On the Combination of several Metals with Oxygen. 375 



On the Amount of Heat produced hj the Combination of several 

 Metals ivith Oxygen. 



Parsonstown, August 1852. 



The reasons spoken of in the preceding paper having led me 

 to the opinion that the heat of chemical combination is not 

 the result either of opposite electricities uniting, or the disen- 

 gagement of any subtle fluid, or any affection of matter which is 

 not met with in simple bodies, but the compensating, or accom- 

 panying and opposite movement among particles, whereby the 

 loss of volume or distance between the particles uniting is ba- 

 lanced; and judging from the theory I advanced, that in a mix- 

 ture of bodies those pai'ticles which could come the closest toge- 

 ther would unite to the exclusion of others, or in other words, 

 would have the greatest affinity, — I concluded that as the heat 

 or expansion is equal, although opposite to the contraction of 

 the combining bodies, it would be a measure of the affinity ex- 

 erted between different substances. I accordingly endeavoured 

 to ascertain the amount of heat liberated by the combination of 

 several substances with oxygen, in order to find whether those 

 which produced most heat were likewise the strongest bases. 

 The method I adopted is partly founded on the inference 1 drew 

 in the paper published in the October Number of the Philoso- 

 phical Magazine, 1851, from the fact I there proved, "that 

 the decomposition of a compound body gives rise to as much 

 cold as the combination of its elements produces heat." I said 

 (12) that "it might be made the means of determining the 

 amount of heat produced by the combination of bodies, as the 

 loss occasioned by their decomposition shows the gain by their 

 combination." 



Knowing, then, the amount of heat produced by the combi- 

 nation of hydi'ogen with oxygen, I knew that if water were de- 

 composed a like amount would be absorbed ; and therefore if 

 any body were placed in contact with water, and could decom- 

 pose it by joining with its oxygen, the amount of heat of such 

 combination could be calculated by adding the heat absorbed by 

 the decomposition to that marked by the thermometer. For in- 

 stance, if potassium be placed in water, the oxygen unites with 

 it, and a certain amount of heat is produced ; but the decompo- 

 sition of the water to supply the oxygen absorbs a certain amount 

 also ; the latter nmst be added to the former, and the sum is the 

 quantity of heat the combustion of potassium in oxygen would 

 produce. If the addition of sulphuric acid be necessary to make 

 the metal continue the decomposition of the water, as in the case 

 of zinc, then the heat ])roduced by the combination of the oxide 

 with tlie acid must be allowed for ; and in cases (such as copper)' 



