66 Royal Society : — 



and liquids into solids, and the reverse ; and also in chemical combi- 

 nations and decompositions ; and therefore that the space as well as 

 the matter of which volume is composed can be only added to or 

 taken away in what is called its combining equivalent. 



In order to find whether the heat of chemical combination, which 

 is taken as equivalent to the alteration of internal space, is equally 

 produced by the same substance uniting with others, or if not, if it 

 is given out in multiple proportion, oxygen is made to combine with 

 several other simple bodies, and the alteration of temperature noted. 



The method of oxidizing these substances, the details of each pro- 

 cess being given in the paper, consisted in dissolving them in some 

 suitable menstruum, — for instance, in sulphuric acid, liquor of potass, 

 and nitric acid. When the two former are used, water is decom- 

 posed to oxidize the dissolved body ; in the last case, the nitric acid 

 is resolved into oxygen and binoxide of nitrogen, the former of which 

 unites with the substance to be oxidized, the latter escaping. Other 

 combinations and decompositions at the same time take place (as 

 detailed in the paper), and being taken into account (decompositions 

 absorbing as much heat as is produced by the combination of the 

 constituents), the alteration of temperature by the oxidation alone 

 is arrived at. 



In this manner eighteen diiferent metals were oxidized, but the 

 heat of oxidation was obtained satisfactorily only with twelve. Other 

 experimenters (Favre and Silbermann and Andrews) have, with a 

 different object in view, found the heat of oxidation of fourteen 

 other substances ; their conclusions are added as being from un- 

 prejudiced sources, and the result of all the experiments is brought 

 together in a table, in order to see whether the law of multiple pro- 

 portion exists. The numbers found by the different experimenters 

 are all calculated to the same standard. The unit of heat is the 

 amount necessary to raise the temperature of 1000 grains of water 

 1° Fahr., and the quantity of the metal oxidized is an equivalent of 

 each, oxygen = 1 . 



To find whether the law extends to change of state when no 

 chemical combination takes place, the amount of heat given out by 

 the condensation of an equivalent of steam, and by the solidification 

 of an equivalent of water, is given. The following is the table giving 

 the thermal equivalents of the several substances, the names of the 

 experimenters, and the ratio of proportion. It is to be remarked, 

 that the condensation of steam being in multiple proportion with the 

 other thermal equivalents, the expansion of all other bodies into 

 vapour must be included ; for I showed in the Philosophical Maga- 

 zine for January 1852 (page 48), that all bodies expand into vapour 

 in some multiple of their atomic volumes, and their atomic volumes 

 being in ratio also, their expansion or gain of internal space in this 

 definite change must be in multiple proportion. 



