Prof. Regnault on the Specific Heat of some Simple Bodies. 123 



In each of these experiments the quantity of boracic acid 

 formed was determined: in the first 0'56 grm. was found; so 

 that at the moment of immersion the brass vessel contained 

 19 gr, 95 of boron, and 0*56 of boracic acid. In like manner in 

 Experiment II. there were — 



Boron 19^10 



Boracic acid .... 0*35 



Lastly, in the third experiment there were — 



Boron 18^-72 



Boracic acid .... 0*49 



The specific heat of anhydrous boracic acid is 0*2374 (Ann. de 

 Chim. et de Phys. 3rd series, vol. i. p. 148). If there were no 

 other sources either of the disengagement or absorption of heat, 

 the perturbation produced by the presence of the boracic acid 

 could be calculated. But the boracic acid is probably formed in 

 the anhydrous state in the bath ; in the water of the calorimeter 

 it changes into hydrated acid, which dissolves more or less com- 

 pletely in this water during the time which elapses between 

 immersion and the observation of the stationary temperature. 

 These are new sources of error which I was not able to take into 

 account. 



Simply making the correction due to a replacement of part of 

 the boron by boracic acid, the specific heat of boron is found to 

 be— 



1 0-4053 



II 03483 



III 0-3598 



These values agree very little with each other, and I think they 

 cannot even be regarded as approximate. 



I then tried to study amorphous boron in the isomeric modi- 

 fication which it experiences, according to M. Deville, when 

 heated to 200° in an oil-bath in a current of hydrogen. I placed 

 in a glass flask discs of amorphous boron which had been pre- 

 pared by percussion. The flask having been placed in an oil- 

 bath, a current of hydrogen was passed through, and the tem- 

 perature of the oil-bath gradually raised to 200°, where it was 

 maintained for about half an hour. In this experiment I did 

 not observe either incandescence, or any visible phenomenon of 

 molecular modification. The oil-bath having been removed, the 

 current of hydrogen was continued for two hours. The sub- 

 stance had not changed in appearance; but when I was trans- 

 ferring the discs from the flask into a porcelain capsule, they 

 took fire one after the other, and burned with a lively incan- 

 descence. A funnel placed immediately over the ignited boron 

 was immediately covered with abundant drops of water. 



