SPECIFIC HEAT OF ATOMS. 125 



other in analogous compounds, the first remains unaltered, 

 while the last must be reduced to two-thirds of its present 

 amount. 



It must be concluded then, that elementary atoms have not 

 necessarily the same capacity for heat, although a simple re- 

 lation appears always to exist between their capacities. The 

 capacities of the three gaseous elements, oxygen, hydrogen and 

 nitrogen, may likewise be adduced in support of such a relation, 

 provided they are the same for equal volumes of the gases, 

 agreeably to the observations of Dulong. But this relation can 

 only be looked for between bodies while under the same physi- 

 cal condition, and perhaps agreeing in other circumstances 

 also, for the capacity for heat of the same body is known to 

 vary under the different forms of solid, liquid and gas; and, 

 indeed, while the body is in the same state, its capacity ap- 

 pears not to be absolutely constant, but to increase perceptibly 

 at elevated temperatures (page 23). 



The capacities of compound atoms have not been submitted 

 to a sufficiently extensive examination to determine whether 

 equally simple relations subsist generally among them. In 

 two classes of analogous combinations, however, the capacities 

 of the atoms for heat have been found by M. Neumann to 

 approach so closely, that they may be admitted to be the same, 

 the differences being sufficiently accounted for by the errors of 

 observation unavoidable in such delicate researches. 



Of equal weights. Of atomic weights. 



Specific heat of Specific heat of 



same weight of atom of water 



water being 1. being 1. 



Carbonate of lime . . 0.2044 . 0.1148 



Carbonate of barytes . . 0.1080 . 0.1181 



Carbonate of iron . . 0.1819 . 0.1156 



Carbonate of lead . . 0.0810 . 0.1200 



Carbonate of zinc . . 0.1712 . 0.1187 



Carbonate of strontian . 0.1445 . 0.1184 

 Dolomite (carbonates of lime and 



magnesia) . . . 0.2111 . 0.1121 



Mean . 0.1168 

 A small class of sulphates presented a similar result : 



Of equal weights. Of atomic weights 



Sulphate of barytes . . 0.1068 . 0.1384 



