﻿90 M. Dumas's Re?na?*ks on Affinity. 



Potash and sulphuric acid = sul-") „ 



phate of potash J 



Alumina and sulphuric acid = sul-^S „ , 



phate of alumina .... J 

 Sulphate of potash and sulphate of 1 tt f 



alumina = alum .... J 

 Alum and water = crystallized \™ ,i , , 



alum J 



Beyond this term combination becomes impossible, as we 

 know ; and crystallized alum appears the last product which can 

 be realized with this order of compounds. 



Conversely : — 



Crystallized alum heated to 120° becomes anhydrous. 



Anhydrous alum heated to redness is converted into sulphu- 

 rous acid, oxygen, alumina, sulphate of potash. 



Sulphurous acid, sulphate of potash, and alumina, when raised 

 to extreme temperatures, are themselves converted into oxygen, 

 sulphur, potassium, and aluminium. 



The elements which combine lose heat. Therefore the ele- 

 ments of a chemical compound which separate must be raised 

 to a temperature which is higher the greater the heat they have 

 emitted in combining. 



Heat being regarded as motion, combination would consist in 

 a diminution of this motion ; it would cease to be possible when 

 the molecules of the compound had no more heat to lose. 



Whatever be the manner in which this heat intervenes in the 

 formation and destruction of chemical compounds, we must see 

 in it the sum and the expression of all the forces put in play in 

 the successive production of the various agglomerates of a com- 

 pound, or for their disaggregation. And it was with a grand 

 perception of the true nature of chemical phenomena that La- 

 voisier in his equations placed heat in the same rank as matter, 

 and that he attached such great importance to the calorimetrical 

 investigations which so long occupied him. 



The extension which M. Regnault has given them, as regards 

 specific heats, and that which they have received from M. Favre 

 in all that concerns the disengagement of heat at the moment 

 of combination, prepare chemistry for passing from the epoch 

 in which it only considered matter to that in which it will take 

 force into consideration. 



The new researches to which the mechanical theory of heat 

 has given rise have recalled the attention of chemists to the me- 

 chanical theory of heat stated by Jules Robert Meyer. This 

 profound physicist considers chemical phenomena due to an 

 attractive force which precipitates atoms against each other. 



