﻿ATOMIC HEAT TO CRYSTALLINE FORM. 131 



oxides, quand on les soumet a une chaleur graduellement croissante. II sa pro- 

 duit alors nn changement dans la disposition moleculaire du corpse, un changement 

 d'agregation qui se manifeste dans les caracteres chimiques. En effet, la substance 

 qui etait facilement soluble dans les acides, avant son incandescence, est devenue tres 

 difficilement soluble, quelquefois meme insoluble apres. L'incandescence s'explique 

 facilement par une diminution subite dans la capacite calorifique du corps, qui degage 

 instantanement de la substance une quantite considerable de chaleur qui auparavant 

 etait latente ; cette chaleur, au moment oil elle devient libre produit necessairement 

 une elevation therm ometrique qui porte pendant quelques instants la substance a Tin- 

 candescence, quand elle n' etait encore portee qu' au rouge sombre par la chaleur ex- 

 terieure."* 



In the Annates de Ghimie et de Physique, (ler ser. t. 70, p. 407,) Gay-Lussac has 

 published some observations upon certain bodies whose solubility he shows to be deter- 

 mined by temperature alone. These observations lead, moreover, to the supposition 

 that all spontaneous precipitations are due to differences in temperature. 



Many elementary bodies in uniting to form compounds, suffer a contraction in 

 volume. Now, M. Filhol has shown, that in those compounds whose chemical 

 properties are very analogous, the co-efficients of contraction are sensibly the same.f 

 Analogous properties seem to be associated with analogies in calorific condition. 



It would be superfluous to adduce other examples of the active character of caloric. 



From the laborious and carefully conducted experiments of many eminent physi- 

 cists, we may infer that in the most, if not all bodies, the combined heat varies to a 

 greater or less extent in different specimens. Examples of this we find in carbon, 

 sulphur, &c. Accompanying this variation, and in all probability caused by it, we 

 find a change in form, condition, physical and chemical properties and the like. 

 Indeed it is difficult to conceive how any change, even the slightest, in the heat of a 

 body, could be unaccompanied by some alteration in the ponderable matter. The 

 extreme sensitiveness of heat or caloric is evinced in every chapter of its endless 

 history. It is very rational to suppose, therefore, that the influence of caloric in 

 moulding ponderable matter into definite forms, must in a certain measure vary with 

 the degree of aggregation of the body, which state of aggregation is indeed in great 

 measure contingent upon the amount of caloric itself. Increased aggregation is gene- 

 rally an indication of diminished calorific capacity. In colcothar and the diamond 

 we have beautiful examples of this fact. In condensing very strongly, a body often 

 completely loses its most characteristic chemical properties. Heat acting upon two 

 dissimilar pieces of metal soldered together, gives rise to electrical phenomena ; acting 

 upon water, produces motor effects. From such conspicuous examples we are forced 



* Regnaulfc, Ann. de Chim. et de Phys. 3me Ser. i. 188--9. 

 ■j- Annales de Chim. et de Phys., 3 me ser. t. xxi., p. 415. 



