D. CHEMISTRY AND METALLURGY. 213 



having two apertures in it, through one of which a thermom- 

 eter, bent at right angles, is inserted, in such a way that 

 the bulb can be immersed in the liquid or the vapor at pleas- 

 ure, while upon the other is screwed a condenser, consisting 

 of two concentric cylinders. At diametrically ojoposite points 

 at the bottom of the boiler the ends of a small curved spiral- 

 shaped tube are inserted. This tube, filled with the same 

 liquid as the boiler, passes directly through the chimney of 

 a lamp, and consequently receives upon a small surface the 

 whole of the heat of the lamp. The fluid, thus gradually 

 warmed, circulates through the tube and the boiler, until the 

 whole of it has reached the boiling point, when the thermom- 

 eter becomes stationary, and will remain so for ten minutes. 

 A horizontal movable scale is fixed to the top of the boil- 

 er, by comparing which with the thermometer the amount 

 of alcohol is indicated in degrees from up to 25. 14 C, 

 CCXIIL, 87. 



SPECIFIC HEAT OF CARBON, BORON, AND SILICON. 



In 1819 Dulong and Petit discovered that when the spe- 

 cific heat of a solid element was multiplied by its atomic 

 weight, the product was a constant quantity in the neighbor- 

 hood of 6. Later, however, it was found that carbon, boron, 

 and silicon were apparent exceptions to this rule. These 

 elements have been studied in this direction by many exper- 

 imenters with very discordant results; as, for instance, some 

 found that the different modifications of carbon had the 

 same specific heat, others that they varied widely. The 

 subject has lately been thoroughly worked up by Dr. H. 

 Fried rich Weber, whose results at last seem to be conclusive. 

 Carbon he examined as diamond, graphite, coal, and charcoal, 

 and boron and silicon in their crystalline varieties. His ex- 

 periments were conducted at temperatures varying from 

 80 to +1000 Centigrade, and with the finest modern ap- 

 paratus. With all three of the elements above named the 

 specific heat increases very rapidly with the temperature. 

 At 600 for carbon and boron, and at 200 for silicon, this in- 

 crease almost ceases, and the specific heat remains nearly 

 constant. Below 600 the different modifications of carbon 

 give different results, but at and above this temperature they 

 coincide. The constant final values, at the temperatures 



