Prof. Regnault on the Specific Heat of some Simple Bodies. 121 



tiful well-defined crystals. The existence of the natural hydro- 

 silicates would then be readily understood, &c. 



Silicic acid forms, with alcohol and wood-spirit, three silicic 

 ethers like phosphoric acid, while the monobasic acids only form 

 one compound ether. 



M. Wohler has recently described a siliciuretted hydrogen 

 which is spontaneously inflammable in the air, and presents the 

 greatest analogy with phosphuretted hydrogen. 



The protoxide of silicon discovered by the same chemist would 

 correspond to phosphorous acid ; chloride of silicon to chloride of 

 phosphorus, &c. 



But it is difficult to refer to this formula for silicic acid (Si 2 O 5 ) 

 the numerical results which analysis assigns to many compounds 

 of silicon. I confine myself at present to calling the attention 

 of mineralogists to this subject. Moreover it is possible that 

 silicon presents in its calorific capacity anomalies like those 

 which I have met with for carbon in its different conditions. 

 The specific heat of crystallized or melted silicon would not be 

 that which appertains to silicon in its compounds. 



Boron, 



The atomic weight of boron is as uncertain as that of silicon; and 

 chemists can give no definite reasonfor fixing the formula of boracic 

 acid. The formula BoO 3 is usually adopted, and then borax is 

 regarded as a neutral borate of soda. In the hope of elucidating 

 this question, a great interest attached to the determination of 

 the specific heat of boron, and I have successively made experi- 

 ments upon all the specimens of boron which I could procure. 



M. H. St. -Claire Deville distinguishes three varieties of boron : — ■ 

 1, amorphous boron ; 2, graphitoidal boron ; and 3, crystallized 

 boron. 



I worked with all three varieties, and proceed to detail the 

 Results which I have obtained. 



1. Amorphous Boron. 

 The amorphous boron was prepared in M. St. -Claire Deville's 

 laboratory. I washed it repeatedly with distilled water, and 

 then dried it under the receiver of an air-pump. In order to 

 determine with some accuracy the specific heat of this pulve- 

 rulent substance, I compacted it in the form of cylindrical discs, 

 by compressing it with the blows of a hammer in a lapidary's 

 mortar. These discs were placed for six days in vacuo over sul- 

 phuric acid, and were then placed in a basket of brass wire. To 

 prevent the boron from absorbing oxygen by being raised to the 

 elevated temperature of the bath, the inverse method was 

 adopted, that is, the boron was cooled in the apparatus which I 

 have described. 



