed above may be very 

 exactly represented by the following expression, in their relation 

 to the temperature T measured from absolute zero : — 



e 

 (A, B, a, g= constants; A>B; q>a.) On the ' supposition 

 that this expression represents the relation of the specific heat 

 to the temperature for temperatures < —80° and >260° (mea- 

 sured from the ordinary zero), A^-B will represent the limit of 

 value attained by the specific heat of boron at low temperatures, 

 and A will represent the final constant value attained at high 

 temperatures. The value of A calculated from the above equa- 

 tion is about 0*49 ; this may be attained at a medium red heat. 

 From an inspection of the curve (PL VII.) representing the spe- 

 cific heat of boron between —-40° and +230®, it will be seen 

 that in the dotted part a value of about 0*50 is attained. 



As soon as I can obtain 2 or 3 grms. of pure boron I shall 

 continue my experiments with the view of testing the accuracy 

 of the above anticipation. Considering the rapid increase in the 

 value of the specific heat of boron as the temperature increases 

 until a certain point is reached, and the gradual diminution in 

 the velocity of this increase after that point, I feel justified in 

 concluding that it is very probable indeed that at higher tempe- 

 ratures the specific heat attains a constant Value represented (in 

 round numbers) by the fraction 0*50, and that therefore the 

 number 11, which is generally accepted as the atomic weight of 

 boron, is really the atomic weight; further, that the atomic 

 heat of boron is about 5*5, and that therefore at a red heat boron 

 obeys the law o/Dulong and Petit. 



IV. The Specific Heat of Crystallized Silicon. 

 1*123 grm. of material was used ; it consisted of small bril- 

 liant steel-grey crystals, which were prepared in Professor Ram- 

 melsberg's laboratory by reducing silicon-calcium fluoride with 

 zinc and sodium. The results of a first series of experiments, in 

 which the silicon was enclosed in a glass vessel, were rejected, 

 and another series was undertaken in which a vessel of tinfoil 

 weighing about 0*2 grm. was employed. After each experiment 

 the crystals were removed, dried at 150°, and placed in a fresh 

 vessel ; the weight of the material gradually decreased from 

 1*123 to 1*045 grm. A platinum spiral which was used as a 

 sinker weighed 0*501 grm., and had a mean specific heat be- 

 tween 0° and T equal to 0*03]9 + 0*000004T. 



